DCL-11-097, License Amendment Request 11-05, Evaluation Process for New Seismic Information and Clarifying the Diablo Canyon Power Plant Safe Shutdown Earthquake: Difference between revisions

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| case reference number = PG&E Letter DCL-11-097, DCL-11-097
| case reference number = PG&E Letter DCL-11-097, DCL-11-097
| document type = Letter type:DCL, License-Application for Facility Operating License (Amend/Renewal) DKT 50, Report, Technical, Technical Specifications, Updated Final Safety Analysis Report (UFSAR)
| document type = Letter type:DCL, License-Application for Facility Operating License (Amend/Renewal) DKT 50 Report Technical Technical Specifications, Updated Final Safety Analysis Report (UFSAR)
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=Text=
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{{#Wiki_filter:El PacificGas and ElectricCompany-                                                    James R.Becker Site Vice President Diablo Canyon Power Plant Mail Code 104/5/601 P 0. Box 56 Avila Beach, CA 93424 805.545.3462 Internal: 691.3462 Fax: 805.545.6445 October 20, 2011 PG&E Letter DCL-1 1-097 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Diablo Canyon Units 1 and 2 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 License Amendment Request 11-05, "Evaluation Process for New Seismic Information and Clarifyinq the Diablo Canyon Power Plant Safe Shutdown Earthquake"
{{#Wiki_filter:}}
 
==Dear Commissioners and Staff:==
 
Pursuant to 10 CFR 50.90, Pacific Gas and Electric Company (PG&E) hereby requests approval of the enclosed proposed amendment to Facility Operating License Nos. DPR-80 and DPR-82 for Units 1 and 2 of the Diablo Canyon Power Plant (DCPP), respectively. The enclosed license amendment request (LAR) proposes to revise the current licensing basis, as described in the Final Safety Analysis Report Update (FSARU) and Technical Specifications (TS), to provide requirements for the actions, evaluations, and reports necessary when PG&E identifies new seismic information relevant to the design and operation of DCPP.
Through this LAR, PG&E proposes to: (1) clearly define an evaluation process for newly identified seismic information and incorporate ongoing commitments associated with the Long Term Seismic Program (LTSP) into the FSARU; and (2) clarify, consistent with the NRC Supplemental Safety Evaluation Report 7, that the 1977 Hosgri earthquake is the equivalent of DCPP's safe shutdown earthquake, as defined in 10 CFR 100, Appendix A.
The enclosure to this letter contains the evaluation of the proposed change.
Attachments 1 and 2 of the enclosure include proposed TS markup and retyped pages, respectively. Attachment 3 of the enclosure includes FSARU markup pages.
Attachment 4 of the enclosure includes a summary of regulatory commitments and changes. Attachments 5 through 7 of the enclosure include Chapters 5 through 7 of the 1988 LTSP Final Report, respectively.
PG&E has determined that this LAR does not involve a significant hazard consideration per 10 CFR 50.92. Pursuant to 10 CFR 51.22(b), no environmental 00 A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
* Comanche Peak - Diablo Canyon
* Palo Verde
* San Onofre
* South Texas Project
* Wolf Creek
 
Document Control Desk                                                      PG&E Letter DCL-1 1-097 October 20, 2011 Page 2 impact statement or environmental assessment is required in connection with the issuance of this amendment.
PG&E requests approval of this LAR by September 29, 2012. PG&E requests that the license amendments be made effective upon NRC issuance, to be implemented within 180 days from the date of issuance.
During a June 29, 2011, telephone conference call with the NRC staff, PG&E was requested to provide a comparison of the current Standard Review Plan (SRP) with DCPP's licensing basis. The SRP comparison will be provided in a separate letter.
PG&E is making a regulatory commitment (as defined by NEI 99-04) in this letter.
This letter also includes a revision to an existing regulatory commitment. of the enclosure summarizes the regulatory commitment and the revision to an existing regulatory commitment made in this letter.
In accordance with 10 CFR 50.91, PG&E is notifying the State of California of this LAR by transmitting a copy of this letter and enclosure to the designated State Official.
If you have any questions or require additional information, please contact Mr. Tom Baldwin at (805) 545-4720.
I state under penalty of perjury that the foregoing is true and correct.
Executed on October 20, 2011.
Sincerely, James  i    Beckrer Site Vice President mjrm/gwh2/50350163
 
==Enclosure:==
Evaluation of the Proposed Change cc/enc:          Gary W. Butner, California Department of Public Health Elmo E. Collins, NRC Region IV Michael S. Peck, NRC, Senior Resident Inspector James T. Polickoski, NRR Project Manager Alan B. Wang, NRR Project Manager cc:              Diablo Distribution A member  of the STARS  (Strategic  Teaming and  Resource Sharing)  Alliance Callaway - Comanche Peak
* Diablo Canyon
* Palo Verde
* San Onofre  - South Texas Project
* Wolf Creek
 
Enclosure PG&E Letter DCL-11-097 Evaluation of the Proposed Change
 
==Subject:==
License Amendment Request 11-05, "Evaluation Process for New Seismic Information and Clarifyinq the Diablo Canyon Power Plant Safe Shutdown Earthquake"
: 1.
 
==SUMMARY==
DESCRIPTION
: 2. BACKGROUND
: 3. DETAILED DESCRIPTION
: 4. TECHNICAL EVALUATION
: 5. REGULATORY EVALUATION 5.1  Applicable Regulatory Requirements/Criteria 5.2  Precedent 5.3  Significant Hazards Consideration 5.4  Conclusions
: 6. ENVIRONMENTAL CONSIDERATION
: 7. REFERENCES ATTACHMENTS:
: 1. Technical Specification Page Markups
: 2. Retyped Technical Specification Pages
: 3. FSAR Update Changes
: 4. Summary of Regulatory Commitments
: 5. Chapter 5 of the 1988 Long Term Seismic Program Final Report
: 6. Chapter 6 of the 1988 Long Term Seismic Program Final Report
: 7. Chapter 7 of the 1988 Long Term Seismic Program Final Report 1
 
Enclosure PG&E Letter DCL-1 1-097
 
==SUMMARY==
DESCRIPTION This letter is a request to amend Facility Operating License Nos. DPR-80 and DPR-82 for Units 1 and 2 of the Diablo Canyon Power Plant (DCPP),
respectively.
This, License Amendment Request (LAR) proposes to address licensing basis issues with respect to evaluations of new seismic information and to clarify that the 1977 Hosgri Earthquake spectrum (HE) is the equivalent of DCPP's safe shutdown earthquake (SSE).
The current DCPP licensing basis lacks a clear process for evaluating new seismic information. The proposed change would clearly define the evaluation to be performed upon discovery of new seismic information, and addresses Unresolved Item 05000275; 323/2011002-03, "Requirement to Perform an Operability Evaluation Following Receipt of New Seismic Information."
(Reference 15)
The proposed amendment would add the following new Technical Specification (TS) Administrative Controls Programs:
(1)        TS 5.5.20, "Long Term Seismic Program" (LTSP) to provide for ongoing review and evaluation of new seismic information and associated methodologies. The proposed evaluation process for new seismic information follows the seismic margin assessment performed by the LTSP compared to the HE. As described in Section 4 of this enclosure, "Technical Evaluation," under Subheading "1991 LTSP DGMRS as the comparison for new ground motion spectra," new seismic information will only be compared to the 1991 LTSP ground motion spectrum.
(2)        TS 5.6.11, "Long Term Seismic Program Report" to inform the NRC of new, peer-reviewed seismic information that might affect the seismic risk to DCPP.
PG&E proposes to use the square-root-of-the-sum-of-squares (SRSS) method for the evaluation of load combinations of seismic with loss-of-coolant accident (LOCA). This method of combination is consistent with NUREG-0484, "Combining Dynamic Loads," Revision 1.
PG&E is in the process of performing evaluations for the combination of HE seismic loads with LOCA loads for reactor coolant system (RCS) loop piping and certain primary equipment. The above proposal to use SRSS as the methodology for evaluating the combination of seismic and LOCA loads is needed to address a non-conforming condition (DCPP corrective action program 2
 
Enclosure PG&E Letter DCL-1 1-097 Notification 50403189 and 50403377). PG&E anticipates that the evaluations will be completed after NRC review of this LAR and issuance of a license amendment.
The proposed amendment clarifies that the HE is the equivalent of DCPP's SSE to be used to demonstrate that the design basis requirements associated with the SSE continue to be met. The proposed amendment clarifies ongoing commitments to evaluate new seismic information for its significance to DCPP, maintain a seismic instrumentation program, and to design and construct future additions and modifications to DCPP in accordance with the existing seismic design basis.
The current DCPP Final Safety Analysis Report Update (FSARU) contains inconsistencies with documents issued by the NRC identifying the SSE for DCPP. While DCPP was licensed prior to 10 CFR 100, the definition of SSE (10 CFR 100, Appendix A) is:
[SSE]
maximum is that earthquake earthquake    which is potential  based upon consideringthean evaluation regional andof the geology local and seismology and specific characteristicsof local subsurface material.
It is that earthquake which produces the maximum vibratoryground motion for which certain structures,systems, and components are designed to remain functional. These structures, systems, and components are those necessary to assure: (1) The integrity of the reactor coolant pressure boundary, (2) The capability to shut down the reactor and maintain it in a safe shutdown condition, or (3) The capabilityto prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of this part.
Although DCPP is not a 10 CFR 100 licensed plant, the HE fits this definition for DCPP and; therefore, has appropriately been identified by the NRC as the equivalent of the DCPP SSE. In order to align the FSARU with the NRC conclusions in Supplemental Safety Evaluation Report (SSER) 7 during the DCPP licensing reviews and to eliminate regulatory uncertainty, PG&E proposes to incorporate the NRC's position that the HE (not the double design earthquake (DDE)) is the equivalent of DCPP's SSE, as defined in 10 CFR 100, Appendix A.
: 2. BACKGROUND The NRC's predecessor agency, the Atomic Energy Commission (AEC), issued a construction permit (CP) for DCPP Unit 1 on April 23, 1968, and for Unit 2 on December 9, 1970. In 1975, the regulatory functions of the AEC were assumed by the NRC. After construction was complete, the NRC issued operating licenses (OLs) for DCPP. The NRC issued a full-power OL for Unit 1 on November 2, 1984, and for Unit 2 on August 25, 1985.
3
 
Enclosure PG&E Letter DCL-1 1-097 Before the NRC issued the DCPP CP, PG&E conducted geological and seismic investigations to validate the acceptability of the site. These investigations included regional studies and detailed onshore site investigations consisting of trenching, core drilling, and geological mapping in the vicinity of the site. During the time of the DCPP CP review, the NRC regulation that currently governs seismic design (10 CFR 100, Appendix A) was in the early stages of development, and the concepts of the SSE and operating basis earthquake (OBE) were still being developed.
At the time the CP was issued, PG&E concluded, and the AEC concurred, that the earthquake design bases for Diablo Canyon would be a peak horizontal ground acceleration (PGA) of 0.4 g for safety-related structures and a PGA of 0.2 g for operational-related structures. These seismic design criteria were based on consideration of two design-basis earthquakes: a magnitude 7.25 earthquake on the Nacimiento fault 20 miles from the site, and a magnitude 6.75 aftershock at the site associated with a large earthquake on the San Andreas fault. It was also concluded at that time that there was no surface displacement hazard (capable fault) in the site vicinity. This conclusion was based on the absence of any displacement of the 80,000 year-old and 105,000 year-old marine terraces underlying the site area.
Later, while geological investigations in support of the DCPP OL applications were under way, oil company geoscientists discovered that a major zone of faulting existed a few miles off shore from the plant site. This proprietary offshore geophysical information was made public in 1971. When the DCPP Final Safety Analysis Report (FSAR) was initially submitted for NRC review in 1973, it briefly described the offshore fault zone, calling it the East Boundary Fault Zone.
During the next few years, in response to NRC Staff requests for additional information, PG&E investigated this fault zone. In addition, the U.S. Geological Survey (USGS), with NRC funding, conducted numerous offshore investigations of the fault zone. The zone was later renamed the Hosgri fault. Based on the results of these studies, recommendations by the USGS, and the issuance of 10 CFR 100, Appendix A (1973), the NRC established that the equivalent SSE for DCPP is a horizontal PGA of 0.75g based on a postulated magnitude 7.5 earthquake on the Hosgri fault 5 kilometers (km) (3 miles) from the DCPP site.
Subsequently, PG&E reanalyzed and upgraded the plant to accommodate the new (Hosgri) seismic design basis in compliance with General Design Criteria (GDC) 2 (1967) and Safety Guide (SG) 29. The Hosgri earthquake is the most severe natural phenomena (earthquake) (GDC 2) that produces the largest vibratory ground motion at the plant site (10 CFR 100, Appendix A). All safety-related SSCs at DCPP have been designed to remain functional if an SSE occurs (SG 29). These SSCs are those necessary to assure: (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shutdown the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or 4
 
Enclosure PG&E Letter DCL-1 1-097 mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of 10 CFR Part 100 (SG 29 and Appendix A to Part 100).
The DCPP seismic design basis was reviewed and accepted by the NRC Staff in SSER 7. The NRC stated that:
        ...although the applicant does not agree, we now considerthe Hosgri event to be the safe shutdown earthquake for the site, or at least its equivalent.
The structures,systems and'components that are being qualified for the Hosgri event in the seismic reevaluation are describedin the various chapters of the Hosgrireevaluation report (Amendment 50 and subsequent amendments to the operating license application). These plant features are those necessary to assure (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shutdown the reactorand maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of 10 CFR Part 100.
The Atomic Safety and Licensing Board (ASLB) hearing of September 27, 1979, also concluded that a 7.5 magnitude earthquake on the Hosgri fault was conservative for the SSE for DCPP (LBP-79-26, 10 NRC 453 (1979). The ASLB stated:
Accordingly, the Board concludes that a 7.5 magnitude earthquake is a very conservative value for the safe shutdown earthquake. We also find that the requirementimposed by the Staff that a 7.5 magnitude earthquakebe used by the applicantin its seismic analyses is reasonable and meets regulatoryrequirements.
The Board finds that the Applicant has demonstrated through appropriate analysis and tests that Category I structure, systems and components will perform as requiredduring the seismic load of the safe shutdown earthquake.
The Board finds that Category I structure, systems and components will be adequate to assure (a) the integrity of the reactorcoolant pressure boundary,and (b) the capability to shutdown the reactorand maintain it in a safe condition.
The seismic design basis for DCPP was reviewed by the NRC's Advisory Committee on Reactor Safeguards (ACRS). On July 14, 1978, the ACRS issued a letter report to the Commission stating that it had completed its review of the OL application. The ACRS letter concluded that if due consideration were given 5
 
Enclosure PG&E Letter DCL-1 1-097 to the items in its report, and subject to completion of the necessary plant modifications and preoperational testing, there was reasonable assurance that Units 1 and 2 could be operated at full power without undue risk to the health and safety of the public.
With regard to seismic issues, the ACRS stated:
The ACRS notes that, for distances less than 10 km from the earthquake source, there are currentlyno strong motion data for shocks largerthan magnitude 6 and few reliable data for shocks of magnitude 5 and 6. Also, the theory and analyses of earthquake and seismic wave generation,of seismic wave transmission and attenuation,and of soil-structure interactionare in a state of active development. The Committee recommends that the seismic design of Diablo Canyon be reevaluated in about ten years taking into account applicable new information.
It was this recommendation that eventually led to issuance of the conditions on the DCPP Unit I low-power and full-power OLs requiring a reevaluation of the seismic design bases of the plant. After public hearings before the NRC's ASLB and Atomic Safety and Licensing Appeal Board, and meetings with the NRC, OLs were issued for both DCPP units 1 and 2. License condition, Item 2.C.(7) was placed on Unit 1 Facility OL DPR-80 and reads as follows:
    "Seismic Design Bases Reevaluation Program PG&E shall develop and implement a program to reevaluate the seismic design bases used for the Diablo Canyon Nuclear Power Plant.
The program shall include the following Elements:
: 1) PG&E shall identify, examine, and evaluate all relevant geologic and seismic data, information, and interpretationsthat have become available since the 1979 ASLB hearing in order to update the geology, seismology and tectonics in the region of the Diablo Canyon NuclearPowerPlant. If needed to define the earthquakepotential of the region as it affects the Diablo Canyon Plant,PG&E will also reevaluate the earlierinformation and acquire additionalnew data.
: 2) PG&E shall reevaluate the magnitude of the earthquakeused to determine the seismic basis of the Diablo Canyon Nuclear Plant using the information from Element 1.
: 3) PG&E shall reevaluate the ground motion at the site based on the results obtained from Element 2 with full consideration of site and otherrelevant effects.
: 4) PG&E shall assess the significance of conclusions drawn from the seismic reevaluationstudies in Elements 1, 2, and 3, utilizing a 6
 
Enclosure PG&E Letter DCL-1 1-097 probabilisticrisk analysis and deterministicstudies, as necessary, to assure adequacy of seismic margins.
PG&E shall submit for NRC staff review and approval a proposedprogram plan and proposed schedule for implementation by January30, 1985. The.
program shall be completed and a final report submitted to the NRC three years following the approval of the program by the NRC staff PG&E shall keep the staff informed on the progress of the reevaluation program as necessary,but as a minimum will submit quarterlyprogress reports and arrangefor semi-annual meetings with the staff PG&E will also keep the ACRS informed on the progress of the reevaluationprogram as necessary, but not less frequently than once a year."
The license condition was imposed because of: (1) the substantial amount of offshore exploration for hydrocarbons, (2) significant advances in geology, seismology, and geophysics that had occurred since the beginning of the site review, and (3) the ACRS recommendation quoted above.
The NRC's review and acceptance of PG&E's response to License Condition 2.C.(7), are discussed in NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No. 34, dated June 1991 (SSER 34), and in NRC letter dated April 14, 1992, "Transmittal of Safety Evaluation Closing Out Diablo Canyon Long-Term Seismic Program (TAC Nos. M80670 and M80671)." SSER 34, Section 2.5.2.4, "Seismology Conclusions," included a restatement of two PG&E commitments with respect to ongoing activities associated with the implementation of the LTSP. These commitments are based on PG&E Letter DCL-91-091, "Benefits and Insights of the Long Term Seismic Program," dated April 17, 1991.
PG&E's reevaluation effort was named the "Long Term Seismic Program." The objective of the LTSP was to satisfy the license condition set forth above, using new techniques and data developed since 1979, to reevaluate the seismic design bases. The LTSP consisted of three phases. The Program Plan was developed in Phase I. In Phase II, the Program Plan was refined and the scope of work was focused and priorities established. In Phase III, the program tasks were implemented and documented.
With regard to the License Condition, Element 1, the NRC reviewed PG&E submittals and concluded that PG&E identified, examined, and evaluated all relevant geologic and seismic data and interpretations since the 1979 ASLB hearing. PG&E updated the geology, seismology, and tectonic characteristics of the DCPP region. PG&E reevaluated selected earlier information and acquired new data relating to the earthquake potential in the region as it affects DCPP.
(Reference 2) 7
 
Enclosure PG&E Letter DCL-1 1-097 The NRC Staff found that the geological, seismological, and geophysical investigations and analyses conducted by PG&E and its consultants for the LTSP were the most extensive, thorough, and complete ever conducted for a nuclear facility in the United States, and advanced the state of knowledge in these disciplines significantly. On this basis, the NRC found that PG&E complied with License Condition Element 1 in an acceptable manner. (Reference 2)
License Condition Element 2 required that PG&E reevaluate the magnitude of the earthquake used to determine the seismic design basis at DCPP using the information developed for Element 1. The NRC reviewed the information submitted by PG&E and found that the conclusion reached during the Staffs review of the DCPP OL application, that the 1977 characterization of the Hosgri fault is the seismic source that could cause the maximum vibratory ground motion at the DCPP site, is still valid. The maximum credible earthquakes that could occur on any other fault or fault zone in the site vicinity would produce smaller ground motions at the site. PG&E concluded that the maximum earthquake associated with the Hosgri fault zone has a magnitude of 7.2 and could be located on the strand of the Hosgri that is nearest the site (the closest epicentral distance from the DCPP site is 4.5 km). The NRC reviewed the' PG&E conclusion and found it acceptable. On this basis, the Staff found that PG&E met License Condition, Element 2. (Reference 2)
License Condition, Element 3 required that PG&E reevaluate the ground motion at the site with full consideration of site and other relevant effects. In order to determine the ground motion at the site, one necessary piece of data is an estimate of the style of faulting on the controlling fault. This is important because regression analyses of the empirical ground-motion database show that reverse-slip motion on the Hosgri fault would produce higher ground motion at the site than strike-slip motion, for the same earthquake magnitude. In the 1988 LTSP Final Report, PG&E concluded that earthquake motion on the Hosgri fault is best characterized as 65 percent strike-slip, 30 percent oblique-slip (midway between strike-slip and reverse-slip), and 5 percent thrust-slip (reverse-slip with a low dip angle). On the basis of its review and the advice of its consultants, the NRC found that the style of faulting on the Hosgri fault is predominantly right-lateral strike-slip, with a subordinate but substantial reverse (vertical) component.
Specifically, the NRC concluded that ground motion at the site should be evaluated for an earthquake on the Hosgri fault that is two thirds strike-slip and one third reverse-slip.
The NRC reviewed PG&E's empirical ground-motion attenuation model and numerical modeling studies and performed an independent attenuation study to estimate ground motion at the DCPP site. The NRC's analysis was based on the NRC's estimate (described above) of the ratio of strike-slip to reverse-slip motion expected from an earthquake on the Hosgri fault. The resulting independently estimated ground-motion spectra at the plant site were compared to the spectra developed by PG&E for the LTSP.
8
 
Enclosure PG&E Letter DCL-11-097 The results showed that the NRC's estimates of both the 50th and 84th percentile horizontal ground-motion spectra at the site is equal to or less than the PG&E spectra at frequencies above 1 Hz, but exceed the PG&E spectra at frequencies at and below 1 Hz. For vertical ground motion, the NRC's 84th percentile vertical spectra exceed the PG&E vertical spectra over the frequency range from 1 to 10 Hz. PG&E met License Condition Element 3 by its reevaluation of ground motion at the site. To fully satisfy License Condition, Element 4, PG&E had to demonstrate that the plant structures can withstand these exceedances. PG&E submitted additional analyses to confirm LTSP conclusions that the seismic margins for structures and equipment at DCPP are adequate to accommodate the NRC's spectral estimates of horizontal and vertical ground motions defined in SSER 34 in PG&E Letters DCL-91-313 and DCL-92-077, dated December 26, 1991, and April 3, 1992, respectively. NRC letter, dated April 17, 1992, "Transmittal of Safety Evaluation Closing out Diablo Canyon Long-Term Seismic Program (TAC Nos. M80670 and M80671)," documented the NRC's review of these confirmatory analyses, concluding that the seismic margins of the structures, systems, and components (SSCs) at DCPP reported in the 1988 LTSP Final Report are adequate even after considering the NRC's estimate of increased seismic ground motions.
License Condition, Element 4 required PG&E to assess the significance of the conclusions drawn from License Condition, Elements 1, 2, and 3 using probabilistic and deterministic methods, as necessary, to assess seismic margin adequacy. PG&E performed a deterministic analysis as Well as a probabilistic risk assessment (PRA) and concluded that the plant seismic margins are adequate.
PG&E performed detailed soil-structure interactions (SSI) analyses to determine the effects of dynamic interaction between the plant structures and the foundation rock underlying the plant on the seismic response of plant structures.
The analyses showed that the effects of ground motion incoherence and embedment of structures lumped into the "tau effect" in previous studies reduce the seismic response of some plant structures, but not others.- The NRC found, based on its review of PG&E analyses and on analyses conducted by NRC consultants, that the PG&E SSI analyses were comprehensive, thorough, and acceptable.
The PRA analysis conducted by PG&E included both internal and external events. The objectives of the PRA were to: (1) assess the importance of various structures and items or equipment to seismic risk; and (2) put the seismic risk in perspective by comparing it to the risk from other external and internal initiators.
Risk in this context refers primarily to the estimated core damage frequency (CDF). The PRA results indicated that the mean overall CDF for DCPP was similar to that of other nuclear plants.
PG&E performed deterministic comparisons using its LTSP ground-motion estimates and showed that the major plant structures at DCPP have adequate 9
 
Enclosure PG&E Letter DCL-1 1-097 seismic margins. As described above, the NRC's estimates of horizontal and vertical ground-motion spectra exceed PG&E's estimates and resulted in the NRC requiring PG&E to perform additional analyses to confirm LTSP conclusions that the seismic margins for structures and equipment at DCPP are adequate to accommodate the NRC's spectral estimates of horizontal and vertical ground motions. The NRC's review of these additional analyses concluded that the seismic margins of the SSCs at DCPP reported in the 1988 LTSP Final Report are adequate even after considering the NRC's estimate of increased seismic ground motions.
The NRC reviewed PG&E's PRA and deterministic analyses of selected SSCs and found them acceptable and concluded that PG&E met License Condition, Element 4, and therefore finding that License Condition 2.C.(7) of OL-DPR-80 was met. The NRC Staff summarized their review and conclusions about the LTSP in Supplement No. 34 to the Safety Evaluation Report (SER) (Reference 2), and NRC letter dated April 14, 1992, "Transmittal of Safety Evaluation Closing out Diablo Canyon Long-Term Seismic Program (TAC Nos. M80670 and M80671)." In these conclusions, the NRC also noted that the seismic qualification basis for Diablo Canyon will continue to be the original design basis plus the HE evaluation basis, along with the associated analytical methods, initial conditions, etc. For future plant design modifications, the NRC concluded that the LTSP spectra, increased to envelope the exceedances in the vertical and horizontal spectra discussed in Section 2.5.2.3 of SSER 34, should be used to verify that the plant high-confidence-of-low-probability of failure (HCLPF) values remain acceptable.
As part of the ongoing review process, PG&E made the following commitments at a public meeting on March 15, 1991, and in a letter to the NRC (Reference 3):
(1) continue to maintain a strong geosciences and engineering staff to keep abreast of new geological, seismic, and seismic engineering information and evaluate it with respect to its significance to DCPP, and (2) continue to operate a strong-motion accelerometer array and the coastal seismic network, although likely with fewer stations than are currently operating. Since some issues (i.e.,
slip type of the Hosgri, the characterization of the Southwest Boundary Zone, and ground-motion estimates for oblique-slip earthquakes) are controversial because of the lack of definitive evidence, future geoscience discoveries may allow a more robust conclusion for these issues.
PG&E has continued to fulfill these commitments through its ongoing geosciences research and evaluations. However, an evaluation process for new seismic information with NRC approved acceptance criteria is not specifically defined in DCPP's current licensing basis. The purpose of the proposed change to the FSARU and TS is to clearly define an evaluation process for newly identified seismic information.
10
 
Enclosure PG&E Letter DCL-1 1-097
: 3. DETAILED DESCRIPTION Proposed Amendment The following changes are proposed to TS 5.0, "Administrative Controls":
A new TS Program 5.5.20, "Long Term Seismic Program" stating:
This program provides ongoing review and evaluation of new seismic information and associated methodologies. The program shall include the following:
: a. A staff to keep abreast of new geological, seismic, and seismic engineering information and evaluate it with respect to its significance to DCPP;
: b. Operation of a strong-motion accelerometer array and the coastal seismic network;
: c. Verification that plant seismic margins remain acceptable for plant additions and modifications when checked against insights and knowledge gained from the Long Term Seismic Program, as identified in FSARU Section 3.7.6;
: d. Deterministic seismic margin acceptance criteria for operability determinations;
: e. Peer review process requirements for seismic probabilistic risk assessment revisions;
: f. Peer review process requirements for seismic model or methodology revisions; and
: g. Minimum requirements for the Seismic Advisory Board (SAB).
The above incorporates existing commitments into the TS as 5.5.20.a and 5.5.20.b, with "strong geosciences and engineering staff' revised to "staff' in 5.5.20.a.
A new TS Reporting Requirement 5.6.11, "Long Term Seismic Program Report" stating:
A report shall be submitted once every 10 years, based on the submittal date of the previous update. An updated report will be submitted in less than 10 years if new peer reviewed seismic information becomes available that would significantly increase the risk to DCPP. The report shall include the following information:
11
 
Enclosure PG&E Letter DCL-11-097
: a. Geology/seismology/geophysics/tectonics investigations,
: b. Seismic source characterization,
: c. Characterization of ground motions,
: d. Soil/structure interaction analysis,
: e. Probabilistic risk analysis,
: f. Deterministic evaluations,
: g. Assessment of the adequacy of seismic margins,
: h. Documentation of the review performed by the Seismic Advisory Board (SAB) and the resolution of the SAB's comments if performed in less than 10 years, and
: i. Documentation of the review performed by the Senior Seismic Hazards Analysis Committee for 10 year updates.
There is no change to the TS Bases associated with this LAR.
The proposed FSARU changes generally can be sorted into the following categories:
: 1. Clarifying the 1977 Hosgri earthquake spectrum as DCPP's SSE
: 2. Proposed method of evaluation of new seismic information
: 3. Clarification of ongoing commitments associated with LTSP The specific changes are included in Attachment 3 of this enclosure. Some of the markup pages address multiple categories (from above), provide reference to another change, or provide clarification based on historic information. In these cases, they are listed based on the best fit. These following lists are provided for convenience only.
Clarifying the 1977 Hos-qri Earthquake Spectrum as DCPP's SSE The followinq FSARU sections are revised to address the SSE:
FSARU Section                                    Title 1.2.1.6              Seismology 2.5.1                  Basic Geologic and Seismic Information 2.5.2.2                Underlying Tectonic Structures 2.5.2.5                Earthquake History 12
 
Enclosure PG&E Letter DCL-1 1-097 The following FSARU sections are revised to address the SSE:
FSARU Section                                  Title 2.5.2.7          Identification of Active Faults 2.5.2.8          Description of Active Faults 3.1.2.2          Criterion 2, Performance Standards (Category A) 3.2              Classification of Structures, Systems, and Components 3.2.1            Seismic Classification 3.2.2            Design Classification 3.2.3            Quality Assurance Classification 3.2.4            Piping Classification Symbols 3.2.5            System Quality Group Classifications 3.2.5.1          Design Class I, Quality/Code Class I Fluid Systems and Fluid System Components 3.2.5.2          Design Class I, Quality/Code Class II Fluid Systems and Fluid System Components 3.2.5.3          Design Class I, Quality/Code Class Ill Fluid System Components 3.2.5.4          Other Fluid Systems and Fluid System Components 3.2.5.5          Summary of System Quality Group Classifications
-3.2.6            References
-3.2.7            Reference Drawings 3.7.1.1.1        Design Earthquake (DE)          nt 3.7.1.1.2        Double Design Earthquake-(DDE)
.3.7.1.1.3          1977 Hosgri Earthquake (HE) 3.7.3.15.3        Control Rod Drive Mechanism Evaluation 3.7.3.15.4        CRDM Support System Evaluation
-3.8.1.1          Description of the Containment 3.9.3.1          Core and Internals Integrity Analysis (Mechanical Analysis) 3.9.3.5.1        Blowdown Forces Due to Cold and Hot Leg Break 3.10.2.7.1        4160 V Metal-Clad Switchgear 3.10.2.32.1        RVLIS/Incore Thermocouple Cabinets Table 4.1-3        Design Loading Conditions for Reactor Core Components 5.2.1.5.4          Faulted Conditions 5.2.1.7            Design of Active Pumps and Valves 5.2.1.11          Analysis Method for Faulted Condition 5.2.1.14          Stress Analysis for Faulted Condition Loadings (DDE and LOCA) 5.2.1.15 (New)    StressAnalysis for Faulted Condition Loadings (Hosgri and LOCA) 5.2.1.15.1        Integrated Reactor Coolant Loop Analysis 5.2.1.15.2        Steam Generator Evaluation 5.2.1.15.3        Reactor Coolant Pump Evaluation 5.2.1.15.4        Reactor Vessel Evaluation 5.2.1.1.15.8      Primary Equipment Support Evaluation 5.2.1.15.9        Pressurizer Evaluation Table 5.2-6        Load Combinations and Stress Criteria for Westinghouse 13
 
Enclosure PG&E Letter DCL-1 1-097 The following FSARU sections are revised to address the SSE:
FSARU Section                                    Title Primary Equipment Table 5.2-8          Loading Combinations and Acceptance Criteria for Primary Equipment Supports Table 5.2-16        Reactor Coolant Boundary Leakage Detection System 6.3.1.4.3            Seismic Requirements 9.1.1.2              Facilities Description Appendix 9.5B        Regulatory Compliance Summary Appendix 9.5C        Reactor Coolant Pump Oil Collection System, Evaluation to 10 CFR 50, Appendix R, Section 111.0 Section 15          Accident Analysis 15.4.5.1.2          Probability of Activity Release Table 15.4.1-7A      Unit 1 Plant Operating Range Allowed by the Best-Estimate Large Break LOCA Analysis Table 15.4.1-7B      Unit 2 Plant Operating Range Allowed by the Best-Estimate Large Break LOCA Analysis Proposed Method of Evaluation of New Seismic Information Proposed Method of Evaluation of New Seismic Information FSARU Section                                    Title 2.5.6.1 (New)          Ongoing Geological and Seismological Investigations 2.5.6.2 (New)          Evaluation of Updated LTSP Ground Motions 2.5.6.2.1 (New)        Seismic Margin Evaluation 2.5.6.2.1.1 (New)      Approved Minimum Seismic Margins Less Than 1.3 2.5.6.2.2 (New)        Probabilistic Risk Assessment Evaluation 2.5.6.3 (New)          LTSP Configuration Control 2.5.6.4 (New)          Elements of a Seismic Margins Evaluation 2.5.7                  References Figure 2.5-38 (New) Flowchart for Evaluation of Updated LTSP Ground Motion Figure 2.5-39 (New) 1991 LTSP Fragility Curve Representation Figure 2.5-40 (New) Schematic Illustration for the Determination of Seismic Margins Clarification of Ongoing Commitments Associated with LTSP Clarification of Onqoing Commitments Associated with LTSP FSARU Section                                    Title 2.5                    Geology and Seismology 2.5.2.9                "Design and Licensing Basis Earthquakes 2.5.2.9.1              Maximum Earthquake (Design Earthquake) 2.5.2.9.2 (New)        Double Design Earthquake 14
 
Enclosure PG&E Letter DCL-1 1-097 (Th~rifio~tion of Oncininci flommitm~nts A    oci~t~d with I TSP FSARU Section                                      Title 2.5.2.9.3                1977 Hosgri Earthquake 2.5.2.9.4 (New)          1991 Long Term Seismic Program Spectra 2.5.2.10 (New)            Ground Accelerations and Response Spectra 2.5.2.10.1                Maximum Earthquake (Design Earthquake) 2.5.2.10.2 (New)          Double Design Earthquake 2.5.2.10.3                1977 Hosgri Earthquake 2.5.2.10.4 (New)          1991 Long Term Seismic Program Spectra 2.5.4.9                  Earthquake Design Basis 2.5.6                    Long Term Seismic Program Figure 2.5-33 (New)      Free Field Spectra - Horizontal 1991 LTSP (84th Percentile Nonexceedance) As Modified Per SSER-34 Figure 2.5-34 (New)      Free Field Spectra - Vertical 1991 LTSP (84th Percentile Nonexceedance) As Modified Per SSER-34 Figure 2.5-35 (New)      Free Field Spectra - Horizontal LTSP (PG&E 1988)
Ground Motion vs. Hosgri (Newmark 1977)
Figure 2.5-36 (New)        1988 LTSP Seismic Hazard Curve Figure 2.5-37 (New)        1991 LTSP Uniform Hazard Spectrum 3.7.1                    Seismic Input 3.7.1.1                  Design Response Spectra 3.7.1.1.4 (New)            1991 Long Term Seismic Program Earthquake (LTSP) 3.7.1.2                    Design Response Spectra Derivation 3.7.1.2.1                Design Earthquake (DE) and Double Design Earthquake-(DDE) Derivation 3.7.1.2.2                  1977 Hosgri Earthquake Derivation 3.7.1.2.3 (New)            1991 Long Term Seismic Program Earthquake (LTSP) 3.7.4                    Seismic Instrumentation Program" (Section 3.7.4 subsections renumbered) 3.7.4.1                  Seismic Monitoring System 3.7.4.1.1                Comparison with NRC Regulatory Guide 1.12, Revision 2 3.7.4.1.2                  Description of Instrumentation 3.7.4.1.2.1                Strong Motion Triaxial Accelerometers 3.7.4.1.3                  Control Room Operator Notification 3.7.4.1.4                  Comparison of Measured and Predicted Responses 3.7.4.2 (New)              Central Coast Seismic Network 3.7.6 (New)              Application of the LTSP to Modifications and Additions (previous content deleted - redundant to FSARU Section 3.2) 3.7.6.1 (New)              Basis for Selection of LTSP Evaluation Scope 3.7.6.1.1 (New)            Modifications and Additions in the LTSP Evaluation Scope 3.7.6.1.2 (New)            Modifications and Additions Excluded from LTSP Evaluation Scope 3.7.6.2 (New)              LTSP Evaluation Process 3.7.6.2.1 (New)            Fragility Analysis Method 15
 
Enclosure PG&E Letter DCL-1 1-097 Clarification of Onaoina Commitments Associated with LTSP FSARU Section                                      Title 3.7.6.2.2 (New)            Conservative Deterministic Failure Margins Method 3.7.6.2.3 (New)            Earthquake Experience Data Method 3.7.7                      References Table 3.7-25 (New)          High Confidence Low Probability of Failure (HCLPF 84 )
Capacities and Seismic Margins for Civil Structures Table 3.7-26 (New)          High Confidence Low Probability of Failure (HCLPF 84 )
Capacities and Seismic Margins for Equipment and Components Figure 3.7-29 (New) Sample Free Field Ground Motion LTSP Analysis Longitudinal Component Figure 3.7-30 (New)        Sample Free Field Ground Motion LTSP Analysis Transverse Component Figure 3.7-31 (New)        Sample Free Field Ground Motion Comparison to Target Spectrum - LTSP Analysis - Longitudinal Component -
5% Damping Ratio Figure 3.7-32 (New)        Sample Free Field Ground Motion Comparison to Target Spectrum - LTSP Analysis - Transverse Component -
5% Damping Ratio Figure 3.7-33 (New)        LTSP Evaluation Process for Plant Additions and Modifications Table 3.9-9                List of Active Valves (Notes revised)
: 4. TECHNICAL EVALUATION Incorporatinq the NRC's Position from SSER 7 / SSER 34 on the 1977 Hosgri Earthquake Spectrum as DCPP's SSE The ASLB in a Partial Initial Decision, dated September 27, 1979, concluded that (page 490) the 0.75g acceleration assigned to the SSE to be an appropriately conservative value for the maximum vibratory ground acceleration that could occur at the DCPP site. As discussed in the Background section, the NRC stated in SSER 7 (pages 2-5) that they consider the Hosgri event to be the SSE for this site, or at least its equivalent. Accordingly, PG&E is updating the FSARU to align with the conclusions in the licensing reviews that the maximum ground acceleration that could occur at the site, the HE, is the equivalent of the DCPP SSE.
The SSCs necessary to assure: (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shutdown the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of 10 CFR Part 100, were qualified for the HE as described in the various chapters of the Hosgri reevaluation report (Amendment 50 and 16
 
Enclosure PG&E Letter DCL-11-097 subsequent amendments to the operating license application). Because PG&E used criteria that was current at the time of the reevaluation in determining what items should be qualified, there were some differences between the set of items identified as part of the reevaluation and the set that was originally designated Seismic Category I. The NRC reviewed the set of designations developed as part of the reevaluation in two ways. Note that the classification system for SSCs is unique to DCPP and does not explicitly use the term "Seismic Category I."
Equivalencies between DCPP's classification system and that used by the NRC in Regulatory Guide (RG) 1.29 are described in FSARU Section 3.2.1.
In the first review, the NRC applied the criteria as documented in RG 1.29, "Seismic Design Classification," to determine the SSCs that need to be designed to withstand the effects of the HE and remain functional. As in the original review, the NRC concluded that SSCs important to safety that are designed to withstand the effects of the HE and remain functional have been properly classified in conformance with the NRC's regulations, the applicable RG, and industry standards. Note that the SG 29, "Seismic Design Classification," is DCPP's current licensing basis, not RG 1.29, but these two documents contain similar provisions. In accordance with the NRC's normal acceptance criteria, qualification of these items for the HE provides reasonable assurance that the plant will perform in a manner providing adequate safeguards for the health and safety of the public with respect to earthquake safety. The criteria, as documented in RG 1.29, continues to be applied to ensure that the required SSCs are designed to withstand the effects of the HE and remain functional.
In the second review, at the NRC's request, PG&E considered the equipment and procedures necessary to achieve long-term cold shutdown conditions after the HE, assuming that: (1) only equipment qualified for the'event would be available, (2) single failures may occur in that equipment, and (3) offsite power may be lost for an extended period of time. PG&E submitted the results of this evaluation to the NRC in a letter dated January 26, 1978.
The NRC reviewed the capability to cool the plant to cold shutdown conditions and provide long-term cooling and concluded that PG&E demonstrated that sufficient systems are available for residual heat removal with or without offsite power and assuming a single failure in accordance with Criterion 34 of the GDC.
Similarly, these systems are qualified for operation in the event of the HE in accordance with Criterion 2 of the GDC (SSER 7 pages 3-1 thru 3-4, and SSER 8 pages 3-1 thru 3-3).
The evaluation methods used for HE were generally the same as those used in the original seismic design with the approval of different methods of analysis for the items listed in SSER 7 Sections 3.8.5.3, 3.9.3.2, and 3.10.2, which the NRC concluded are conservative and provide adequate safety margins in the design of Category I components.
The HE evaluation methods for structures use the following deviations from the methods used for the DE and DDE seismic analyses, as discussed in SSER 7:
17
 
Enclosure PG&E Letter DCL-11-097 (1)  The use of damping values recommended in RG 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 0, unless the use of a later revision has been approved by the NRC for specific applications. In most cases, the damping values used for the DE and DDE analyses were conservative relative to the values recommended in RG 1.61, resulting in larger calculated responses.
The NRC concluded, in SSER 7, that the use of higher damping values consistent with the guidance provided in RG 1.61 is realistic and acceptable.
(2)  Average values of material properties, from tests of the actual materials installed, are used to determine allowable stress levels instead of using code specified minimum material properties, as was used for the DE and DDE seismic analyses.
The NRC concluded in SSER 7 that the use of actual material strengths is acceptable since some margin remains. For concrete, the appropriate average 28-day test strength is used. Since concrete continues to gain strength with age after 28 days, the installed concrete will be stronger. For steel, average mill test strength is used. Since the steel is ductile and the structures are designed to remain below yield (with a limited number of exceptions), margin remains.
(3)  Ductility (yielding) in structures is allowed in certain cases. Structural ductility has not generally been used. Where used, it is justified for each specific case. Appropriate assurance is made that seismic inputs to systems and equipment is not underestimated due to structural ductility in such instances. (This can readily be done by calculating the inputs to systems and equipment separately, assuming the structure does not yield).
Based on these conditions, the NRC considered the use of structural ductility acceptable. Ductility was not used in the DE and DDE seismic analyses.
(4) Fixed base mathematical models are used for structures and above ground tanks. A SSI analysis, as was done for DE and DDE, is not necessary for the HE evaluation, due to the stiffness of the rock foundation material.
The use of fixed base analyses is consistent with the NRC's current criteria for rock sites such as the DCPP site. The NRC concluded in SSER 7 that this method precludes the reduction of the ground motion that often results from SSI analyses using deconvolution and is considered acceptable.
(5) The horizontal ground response spectra are adjusted to account for foundation size effects in relation to ground motion waves (nonsynchronized ground motion or spatial incoherence). Such 18
 
Enclosure PG&E Letter DCL-1 1-097 adjustments to the horizontal ground response spectra were not included in the DE and DDE seismic analyses.
The NRC concluded in SSER 7 that where such credit is taken in relation to the usual procedure of assuming synchronized ground motion; an appropriate consideration of other effects of nonsynchronized ground motion such as torsion is also included.
This is accomplished by assuming an artificial eccentricity between the center of mass and center of rigidity of the building. This is above and beyond any actual (geometric) eccentricity, which is also computed and accounted for. The effect of this artificial eccentricity is to force the horizontal ground motion that is used in the analysis to create additional torsional motions about the vertical axis.
An eccentricity of five percent or seven percent of the width of the structures is assumed, depending on the technique used to combine the torsional with the translational responses. This is in addition to any actual eccentricity of the structures. The five percent eccentricity is used when the torsional and translational responses are combined by the absolute sum rule, and the seven percent eccentricity is used when the two responses are combined by the SRSS rule. The greater of the combined responses is used.
With regard to floor response spectra, the torsional floor response spectra at the center of mass is calculated using actual (geometric) eccentricity of the structure in addition to an assumed eccentricity equal to five percent of the structural dimension. The NRC concluded that these approximating techniques represented a step towards more realistic modeling of structural responses and were therefore found to be acceptable.
(6)  A vertical response dynamic analysis is performed rather than assuming an invariant vertical acceleration throughout the structures as was done for the DE and DDE analyses. This is consistent with the structural dynamic analysis methods applicable at the time of the Hosgri evaluation.
The NRC concluded in SSER 7 that the use of a vertical response dynamic analysis is more accurate than the methodology used for the DE and DDE analyses and is therefore acceptable.
(7)  A modified procedure is used for smoothing and widening of the raw floor response spectra. The smoothing is done by averaging of floor response spectra, except at the peaks, where it is widened by 15 percent on the low frequency side and five percent on the high frequency side without reduction of the peaks. In the analysis for the DE and DDE, the peaks were widened by 10 percent on both sides after being lowered by 10 percent.
19
 
Enclosure PG&E Letter DCL-11-097 The purpose of widening the peaks is to account for possible variations in the predicted structural frequencies. At the time of the Hosgri reevaluation, the NRC's criteria indicate widening by 15 percent on both sides of the peaks. However, since actual material strengths are being used in the reevaluation, the calculated structural stiffness is closer to the maximum stiffness than usual, indicating a lesser need for peak broadening on the high frequency side. For these reasons, the NRC considered the approach used for the HE evaluation as acceptable.
(8)  In combining structural responses at each point, responses due to horizontal excitation in two directions are combined with the response due to vertical excitation by the SRSS rule. In the analysis for DE and DDE, one response due to horizontal excitation and one response due to vertical excitation were combined by the absolute sum method. The process was repeated for the other horizontal component and the more limiting result was employed for design.
This approach corresponds to the recommendations of RG 1.92, "Combining Modal Responses and Spatial Components in Seismic Response Analysis," December 1974. The NRC determined that this approach is acceptable (SSER 7, Section 3.8.5.3).
The HE evaluation methods for mechanical systems and components use the following deviations from the methods used for the DE and DDE seismic analyses:
(1)  Damping values recommended in RG 1.61, Revision 0, are generally used.
Damping values from a later revision for RG 1.61 has been approved by the NRC for specific applications. In most cases, the damping values used for the DE and DDE analyses were conservative relative to the values recommended in RG 1.61, resulting in greater calculated responses.
The NRC concluded in SSER 7 that the use of higher damping values consistent with the guidance provided in RG 1.61 is realistic and acceptable.
(2)  Actual material properties are used, where available, in lieu of code specified minimum properties to establish allowable stress limits to justify structural integrity where the calculated stress exceeded the limits of The American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). The ASME Code allowable values were used in the DE and DDE analysis.
Allowable stress values are established using the bases prescribed by Appendix III of Section III of the ASME Code so that the factors of safety used in the code are preserved. For this reason, the NRC considered the use of actual material properties acceptable.
20
 
Enclosure PG&E Letter DCL-1 1-097 (3)    The responses to HE loads or the DDE loads (whichever is more limiting) are combined with the response due to normal operation and the response due to LOCA loads.
This is a conservative method which results in the RCS being designed for loads well in excess of those calculated for a seismic event alone without a pipe break. Even though the assumed seismic event is not expected to cause a pipe break in a seismically designed piping system, these loads are combined for design purposes to produce extra margin (SSER 7, Section 3.9.3.2).
In a letter dated November 10, 1977, the NRC requested the following:
In assessing the design adequacy of piping, other pressure retaining components and their supports, the combination of loads due to Hosgri earthquake and the loss of coolant accident (LOCA) has to be considered.
In the subject report, however, this effect was not considered. Submit the results of your analysis which consider the effects of combining the normal operating loads, the earthquake loads and the LOCA loads. Explain and justify the method of load combination.
In response to this request, PG&E submitted the Westinghouse report titled, "Response to Combinations of Calculated Loads for Pipe Break and Earthquake," as part of Appendix F to the PG&E report, "Seismic Evaluation for Postulated 7.5M Hosgri Earthquake." As part of this evaluation the combination of a postulated LOCA and seismic event were considered in the following four ways:
a)      No combination, seismic alone b)      No combination, LOCA alone c)      Seismic and LOCA by absolute summation d)      Seismic and LOCA by SRSS The evaluation of the effects of these various combinations showed that calculated stresses for the RCS were below allowable values with the exception of the following:
a)    For both the absolute summation and SRSS combinations of LOCA and seismic, the stress in the fuel grid exceeds the strength based on testing.
Exceeding grid strength allowables cause minor deformation in the grid.
The resulting flow reduction has been evaluated and shown not to significantly affect the emergency core cooling system (ECCS) performance of the system.
b)    For the absolute summation combination of LOCA and seismic, the computed stresses for the reactor internals, the reactor coolant pump 21
 
Enclosure PG&E Letter DCL-11-097 supports, and the reactor vessel support were over the allowable values by a small amount. However, these exceedances do not affect the function of the supports or internals.
The evaluation demonstrated that the entire primary system is capable of withstanding the simultaneous occurrence of the peak loads of the HE or DDE and a LOCA without compromising its ability to safely shut down the system and retain it in a shutdown condition.
SSER 7 documents the NRC's review and approval of this evaluation. The NRC concluded that the evaluation was acceptable based on the conservative process of requiring that the peak responses to the seismic and LOCA loads be combined on an absolute summation basis. However, the NRC's acceptance of the evaluation is inconsistent with the results of the evaluation determining that four components exceeded allowable values when using the absolute sum method.
PG&E proposes to use the SRSS method for the evaluation of load combinations of seismic with LOCA. This method of combination is consistent with NUREG-0484, "Combining Dynamic Loads," Revision 1.
The HE evaluation methods for electrical equipment use the seismic qualification methods of RG 1.100, Revision 1, "Seismic Qualification of Electrical Equipment for Nuclear Power Plants," and IEEE Standard 344-1975, "IEEE Recommended Practice for Seismic Qualification of Class 1E Equipment for Nuclear Power Generating Stations." Electrical equipment was originally qualified for the DDE in accordance with IEEE Standard 344-1971, "IEEE Guide for Seismic Qualification of Class I Electrical Equipment for Nuclear Power Generating Stations." The methods identified in RG 1.100, Revision 1, and IEEE Standard 344-1975 were used, per the NRC's request, during the Hosgri reevaluation of components where the original qualification level did not envelope the required seismic inputs to equipment for the HE.
With the use of the previously approved methods of analysis to the original design analysis, it has been demonstrated that the SSCs necessary to assure:
(1) the integrity of the reactor coolant pressure boundary; (2) the capability to shutdown the reactor and maintain it in a safe shutdown condition; or (3) the capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of 10 CFR Part 100 were qualified for the HE. Therefore the DCPP SSE can be clarified as the HE.
Proposed Method of Evaluation of Updated Seismic Information, Seismic Margin Evaluation, and 1991 LTSP Design Ground Motion Response Spectrum (DGMRS) as the comparison for new ground motion spectra The use of the 1991 LTSP DGMRS as the comparison spectra for new ground motion spectra is justified because the 1977 HE (DCPP SSE) envelopes the 22
 
Enclosure PG&E Letter DCL-1 1-097 1991 LTSP with the exception of minor exceedances in the high frequency range (greater than approximately 15 Hz), which were approved by the NRC in SSER 34, Section 3.8.1.1. This conclusion is supported by SSER 34, Section 3.8.1.4, "Comparison of LTSP and Seismic-Qualification-Basis Response Spectra":
Originally,PG&E did not make a one-to-one comparison of the response spectra resulting from LTSP site-specific ground motions with the seismic-qualification-basisspectra (that were preparedat different times) from two other earthquakes,the double-design earthquake and the Hosgri earthquake.
PG&E based this decision on the lack of direct comparabilitydue to the differences between the LTSP assumptions and analysis methodology and those adopted for the Hosgri reevaluations. Although generally agreeing with PG&E's arguments in this area, during its review of the L TSP, the staff requiredPG&E to make this comparison to be able to judge the level of demand resulting from the L TSP ground motion. If the Hosgri responses were found to be greaterthan the L TSP responses, then no additional evaluation would be needed.
In order to be consistent with the approach used by PG&E under the initial implementation of the LTSP as discussed above, the updated DGMRS associated with new seismic information will be compared to the 1991 LTSP DGMRS, and no additional evaluations to the DE or DDE DGMRS need be performed. The comparison of the updated DGMRS to the 1991 LTSP DGMRS implicitly includes a comparison to the 1977 HE DGMRS, based on the comparison of the 1991 LTSP DGMRS and the 1977 HE DGMRS discussed in SSER 34, Section 3.8.1.1.
The DE and DDE seismic design basis is based on historical predictions of two specific faults, the Nacimiento and the San Andreas. The seismic design basis criteria for the DE and DDE were established in the original September 28, 1973, FSARU, Section 3.7. Proposed changes to FSARU Sections 3.7.1.1.1, 3.7.1.1.2, and 3.7.1.1.3, included in Attachment 3 of this enclosure, describe the DE, DDE, and HE. The DDE design response spectra were made twice that of the DE.
The design damping values were established as follows:
Type of Structure                % Critical      % Critical Damping - DE      Damping - DDE Containment structures and all internal          2.0                5.0 concrete structures Other conventionally reinforced concrete          5.0              5.0 structures above ground, such as shear walls or rigid frames Welded structural steel assemblies                1.0              1.0 23
 
Enclosure PG&E Letter DCL-1 1-097 Bolted or riveted steel assemblies                  2.0                2.0 Vital piping systems                                0.5                0.5 Foundation rocking
* 5.0                5.0
* Five percent of critical damping is used for structures founded on rock for the purpose of computing the response in the rocking mode, and seven percent of critical damping is used for the purpose of computing the response in the translation mode.
There are situations in the current seismic design evaluations indicating that in-building response spectra for the DE and DDE have larger peak accelerations than those for the HE. These occurrences are due to the use of original DE and DDE seismic design basis criteria for SSI modeling and the use of damping values based on seismic design knowledge of the early 1970 time period. The DE and DDE seismic design criteria remain unchanged to this day and will remain fixed design criteria, not subject to modification as a result of new seismic information. Updated ground motions based on new seismic information will be compared to the 1991 LTSP DGMRS that~was compared to the 1977 Hosgri DGMRS per the LTSP process. The design criteria for the HE does not include SSI modeling (replaced with a fixed based model for free-field ground motion/structure interaction) and used the more contemporary damping values based on RG 1.61. The NRC acknowledged the conservatisms in the original design criteria for the DDE in SSER 7, Section 3.7:
In a few individual cases, the applicanthas demonstratedthat the double design earthquake loads determined from the originalanalysis are more limiting than Hosgri event loads. This may at first appearconfusing and raise a question as to how the originalcan be so conservative as to exceed the Hosgri event loads. It can happen in a few cases due to highly conservative assumptions or methods in the original analysis. In any event, if the applicant has used a load in the originaldesign and can now demonstrate that the Hosgri event load is less, we considerthis to be a sufficient load determination.
Where the original analysis is more limiting, the applicanthas chosen not to take credit for the lesserHosgri event loads, but ratherto use the more limiting double design earthquake loads.
Also, in SSER 7, Section 3.7, the NRC stated:
[W]e discussed the applicant'soriginal seismic design methods and procedures and found them acceptable in relation to the originalseismic design criteria. This conclusion has not been changed.
With regardto the design earthquake or operatingbasis earthquake, we have concluded in Section 2.5 of this supplement that the originaloperatingbasis earthquake remains unchanged for this site. Accordingly, there is no need for 24
 
Enclosure PG&E Letter DCL-1 1-097 any further work by the applicantwith regardto operating basis earthquake design matters.
In SSER 34, Section 1.4, the NRC noted that the seismic qualification for DCPP will continue to be the original design basis (i.e., DE and DDE) plus the Hosgri evaluation basis, along with the associated analytical methods, initial conditions, etc.
The objective of the proposed LTSP deterministic seismic margin evaluation is different from that of the DCPP seismic design basis evaluations associated with the DE, DDE, and HE. The objective of the DCPP seismic design basis evaluations associated with the DE, DDE, and HE is to demonstrate that the capacity of plant SSCs meet or exceed specified seismic criteria, rather than to quantify seismic margins. The objective of the proposed LTSP deterministic margin evaluation method for new ground motion information is to evaluate the plant seismic margins by comparing the HCLPF capacity of SSCs (not the code based capacities) with the seismic demands associated with the updated ground motions. The 1991 LTSP deterministic, horizontal, ground-motion spectra were compared to the 1977 Hosgri evaluation spectra that were used as the licensing basis for DCPP (1988 LTSP Final Report, Figure 7-2). The 1991 LTSP deterministic spectra were used to provide assurance that the plant HCLPF capacity estimates are at least equal to the seismic demand (SSER 34 page 3-42).
The identification of new seismic information will not impact the requirement that the design of DCPP SSCs satisfy the design criteria associated with the DE, DDE, and HE. The DE and DDE design criteria, and input ground-motion response spectra, will remain unchanged by the identification of new seismic information. As a result, there will be no impact on the DE and DDE evaluations of SSCs. The HE design criteria will remain unchanged by the identification of new seismic information. However, if the ground motion spectra associated with the new seismic information were to exceed both the 1991 LTSP spectra and the 1977 HE spectra, at any frequency, it will be necessary to revise the HE input
,ground-motion response spectra to envelop that associated with the new seismic information and update the HE evaluations of SSCs. In this case, a LAR will be required to revise the HE input ground-motion response spectra. The proposed process for the evaluation of new seismic information is based on the seismic margins approach, as was previously utilized under PG&E's initial implementation of the LTSP (1985 through 1991), which ensures that SSCs can perform their safety functions as specified in GDC 2 and 10 CFR 100, Appendix A, during and after a SSE.
The process for evaluation of updated seismic hazard information is as follows
,(proposed FSARU Figure 2.5-38):
25
 
Enclosure PG&E Letter DCL-1 1-097 DCPP Long Term Seismic Program Update Eveakation of Updated Seim* Hazard Information Flowchart A- Overview Proeoms  for Updates to I* Long Term Selsmic Progrom (LTSP)
SesmIc Prbabillic Rls and Selamic Margira Assesamnot (to be performed on a 10 year kfrv&
Updated LTSP Seismic Hazard hPu Inform in RaclMvd by DCPP or Ten Years Skie Prior Update Seah-nic Margin Assamnt Prv#-  P iFt S&tnr PW~tsviwed L~datec LTSP Irkmabon to                    a NcerReqMtor Commisson (PFC) I Nuclear Reaeto Ragu&abn (NRR)
Roeata  10 Tý  Yearý oyý`
Ir1ervaI 26
 
Enclosure PG&E Letter DCL-11-097 DCPP~oTerm Seismic Program Updatel M=Updsted Seismic Hazard Informiationi Fkwihart B - Seismic Marairs Asesesmert Updtad 8iefyt H"Wv k*Ntmtiofl for 8i~cMrr AawswroM (SMA) Received bv DOW c.' 10 Yee      n (DOW$)
dt
                                                        - UPd~d DduWib"e GM~MgWc' f.,. Repmse
                                                                                    '7md 0R
                                                                              -'wopebyi    LO
                                                                      - 7    UpDGsdOOS N                          Yet L"M mWaMde LHmtCLPF  caigm" aVem..        sor                                LMP7d)MlSy of e§W"(HCLPF)
Mo LNef CLP Reeumn FPWM 81m*k Mero forknWWedGkjck 1 yvkwfe endCuiy.teaft OMC.)wift L~MM DGMRS    I 1          ~HCtPF  C      et*
ifwe we
            &WTOO- epw7 U-9                ~          i, yet                                          Yes 1
                                                                    &Abff*UNA.. knu41Od, R"gueg WAV ISfT7  NO    COWN CMvip MOdNIOaM!l                                      ~.tw(RM Wd ehifl*  of I 3M NcIHQPled"e R*C- O-F I  UCeet WfMunied
                                                ...  ..    .            Wp,, t.dpi LTW*OOAS. (4m FA~AI.                      4 W    9ICLPP Rcqwds  Ii Notes:
: 1) Or greater than or equal to the approved seismic margin exceptions for certain SSCs discussed in FSARU Section 25.6.211
: 2) Unless the SSC is one of the approved seismic margin exceptions below 1 0 discussed in FSARU Section 2.5.6.2.1,1.
: 3) Or to achieve the minimum approved seismic margin exception discussed in FSARU Section 2.5.6.2.1.1.
27
 
Enclosure PG&E Letter DCL-1 1-097
[  DCPP Long Term Seismic Program Update Evaklation of Updated Seismic Hazard Information Flowcart C - Seismic Probabilistic Risk Assessment sr~  PON  "
P*cwd'u A Updltd SOaM Hazard Irformation for Seilsic Probeatil      Risk Assesmrent (SPRA)
Received by DCPP or 10 Yew Update
                                - Updated Sdi*1,~i    CuwwdO (84C) up"OId UQftdMOOM~    90nI Sup (68)
Condct SPRA to Determine SeismiCore Daerage Frequency (scon Notify Nuclear Regulatory Commission (NRC)
Dccuen.ot Updated SH-C, GMSS, FragNies, and inDCPP Records Methods for recomputingi the HCLPF capacities of affected SSCs The determination of the HCLPF capacities of individual SSCs is dependent on a number of factors, including the shape of the ground-motion response spectrum and the fundamental frequency of the SSC. Each SSC within the scope of the LTSP seismic margins evaluation will be screened, considering the shape of the ground-motion response spectrum associated with the new seismic information, and the SSC's fundamental frequency, to determine if recomputation of the HCLPF capacity is required. If the recomputation of the HCLPF capacity of an SSC is required, the use of the fragility analysis, conservative deterministic 28
 
Enclosure PG&E Letter DCL-1 1-097 failure margin (CDFM), and earthquake experience data methods are acceptable.
The fragility analysis method used during the original implementation of the LTSP is based on the methods described in Chapter 6 of the 1988 LTSP Final Report.
The fragility curves (see FSARU Figure 2.5-39 for sample curve) are tied to the 5 percent damped spectral acceleration value, averaged between 3 and 8.5 Hz.
The computation of fragilities going forward for evaluation of updated LTSP seismic hazards input will be based on the methods described in ASME/ANS RA-Sa-2009, as modified by Regulatory Guide 1.200, Revision 2.
General guidelines of the application of the CDFM method are provided in EPRI NP-6041-SL. The CDFM method used during the original implementation of the LTSP are as described in PG&E Report titled, "Additional Deterministic Evaluations Performed to Assess Seismic Margins of the Diablo Canyon Power Plant Units 1 and 2," with the HCLPF capacities tied to the 5 percent damped spectral acceleration value, averaged between 3 and 8.5 Hz. The same methodology may be used for the computation of CDFM going forward for evaluation of updated LTSP seismic hazards. This CDFM method was reviewed and audited by the NRC and was concluded to be acceptable in SSER 34.
The earthquake experience data method was previously implemented under the LTSP for developing the HCLPF capacities of components associated with the 230 kV switchyard (e.g., transformers, breakers, switches) in response to the NRC's request for PG&E to reassess the 230 kV switchyard fragility with component performance information available from the Loma Prieta earthquake.
Details of the application of the earthquake experience data method at DCPP are described in PG&E report "Long Term Seismic Program - Seismic Capacity of the 230 kV Switchyard" submitted to the NRC as part of PG&E Letter DCL-90-205, dated August 10, 1990. The reassessment resulted in the fragility of the 230 kV switchyard to be revised with the median capacity of 1.40g and an HCLPF of 0.70g. The NRC conducted an additional sensitivity study and, in general, concurred with this finding, as documented in SSER 34 (pages 23-68).
The same methodology may be used for the computation of HCLPF capacities for new components, modifications to existing components, or as input to the evaluation of updated LTSP seismic hazards input.
The scope of the SSCs to be evaluated for the impact of exceedances The SSCs within the scope of the LTSP, including the current seismic margins, is provided in FSARU Tables 3.7-25 and 3.7-26. The scoping was initially developed based on the methods and evaluations described in PG&E Letter DCL-86-022, "Long Term Seismic Program - Results of Phase II Scoping Study,"
which identified the SSCs for which the seismic fragility data were required for LTSP Phase II PRA studies by the principal PRA investigator Pickard, Lowe, and Garrick, Inc. (PL&G) on the basis of their earlier experience with similar Westinghouse plants, a study of DCPP design documents, as well as physical 29
 
Enclosure PG&E Letter DCL-1 1-097 review of the plant systems. The Phase II PRA scoping studies identified the dominant risk contributors to the overall seismic risk.
Subsequent to the initial scoping, SSCs have been and will continue to be added to these tables to meet the criteria identified in PG&E Letter DCL-91-178, "Long Term Seismic Program - Future Plant Modifications," dated July 16, 1991, for the application of the LTSP to modifications and additions implemented at DCPP after 1991 (restated and updated in FSARU Section 3.7.6). In addition, the seismic margins for the individual SSCs will be updated, as necessary, based on modifications to DCPP or the recomputation of HCLPF capacities.
Maintaining a minimum seismic margin of 1.3 If the deterministic seismic margin evaluation determines that the minimum seismic margin remains greater than 1.3, except for SSCs identified having an acceptable seismic margin below 1.3 in FSARU Tables 3.7-25 and 3.7-26, the updated response spectrum is acceptable. Consistent with the commitment made in PG&E Letter DCL-91-178, the target HCLPF84 capacity of 2.6 g is maintained at DCPP, based on use of a seismic demand of 1.94 g (84th percentile site specific spectrum) and an upper bound seismic load factor of 1.3.
The exceptions for SSCs identified having an acceptable seismic margin below 1.3 in FSARU Tables 3.7-25 and 3.7-26 falls into two categories. The first category is SSCs that are maintained with a seismic margin between 1.3 and 1.14. The second category is SSCs that are maintained with a seismic margin below 1.0.
For the first category, the basis for maintaining the SSCs seismic margin below 1.3, but above 1.14 is consistent with the acceptable seismic margins committed to in PG&E Letter DCL-91-178 to review future plant modifications in light of the findings of the LTSP. DCL-91-178 stated the following:
Step 3:    The HCLPF84capacities for the "screened-in"items (from Step 2) will be checked using either the FragilityAnalysis method or the Conservative DeterministicFailureMargin method. If the new capacitiesare significantlyless than those reportedin the Tables 7-1 and 7-2 of the Long Term Seismic ProgramFinal Report, considerationwill be given to redesign of the modifications so that capacitiesare consistent with those reported in the Final Report, including the guidelines given below. If redesign is not possible, proceed to Step 4.
A modification is considered to reduce the HCLPF84capacities significantly if any of the following occurs:
* Turbine Building: The revised HCLPF84capacity is reduced from that reportedin the FinalReport (Table 7-4).
30
 
Enclosure PG&E Letter DCL-1 1-097
                . New and otherexisting structures: The revised HCLPF84 capacities are less than 2.6 g.
* New and existing equipment: The revised HCLPFUcapacities are less than 2.6 g (See CommentaryA).
* 230 kV Switchyard: The revised HCLPFUcapacitiesare reduced from those reportedin the PG&E Letter DCL-90-205.
Step 4:    The overall Plantseismic margin or the Plantseismic risk is reviewed under this step. Either of the following two alternatives can be followed to ensure continued seismic adequacyof the Plant.
Alternative 1 - DeterministicStudies The HCLPF84capacityof the modified item shall be at least 1.14 times the Programseismic demand.
Alternative 2 - Probabilistic Risk Assessment Studies The revised fragilityof the modified item shall be such that the calculatedrisk of core damage due to the Program'sseismic events is comparable to that shown in Table 6-54 of the Final Report.
SSER 34 documented the NRC's review of the seismic margins resulting from the 1988 LTSP Final Report deterministic evaluations confirming that the major plant structures and equipment at DCPP have adequate seismic margins. In SSER 34, the NRC acknowledged PG&E's commitment in DCL-91-178 to review future plant modifications in the light of the findings of the LTSP. As part of this LAR, the commitment of Step 4 from DCL-91-178 will be revised to be consistent with the proposed evaluation process for new seismic information. The evaluation process proposed in this LAR requires that the seismic margin for plant additions and plant modifications be maintained at or above 1.3, unless the minimum seismic margin below 1.3 is identified in FSARU Table 3.7-25 and 3.7-26 due to previous review and approval by the NRC, while Step 4 of DCL-91-178 permitted a minimum seismic margin of 1.14 for plant additions and plant modifications..
For the second category, SSCs with a seismic margin below 1.0 are limited to SSCs within the 4160 V (Vital) and 230 kV electrical power systems. PG&E -
identified relays that affect components necessary for safe shutdown using the circuit analyses as discussed in Section 23.3 of SSER 34. Functional failure fragilities of relays were evaluated only for those relays considered to be chatter sensitive. The median strength factor for chatter mode was estimated using the generic equipment ruggedness spectrum, the cabinet amplification factor, and the floor spectral acceleration. The relay chatter failure mode fragilities were 31
 
Enclosure PG&E Letter DCL-1 1-097 derived to be 1.57 g as compared to the 84 percent site-specific ground-motion demand of 1.94 g, equating to a seismic margin of 0.81. The NRC found this seismic margin to be acceptable because the relays have reset capability from the control room, and therefore the relay chatter failure mode does not significantly impact the estimate of CDF (SSER 34 - Page 3-26).
The 230 kV switchyard has a HCLPF capacity of 0.84 g equating to a seismic margin of 0.43. A key feature in the PRA is the treatment of the fragility for the 230 kV switchyard. Given the loss of offsite power, the diesel generators are expected to have to function (with some chance of not functioning) for at least 24 hours. Recovery of seismically failed offsite power within 24 hours of the earthquake was assumed in the quantification performed in Chapter 6 of the 1988 LTSP Final Report. Based on previous California earthquake experience, the 230 kV line is expected to survive an earthquake. The NRC reviewed the treatment of the fragilities for the 230 kV switchyard in the PRA and determined that this contribution to the CDF as being acceptable in SSER 34.
Therefore the SSCs will maintain a seismic margin that is consistent with margins previously reviewed and found acceptable by the NRC.
SSCs operable with seismic margin of greater than or equal to 1.0 If the evaluation determines that the minimum seismic margin is below 1.3, but equal to or above 1.0, or is an SSC identified in FSARU Tables 3.7-25 and 3.7-26 as being acceptable to have a minimum seismic margin below 1.0, the applicable SSCs are determined to be operable. The seismic margin for an SSC is determined by comparing the SSCs HCLPF capacity to the 84th percent site-specific, 5 percent damped, spectral acceleration averaged from 3 to 8.5 Hz associated with the updated ground motion information. The proposed evaluation process for new seismic information would allow SSCs with a seismic margin of 1.0 or greater to be considered operable, but would require the implementation of modifications to impacted SSCs to achieve a minimum seismic margin of 1.3, or restore the SSCs seismic margin to the level that is identified in FSARU Tables 3.7-25 and 3.7-26 if its seismic margin is identified as being below 1.3. The proposed evaluation process also requires a seismic probabilistic risk assessment (SPRA) be conducted to determine the impact that the new seismic information has on the SCDF, which will be communicated to the NRC.
If the engineering evaluations determine that the seismic margin for applicable SSCs is less than 1.0, except for those SSCs identified in FSARU Tables 3.7-25 and- 3.7-26 as being acceptable having a seismic margin less than 1.0, the need for an operability determination shall be addressed in accordance with the DCPP operability determination procedure and documented in the corrective action program. For SSCs already identified as having a seismic margin of less than 1.0, and seismic margin is further reduced, an operability determination is also required.
32
 
Enclosure PG&E Letter DCL-1 1-097 Seismic Probabilistic Risk Assessment Evaluation Method for development of fragility curves The fragility analysis method used during the original implementation of the LTSP is described in Chapter 6 of the 1988 LTSP Final Report. The fragility curves (see FSARU Figure 2.5-39 for sample curve) are tied to the 5 percent damped spectral acceleration value, averaged between 3 and 8.5 Hz. The computation of fragilities going forward for evaluation of updated LTSP seismic hazards input will be based on the methods described in ASME/ANS RA-Sa-2009, as modified by RG 1.200, Revision 2.
Method of conducting a Seismic Probabilistic-Risk Assessment A gap assessment of the DCPP PRA is currently underway. Outstanding gaps against Capability Category II of ASME/ANS RA-Sa-2009 will be addressed as part of any SPRA update. The next SPRA update will be completed within 2 years following issuance of (currently draft) NRC Generic Letter 201 1-XX, Seismic Risk Evaluations for Operating Reactors.
Documentation of LTSP Update The periodic updates of the LTSP evaluation being documented in a peer-reviewed report is proposed to be submitted to the NRC on a 10-year interval, and more frequently based on significant peer reviewed information justifying it.
These updates will contain the information identified in the proposed TS Reporting Requirement 5.6.11, "Long Term Seismic Program Report." The reporting interval is consistent with the seismic hazards technical communities recommended maximum update interval. The proposed report content is consistent with the content of the 1988 LTSP Final Report, with the addition of documentation of the review performed by the SAB and the resolution of the SAB's comments for updates less than ten years and review by the SSHAC process and resolution of SSHAC comments for ten year updates. The first report will be submitted no later than 10 years from the date of issuance of the license amendment associated with this LAR.
Clarification to Ongoing Commitments Associated with LTSP On March 15, 1991, the NRC Staff met with PG&E to discuss the LTSP. This meeting included a presentation by PG&E Staff describing the continuing LTSP activities for DCPP (Reference 4, Enclosure 5):
"    Maintain a high level of technicalexpertise in geology, seismology, and earthquake engineering to effectively address future seismic issues
"    Operate the strong-motion array at and near the Diablo Canyon site 33
 
Enclosure PG&E Letter DCL-11-097
"  Operate the Central Coast Seismic Network in the region of Diablo Canyon
* Maintain knowledge of earthquakes occurringelsewhere sufficient to rapidly evaluate their significance to Diablo Canyon As a follow-up to the public meeting, PG&E provided a summary of the benefits and insights of the LTSP in a letter to the NRC dated April 17, 1991 (Reference 3). This letter included a summary of PG&E plans for ongoing activities in support of the LTSP, described as the "Framework for the Future" (Enclosure to Reference 3):
PG&E recognizes the value of the Long Term Seismic Programin the future operationof the Diablo Canyon Power Plant, and we plan to support key technical activities and associatedpersonnel into the future.
Data Bases and Instrumentation One of the more significant benefits of the Long Term Seismic Programhas been the creation of a comprehensive data base. We will continue to use and develop this data set in assessments relatedto the Diablo Canyon site, as well as the sites of other PG&E facilities in the South-Central Californiaregion. We plan to monitor and evaluate technological advances and new data as they become available. We will use the probabilisticrisk assessment developed during the Programas a tool to provide insight into the continued safe operation of the Plant. The Central Coast Seismic Network will continue to monitor micro earthquakeactivity in the region, and will assist us in accurately locating and characterizingrelevant earthquakes. The strong-motion array will continue to operate to help us assess site response to ground motions.
Focus for Addressinq Seismic Issues The Long Term Seismic Program will allow PG&E to anticipateand respond in a timely manner to new issues and concerns as they arise. For example, through,the expertise available in the Long Term Seismic Program, we were able to test and verify the results of the Program'sground motion evaluation by using the new data from the October 17, 1989, Loma Prieta earthquake, a well-recorded event. This ability provided increasedconfidence that new earthquakes are not likely to produce surprisingor conflicting data. The Long Term Seismic Programwill continue to provide a focus for addressingseismic issues related to Diablo Canyon.
The NRC Staff summarized its review and conclusions about the LTSP in SSER 34 (Reference 2).
34
 
Enclosure PG&E Letter DCL-11-097
* The NRC Staffs conclusions regarding the relationship between the LTSP and the seismic qualification basis for DCPP are given in SSER 34, Section 1.4, Summary of Staff Conclusions (Reference 2):
The staff notes that the seismic qualification basis for Diablo Canyon will continue to be the original design basis plus the Hosgri evaluation basis, along with the associatedanalyticalmethods, initial conditions, etc. The L TSP has served as a useful check on the adequacy of the seismic margins and has generally confirmed that the margins are acceptable. For future plant design modifications, the staff concludes that LTSP spectra, increased to envelope the exceedances in the vertical and horizontalspectra discussed in Section 2.5.2.3 of this SSER, should be used to verify that the plant high confidence of low probabilityof failure (HCLPF)values remain acceptable (Section 3.3 of this SSER). PG&E has agreed (Shiffer, 19911) to review future plant modifications in the light of the findings of the LTSP, and is currently developing an implementation procedure for that purpose.
The NRC Staff recognized that the LTSP response spectrum exceeded the design basis 7.5M Hosgri response spectrum at high frequencies, but indicated that revisions to the design basis earthquakes were not required.
This is discussed in SSER 34, Section 3.8.1.1 (Reference 2):
The ground-motion input data used in the deterministicevaluation were the 84th percentile, 5 percent damped, horizontal and vertical, site-specific LTSP accelerationresponse spectra resulting from the MME.
The LTSP site-specific, horizontal, ground-motion response spectra (SSRS) for 5 percent damping due to the MME and the 1977 Hosgri evaluation spectrum are compared in Figure 7-2 of the LTSP Final Report (reproducedhere as Figure 3.1). It may be seen from this figure that the Hosgri evaluation spectrum is greaterthan the LTSP 50th percentile (median) spectrum at all frequencies, and is greater than the 84th percentile spectrum (called the "LTSP spectrum"in this section of the SSER) at all frequencies less than about 15 Hz. The magnitude of the exceedance at frequencies above 15 Hz is approximately 10 percent. On the basis of PG&E's margins evaluation discussed in Section 3.8.1.7 of this SSER, the staff concludes that these high-frequency spectral exceedances are not significant.
PG&E's commitments for the ongoing activities in support of the LTSP are restated in SSER 34, Section 2.5.2.4, Seismology Conclusions (Reference 2):
PG&E made the following commitments at the public meeting on March 15, 1991, and in a letter from PG&E to the NRC (Shiffer, 1991f):
(1) to continue to.maintain a strong geosciences and engineering staff to keep abreastof new geological, seismic, and seismic engineering 35
 
Enclosure PG&E Letter DCL-1 1-097 information and evaluate it with respect to its significance to Diablo Canyon, and (2) to continue to operate a strong-motion accelerometer array and the coastal seismic network, although likely with fewer stations than are currently operating. Since some issues (i.e., slip type of the Hosgri, the characterizationof the Southwest Boundary Zone, and ground-motion estimates for oblique-slip earthquakes)are controversialbecause of the lack of definitive evidence, future geoscience discoveries may allow a more robust conclusion for these issues.
PG&E's commitment to review certain future plant modifications in light of the findings of the LTSP is provided in FSARU Sections 2.5 and 3.7. The proposed change captures the commitments for ongoing activities in support of the LTSP in the FSARU, and provides details of the process employed by PG&E in implementing these commitments. By including this information in the FSARU, any change to the program would be subject to the provisions of 10 CFR 50.59; and evaluated to determine if the change requires prior NRC approval.
: 5. REGULATORY EVALUATION 5.1    Applicable Regulatory Requirements/Criteria In Regulatory Issue Summary 2000-17, "Managing Regulatory Commitments Made by Power Reactor Licensees to the NRC Staff," dated September 21, 2000, the NRC informed licensees that the Nuclear Energy Institute document NEI 99-04, "Guidelines for Managing NRC Commitment Changes," contains acceptable guidance for controlling regulatory commitments and encouraged licensees to use the NEI guidance or similar administrative controls to ensure that regulatory commitments are implemented and that changes to the regulatory commitments are evaluated and, when appropriate, reported to the NRC.
NEI 99-04 defines a "regulatory commitment" as an explicit statement to take a specific action agreed to, or volunteered by, a licensee and submitted in writing on the docket to the NRC. This proposed change ensures that the commitments made to the NRC at the public meeting on March 15, 1991, and in a letter from PG&E to the NRC, dated April 17, 1991, regarding ongoing activities in support of the LTSP. are effectively controlled.
10 CFR 50.59, "Changes tests and experiments," establishes the conditions under which licensees may make changes to the facility or procedures and conduct tests or experiments without prior NRC approval.
Proposed changes, tests, and experiments that satisfy the definitions and one or more of the criteria in the rule must be reviewed and approved by the NRC before implementation. The proposed change revises the licensing basis, as described in the FSARU and TS, to include discussions of the actions and requirements associated with PG&E's ongoing activities 36
 
Enclosure PG&E Letter DCL-11-097 in support of the LTSP (response to Condition No. 2.C.(7) of Facility Operating License DPR-80). A codified change process for evaluating any future changes to the LTSP is provided in 10 CFR 50.59.
Appendix A to 10 CFR 100, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," establishes that the nuclear power plant shall be designed so that, if the SSE occurs, certain SSCs will remain functional.
These SSCs are those necessary to assure: (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shut down the reactor and maintain it in a safe condition, or (3) the capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of this part. In addition to seismic loads, including aftershocks, applicable concurrent functional and accident-induced loads shall be taken into account in the design of these safety-related SSCs. The design of the nuclear power plant shall also take into account the possible effects of the safe shutdown earthquake on the facility foundations by ground disruption, such as fissuring, differential consolidation, cratering, liquefaction, and landsliding.
FSARU Sections 2.5, 3.2.1, and 3.7.1.1 discuss that DCPP's design had been established prior to the issuance of 10 CFR 100, Appendix A, and provide a comparison to 10 CFR 100, Appendix A requirements.
Paragraph 50.36(c)(5) of 10 CFR, "Administrative controls," establishes that "[a]dministrative controls are the provisions relating to organization and management, procedures, recordkeeping, review and audit, and.
reporting necessary to assure operation of the facility in a safe manner.
Each licensee shall submit any reports to the Commission pursuant to approved technical specifications as specified in 10 CFR 50.4."
GDC 2, "Design Bases for Protection Against Natural Phenomena,"
establishes those systems and components of reactor facilities that are essential to the prevention of accidents which could affect the public health and safety, or to mitigation of their consequences, shall be designed, fabricated, and erected to performance standards that will enable the facility to withstand, without loss of the capability to protect the public, the additional forces that might be imposed by natural phenomena such as earthquakes, tornadoes, flooding conditions, winds, ice, and other local site effects. The design bases so established shall reflect: (1) appropriate consideration of the most severe of these natural phenomena that have been recorded for the site and the surrounding area, and (2) an appropriate margin for withstanding forces greater than those recorded to reflect uncertainties about the historical data and their suitability as a basis for design. FSARU Section 3.1.2.2 and Appendix 3.1A discuss compliance with GDC 2.
SG 29, "Seismic Design Criteria" establishes "a method acceptable to the NRC staff for identifying and classifying those features of light-water-37
 
Enclosure PG&E Letter DCL-11-097 cooled nuclear power plants that should be designed to withstand the effects of the SSE." FSARU Section 3.7 discusses compliance with SG 29.
With the proposed revisions to the DCPP TS and FSARU, DCPP continues to meet the requirements of 10 CFR 50.59, 10 CFR 50.36, GDC 2, and SG 29.
With the use of the previously approved HE methods of analysis, which are different than those used for the original design analysis for the DE and DDE, as identified in SSER 7 Sections 3.8.5.3 and 3.9.3.2, it has been demonstrated that the SSCs necessary to assure: (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shutdown the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of 10 CFR 100, were qualified for the HE.
5.2  Precedent
    'The LTSP, developed in response to License Condition No. 2.C.(7) of DCPP Facility OL DPR-80, provides an acceptable regulatory mechanism for reevaluating the DCPP seismic design bases taking into account new seismic information, and for assessing the significance of the conclusions of the seismic reevaluation to ensure adequacy of seismic margins.
During the time period between the issuance of SSER 34 (1991) and the present, PG&E has continuously gathered seismic data, both locally (through the seismic instrumentation in the vicinity of DCPP) and globally (through review of earthquake records and field reconnaissance associated with major earthquakes worldwide), participated in technical research (through participation in the Pacific Earthquake Engineering Research Center, through a cooperative research agreement with the USGS, and through collaboration with other industry and governmental agencies), and evaluated the significance of any new information relative to the seismic evaluation of DCPP.
38
 
Enclosure PG&E Letter DCL-1 1-097 5.3  Sigqnificant Hazards Consideration The proposed change would revise the licensing basis as documented in the Final Safety Analysis Report Update (FSARU) and technical specifications (TS) to include discussions of the actions and requirements associated with PG&E's ongoing activities in support of the Long Term Seismic Program (LTSP) (response to Condition No. 2.C.(7) of Facility Operating License DPR-80) and clarify the Hosgri Earthquake spectrum (HE) as Diablo Canyon Power Plants (DCPP's) equivalent safe shutdown earthquake (SSE). The LTSP provides an acceptable regulatory mechanism for reevaluating the DCPP seismic design bases taking into
    .account new seismic information, and for assessing the significance of the conclusions of the seismic reevaluation to assure adequacy of seismic margins.
Consistent with NUREG-0484, "Combining Dynamic Loads," Revision 1, PG&E proposes to use the square-root-of-the-sum-of-squares (SRSS) method for evaluations of seismic and loop pipe rupture load combinations.
The NRC's review and acceptance of PG&E's response to License Condition 2.C.(7), are discussed in NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No. 34, dated June 1991 (SSER 34), and in NRC letter dated April 14, 1992, "Transmittal of Safety Evaluation Closing Out Diablo Canyon Long-Term Seismic Program (TAC NOS. M80670 and M80671)." SSER-34, Section 2.5.2.4, "Seismology Conclusions," included a restatement of two PG&E commitments with respect. to ongoing activities associated with the implementation of the LTSP. These commitments are based on PG&E Letter DCL-91-091, J.D. Shiffer (PG&E) to NRC, "Benefits and Insights of the Long Term Seismic Program," dated April 17, 1991. PG&E proposes to incorporate the implementation of these commitments with the evaluation of new seismic information into the FSARU, Section 2.5, "Geology and Seismology," and Section 3.7, "Seismic Design." PG&E also proposes to incorporate the ongoing review and evaluation of new seismic information and methodologies, and reporting requirements, associated with the LTSP into new administrative control TS 5.5.20, "Long Term Seismic Program," and 5.6.12, "Long Term Seismic Program Report."
PG&E has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:
39
 
Enclosure PG&E Letter DCL-1 1-097
: 1. Does the change involve a significant increasein the probability or consequences of an accident previously evaluated?
The changes proposed by this LAR clarify the licensing basis as documented in the FSARU and TS to incorporate the HE as DCPP's equivalent SSE consistent with the NRC conclusions in Supplemental Safety Evaluation Report (SSER) 7, describe an acceptable methodology for evaluating the effect of new seismic information on DCPP's ability to achieve safe shutdown, and for assessing the significance of the conclusions of the seismic reevaluation to assure adequacy of seismic margins. The proposed changes include specifying the use of the SRSS method for evaluations of seismic and loop pipe rupture load combinations.
The changes proposed by this LAR do not change design requirements and does not involve any physical change to any structures, systems, and components (SSC), nor does it affect the ability of any SSC to function in response to design-basis seismic events or other previously evaluated accidents, including the previous definitions and assumptions regarding design earthquake (DE), double design earthquake (DDE), and HE. It is unrelated to the probability of occurrence or the consequences of those events or accidents.
Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
: 2. Does the change create the possibility of a new or different kind of accidentfrom any accidentpreviously evaluated?
The changes proposed by this LAR do not change design requirements and do not involve changes to any plant SSCs, nor do they involve changes to any plant operating practice or procedure. No credible new failure mechanisms, malfunctions, or accident initiators not considered in the design and licensing bases are created that would create the possibility of a new or different kind of accident. The proposed changes would provide an agreed to process for evaluating new seismic information.
Therefore the proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.
: 3.      Does the change involve a significantreduction in a margin of safety?
The changes proposed by this LAR change do not change design requirements and do not involve any physical changes to the plant or alter the manner in which plant systems are operated, maintained, modified, 40
 
Enclosure PG&E Letter DCL-11-097 tested, or inspected. The proposed changes do not alter the manner in which safety limits, limiting safety system settings, or limiting conditions for operation are determined. The safety analysis acceptance criteria are not affected by this change. The proposed changes will not result in plant operation in a configuration outside the design basis. The proposed LAR change does not adversely affect systems that respond to safely shutdown the plant and to maintain the plant in a safe shutdown condition.
The proposed evaluation methodology, based on that used during the original implementation of the LTSP, will ensure that the seismic margins, relative to the 1977 HE response spectra, accepted by the NRC in 1991, are maintained.
The use of the SRSS method for evaluating the combination of seismic and LOCA load combinations is commonly used in seismic analysis and is appropriate when combining statistically independent transient functions.
This method is consistent with NUREG-0484, Revision 1.
Therefore, the changes proposed by this LAR do not involve a significant reduction in a margin of safety.
Based on the above evaluation, PG&E concludes that the changes proposed by this LAR satisfies the no significant hazards consideration standards of 10 CFR 50.92(c), and accordingly a no significant hazards finding is justified.
5.4      Conclusions In conclusion, based on the considerations discussed above: (1) There is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
: 6. ENVIRONMENTAL CONSIDERATION PG&E has evaluated the proposed amendment and has determined that the proposed amendment does not involve: (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.
41
 
Enclosure PG&E Letter DCL-1 1-097
: 7. REFERENCES
: 1. Diablo Canyon Power Plant, Units 1 and 2, Final Safety Analysis Report Update, Revision 19
: 2. NRC, NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No. 34, dated June 1991
: 3. PG&E Letter DCL-91-091, J.D. Shifter (PG&E) to USNRC, "Benefits and Insights of the Long Term Seismic Program," dated April 17, 1991
: 4. NRC, "Summary of March 15, 1991, Public Meeting to Discuss Diablo Canyon Long Term Seismic Program (TAC Nos. 55305 and 68049),"
Docket Nos. 50-275 and 50-323, dated March 22, 1991
: 5. NRC, Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No. 7, dated May 26, 1978
: 6. PG&E Letter DCL-90-226, "Long Term Seismic Program Additional Deterministic Evaluations," dated September 18, 1990
: 7. PG&E Letter DCL-91-143, J.D. Shifter (PG&E) to USNRC, "Long Term Seismic Program - Implementation of the Results of the Program," dated May 29, 1991
: 8. PG&E Letter DCL-91-178, J.D. Shiffer (PG&E) to USNRC, "Long Term Seismic Program - Future Plant Modifications," dated July 16, 1991
: 9. Atomic Safety and Licensing Board, Partial Initial Decision LBP-79-26, "Pacific Gas and Electric Company - Diablo Canyon Nuclear Power Plant (Units 1 and 2), dated September 27, 1979
: 10. NCR Safety Guide 29, "Seismic Design Classification," dated July 7, 1972
: 11. PG&E Letter DCL-88-192, "Long Term Seismic Program Completion,"
dated July 31, 1988
: 12. PG&E Letter DCL-91-027, "Addendum to Long Term Seismic Program Final Report," dated February 13, 1991
: 13. NRC, "Transmittal of Safety Evaluation Closing Out Diablo Canyon Long-Term Seismic Program (TAC Nos. M80670 and M80671)," dated April 17, 1992 42
 
Enclosure PG&E Letter DCL-1 1-097
: 14. PG&E Letter to NRC, "Amendment No. 50 to the Operating License Application for Diablo Canyon Power Plant Units 1 and 2; 'Seismic Evaluation for Postulated 7.5M Hosgri Earthquake,"' dated June 5, 1977
: 15. NRC Letter to PG&E, "Diablo Canyon Power Plant- NRC Integrated Inspection 05000275/2011002 AND 05000323/2011002," dated May 11, 2011, Unresolved Item: 05000275; 323/2011002-03 43
 
Enclosure Attachment 1 PG&E Letter DCL-1 1-097 Technical Specification Page Markups Insert 5.5.20 5.5.20 Long Term Seismic Program This program provides ongoing review and evaluation of new seismic information and associated methodologies. The program shall include the following:
: a. A staff to keep abreast of new geological, seismic, and seismic engineering information and evaluate it with respect to its significance to DCPP;
: b. Operation of a strong-motion accelerometer array and the coastal seismic network,
: c. Verification that plant seismic margins remain acceptable for plant additions and modifications when checked against insights and knowledge gained from the Long Term Seismic Program, as identified in FSARU Section 3.7.6;
: d. Deterministic seismic margin acceptance criteria for operability determinations;
: e. Peer review process requirements for seismic probabilistic risk assessment revisions;
: f. Peer review processes requirements for seismic model or methodology revisions; and
: g. Minimum requirements for the Seismic Advisory Board (SAB).
Insert 5.6.11 5.6.11 Long Term Seismic Program Report A report shall be submitted once every 10 years, based on the submittal date of the previous update. An updated report will be submitted in less than 10 years if new peer reviewed seismic information becomes available that would significantly increase the risk to DCPP. The report shall include the following information:
1
 
Enclosure Attachment 1 PG&E Letter DCL-11-097
: a. Geology/seismology/geophysics/tectonics investigations,
: b. Seismic source characterization,
: c. Characterization of ground motions,
: d. Soil/structure interaction analysis,
: e. Probabilistic risk analysis,
: f. Deterministic evaluations,
: g. Assessment of the adequacy of seismic margins,
: h. Documentation of the review performed by the Seismic Advisory Board (SAB) and resolution of the SAB's comments if performed in less than 10 years, and
: i. Documentation of the review performed by the Senior Seismix Hazards Analysis Committee for 10 year updates.
2
 
Programs and Manuals 5.5 5.5 Programs and Manuals (continued) 5.5.19 Control Room Envelope Habitability Program A Control Room Envelope (CRE) Habitability Program shall be established and implemented to ensure that CRE habitability is maintained such that, with an OPERABLE Control Room Ventilation System (CRVS), CRE occupants can control the reactor safely under normal conditions and maintain it in a safe condition following a radiological event, hazardous chemical release, or a smoke challenge. The program shall ensure that adequate radiation protection is provided to permit access and occupancy of the CRE under design basis accident (DBA) conditions without personnel receiving radiation exposures in excess of 5 rem whole body or its equivalent to any part of the body for the duration of the accident. The program shall include the following elements:
: a.      The definition of the CRE and the CRE boundary.
: b.      Requirements for maintaining the CRE boundary in its design condition, including configuration control and preventive maintenance.                        /
: c.      Requirements for (i) determining the unfiltered air inleakage past the CRE boundary into the CRE in accordance with the testing methods and at the Frequencies specified in Sections C.1 and C.2 of Regulatory Guide 1.197, "Demonstrating Control Room Envelope Integrity at Nuclear Power Reactors,"
Revision 0, May 2003, and (ii) assessing CRE habitability at the Frequencies specified in Sections C.1 and C.2 of Regulatory Guide 1.197, Revision 0.
: d.      Measurement, at designated locations, of the CRE pressure relative to all external areas adjacent to the CRE boundary during the pressurization mode of operation by one train of the CRVS, operating at the flow rate required by the VFTP, at a Frequency of 24 months on a STAGGERED TEST BASIS. The results shall be trended and used as part of the 24 month assessment of the CRE boundary.
: e.      The quantitative limits on unfiltered air inleakage into the CRE. These limits shall be stated in a manner to allow direct comparison to the unfiltered air inleakage measured by the testing described in paragraph c. The unfiltered air inleakage limit for radiological challenges is the inleakage flow rate assumed in the licensing basis analyses of DBA consequences. Unfiltered air inleakage limits for hazardous chemicals must ensure that exposure of CRE occupants to these hazards will be within the assumptions in the licensing basis.
: f.      The provisions of SR 3.0.2 are applicable to the Frequencies required by paragraphs c and d for determining CRE unfiltered inleakage and assessing CRE habitability, and measuring CRE pressure and assessing the CRE boundary.
DIABLO CANYON - UNITS 1 & 2                    5.0-17a        Unit 1 - Amendment No.-4f; Unit 2 - Amendment No.-eeý-
 
Reporting Requirements 5.6 5.6 Reporting Requirements (continued) 5.6.10 Steam Generator (SG) Tube Inspection Report A report shall be submitted within 180 days after the initial entry into MODE 4 following completion of an inspection performed in accordance with the Specification 5.5.9, Steam Generator (SG) Program. The report shall include:
: a. The scope of inspections performed on each SG,
: b. Active degradation mechanisms found,
: c. Nondestructive examination techniques utilized for each degradation mechanism,
: d. Location, orientation (if linear), and measured sizes (if available) of service induced indications,
: e. Number of tubes plugged during the inspection outage for each active degradation mechanism,
: f. Total number and percentage of tubes plugged to date, and
: g. The results of condition monitoring, including the results of tube pulls and in-situ testing.
DIABLO CANYON - UNITS 1 & 2                  5.0-23    Unit 1 - Amendment No.4-6 Unit 2 - Amendment No. 4,99,-
4r
 
Enclosure Attachment 2 PG&E Letter DCL-11-097 Retyped Technical Specification Pages Remove Page                                Insert Page 5.0-17a                                    5.0-17a 5.0-17b 5.0-23                                    5.0-23 5.0-23a 1
 
Programs and Manuals 5.5 5.5 Programs and Manuals (continued) 5.5.19 Control Room Envelope Habitability Program A Control Room Envelope (CRE) Habitability Program shall be established and implemented to ensure that CRE habitability is maintained such that, with an OPERABLE Control Room Ventilation System (CRVS), CRE occupants can control the reactor safely under normal conditions and maintain it in a safe condition following a radiological event, hazardous chemical release, or a smoke challenge. The program shall ensure that adequate radiation protectionis provided to permit access and occupancy of the CRE under design basis accident (DBA) conditions without personnel receiving radiation exposures in excess of 5 rem whole body or its equivalent to any part of the body for the duration of the accident. The program shall include the following elements:
: a.      The definition of the CRE and the CRE boundary.
: b.      Requirements for maintaining the CRE boundary in its design condition, including configuration control and preventive maintenance.
: c.      Requirements for (i) determining the unfiltered air inleakage past the CRE boundary into the CRE in accordance with the testing methods and at the Frequencies specified in Sections C.1 and C.2 of Regulatory Guide 1.197, "Demonstrating'Control Room Envelope Integrity at Nuclear Power Reactors,"
Revision 0, May 2003, and (ii) assessing CRE habitability at the Frequencies specified in Sections C.1 and C.2 of Regulatory Guide 1.197, Revision 0.
: d.      Measurement, at designated locations, of the CRE pressure relative to all external areas adjacent to the CRE boundary during the pressurization mode of operation by one train of the CRVS, operating at the flow rate required by the VFTP, at a Frequency of 24 months on a STAGGERED TEST BASIS. The results shall be trended and used as part of the 24 month assessment of the CRE boundary.
: e.      The quantitative limits on unfiltered air inleakage into the CRE. These limits shall be stated in a manner to allow direct comparison to the unfiltered air inleakage measured by the testing described in paragraph c. The unfiltered air inleakage limit for radiological challenges is the inleakage flow rate assumed in the licensing basis analyses of DBA consequences. Unfiltered air inleakage limits for hazardous chemicals must ensure that exposure of CRE occupants to these hazards will be within the assumptions in the licensing basis.
: f. The provisions of SR 3.0.2 are applicable to the Frequencies required by paragraphs c and d for determining CRE unfiltered inleakage and assessing CRE habitability, and measuring CRE pressure and assessing the CRE boundary.
(continued)
DIABLO CANYON - UNITS I & 2                        5.0-17a        Unit I - Amendment No. 204, Unit 2 - Amendment No. 202,
 
Programs and Manuals 5.5 5.5 Programs and Manuals (continued) 5.5.20 Lonq Term Seismic Pro-ram This program provides ongoing review and evaluation of new seismic information and associated methodologies. The program shall include the following:
: a. A staff to keep abreast of new geological, seismic, and seismic engineering information and evaluate it with respect to its significance to DCPP;
: b. Operation of a strong-motion accelerometer array and the coastal seismic network;
: c. Verification that plant seismic margins remain acceptable for plant additions and modifications when checked against insights and knowledge gained from the Long Term Seismic Program, as identified in FSARU Section 3.7.6;
: d. Deterministic seismic margin acceptance criteria for operability determinations;
: e. Peer review process requirements for seismic probabilistic risk assessment revisions;
: f. Peer review processes requirements for seismic model or methodology revisions; and
: g. Minimum requirements for the Seismic Advisory Board (SAB).
5.0-17b      Unit 1 - Amendment No.
DIABLO CANYON - UNITS 1 & 2                                      Unit 2 - Amendment No.
 
Reporting Requirements 5.6 5.6 Reporting Requirements (continued) 5.6.10 Steam Generator (SG) Tube Inspection Report A report shall be submitted within 180 days after the initial entry into MODE 4 following completion of an inspection performed in accordance with the Specification 5.5.9, Steam Generator (SG) Program. The report shall include:
: a.      The scope of inspections performed on each SG,
: b.      Active degradation mechanisms found,
: c.      Nondestructive examination techniques utilized for each degradation mechanism,
: d.      Location, orientation (if linear), and measured sizes (if available) of service induced indications,
: e.      Number of tubes plugged duri.ng the inspection outage for each active degradation mechanism,
: f.      Total number and percentage of tubes plugged to date, and
: g.      The results of condition monitoring, including the results of tube pulls and in-situ testing.
5.6.11 Long Term Seismic Program Report A report shall be submitted once every 10 years, based on the submittal date of the previous update. An updated report will be submitted in less than 10 years if new peer reviewed seismic information becomes available that would significantly increase the risk to DCPP. The report shall include the following information:
: a.      Geology/seismology/geophysics/tectonics investigations,
: b.      Seismic source characterization,
: c.      Characterization of ground motions,
: d.      Soil/structure interaction analysis,
: e.      Probabilistic risk analysis,
: f.      Deterministic evaluations,
: g.    *Assessment of the adequacy of seismic margins,
: h.      Documentation of the review performed by the Seismic Advisory Board (SAB) and resolution of the SAB's comments if performed in less than 10 years, and (continued)
DIABLO CANYON - UNITS I & 2                    5.0-23    Unit 1 - Amendment No. 498, Unit 2 - Amendment No. 499,
 
Reporting Requirements 5.6 5.6 Reporting Requirements 5.6.11 Long Term Seismic Procqram Report (continued)
: i. Documentation of the review performed by the Senior Seismic Hazards Analysis Committee for 10 year updates.
5.0-23a  Unit I - Amendment No.
DIABLO CANYON - UNITS 1 & 2                            Unit 2 - Amendment No.
 
Enclosure Attachment 3 PG&E Letter DCL-1 1-097 Final Safety Analysis Report Update Changes I
 
DCPP UNITS 1 & 2 FSAR UPDATE 1.2.1.6 Seismology Seismological investigations were undertaken to determine the potential for earthquakes in the site area, to form a basis of the establishment of seismic design criteria, and to evaluate the adequacy of seismic design margins for the plant (Section 2.5). Records indicate that seismic activity within 20 miles of Diablo Canyon has been very low compared to other parts of California. Until PG&E's seismological investigation of the Hosgri fault zone located approximately 3 miles offshore, the seismically significant fault system nearpest the site was considered to be the Nacimiento Fault located about 20 miles away as discussed in Section 2.5.2.9. The largest earthquake known to have been associated with this fault system occurred at an epicentral distance to the site of about 44 miles. It is listed with a Richter magnitude 6.
A Richter maqnitude 7.5 earthquake was postulated for the Hosqri fault, as discussed in Section 2.5.2.9.3. At its closest point, the San Andreas Fault passes some 48 miles from the site.
PG&F'6 r.evaluation of the plant's .apabiity to withstand a postulated Richter Magnitude 7.5
.HE g.i" ..earthquake is dis.us.ed in Sec.tion 3.7.
I 1.2-1
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5    GEOLOGY AND SEISMOLOGY This section presents the findings of the regional and site-specific geologic and seismologic investigations of the Diablo Canyon Power Plant (DCPP) site..          .eFmation-presented is in oempliance With thc critcria in Appendix A of 10 CFR 100O-an4-meets-the form-at and c;ontent
                    .r-      cmm;ndations o,f Regulatory Guide 1.70, Rcvision-1 In order to capture the historical progress of the geological and seismological investigations associated with the DCPP site, information pertaining to the following three time periods are described herein:
(1)    Pre-Construction/Early-Construction Phase: investigations performed in support of the Preliminary Safety Analysis Report (circa 1967), prior to the issuance of the Unit 1 construction permit, through the early stages of the construction of Unit (circa 1971). See Sections 2.5.1 through 2.5.2.8.
2.5.2.9.1, 2.5.2.9.2, 2.5.2.10.1, and 2.5.2.10.2.
(2)    Hosgri Evaluation Phase: investigations performed in response to the identification of the offshore Hosgri fault zone (circa 1971) through the issuance of the Unit 1 operating license (circa 1984). See Sections 2.5.1
              .through 2.5.2.8, 2.5.2.9.3 and 2.5.2.10.3 (3)    Long Term Seismic Program (LTSP) Phase: investigations performed in response to the License Condition Item No. 2.C.(7) of the Unit 1 operating license (circa 1985) through the removal of the License Condition (circa 1991), including current on-going investigations. See Sections 2.5.2.9.4, 2.5.2.10.4, and 2.5.6.
Overview Location of earthquake epicenters within 200 miles of the plant site, and faults and earthquake epicenters within 75 miles of the plant site for either magnitudes or intensities, respectively, are shown in Figures 2.5-2, 2.5-3, and 2.5-4 (through 1971). A geologic and tectonic map of the region surrounding the site is given in -,,. sheets efshown in Figure 2.5-5, and detailed information about site geology is presented in Figures 2.5-8 through 2.5-16. Geology and seismology are discussed in detail in Sections 2.5.1 through 2.5.4. Additional information on site geology is contained in References I and 2.
On. November 2, 1981, the NRC issued the Diablo Canyon Un~it 1 Facility Operating License DPR 80. in DPR 80, License Condition item 2.G.(7), the NRC stated, in part:
        "PG&E shall develop and implement ! program to reevaluate the seismic design bases used for the Doablo Canyon Power Plan."
2.5-1
 
DCPP UNITS 1 & 2 FSAR UPDATE
        .,&E'sr.cvaluation effort in resp0ec tG the lic.nSe condition was titlcd the "Long
-T-e,,m,, Seio    . Program" (L TSP. PG&E*_ ....... d,          ,mitted to the NIRC the ,,*;.,.*
d -Sub*.
Repert of the Diable Canyon Long Term Seismic Progra"                in July 198800-84etween-1988 and 1991, the NRC performed an          . extnsi,.
                                                  .        reiew of the Final Repot, and PG&E peparled and submitted written responses to fiomal NRC questions.in February 1901, PfGE  inveissue the "Addendum to the 1988 Final Report of the Diable Canyon LoRg Term Seviesi eionms areprsin June 199A1, the NRC issued Supplement Number              r3  to the Diablo Canyon Sae      valuat        ion Repoer (SSERith 4 . inowhircih thoe nR conludecd that PG&E had satisfied License Condition 2.G.(7) of Facility Operating License DPR 80. In the SSER the NRC requested          Sertain    cobfirmatoC'yanalyses 4r6m PG&E, and PG&E Subequently submitted the requested analyses. The NRC's final acceptance of the LTSP is documented *in        a letter to PG&efdated April 17,409072(4 The LTSP contains extensive data bases and analyses that update the basic geologic and seismic inforatieon in this section of the FSAR Update. Hfowseouef, the LTs material does not addfess or alter the curhent design licensing basis for the pln and thus is not included in the FSAR Update-.
A complete listing of bibliographiG references to the LTSP reports and other documents may be feund in Refernces 40, 1 and 12.
Detailed supporting data pertaining to this section are presented in Appendices 2.5A, 2.5B3, 2.5C, and 2.5D of Reference 27 in Section 2.3. Geologic and seismic information from investigations that responded to Nuclear Regulatory Commission (NRC) licensing review questions are presented Appendices 2.5E and 2.5F of the same reference_
Hosnri evaluation                    ief synopsis of the information presented in Reference 27 (Section 2.3) is given below.
The DCPP site is located in San Luis Obispo County approximately 190 miles south of San Francisco and 150 miles northwest of Los Angeles, California. It is adjacent to the Pacific Ocean, 12 miles west-southwest of the city of San Luis Obispo, the county seat.
The plant site location and topography are shown in Figure 2.5-1.
The site is located near the mouth of Diablo Creek w~hich flows out of the San Luis Range, the dominant feature to the northeast. The Pacific Ocean is southwest of the site. Facilities for the power plant are located on a marine terrace that is situated between the mountain range and the ocean.
The terrace is bedrock overlain by surficial deposits of marine and nonmarine origin.
Seismic Category I structures at the site are situated on bedrock that is predominantly stratified marine sedimentary rocks and volcanics, all of Miocene age. A more extensive discussion of the regional geology is presented in Section 2.5.1.1 and site geology in Section 2.5.1.2.
Several investigations were performed at the site and in the vicinity of the site during the pre-co nstructio n/early-construction investigation phase to determine: potential vibratory 2.5-2
 
DCPP UNITS 1 & 2 FSAR UPDATE ground motion characteristics, existence of surface faulting, and stability of subsurface materials and cut slopes adjacent to Seismic Category I structures. Details of these investigations are presented in Sections 2.5.2 through 2.5.5. Consultants retained to perform these studies included: Earth Science Associates (geology and seismicity),
John A. Blume and Associates (seismic design and foundation materials dynamic response), Harding-Lawson and Associates (stability of cut slope), Woodward-Clyde-Sherard and Associates (soil testing), and Geo-Recon,. Incorporated (rock seismic velocity determinations). The findings of these consultants are summarized in this section and the detailed reports are included in Appendices 2.5A, 2.5B, 2.5C, 2.5D, 2.5E, and 2.5F of Reference 27 in Section 2.3.
Geologic investigation during the pre-construction/early-construction phase of the Diablo Canyon coastal area, including detailed mapping of all natural exposures and exploratory trenches, yielded the following basic conclusions:
('1)  The area is underlain by sedimentary and volcanic bedrock units of Miocene age. Within this area, the power plant site is underlain almost wholly by sedimentary strata of the Monterey Formation, which dip northward at moderate to very steep angles. More specifically, the reactor site is underlain by thick-bedded to almost massive Monterey sandstone that is well indurated and firm. Where exposed on the nearby hillslope, this rock is markedly resistant to erosion.
(2)  The bedrock beneath the main terrace area, within which the power plant site has been located, is covered by 3 to 35 feet of surficial deposits.
These include marine sediments of Pleistocene age and nonmarine sediments of Pleistocene and Holocene age. In general, they are thickest in the vicinity of the reactor site.
(3)  The interface between the unconsolidated terrace deposits and the underlying bedrock comprises flat to moderately irregular surfaces of Pleistocene marine planation and intervening steeper slopes that also represent erosion in Pleistocene time.
(4)  The bedrock beneath the power plant site occupies the southerly flank of a major syncline that trends west to northwest. No evidence of a major fault has been recognized within or near the coastal area, and bedrock relationships in the exploratory trenches positively indicate that no such fault is present within the area of the power plant site.
(5)  Minor surfaces of disturbance, some of which plainly are faults, are present within the bedrock that underlies the power plant site. None of these breaks offsets the interface between bedrock and the cover of terrace deposits, and none of them extends upward into the surficial cover. Thus, the latest movements along these small faults must have antedated erosion of the bedrock section in Pleistocene time.
2.5-3
 
DCPP UNITS 1 & 2 FSAR UPDATE (6)    No landslide masses or other gross expressions of ground instability are present within the power plant site or on the main hillslope east of the site.
Some landslides have been identified in adjacent ground, but these are minor features confined to the naturally oversteepened walls of Diablo Canyon.
(7)    No water of subsurface origin was encountered in the exploratory trenches, and the level of permanent groundwater beneath the main terrace area probably is little different from that of the adjacent lower reaches of the deeply incised Diablo Creek.
2.5.1 BASIC GEOLOGIC AND SEISMIC INFORMATION This section presents the basic geologic and seismic information for DCPP site and surrounding region, resulting from investigations performed during the pre-construction/
early-construction phase. Information contained herein has been obtained from literature studies, field investigations, and laboratory testing and is to be used as a basis for evaluations required to provide a safe design for the facility. The basic data contained in this section and in Reference 27 of Section 2.3 are referenced in several other sections of this FSAR Update. Additional information, developed during the Hosgri evaluation and LTSP evaluation phases are described in Sections 2.5.2.9.3 and 2.5.6, respectively.
p 2.5-4
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.2 VIBRATORY GROUND MOTION 2.5.2.1 Geologic Conditions of the Site and Vicinity DCPP is situated at the coastline on the southwest flank of the San Luis Range, in the southern Coast Ranges of California. The San Luis Range branches from the main coastal mountain chain, the Santa Lucia Range, in the area north of the Santa Maria Valley and southeast of the plant site, and thence follows an alignment that curves toward the west. Owing to this divergence in structural grain, the range juts out from the regional coastline as a broad peninsula and is separated from the Santa Lucia Range by an elongated lowland that extends southeasterly from Morro Bay and includes Los Osos and San Luis Obispo Valleys. It is characterized by rugged west-northwesterly trending ridges and canyons, and by a narrow fringe of coastal terraces along its southwesterly flank.
Diablo Canyon follows a generally west-southwesterly course from the central part of the range to the north-central part of the terraced coastal strip. Detailed discussions of the lithology, stratigraphy, structure, and geologic history of the plant site and surrounding region are presented in Section 2.5.1.
2.5.2.2 Underlying Tectonic Structures Evidence pertaining to tectonic and seismic conditions in the region of the DCPP site,.
developed during the pre-construction/early-construction phase is summarized later in the section, and is illustrated in Figures 2.5-2, 2.5-3, 2.5-4, and 2.5-5. Table 2.5-1 includes a summary listing of the nature and effects of all significant historic earthquakes within 75 miles of the site that have been reported through the end of 1971. Table 2.5-2 shows locations of 19 selected earthquakes that have been investigated by S. W. Smith. Table 2.5-3 lists the principal faults in the region that were identified during the pre-construction/early-construction phase and indicates major elements of their histories of displacement, in geological time units.
Prior to the start of construction of DCPP, Benioff and Smith(5)-ha4ve assessed the maximum earthquakes to be expected at the site, and John A. Blume and Associates(6'7 ) have derived the site vibratory motions that could result from these maximum earthquakes (see Section 2.5.2.9.1). An extensive discussion of the geology of the southern Coast Ranges, the western Transverse Ranges, and the adjoining offshore region is presented in Appendix 2.5D of Reference 27 of Section 2.3. Tectonic features of the central coastal region are discussed in Section 2.5.1.1.2, Regional Geologic and Tectonic Setting.
Additional information of the tectonic and seismic conditions was gathered during the Hosgri evaluation and LTSP evaluation phases, as discussed in Sections 2.5.2.9.3 and 2.5.2.9.4, respectively.
2.5-5
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.2.3 Behavior During Prior Earthquakes Physical evidence that indicates the behavior of subsurface materials, strata, and structure during prior earthquakes is presented in Section 2.5.1.2.5. The section presents the findings of the exploratory trenching programs conducted at the site.
2.5.2.4 Engineering Properties of Materials Underlying the Site A description of the static and dynamic engineering properties of the materials underlying the site is presented in Section 2.5.1.2.6, Site Engineering Properties.
2.5.2.5 Earthquake History The seismicity of the southern Coast Ranges region is known from scattered records extending back to the beginning of the 19th century, and from instrumental records dating from about 1900. Detailed records of earthquake locations and magnitudes became available following installation of the California Institute of Technology and University of California (Berkeley) seismograph arrays in 1932.
A plot of the epicenters for all large historical earthquakes and for all instrumentally recorded earthquakes of Magnitude 4 or larger that have occurred within 200 miles of DCPP site, through the end of 1971, is given in Figure 2.5-2. Plots of all historically and instrumentally recorded epicenters, through the end of 1971-, and all mapped faults within about 75 miles of the site, known through the end of 1971, are shown in Figures 2.5-3 and 2.5-4.
A tabulated list of seismic events through the end of 1971, representing the computer printout from the Berkeley Seismograph Station records, supplemented with records of individual shocks of greater than Magnitude 4 that appear only in the Caltech records, is included as Table 2.5-1. Table 2.5-2 gives a summary of revised epicenters of a representative sample of earthquakes off the coast of California near San Luis Obispo, as determined by S. W. Smith.
2.5-6
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.2.7 Identification of Active Faults Faults that have evidence of recent activity and have portions passing within 200 miles of the site, as known through the end of 1971, are identified in Section 2.5.1.1.2.
2.5.2.8 Description of Active Faults Active faults that have any part passing within 200 miles of the site, as known through the end of 1971, are described in Section 2.5.1.1.2. Additional active faults were identified during the Hosgri and LTSP evaluation phases, as described in Sections 2.5.2.9.3 and 2.5.2.9.4, respectively.
2.5.2.9 Maximum E.thuak,*,        Design and Licensing Basis Earthquakes The seismic design and evaluation of DCPP is based on the earthquakes described in the followinq four subsections. Refer to Section 3.7 for the design criteria associated with the application of these earthquakes to the structures, systems, and components.
2.5.2.9.1 Maximum Earthquake (Design Earthquake)
Durinq the pre-construction phase, Benioff and Smith, in reviewing the seismicity of the region around DCPP site, determined the maximum earthquakes that could reasonably be expected to affect the site. Their conclusions regarding the maximum size earthquakes that can be expected to occur during the life of the reactor are listed below:
(1)    Earthquake A: A great earthquake may occur on the San Andreas fault at a distance from the site of more than 48 miles. It would be likely to produce surface rupture along the San Andreas fault over a distance of 200 miles with a horizontal slip of about 20 feet and a vertical slip of 3 feet.
The duration of strong shaking from such an event would be about 40 seconds, and the equivalent magnitude would be 8.5.
(2)    Earthquake B: A large earthquake on the Nacimiento (Rinconada) fault at a distance from the site of more than 20 miles would be likely to produce a 60 mile surface rupture along the Nacimiento fault, a slip of 6 feet in the horizontal direction, and have a duration of 10 seconds. The equivalent magnitude would be 7.5.
(3)    Earthquake C: Possible large earthquakes occurring on offshore fault systems that may need to be considered for the generation of seismic sea waves are listed below:
2.5-7
 
DCPP UNITS 1 & 2 FSAR UPDATE Length of                                          Distance Location              Fault Break        Slip, feet      Magnitude      to Site Santa Ynez Extension        80 miles          10 horizontal      7.5          50 miles Cape Mendocino, NW          100 miles          10 horizontal      7.5          420 miles Extension of San Andreas fault Gorda Escarpment            40 miles            5 vertical or                  420 miles 7 horizontal (4)    Earthquake D: Should a great earthquake occur on the San Andreas fault, as described in "A" above, large aftershocks may occur out to distances of about 50 miles from the San Andreas fault, but those aftershocks which are not located on existing faults would not be expected to produce new surface faulting, and would be restricted to depths of about 6 miles or more and magnitudes of about 6.75 or less. The distance from the site to such aftershocks Would thus be more than 6 miles.
A further avscssment of the s            petentihal of faults mapped in the region Of DbPP
                                      -ismic site has bccn made follewing the extensivc additional studies of On and off-shorc Section 2.3. This was done interms of ebseismd HOlcpene actiaity, to achieve asscssmc(t of what scismic activity iSreasnably proebable, in tsrMs of obsalied late PdciSteccnc activity, fault dimernionS, and style of dseifmiation.
PG&Eo  was eqursted by the NRe to evaluate the planrt's apability to withstand a postulated Richter Magnitude 7.5 ea8thquake ccntcrcd along an offshore zone of gcologic. faulting, generally referred to as the "Hosgri fault." The detailed m~ethods, Fcsults, and plant medifications performed based on this evaluation arc dealt with in SeeUien 3.7.
The available information sugg -sts-auggegsted that the faults in this region can be associated with contrasting general levels of seismic potential. These are as follows:
(1)    Level I1:Potential for great earthquakes involving surface faulting over distances on the order of 100 miles: seismic activity at this level should occur only on the reach of the San Andreas fault that extends between the locales of Cajon Pass and Parkfield. This was the source of the 1857 Fort Tejon earthquake, estimated to have been of Magnitude 8.
(2)    Level 11: Potential for large earthquakes involving faulting over distances on the order of tens of miles: seismic activity at this level can occur along offshore faults in the Santa Lucia Bank region (the likely source of the-2.5-8
 
DCPP UNITS 1 & 2 FSAR UPDATE Magnitude 7.3 earthquake of 1927), and possibly along the Big Pine and Santa Ynez faults in the Transverse Ranges.
Although the Rinconada-San Marcos-Jolon, Espinosa, Sur-Nacimiento, and San Simeon faults do not exhibit historical or even Holocene activity indicating this level of seismic potential, the fault dimensions, together with evidence of late Pleistocene movements along these faults, suggest that they may be regarded as capable of generating similarly large earthquakes.
(3)    Level IIl: Potential for earthquakes resulting chiefly from movement at depth with no surface faulting, but at least with some possibility of surface faulting of as much as a few miles strike length and a few feet of slip:
Seismic activity at this level probably could occur on almost any major fault in the southern Coast Ranges and adjacent regions.
From the observed geologic record of limited fault activity extending into Quaternary time, and from the historical record of apparently associated seismicity, it can be inferred that both the greater frequency of earthquake activity and larger shocks from earthquake source structures having this level of seismic potential probably will be associated with one of the relatively extensive faults. Faults in the vicinity of the San Luis Range that may be considered to have such seismic potential include the West Huasna, Edna, and offshore Santa Maria Basin East Boundary zone.
(4)    Level IV: Potential for earthquakes and aftershocks resulting from crustal movements that cannot be associated with any near-surface fault structures: such earthquakes apparently can occur almost anywhere in the region.
This information forms the basis of the Desiqn Earthquake, described in Section 2.5.2.10.1.
2.5.2.9.2 Double Design Earthquake In order to assure adequate reserve seismic resistinq capability of safety related structures, systems, and components, an earthquake producing two-times the acceleration values of the Desiqn Earthquake is-was also considered (Reference 51).
2.5.2.9.3 1977 Hosgri Earthquake In 1976. subsequent to the issuance of the construction permit of Unit 1, PG&E was requested by the NRC to evaluate the plant's capability to withstand a postulated Richter Magnitude 7.5 earthquake centered along an offshore zone of geologic faulting, generally referred to as the "Hosgri fault." Details of the investiqations associated with 2.5-9
 
DCPP UNITS 1 & 2 FSAR UPDATE this fault are provided in Appendices 2.5D, 2.5E, and 2.5F of Reference 27 in Section 2.3. An overview is provided in Section 2.5.2.10.3.
During the Hosqri evaluation Phase, a further assessment of the seismic potential of faults mapped in the region of DCPP site was made following the extensive additional studies of on- and offshore geology, and are reported in Appendix 2.5D of Reference 27 of Section 2.3. This was done in terms of observed Holocene activity, to achieve assessment of what seismic activity is probable, in terms of observed late Pleistocene activity, fault dimensions, and style of deformation.
2.5.2.9.4 1991 Long Term Seismic Program Earthquake License Condition No. 2.C.(7) of the Unit 1 Operating License included the following elements pertaining to the seismic design basis for DCPP:
(1)    PG&E shall identify, examine, and evaluate all relevant geologic and seismic data, information, and interpretations that have become available since the 1979 ASLB hearing in order to update the geology, seismology and tectonics in the region of the Diablo Canyon Nuclear Power Plant. If needed to define the earthquake potential of the region as it affects the Diablo Canyon Plant, PG&E will also reevaluate the earlier information and acquire additional new data.
(2)    PG&E shall reevaluate the magnitude of the earthquake used to determine the seismic basis of the Diablo Canyon Nuclear Plant using the information from Element 1.
(3)    PG&E shall reevaluate the ground motion at the site based on the results obtained from Element 2 with full consideration of site and other relevant effects.
(4)      PG&E shall assess the significance of conclusions drawn from the seismic reevaluation studies in Elements 1, 2 and 3, utilizing a probabilistic risk analysis and deterministic studies, as necessary, to assure adequacy of seismic margins.
PG&E's evaluations in response to these elements of the license condition included the development of significant additional data applicable to the geology, seismology, and tectonics of the DCPP region. Based on this data, PG&E identified four capable faults, the Hosgri, Los Osos, San Luis Bay, and Wilmer Avenue faults, requiring evaluation as potential seismic sources (Reference 40, Chapter 3). However, PG&E determined that the governing earthquake for the LTSP deterministic seismic margins review of DCPP (84th percentile ground motion response spectrum) is a Richter Magnitude 7.2 earthquake centered along an offshore zone of geologic faulting, generally referred to as the "Hosgri fault." Details are provided in References 40 and 41. New faults were introduced and evaluated in the 1988 LTSP Report. Details are provided in Reference 40, Chapter 2.0 and summarized in SSER 34, Section 2.5.1, "Geology" and 2.5.2, "Seismology".
2.5-10
 
DCPP UNITS 1 & 2 FSAR UPDATE The NRC's review of PG&E's evaluations is documented in References 42 and 43.
2.5.2.10 Ground Accelerations and Response Spectra The seismic design and evaluation of DCPP is based on the earthquakes described in the following four subsections. Refer to Section 3.7 for the design critera associated with the application of these earthquakes to the structures, systems, and components.
2.5.2.10.1 Maximum Earthquake (Design Earthquake)
During the pre-construction/early-construction phase, tT-he maximum ground acceleration that would occur at DCPP site has-beenwas estimatbd for each of the postulated earthquakes listed in Section 2.5.2.9, using the methods set forth in References 12 and 24. The plant site acceleration is-was primarily dependent on the following parameters: Gutenberg-Richter magnitude and released energy, distance from the earthquake focus to the plant site, shear and compressional velocities of the rock media, and density of the rock. Rock properties are discussed under Section 2.5.1.2.6, Site Engineering Properties.
The maximum rock accelerations that would occur at the DCPP site are-were estimated as:
Earthquake A. .  . . 0.10 g              Earthquake C. .  . . 0.05 g Earthquake B. .  . . 0.12 g              Earthquake D. .  . . 0.20 g In addition to the maximum acceleration, the frequency distribution of earthquake motions is-was important for comparison of the effects on plant structures and equipment. In general, the parameters affecting the frequency distribution are distance to the rupture plane, properties of the transmitting media, length of faulting, focus depth, and total energy release. Radiated E-earthquakes energy that might reach the site after traveling over great distances willwoul4d tend to have their high frequency waves filtered out. Earthquakes ruptures that might be centered close-to the site would-will tend to produce wave forms at the site having minor low frequency characteristics.
In order to evaluate the frequency distribution of earthquakes, the concept of the response spectrum wais used.
Using the attenuation relations available at the time, fWor nearby earthquakes, the resulting response spectra accelerations would-peaked sharply at short periods and would-decayed rapidly at longer periods. Earthquake D would-produced such response spectra. The March 1957 San Francisco earthquake as recorded in Golden Gate Park (S80WE component) was the same type. It produced a maximum recorded ground acceleration of 0.13 g (on rock) at a distance of about 8 miles from the epicenter. Since Earthquake D hads an assigned hypocentral distance of 12 miles, it would-was be-expected to produce response spectra similar in shape to those of the 1957 event.
2.5-11
 
DCPP UNITS 1 & 2 FSAR UPDATE Large earthquakes centered at some distance from the plant site weuld-tended to produce response spectra accelerations that peaked at longer periods than those for nearby smaller shocks. Such spectra maintained a higher spectral acceleration throughout the period range beyond the peak period. Earthquakes A and C awere events that wou-tended to produce this type of spectra. The intensity of shaking as indicated by the maximum predicted ground acceleration showeds that Earthquake C would always have lower spectral accelerations than Earthquake A.
Since the two shocks would have approximately the same shape spectra, Earthquake C would always have lower spectral accelerations than Earthquake A, and it wais therefore eliminated from further consideration. The north-south component of the 1940 El Centro earthquake produced response spectra that emphasized the long period characteristics described above. Earthquake A, because of its distance from the plant site, weuldas be expected to produce response spectra similar in shape to those produced by the El Centro event. Smoothed response spectra for Earthquake A were constructed by normalizing the El Centro spectra to 0.10 g. These spectra, however, showed smaller accelerations than the corresponding spectra for Earthquake B (discussed in the next paragraph) for all building periods, and thus Earthquake A wais also eliminated from further consideration.
Earthquake B-would-tended to produce response spectra that emphasize the intermediate period range in as much as the epicenter wais not close enough to the plant site to produce large high frequency (short-period) effects, and it wais too close to the site and too small in magnitude to produce large low frequency (long-period) effects.
The N69°W component to the 1952 Taft earthquake produced response spectra having such characteristics. That shock was therefore used as a guide in establishing the shape of the response spectra that waseuld-be expected for Earthquake B.
Following several meetings with the AEC staff and their consultants, the following two modifications were made in order to make the criteria more conservative:
(1)    The Earthquake D time-history was modified in order to obtain better continuity of frequency distribution between Earthquakes D and B.
(2)    The accelerations of Earthquake B were increased by 25 percent in order to provide the required margin of safety to compensate for possible uncertainties in the basic earthquake data.
Accordingly, Earthquake D-modified was derived by modifying the S800 E component of the 1957 Golden Gate Park, San Francisco earthquake, and then normalizing to a maximum ground acceleration of 0.20 g. Smoothed response spectra for this earthquake are shown in Figure 2.5-21. Likewise, Earthquake B was derived by normalizing the N69 0W component of the 1952 Taft earthquake to a maximum ground acceleration of 0.15 g. Smoothed response spectra for Earthquake B are shown in Figure 2.5-20. The maximum vibratory motion at the plant site wo-d-.beas produced by 2.5-12
 
DCPP UNITS 1 & 2 FSAR UPDATE either Earthquake D-modified or Earthquake B, depending on the natural period of the vibrating body.
2.5.2.10.2 Double.Design Earthquake The maximum ground acceleration and response spectra for the Double Design Earthquake are twice those associated with the design earthquake, as described in Section 2.5.2.10.1 (Reference 51).
2.5.2.10.3 1977'Hosqri Earthquake As mentioned earlier, based on a review of the studies presented in Appendices 2.5D and 2.5E (of Reference 27 in Section.2.3) by the NRC and the USGS (acting as the NRC's geological consultant), Supplement No. 4 to the NRC Safety Evaluation Report (SER) was issued in May 1976. This supplement included the USGS conclusion that a magnitude 7.5 earthquake could occur on the Hosgri fault at a point nearest to the Diablo Canyon site. The USGS further concluded that such an earthquake should be described in terms of near fault horizontal ground motion using techniques and conditions presented in Geological Survey Circular 672. The USGS also recommended that an effective, rather than instrumental, acceleration be derived for seismic analysis.
The NRC adopted the USGS recommendation of the seismic potential of the Hosgri fault. In addition, based on the recommendation of Dr. N. M. Newmark, the NRC prescribed that an effective horizontal ground acceleration of 0.75g be used for the development of response spectra to be employed in a seismic evaluation of the plant.
The NRC outlined procedures considered appropriate for the evaluation including an adjustment of the response spectra to account for the filtering effect of the large building foundations. An appropriate allowance for torsion and tilting was to be included in the analysis. A guideline for the consideration of inelastic behavior, with an associated ductility ratio, was also established.
The NRC issued Supplement No. 5 to the SER in September 1976. This supplement included independently-derived response spectra and the rationale for their development. Parameters to be used in the foundation filtering calculation were delineated for each major structure. The supplement prescribed that either the spectra developed by Blume or Newmark would be acceptable for use in the evaluation with the following conditions:
(1)    In the case of the Newmark spectra no reduction for nonlinear effects would be taken except in certain specific areas on an individual case basis.
(2)    In the case of the Blume spectra a reduction for nonlinear behavior using a ductility ratio of up to 1.3 may be employed.
2.5-13
 
DCPP UNITS 1 & 2 FSAR UPDATE (3)    The Blume spectra would be adjusted so as not to fall below the Newmark spectra at any frequency.
The development of the Blume ground response spectra, including the effect of foundation filtering, is briefly discussed below. The rationale and derivation of the Newmark ground response spectra is discussed in Appendix C to Supplement No. 5 of the SER.
The time-histories of strong motion for selected earthquakes recorded on rock close to the epicenters were normalized to a 0.75g peak acceleration. Such records provide the best available models for the Diablo Canyon conditions relative to the Hosgri fault zone.
The eight earthquake records used are listed in the table below.
Epicentral                  Peak Depth,                  Distance,                Acceleration Earthquake            M        km Recorded at          km      Component          q Helena 1935            6        5    Helena            3 to 8    EW            0.16 Helena 1935            6      5    Helena            3 to 8    NS            0.13 Daly City 1957          5.3      9    Golden Gate Park 8          N80W          0.13 Daly City 1957          5.3    9    Golden Gate Park    8      NI1E          0.11 Parkfield 1966          5.6      7    Temblor 2            7      S25W          0.33 Parkfield 1966          5.6      7    Temblor 2            7      N65W          0.28 San Fernando 1971      6.6    13    Pacoima Dam          3      S14W          1.17 San Fernando 1971      6.6    13    Pacoima              3      N76W          1.08 The magnitudes are the greatest recorded thus far (September 1985) close in on rock stations and range from 5.3 to 6.6. Adjustments were made subsequently in the period range of the response spectrum above 0.40 sec for the greater long period energy expected in a 7.5M shock as compared to the model magnitudes.
The procedure followed was to develop 7 percent damped response spectra for each of the eight records normalized to 0.75g and then to treat the results statistically according to period bands to obtain the mean, the median,- and the standard deviations of spectral response. At this stage, no adjustments for the size of the foundation or for ductility were made. The 7 percent damped response spectra were used as the basis for calculating spectra at other damping values.
Figures 2.5-29 and 2.5-30 show free-field horizontal ground response spectra as determined by Blume and Newmark, respectively, at damping levels from two to seven percent.
Figures 2.5-31 and 2.5-32 show vertical ground response spectra as determined by, Blume and Newmark, respectively, for two to seven percent damping. The ordinates of vertical spectra are taken as two-thirds of the corresponding ordinates of the horizontal 2.5-14
 
DCPP UNITS 1 & 2 FSAR UPDATE spectra. These response spectra, finalized in 1977, are described as the "1977 Hosgri response spectra ".
2.5.2.10.4 1991 Long Term Seismic Program Earthquake As discussed in Section 2.5.2.9.4, the Long Term Seismic Program, in response to License Condition No. 2.C.(7) determined that the governing earthquake for the deterministic seismic margins evaluation of DCPP (84th percentile ground motion response spectrum) is a Richter Magnitude 7.2 earthquake centered along an offshore zone of geologic faulting, generally referred to as the "Hosgri fault."
Ground motions, and the corresponding free-field response spectra for the LTSP earthquake, were developed by PG&E, as documented in Reference 40. As part of their review of Reference 40, the NRC concluded that spectra developed by PG&E could underestimate the ground motion (Reference 42). As a result, the final spectra, applicable to the LTSP evaluation of DCPP, is an envelope of that developed by PG&E and that developed by the NRC. Figures 2.5-33 and 2.5-34 show the 84th percentile ground motion response spectrum at 5% damping for the horizontal and vertical directions, respectively, described as the "1991 LTSP response spectra". These spectra define the current licensing basis for the LTSP.
Figure 2.5-35 shows a comparison of the horizontal 1991 LTSP response spectrum with the 1977 Newmark Hosgri spectrum (based on Reference 40, Figure 7-2). This comparison indicates that the 1977 Hosgri spectrum is greater than the 1991 LTSP spectrum at all frequencies less than about 15 Hz, but the 1991 LTSP spectrum exceeds the 1977 Hosqiri spectrum by approximately 10 percent for frequencies above 15 Hz. This exceedance was accepted by the NRC in SSER-34 (Reference 42),
Section 3.8.1.1 (Ground-Motion Input for Deterministic Evaluations):
        "On the basis of PG&E's margins evaluation discussed in Section 3.8.1.7 of this SSER, the staff concludes that these high-frequency spectral exceedances are not significant."
In addition, the NRC states in SSER-34 (Reference 42), Section 1.4 (Summary of Staff Conclusions):
        "The staff notes that the seismic qualification basis for Diablo Canyon will continue to be the original design basis plus the Hosqiri evaluation basis, along with the associated analytical methods, initial conditions, etc. The LTSP has served as a useful check of the adequacy of the seismic margins and has generally confirmed that the margins are acceptable."
Therefore, the 1991 LTSP ground motion response spectra supplements, but does not replace or modify, the DE, DDE, or 1977 Hoscqri response spectra described above.
2.5-15
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.4.9 Earthquake Design Basis The earthquakes postulated for DCPP site are discussed in Section 2.5.2.9, and-a discussion of the design response spectra is provided in Section 2.5.2.10, and the application of the earthquake ground motions to the seismic analysis of structures, systems, and components is provided in Section 3.7. Response accGeration c'urves for the site r  t... frm I    Earthquake B and Ea.thquake D modified a,, shown in F.igues 2.5 20  and 2.5  21, respectively. Response spectrum cur(,es for the 7.6M Hosgfi earthquak~e aarc shown in Figurzes 2.5 29 through 2.5 32.
2.5-16
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.6 Long Term Seismic Program On November 2, 1984, the NRC issued the Diablo Canyon Unit 1 Facility Operating License DPR-80. In DPR-80, License Condition Item 2.C.(7), the NRC stated, in part:
        "PG&E shall develop and implement a program to reevaluate the seismic design bases used for the Diablo Canyon Power Plant."
PG&E's reevaluation effort in response to the license condition was titled the "Long Term Seismic Program" (LTSP). PG&E prepared and submitted to the NRC the "Final Report of the Diablo Canyon Long Term Seismic Program" in July 1988 (Reference 40).
Between 1988 and 1991, the NRC performed an extensive review of the Final Report, and PG&E prepared and submitted written responses to formal NRC questions. In February 1991, PG&E issued the "Addendum to the 1988 Final Report of the Diablo Canyon Long Term Seismic Program" (Reference 41). In June 1991, the NRC issued Supplement Number 34 to the Diablo Canyon Safety Evaluation Report (SSER)
(Reference 42) in which the NRC concluded that PG&E had satisfied License Condition 2.C.(7) of Facility Operating License DPR-80. In the SSER the NRC requested certain confirmatory analyses from PG&E, and PG&E subsequently submitted the requested analyses. The NRC's final acceptance of the LTSP is documented in a letter to PG&E dated April 17, 1992 (Reference 43).
The LTSP contains extensive data bases and analyses that update the basic geologic and seismic information in this section of the FSAR Update. The LTSP material does not address or alter the current design licensing basis for the plant. In SSER-34 (Reference 42), the NRC stated, "The Staff notes that the seismic qualification basis for Diablo Canyon will continue to be the original design basis plus the Hosgri Evaluation basis, along with associated analytical methods, initial conditions, etc.
As a condition of the NRC's final acceptance of the LTSP, PG&E committed to ongoing activities in support of the LTSP, described as the "Framework for the Future," in a letter to the NRC, dated April 17, 1991 (Reference 50). These ongoing activities include the following (Reference 42, Section 2.5.2.4):
(1)    To continue to maintain a strong geosciences and engineering staff to keep abreast of new geological, seismic, and seismic engineering information and evaluate it With respect to its significance to Diablo Canyon.
(2)    To continue to operate a strong-motion accelerometer array and the coastal seismic network, although likely with fewer stations than currently operatinq.
The implementation of Activity (1) is described in the following sections: the implementation of Activity (2) is described in Section 3.7.4.
2.5-17
 
DCPP UNITS 1 & 2 FSAR UPDATE A complete listing of bibliographic references to the LTSP reports and other documents may be found in References 40, 41 and 42.
2.5.6.1 Ongoingq Geological and Seismological Investigations As discussed in Section 2.5.6, PG&E committed to ongoing geological and seismological investigations in support of the LTSP, and to evaluate the findings with respect to their significance to DCPP (Reference 42, Section 2.5.2.4).
These investigations are performed by the PG&E Geosciences Department, and include the following:
(1)    Maintain knowledge of maior earthquakes occurrinq worldwide in order to evaluate their significance to DCPP (2)    Review near-fault recordings from any large magnitude earthquakes which occur near DCPP, collected through the seismic monitoring system, operated by PG&E at DCPP (Section 3.7.4) and operated by other agencies in the area (3)    Review and/or participate in the development of new ground motion models (e.g., attenuation relationships)
(4)    Review and evaluate potential changes to source characterization for faults near DCPP (5)    Monitor ground motion data for small and moderate earthauakes occurring near DCPP, collected through PG&E's Central Coast Seismic Network The results of these investigations are used by the PG&E Geosciences Department to develop updated estimates of the ground motion applicable to both the deterministic seismic margin and the seismic probabilistic risk assessment (SPRA) parts of the LTSP evaluation of DCPP, as described in Sections 2.5.6.2.1 and 2.5.6.2.2, respectively.
The development of the updated estimates of ground motion response spectra for each fault under consideration, for use in the deterministic seismic margins evaluation is based on the following:
(1)    The source characterization is developed describing the magnitudes, locations, rates, and faulting styles of future potential earthquakes in the DCPP region. Alternative models are developed to capture the center, body, and range of the scientific (epistemic) uncertainty in the source characterization and are modeled using logic trees. The source characterization will be peer reviewed.
2.5-18
 
DCPP UNITS 1 & 2 FSAR UPDATE (2)    The deterministic earthquake magnitude is selected based on the 90th fractile of the mean characteristic maqnitude from the alternative models defined by the logic tree.
(3)    The distance is established based on the shortest distance from the fault to the DCPP power block (4)    The ground motion characterization is developed describing the median and standard deviation of the ground motion for a given magnitude, distance, style-of-faulting for the DCPP site condition. Alternative ground motion prediction equations (GMPEs) are developed to capture the center, body, and range of the scientific (epistemic) uncertainty in the ground motion models using logic trees. The ground motion characterization will be peer reviewed.
(5)    The deterministic ground motion is computed for each GMPE using the 84th percentile level from the aleatory variability.
(6)    The final deterministic ground motion spectrum is given by the weighted geometric mean of the 84th percentile ground motions from the alternative GMPEs.
The development of the updated estimates of spectral shapes and seismic hazard curves for the SPRA evaluation is based on one of the followina:
(1)    A probabilistic seismic hazard analysis (PSHA) is conducted using the source characterization and ground motion characterization described above.
(2)    The uniform hazards spectra (UHS) are computed based on the mean hazard for a suite of hazard levels (e.g. 1E-3, 1 E-4. 1E-5, 1 E-6, 1E-7).
(3)    At each hazard level, the spectral shape will be based on either the UHS or on a suite of scenario spectra that represent realistic earthquakes.
Ifthe scenario spectra approach is used, the suite of scenario spectra is checked to show that the seismic hazard computed from these spectra envelop the mean hazard curves over frequencies from 0.5 to 330 Hz.
The calculations of the ground motions will follow the PG&E Geosciences Department Quality Assurance (QA) procedure (see Section 17.2.1(4)). In addition, the updated ground motion estimates will be peer reviewed by PG&E's Seismic Advisory Board (SAB). The SAB is comprised of a selection of outside industry experts, and members of the academic community,I I in the followingI mareas of knowledge:I
      -    Ground motions 2.5-19
 
DCPP UNITS 1 & 2 FSAR UPDATE
        -  Seismic hazards
        -  Seismic source characterization
        -  Seismic risk
        -  Seismic fragilities The charter of the SAB is to review the updated seismic hazards calculations for changes in methodologies and key modeling assumptions. In most-cases, the full SAB perform their review arld document the results in a single consensus report. However, in some cases, it may only be necessary to have the review performed by those members with expertise in the technical topic under consideration. In such cases, individual reviews, rather than a consensus review, will be provided. A minimum of two SAB members are required for a specific topic.
An official review letter, documenting the SAB's review and conclusions, is required as part of the peer review process. A written response to the SAB's comments will be prepared by PG&E, documenting how the SAB comments were addressed. The official review letter, and written response to the SAB's comment, will be submitted to the NRC as a part of LTSP update process. The regular ten year update to the LTSP Report will be performed consistent with the recommendations of NUREG/CR-6372, "Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and Use of Experts," for a Level 3 Senior Seismic Hazard Analysis Committee.
It should be noted that since these results are associated with the LTSP, and as discussed in Section 2.5.2.10.4, the NRC has indicated that the LTSP does not redefine the seismic design basis for DCPP, the updated estimates of the ground motion are compared with the current licensing basis for the LTSP, as outlined in Sections 2.5.6.2.1 and 2.5.6.2.2. The 1991 LTSP specfra is enveloped by the 1977 Hosqri Earthquake spectrum (Figure 2.5-35) with the exception of exceedances at certain frequencies, as approved by the NRC in SSER 34.
In no case shall the results of the ongoing investigations in support of the LTSP result in changes to the design basis earthquakes: the DE, as described in Section 2.5.2.10.1; the DDE, as described in Section 2.5.2.10.2; or the 1977 Hosgri earthquake, as described in Section 2.5.2.10.3, except if new ground motion spectra were to exceed both the LTSP spectra and the 1977 Hos-qri spectra at any frequency. A license amendment would be required to address these exceedances.
2.5.6.2 Evaluation of Updated LTSP Ground Motions As a result of the ongoing geological and seismological investigations associated with the LTSP, the PG&E Geosciences Department provides updated ground motion information to DCPP, either on a ten year interval or more frequently as the result of significant new discoveries. The updated ground motions for the LTSP earthquake are defined by each of the following:
2.5-20
 
DCPP UNITS 1 & 2 FSAR UPDATE (1)  84th percentile ground motion response spectrum (spectral acceleration vs. frequency). See Figures 2.5-33 and 2.5-34 for examples.
(2)  Mean probabilistic seismic hazard curves (annual frequency of exceedance vs. average spectral acceleration for the 3.0 to 8.5 Hz frequency range) and ground motion spectral shapes. See Figures 2.5-36 and 2.5-37 for examples.
These two characterizations of the updated ground motion serve as input to the seismic margins evaluation and the seismic probabilistic risk assessment evaluation, as described in Sections 2.5.6.2.1 and 2.5.6.2.2, respectively. An overview of the evaluation for updated LTSP ground motions is shown in Figure 2.5-38.
2.5.6.2.1 Seismic Margin Evaluation The seismic evaluations performed in support of the LTSP (References 40 and 41) demonstrated that DCPP has adequate seismic margins for the ground motions defined by the current licensing basis 1991 LTSP ground motions (Figures 2.5-33 and 2.5-34).
The process for the evaluation of the impact of updated deterministic ground motion response spectra on the LTSP seismic margins evaluation is illustrated in Figure 2.5-38, sheet 2. Guidance in the performance of seismic margins evaluations is provided in EPRI NP-6041-SL (Reference 56). An overview of the seismic marqins evaluation performed for the 1991 LTSP is provided in Section 2.5.6.4 and details are provided in References 40 and 41.
Upon receipt of an updated 84th percentile ground motion response spectrum (horizontal and vertical directions, as applicable) from the PG&E Geosciences Department, -i-theupdated spectrum will be compared to the current licensing basis LTSP spectrum. The two possible outcomes of this comparison will be addressed as follows:
(1)  If the updated spectrum is enveloped by the current licensing basis LTSP spectrum, the seismic margins remain adequate and the results of the comparison shall be documented, as descdbed in Seeten-2.56.3Technical Specification 5.6.11, "Long Term Seismic Program Report." Otherwise, proceed to Step (2).
(2)  If the updated spectrum exceeds the current licensing basis LTSP spectrum at any frequency, engineerinq evaluations are required to assess the impact of the updated ground motions on the seismic margins for DCPP and to determine if changes to the current licensing basis LTSP spectrum is required. The engineering evaluations will include the following:
(a)    A review of the frequency range of the exceedance to determine which structures, systems, or components (SSCs) are impacted. At 2.5-21
 
DCPP UNITS I & 2 FSAR UPDATE this point, it may be necessary to regenerate the in-structure response spectra and/or recompute the high-confidences-low-probability-of-failure (HCLPF) capacities of affected SSCs (see Section 3.7.6.2 for discussion of HCLPF capacities).
(b)    An evaluation of the impact of the exceedances on the seismic margins for the affected SSCs. Note that the seismic margins for all SSCs that have the potential to impact SCDF were in the scope of the LTSP and are listed in Tables 3.7-25 and 3.7-26.
(c)    If the minimum seismic margin remains greater than or equal to 1.3 (or greater than or equal to the approved seismic margin exceptions for certain SSCs discussed in Section 2.5.6.2.1.1), the updated response spectrum is acceptable and proceed to Step (3).
Otherwise, proceed to Step (d).
(d)      Ifthe minimum seismic margin is greater than or equal to 1.0 (or greater than or equal to the approved seismic margin exceptions for certain SSCs discussed in Section 2.5.6.2.1.1), the SSC can perform its safety function, proceed to Step (f). Otherwise, proceed to Step (e).
(e)    The applicable TS Limiting Condition for Operation shall be entered for the SSCs having a minimum seismic margin less than 1.0 (unless the SSC is one of the approved seismic margin exceptions below 1.0 discussed in Section 2.5.6.2.1.1). Appropriate compensatory measures are to be implemented if feasible.
(f)    Develop and implement modifications to impacted SSCs to achieve a minimum seismic margin of 1.3 (or to achieve the approved seismic margin exception discussed in Section 2.5.6.2.1.1).
(3)    Process a change to the licensing basis 1991 LTSP spectrum (and 1977 Hosgri spectrum if it is exceeded at any frequency or iustify why a change is not necessary) through the license amendment request process. Once the license amendment has been issued, proceed to Section 2.5.6.3.
2.5.6.2.1.1 Approved Minimum Seismic Margins Less Than 1.3 Even though the target minimum seismic margin for SSCs within the scope ofthe LTSP is 1.3, exceptions to this value have been accepted on a case-by-case basis for certain SSCs. The following provides a summary of these exceptions:
(1)    Exceptions previously approved by the NRC 2.5-22
 
DCPP UNITS 1 & 2 FSAR UPDATE The following exceptions to the target minimum seismic margin of 1.3 are associated with SSCs as the existed during the 1991 LTSP evaluation.
These exceptions were previously approved by the NRC (Reference 42).
(a)    Turbine Building As indicated in Table 3.7-25, the HCLPF84 capacity of the turbine building is 2.21 q, based on the fragility analysis method, giving a seismic margin of 1.14, which is less than the target minimum margin of 1.3. The limiting capacity is associated with the onset of severe structural distress (significant strength degradation) to the maior east-west shear walls. Due to the fact that the turbine houses various components associated with the vital electrc power system (e.g., emergency diesel generators and 4160V vital switchgear) and the vital cooling water system (e.g., component cooling water heat exchangers), coupled with the fact that this is the structure with the lowest seismic capacity, the overall plant fragility is governed by this building.
In order to evaluate the conservatism of the reported HCLPF84 capacity, a rigorous seismic evaluation was performed using state-of-the-art analytical methods beyond those normally employedfor the fragility analysis method. This evaluation utilized multiple non-linear time history analyses (Reference 57) to estimate the seismic capacity associated with the ultimate failure of the structure. The results of these analyses indicated that a realistic estimate of the seismic margin is likely in excess of 1.40. These analyses were reviewed and acceptable by the NRC (Reference 43).
(b)    4160V Vital Switchgear Relay Chatter As indicated in Table 3.7-26, the HCLPF84 capacity associated with chatter of the overcurrent relays in the 4160V vital switchgear is 1.57 g, giving a seismic margin of 0.81, which is less than the target minimum margin of 1.3. However, the failure mode associated with this chatter is recoverable by operator action from the Control Room (resetting the relays), and the probabilities associated with operator action have been included in the PRA model for the system. The PRA model indicates that this failure mode does not have a significant impact on the core damage frequency. This evaluation was reviewed and accepted by the NRC (Reference 43).
2.5-23
 
DCPP UNITS 1 & 2 FSAR UPDATE (c)    230kV Offsite Power System/Switchyard As indicated in Table 3.7-26, the HCLPF84 capacity associated with 230kV offsite power system is 0.84 q, giving a seismic margin of 0.43, which is less than the target minimum marqin of 1.3. This capacity is limited by the failure of ceramic insulators, transformers, and circuit breakers, and is based on the earthquake experience data method (Section 3.7.6.2.3), as documented in Reference 58, Since this system is the primary source of offsite power, it is assumed to be lost due to a maior earthquake, with back-up power provided by the emer-gency diesel generators. However, in order to allow rapid recovery of offsite power, key spare parts are stored onsite. These parts include items such as conductors, connectors, insulators, and transformer bushings. The maintenance of the spare parts is a licensing commitment made in References 40 and 58, as acknowledged by the NRC in Reference 42.
(2) Exceptions Associated with Additions and Modifications The following exceptions to the target minimum seismic margin of 1.3 are associated with additions and modifications implemented subsequent to the completion of the 1991 LTSP evaluation. The acceptance of the lower seismic margin is based on the requirements of Reference 59. which permitted the acceptance of seismic margins as low as 1.14 for plant modifications and additions.
(a)    Integrated Head Assembly Integrated head assemblies (IHAs) were installed in Units 1 and 2 during refueling outage nos. 2R15 and 1R16, respectively. The IHAs are classified as new components which could significantly impact the seismic margins of existing safety-related structures (see Section 3.7.6.1.1), since they are attached to the reactor vessel closure heads and provide support to the control rod drive mechanisms (CRDMs), small bore piping, instrumentation, and cables. An assessment of their impact on the seismic PRA indicated that the key function is the lateral support of the CRDMs, since excess deflection of the CRDMs could impair the downwards movement of the control rods, required for reactor trip.
The HCLPF84 capacity associated with the limiting element of the, CRDM lateral support function of the IHAs, developed based on the conservative deterministic failure margins method (Section 3.7.6.2.2), is 2.40 q, giving a seismic margin of 1.24.
2.5-24
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.6.2.2 Seismic Probabilistic Risk Assessment Evaluation The LTSP evaluation for DCPP also included a Seismic Probabilistic Risk Assessment (SPRA), which estimated the annual seismic core damaae frequency (SCDF)
(References 40 and 41). The process for the SPRA evaluation of the updated seismic hazard information is illustrated in Figure 2.5-38, sheet 3. c If the UHS approach is used, the input-to the SPRA evaluation includes:
(1)  Seismic hazard curves provided by the PG&E Geosciences Department.
See Figure 2.5-36 for an example.
(2)  Ground motion spectral shapes provided by the PG&E Geosciences Department. See Figure 2.5-37 for an example.'
(3)  Fragilities developed in accordance with ASME/ANS RA-Sa-2009 (Reference 54). See Figure 2.5-39 for an example.
Other methods for developing seismic hazard information are allowed provided they are peer reviewed.
The evaluation of the updated seismic hazards information will proceed as follows:
(1)  Conduct SPRA to determine current SCDF value. Note that the SPRA is classified as Capability Category II per ASME/ANS RA-Sa-2009 (Reference 54), as modified by Regulatory Guide 1.200, rev. 2 (Reference
: 55) and is subiect to a peer-review process.
(2)  Report the calculated SCDF to the NRC.
(3)  Document updated seismic hazard information, fragilities, and SDCF in DCPP records.
(4)  Update LTSP documentation.
2.5.6.3 LTSP Configuration Control The implementation of the LTSP seismic PRA relies on several key items to assure an acceptable level of core damage frequency. The following items must be maintained in the proper configuration to assure continued validity of the seismic PRA (Reference 41):
(1)  Diesel Fuel Oil Transfer System In order to assure a reliable supply of fuel oil for the diesel generators, the following features associated with the diesel fuel oil system shall be maintained:
2.5-25
 
DCPP UNITS 1 & 2 FSAR UPDATE (a)    Recirculation lines to allow the system to operate continuously once a start demand has been received for any day tank. level.
(b)    Provisions for the manual operation of the level control valves on the day tanks.
(c)    Provisions for the connection of a portable engine-driven pump to the transfer system.
(2)  Centrifugal Chargqing Pump Backup Cooling In order to assure adequate cooling of the centrifugal changing pump lube oil and seal coolers, in the event of the complete loss of component cooling water, provisions are provided for the use of firewater to cool the pumps. This is accomplished through the use of dedicated hoses to interconnect the firewater header and the charqing pump coolers. This feature is in support of reactor coolant pump seal iniection and seal cooling.
(3)  230kV Offsite Power System Spare Parts In order to ensure post-earthquake restoration of this system in a timely manner, key spare parts for the 230kV offsite power system shall be stored on site.
(4)  4160V Overcurrent Relay Remote Reset In order to recover from breaker trips in the 4160V switchgear, the capability to reset an overcurrent trip from the control room shall be maintained.
(5)  Component Cooling Water and Safety Iniection Valve Control Switches In order to prevent relay chatter-induced position changes for the component cooling water pump discharge valves and the safety iniection pump suction valves, the two-position valve control switches (with maintained contacts) shall be maintained.
2.5.6.4 Elements of a Seismic Margins Evaluation The elements of the seismic margins evaluation are as follows:
(1)  Determine the seismic demand associated with the deterministic -ground motion (Figure 2.5-33). The seismic demand for the ground motion is 2.5-26
 
DCPP UNITS 1 & 2 FSAR UPDATE defined as the 5 percent damped spectral acceleration averaged between 3 and 8.5 Hz. This is illustrated on Figure 2.5-40.
(2)    Determine the seismic capacity of each structure, system, or component (SSC) within the LTSP scope. The seismic capacity for SSCs at DCPP is defined based on the High Confidence Lower Probability of Failure (HCLPF) 5 percent damped spectral acceleration capacity averaged between 3 and 8,5 Hz. This value can be determined using the fragility analysis method (Section 3.7.6.2.1), the conservative deterministic failure margins method (Section 3.7.6.2.2), or the earthquake experience data method (Section 3.7.6.2.3). This is also illustrated on Figure 2.5-40.
(3)    In general, the seismic margin is defined as the ratio of the capacity of the SSC to the demand. However, this value must be adiusted to account for the demand contributions associated with other applicable loads (e.g., deadweight, pressure, thermal).
Note that the process for the seismic margins evaluation, described above, is in terms of the horizontal grbund motion and the capacity of the SSC relative to horizontal input motion. A similar approach can be applied to the vertical ground motion and the capacity of the SSC relative to vertical input motion. However, as discussed in Chapter 6 of Reference 40, the capacities of most SSCs are dominated by their response to horizontal input motion, and the contribution due to vertical input motion is generally small. Therefore, the consideration of the impact of vertical input motion on the seismic margin of a specific SSC will be addressed on a case-by-case basis.
2.5-27
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5.67 REFERENCES
: 1. R. H. Jahns, "Geology of the Diablo Canyon Power Plant Site, San Luis Obispo County, California," 1967-Supplementary Reports I and II, 1968-Supplementary Report Ill, Diablo Canyon PSAR, Docket No. 50-275, (Main Report and Supplementary Report I). Diablo Canyon PSAR, Docket No. 50-323, (All reports, 1966 and 1967).
: 2. R. H. Jahns, "Guide to the Geology of the Diablo Canyon Nuclear Power Plant Site, San Luis Obispo County, California," Geol. Soc. Amer., Guidebook for 66th Annual Meeting, Cordilleran Section, 1970.
: 3. Deleted in Revision 1
: 4. Deleted in Revision 1
: 5. H. Benioff and S. W. Smith, "Seismic Evaluation of the Diablo Canyon Site,"
Diablo Canyon Unit 1 PSAR, Docket No. 50-275. Also, Diablo Canyon Unit 2 PSAR Docket No. 50-323, 1967.
: 6. John A. Blume & Associates, Engineers, "Earthquake Design Criteria for the Nuclear Power Plant - Diablo Canyon Site," Diablo Canyon Unit 1 PSAR, Docket No. 50-275., January 12, 1967. Also, Diablo Canyon Unit 2 PSAR Docket No. 50-323.
: 7. John A. Blume & Associates, Engineers, "Recommended Earthquake Design Criteria for the Nuclear Power Plant - Unit No. 2, Diablo Canyon Site," Diablo Canyon Unit 2 PSAR, Docket No. 50-323, June 24, 1968.
: 8. Deleted in Revision 1
: 9. Deleted in Revision I
: 10. B. M. Page, "Geology of the Coast Ranges of California," E. H. Bailey (editor),
Geology of Northern California, California Division, Mines and Geology, Bull. 190, 1966, pp 255-276.
: 11. B. M. Page, "Sur-Nacimiento Fault Zone of California: Continental Margin Tectonics," Geol. Soc. Amer., Bull., Vol. 81, 1970, pp 667-690.
: 12. J. G. Vedder and R. D. Brown, "Structural and Stratigraphic Relations Along the Nacimiento Fault in the Santa Lucia Range and San Rafael Mountains, California," W. R. Dickinson and Arthur Grantz (editors), Proceedings of Conference on Geoloqic Problems of the San Andreas Fault System, Stanford University Pubis. in the Geol. Sciences, Vol. XI, 1968, pp 242-258.
2.5-28
 
DCPP UNITS 1 & 2 FSAR UPDATE
: 13. C. F. Richter, "Possible Seismicity of the Nacimiento Fault, California," Geol.
Soc. Amer., Bull., Vol. 80, 1969, pp 1363-1366.
: 14. E. W. Hart, "Possible Active Fault Movement Along the Nacimiento Fault Zone, Southern Coast Ranges, California," (abs.), Geol. Soc. Amer., Abstracts with Programs for 1969, pt. 3, 1969, pp 22-23.
: 15. R. E. Wallace, "Notes on Stream Channels Offset by the San Andreas Fault, Southern Coast Ranges, California," W. R. Dickinson and Arthur Grantz (editors),
Proceedings of Conference on Geologic Problems of the San Andreas Fault System, Stanford University Pubis. in the Geol. Sciences, Vol. XI, 1968, pp 242-258.
: 16. C. R. Allen, "The Tectonic Environments of Seismically Active and Inactive Areas Along the San Andreas Fault System," W. R. Dickinson and Arthur Grantz (editors), Proceedings of Conference on Geologic Problems of the San Andreas Fault System, Stanford University Pubis. in the Geol. Sciences, Volume XI, 1968, pp 70-82.
: 17. Deleted in Revision 1
: 18. Deleted in Revision 1
: 19. L. A. Headlee, Geology of the Coastal Portion of the San Luis Range, San Luis Obispo County, California, Unpublished MS thesis, University of Southern California, 1965.
: 20. C. A. Hall, "Geologic Map of the Morro Bay South and Port San Luis Quadrangles, San Luis County, California," U.S. Geological Survey Miscellaneous Field Studies Map MF-511, 1973.
: 21. C. A. Hall and R. C. Surdam, "Geology of the San Luis Obispo-Nipomo Area, San Luis Obispo County, California," Geol. Soc. Amer., Guidebook for 63rd Ann.
Meeting, Cordilleran Section, 1967.
: 22. R. F. Yerkes and R. 0. Castle, "Surface Deformation Associated with Oil and Gas Field Operations in the United States in Land Subsidence," Proceedings of the Tokyo Symposium, Vol. 1, 1ASH/Al HS Unesco, 1969, pp 55-65.
: 23. C. W. Jennings, et al., Geologic Map of California, South Half, scale 1:750,000, California Div. Mines and Geology, 1972.
: 24. John H. Wiggins, Jr., "Effect of Site Conditions on Earthquake Intensity," ASCE Proceedings, Vol. 90, ST2, Part 1, 1964.
2.5-29
 
DCPP UNITS I & 2 FSAR UPDATE
: 25. B. M. Page, "Time of Completion of Underthrusting of Franciscan Beneath Great Valley Rocks West of Salinian Block, California," Geol. Soc. Amer., Bull., Vol. 81, 1970, pp 2825-2834.
: 26. Eli A. Silver, "Basin Development Along Translational Continental Margins,"
W. R. Dickinson (editor), Geologic Interpretations from Global Tectonics with Applications for California Geology and Petroleum Exploration, San Joaquin Geological Society, Short Course, 1974.
: 27. T. W. Dibblee, The Riconada Fault in the Southern Coast Ranges, California.
and Its Significance, Unpublished abstract of talk given to the AAPG, Pacific Section, 1972.
: 28. D. L. Durham, "Geology of the Southern Salinas Valley Area, California,"
U.S. Geol. Survey Prof. Paper 819, 1974, p 111.
: 29. William Gawthrop, Preliminary Report on a Short-term Seismic Study of the San Luis Obispo Region, in May 1973 (Unpublished research paper), 1973.
: 30. S. W. Smith, Analysis of Offshore Seismicity in the Vicinity of the Diablo Canyon Nuclear Power Plant, report to Pacific Gas and Electric Company, 1974.
: 31. H. C. Wagner, "Marine Geology between Cape San Martin and Pt. Sal, South-Central California Offshore; a Preliminary Report, August 1974," USGS Open File Report 74-252, 1974.
: 32. R. E. Wallace, "Earthquake Recurrence Intervals on the San Adreas Fault",
Geol. Soc. Amer., Bull., Vol. 81, 1970, pp 1875-2890.
: 33. J. C. Savage and R. 0. Burford, "Geodetic Determination of Relative Plate Motion in Central California", Jour. Geophys. Res., Vol. 78, No. 5, 1973, pp 832-845.
: 34. Deleted in Revision 1
: 35. Hill, et al., "San Andreas, Garlock, and Big Pine faults, California" - A Study of the character, history, and significance of their displacements, Geol. Soc. Amer.,
Bull., Vol. 64, No. 4,1953, pp 443-458.
: 36. C.A. Hall and C.E. Corbato, "Stratigraphy and Structure of Mesozoic and Cenozoic Rocks, Nipomo Quadrangle, Southern Coast Ranges, California,"
Geol. Soc. Amer., Bull., Vol. 78, No. 5,1969, pp 559-582. (Table 2.5-3, Sheet I of 2).
2.5-30
 
DCPP UNITS 1 & 2 FSAR UPDATE
: 37. Bolt, Beranek, and Newman, Inc., Sparker Survey Line, Plates III and IV, 1973/1974. (Appendix 2.5D, to Diablo Canyon Power Plant Final Safety Analysis Report as amended through August 1980). (See also Reference 27 of Section 2.3.)
: 38. R. R. Compton, "Quatenary of the California Coast Ranges," E. H. Bailey (editor),
Geology of Northern California, California Division Mines and Geology, Bull. 190, 1966, pp 277-287.
: 39. Regulatory Guide 1.70, Revision 1, Standard Format and Content of Safety Analysis Reports for Nuclear Power Plants, USNRC, October 1972.
: 40. Pacific Gas and Electric Company, Final Report of the Diablo Canyon Long Term Seismic Program, July 1988.
: 41. Pacific Gas and Electric Company, Addendum to the 1988 Final Report of the Diablo Canyon Long Term Seismic Program, February 1991.
: 42. NUREG-0675, Supplement No. 34, Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units I and 2, USNRC, June 1991.
: 43. NRC letter to PG&E, Transmittal of Safety Evaluation Closing Out Diablo Canyon Lonq-Term Seismic Program, (TAC Nos. M80670 and M80671), April 17, 1992.
: 44. Pacific Gas and Electric Company, Assessment of Slope Stability Near the Diablo Canyon Power Plant, April 1997.
: 45. Harding Lawson Associates, Liquefaction Evaluation - Proposed ASW Bypass -
Diablo Canyon Power Plant, August 23, 1996.
: 46. Harding Lawson Associates Letter, "Geotechnical Consultation - Liquefaction Evaluation - Proposed ASW ,Bypass - Diablo Canyon Power Plant,"
October 1, 1996.
: 47. Harding Lawson Associates Report, Geotechnical Slope Stability Evaluation -
ASW System Bypass, Unit I - Diablo Canyon Power Plant, July 3, 1996.
: 48. License Amendment Request 97-11, Submitted to the NRC by PG&E Letters DCL-97-150, dated August 26, 1997; DCL-97-177, dated October 14,1997; DCL-97-191, dated November 13,1997; and DCL-98-013, dated January 29, 1998.
: 49. NRC Letter to PG&E dated March 26, 1999, granting License Amendment No. 131 to Unit 1 and No. 129 to Unit 2.
2.5-31
 
DCPP UNITS 1 & 2 FSAR UPDATE
: 50. PG&E letter to the NRC, "Benefits and Insights of the Long Term Seismic Proaram." DCL-91-091. Aoril 17. 1991.
: 51. John A. Blume and Associates letter to PG&E, "Earthquake Design Criteria for the Nuclear Power Plant - Diablo Canyon Site," January 12, 1967.
: 52. Seismic and Geologic Siting Criteria for Nuclear Power Plants, Appendix A to 10 CFR 100.
: 53. PG&E letter to the NRC, "Long Term Seismic Program - Additional Deterministic Evaluations," DCL-90-226, September 18, 1990.
: 54. American Society of Mechanical Engineers/American Nuclear Society, "Addenda to ASME/ANS RA-Sa-2008, Standard for Level 1/Larqe Early Release Frequency Probabilistic Risk Assessment of Nuclear Power Plant Applications," Standard No. ASME/ANS RA-Sa-2009.
: 55. United States Nuclear Regulatory Commission, "An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities," Regulatory Guide 1.200, Revision 2, March 2009.
: 56. Electric Power Research Institute, "A Methodology for the Assessment of Nuclear Power Plant Seismic Margins," Report No. NP-6041-SL, Revision 1, August 1991.
: 57. NTS, Inc., "Probabilistic Evaluation of the Diablo Canyon Turbine Building Seismic Capacity Using Nonlinear Time History Analyses," Report No. 1643.01, December 1988.
: 58. PG&E letter to the NRC, "Long Term Seismic Program - Seismic Capacity of the 230 kV Switchyard," DCL-90-205, October 8, 1990.
: 59. PG&E letter to the NRC, "Long Term Seismic Program - Future Plant Modifications." DCL-91-178. July 16. 1991.
2.5-32
 
DCPP UNITS 1 & 2 FSAR UPDATE 2.5 1.5 0.0 ,      I 0.00  0.20  0.40  0.60  0.80      1.00    1.20  1.40  1.60  1.80  2.00 Period (sec.)
Notes:
: 1. This figure is based on Reference 42. Figure 2.4, FSAR UPDATE UNITS I AND 2 DIABLO CANYON SITE FIGURE 2.5-33 FREE FIELD SPECTRA HORIZONTAL 1991 LTSP (84TH PERCENTILE NON-EXCEEDANCE)
AS MODIFIED PER SSER-34 2.5-33
 
DCPP UNITS 1'& 2 FSAR UPDATE 2.5 5% Dampl ig 2.0 A  1.5
        ,K 1.0 0.5 0.0 L-      A-    £      -    £          -      -
0.0 0 0.20  0,40  0.60  0.80      1.00    120  140  1.60      1.80 2.00 Period (sec.)
Notes:
: 1. This fiaure is based on Reference 42. Fiaure 2.5.
FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 2.5-34 FREE FIELD SPECTRA VERTICAL 1991 LTSP (84TH PERCENTILE NON-EXCEEDANCE)
AS MODIFIED PER SSER-34 2.5-34
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.0 2.5 2.0
                    *, 1.5 1.0 0.5 0.0 0.10          1.00                  10.00            100.00 Frequency (Hz)
Notes:
: 1. This figure is based on Reference 40, Figure 7-2, but the LTSP response spectrum has been adiusted in accordance with Reference 42, Figure 2.5
: 2. This figure is for comparison purposes only and shall not be used for design
: 3. Legend:
    - 1977 Hosgri (Newmark) corresponds to the spectrum shown in Figure 2.5-30
    - 1991 LTSP corresponds to the spectrum shown in Figure 2.5-33 FSAR UPDATE UNITS I AND 2 DIABLO CANYON SITE FIGURE 2.5-35 FREE FIELD SPECTRA - HORIZONTAL LTSP (PG&E 1988) GROUND MOTION HOSGRI (NEWMARK 1977) 2.5-35
 
DCPP UNITS 1 & 2 FSAR UPDATE Mean 1988 LTSP Hazard 0.1
__  _      __              _          I                    _            _    _    ,._
0.01
_-"-*-                                Mean 1988 LTSP Hazard 0.001 0
W 0.0001 Lii C
___    ___    _    __ __I___                  _    __  __    _n_
0.00001 0.000001 0.0000001 0    0.5          1        1.5          2        2.5          3      3.5        4          4.5 Spectral Acceleration, 3.0 to 8.5 Hz (g)
Notes:
: 1. This fiure is based on Reference 40, Figures 6-6 and 6-8.
2: The seismic hazard curve defined in Reference 40 (1988 LTSP) was not affected by the adiustments to the LTSP ground motion response spectra described in Reference 42. Therefore, a seismic hazard curve is not defined for the 1991 LTSP ground motion.
: 3. This figure is for information only and should not be used for the evaluation of the DCPP seismic probabilistic risk assessment.
FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 2.5-36 1988 LTSP SEISMIC HAZARD CURVE 2.5-36
 
DCPP UNITS 1 & 2 FSAR UPDATE I      t    I    i  I  Ai  I I            I      I    I            I  I
: 3.  -,
S2.-
0 Co'                                                                              -Hazard = 10 '5 Hazard = 10 -4 Hazard = 10 -3
: 0. -I                                                                          a l  mu l L a
4
                                                                                                -r rf
* i 0
10                                            10                                          102 Frequency (hertz)
Notes:
: 1. This fiqure is based on Reference 40, Figure 6-9.
: 2. This figure is for information only and should not be used for the evaluation of the DCPP seismic probabilistic risk assessment.
FSAR UPDATE UNITS I AND 2 DIABLO CANYON SITE FIGURE 2.5-37 1991 LTSP UNIFORM HAZARD SPECTRUM 2.5-37
 
DCPP UNITS 1 & 2 FSAR UPDATE DCPP Long Term Seismic Program Update Evaluation of Updated Seismic Hazard Information II[Flowchart                      A - Overview.
        .Process 6or Upae  *to        thbe Long                Prgram rermmSeis (LTSP)
      ' ,., eisn*mic Prob'*bilist-i-c R~isk ind :ei~ni6    *'rgins'Ases~ment;. *-
(to be perf`r*m*      bna. 10-*a irbtera)
                              .2.3/4 Updated LTSP. Seisic Hazsrd Input" Information Recedby D.PP.-.
o.FTen Years S A~c~e-
                          -,r                      Prp        ae Setismic*                                                                Seism ilisic Rsk ssesmentj                              Mrginsý Assessme y P80                                                            Pdlmmýa th,.i fib Sofky Rik Ao,-,11t                                              UAssf  .OcblkvO=tni iOWChart            -5uiltPareiee
                              -- ,NuclearRatrRegulaio FSAR UPDATE UN ITS 1 AND 2 DIABLO CANYON SITE F                                                                                FIGUFRE 2.5-38 FLOWCHART FOR EVALUATION OF UPDATED LTSP GROUND MOTION (SHEET 1 OF 3) 2.5-38
 
DCPP UNITS 1 & 2 FSAR UPDATE DCPP. Long Term Seismic Program Update Evaluation of Updated Seismic Hazard .1hformration Flowchart B - Seismic Margins Assessment Notes:
FSAR UPDATE
: 1) Or -greater than or equal to the approved seismic                                  UNITS I AND 2 marqin exceptions for certain SSCs discussed in                            DIABLO CANYON SITE FSARU Section 2.5.6.2.1.1.
: 2) Unless the SSC is one of the approved seismic                                      FIGURE 2.5-38 marain exceotions below 1.0 discussed in FSARU                      FLOWCHART FOR EVALUATION OF Section 2.5.6.2.1.1.
: 3) Or to achieve the minimum approved seismic                        UPDATED LTSP GROUND MOTION margin exception discussed in FSARU Section                                      (SHEET 2 OF 3) 2.5.6.2.1.1.
2.5-39
 
DCPP UNITS 1 & 2 FSAR UPDATE l DCPP Long Term SeismicOProgram Update Eyaluation of Updated Seismic Hazard Information Flowchart C- Seismic ProbabilisticRisk Assessment Updatedd Seimi*. Hazard Inrmatii fof
        ;- Received by D*CPP.or 10 eaUpdafe'.;:          i          ::
S....-Updated Grounrd.Motion          pectral ,Shape (SS).'    .,
I                                                            I SeisicPrbaistic RisCAssessme6nt(SPRA)
Updaie  Seismi                  _azrdCwe(Hc)
(SCDF')
                  *.:,* -* Upla~ted InputInformalion.,:,..
                          *'.3rated Methgd~o~g$.sien      .Up'd.y*
                                                                -L::
                          -COM        SCoF G-~:*  .                        '
Fia,.gi i ies::-ý6;68:7*
l.-.dcPRepords.*        "
                            -!. ;.-      2,****.*          ..
FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 2.5-38 FLOWCHART FOR EVALUATION OF UPDATED LTSP GROUND MOTION (SHEET 3 OF 3) 2.5-40
 
DCPP UNITS 1 & 2 FSAR UPDATE Best estimate fragility curve 1.00 0.75 C
c1=o 0.50                                                                      Fragility curves having C4i                                      different confidence levels 0.25 Median ground spectral acceleration 0.05 0
0            HCLPF                    v Sa Ground spectral acceleration (Sa)
Notes:
: 1. This fiqure is based on Reference 40, Figure 6-10.
: 2. This figure is for information only and should not be used for the evaluation of the DCPP seismic probabilistic risk assessment.
FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 2.5-39 1991 LTSP FRAGILITY CURVE REPRESENTATION 2.5-41
 
DCPP UNITS 1 & 2 FSAR UPDATE Co t
Ca 8.5, Frequency (Hz)
Notes:
: 1. This figure is based on Reference 40, Figure 7-40.
: 2. This figure is for information only and should not be used for the evaluation of the DCPP seismic margins.
FSAR UPDATE UNITS I AND 2 DIABLO CANYON SITE FIGURE 2.5-40 SCHEMATIC ILLUSTRATION FOR THE DETERMINATION OF SEISMIC MARGINS
-N 2.5-42
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.1.2.2 Criterion 2 - Performance Standards (Category A)
Those systems and components of reactor facilities that are essential to the prevention of accidents which could affect the public health and safety, or to mitigation of their consequences, shall be designed, fabricated, and erected to performance standards that will enable the facility to withstand, without loss of the capability to protect the public, the additional forces that might be imposed by natural phenomena such as earthquakes, tornadoes, flooding conditions, winds, ice, and other local site.effects. The design bases so established shall reflect (a) appropriate consideration of the most severe of these natural phenomena that have been recorded for the site and the surrounding area, and (b) an appropriate margin for withstanding forces greater than those recorded to reflect uncertainties about the historical data and their suitability as a basis for design.
Discussion All systems and components designated Design Class I are designed so that there is no loss of function for ground acceleration associated with the two timos the d*sign ea4r.hq              Design earthquake (DDE) and the Hosgri earthquake (HE), acting in
                ,Double the horizontal and vertical directions simultaneously. The ESF i engiineered safety features are included in the above. The working stresses for Class I items are kept within code allowable values for the Design Earthquake (DE). Seismic classification and seismic design criteria are discussed in Sections 3.2 and 3.7 through 3.10, respectively. Similarly, measures are taken in the plant design to protect against possible effects of tsunamis, lightning storms, strong winds, and other natural phenomena.
The site characteristics are discussed in Chapter 2. Wind design criteria and flood design criteria are found in Sections 3.3 and 3.4, respectively.
3.1-1
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.2    CLASSIFICATION OF STRUCTURES, SYSTEMS, AND COMPONENTS This section provides a guide to the classification of the DCPP structures, systems, and components (SSCs).
Criterion 1 of the July 1967 GDC requires that systems and components essential to the prevention of accidents be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed.
This section describes how Criterion 1 has been implemented by relating the classifications of SSCs to the various criteria, codes, regulations, and standards that dictate specific quality requirements.
In this regard, it is recognized that during the design and construction of DCPP Units 1 and 2, significant industry and regulatory changes were made in establishing common methods of classification, e.g., ANSI N18.2 (Reference 1)04, SG 26 (Reference 2P*, SG 29 (Reference 3)9, and NRC Regulatory Guide (RG) 1.143 (Reference 6)t6. These methods all differ slightly in detail from those used for the DCPP, but the form and intent of all are equivalent, as will be shown in the fo.lowi ng* ,..ssion u    of: (a) the seimic.
classification of SS~s, and (b) the system quality group classification Of preSSUre containing cOMPon.ntS of fluid syst.m" Sections 3.2.1 through 3.2.5.
Classifications of instruments and controls and the associated requirements feo them are discussed in Section 7.1.
The general applicability and requirements of the DCPP classification systems are provided in Tables 3.2-1 and 3.2-2. The classifications of specific SSCs are provided in the DCPP Q-List( (Reference 8). The DCPP Q-List is controlled by a written PG&E procedure. The procedure requires that all non-editorial changes to the contents of the Q-List be reviewed pursuant to the requirements of 10 CFR 50.59. Access to the Q-List is available through hard copy or electronically at PG&E.
3.2.1 SEISMIC CLASSIFICATION Criterion 2 of the July 1967 GDC, and Appendix A to 10 CFR 100, Seismic and Geologic Siting Criteria for Nuclear Power Plants (Reference 11 )", require that nuclear power plant SSCs important to safety be designed to withstand the effects of earthquakes. Specifically, Appendix A to 10 CFR 100 requires that all nuclear power plants be designed for the following two earthquakes:
(1) sehat.,iftThe
              .                safe shutdown earthquake (SSE) is that earthquake which is based on an evaluation of the maximum earthquake potential considering the regional and local geology and seismology and specific characteristic of local subsurface material. It is the earthquake which produces the maximum vibratory ground motion for which certain structures, systems, and components are designed to remain functional.
These structures, systems, and components are those necessary to 3.2-1
 
DCPP UNITS 1 & 2 FSAR UPDATE assureeO..uS, all structur.s and compon.nts important to safety ro...n fURct oal. Plant features important to safety arc these nccessary to ensUre-(a)  the integrity of the reactor coolant pressure boundary, (b)  the capability to shut down the reactor and maintain it in a safe shutdown condition, or (c)  the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures of 10 CFR 100.
(2)    The operating basis earthquake (OBE) is that earthquake which, considering the regional and local geology and seismology and specific characteristics of local subsurface material, could reasonably be expected to affect the plant site during the operating life of the plant; it is that earthquake which produces the vibratory ground motion for which those features of the nuclear power plant necessary for continued operation without undue risk to the health and safety of the public are designed to remain functional.
Since DCPP design and construction had progressed substantially prior to the issuance of Appendix A to 10 CFR 100, different terminology is used for the design basis earthquakes. The following equivalencies have been established between the DCPP design basis earthquakes and those defined in Appendix A to 10 CFR 100:
Thc SSE of Appendix A to 10 CFR 100 is c                  to the DCPP double design-
                                                  'ui'.'alent earthquake (DDE=) (see Rfrences 9 and 10 for final resolution o~f issues raised in Suppl emental Safety Evaluation Reports 7, 8, and 31 relative to the SSE). Similarly, the (1)    The DCPP design earthquake (DE), as described in Section 3.7.1.1.1, is the equivalent of the event that was later defined as the OBE in Appendix A to 10 CFR 100 (see SSER No. 7).
(2)    The DCPP double design earthquake (DDE), as described in Section 3.7.1.1.2, was originally the equivalent of the event that was later defined as the SSE in Appendix A to 10 CFR 100, prior to the discovery of the Hosgri fault.
(3)    The DCPP 1977 Hosgri earthquake (HE), as described in Section 3.7.1.1.3, replaced the DDE as the maximum vibratory ground acceleration that could occur at the site, comparable to the SSE.
3.2-2
 
DCPP UNITS 1 & 2 FSAR UPDATE DCPP'S Gapability to withstand a postulated Righter magnitude 7.5 earthquake ccntcrcd along an off-Shore Zonoe of geologi faulting k~nown as the "Hosgri Fault" has been f          .dGuidancefor determining the seismic classification of SSCs is provided in SG 29 (Reference 3)(3, specifically:
(1)    Those SSCs requiredI ,des***d,-to remain functional in the event of an is provided
                      ,SSE    in SG 29. These plant faturcs, including their foundations and supports, are designated as Seismic Category I in.SG 29.
(2)    Those SSCs not required to remain functional in the event of an SSE are designated as Non-Seismic Category I.
IDPP SS s, and their seismic design classifications comply with the intent of SG 29.
Hewever,-Since DCPP design and construction had progressed substantially prior to the issuance of SG 29, different terminology is eften-used for the classification of SSCs.
The seismic design classification of SSCs is not explicitly identified, instead it is determined based on the combination of several DCPP-specific classification systems:
(1)    Design Classification (see Section 3.2.2)
(2)    Quality Assurance Classification (see Section 3.2.3)
(3)    Piping Symbol (see Section 3.2.4)
(4)    Quality Group/Code Classification (see Section 3.2.5)
(5)    Instrument Classification (see Section 7.1) 3.2.2 DESIGN CLASSIFICATION The design classification system for SSCs is defined in Table 3.2-1. The design classifications of specific SSCs are provided in the DCPP Q-List. The relationships between the DCPP design classifications and the SG 29 seismic categories are as follows:
(1)    Desiqn Class I: Plant features important to safety, including plant features required to assure (1) the integrity of the reactor coolant pressure boundary. (2) the capability to shut down the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of 10 CFR 100.
Plant features designated as Design Class I that-correspond to a subset of the Seismic Category I features, as identified in SG 29 (the remaining Seismic Category I features are designatedas either Design Class II or II, as decribed below). The seismic design requirements for the Design 3.2-3
 
DCPP UNITS 1 & 2 FSAR UPDATE Class I plant features are dependent on whether the design basis function of the equipment dctcrmfn-eS wh.theF    *t is qualified for is active or passive.
Passive components are not required to Perform any function during an earthquake. Passive components Desnl*a*s-                    feaure.. are
                                                        .,.plant designed to maintain their structural integrity when subiected to -inthe-event of beth the DEJDDE, and 1977 HE. They are not required may or may not- to be designed to remain functional during an earthquake.
o.perable for the DDnMDE or HE; the functi*on for a DEODE andnor an HE Active components must be able to perform a function (ability to operate and/or change state), during an earthquake. Active components are designed to:
(a) maintain their structural integrity when subjected to in the event of both the DEJDDE, and HE and (b) remain functional during one or more ofthe design basis earthquakes that they arc required to w~ithstand:- fhe DE (equivalent to the OBE of-SG-29), the DDE (equi.alent to the SSE of SG 29), and/or the postulated Hoegri earthquakeu (1977 HE). The earthquakes applicable to specific components are defined in the Q-List.
The following Design Class I SSCs, including their foundations and supports, are designed to maintain structural integrity and to remain functional when subjected to a DDE or HE, and are subject to the requirements of the Quality Assurance Program (see Section 3.2.3):
(a)  The reactor coolant pressure boundary (b)    The reactor core and reactor vessel internals (c)    Systems [see Note (i) at the end of this list] or portions of systems that are required for emergency core cooling, post-accident containment heat removal, or post-accident containment atmosphere cleanup [see Note (iv) at the end of this listI (d)    Systems or portions of systems that are required for reactor shutdown and residual heat removal (e)  Those portions of the main steam, feedwater, and steam generator blowdown systems extending from and including the secondary side of the steam generators up to and including the outermost containment isolation valves, and connected piping up to and including the first valve (including a safety or relief valve) that is 3.2-4
 
DCPP UNITS 1 & 2 FSAR UPDATE either normally closed or capable of automatic closure during all modes of normal reactor operation [see Note (iv) at the end of this 1 (f)  Auxiliary saltwater, component cooling water, and auxiliary feedwater systems or portions of these systems that are required for emergency core cooling, post-accident containment heat removal, post-accident containment atmosphere cleanup, and residual heat removal (g)  Component cooling water system and seal water systems, or portions of these systems that are required for functioning of other systems or components important to safety (h)  Those portions of systems (other than the radioactive waste management systems) that contain or may contain radioactive material and whose postulated failure could result in conservatively calculated potential offsite exposures in excess of 0.5 rem whole body (or its equivalent to parts of the body) at the site boundary or beyond (i)  Systems or portions of systems that are required to supply fuel for emergency equipment (j)  Systems or portions of systems that are required for (a) post accident monitoring of RG 1.97 Category 1 variables and (b) actuation of systems important to safety (k)  The protection system [see Note (ii) at the end of this list]
(I)  The spent fuel storage pool structure, including the spent fuel racks.
(m) The reactivity control systems, i.e., control rods, control rod drives, and boron injection system, that are required to achieve safe shutdown of the plant (n) The control room, including its associated vital equipment and life support systems, and any structures or equipment inside or outside of the control room whose failure could result in incapacitating injury to the operators (o) Reactor containment structure, including penetrations [see Note (iv) at the end of this list]
(p) Systems or portions of systems that are required to provide heating, ventilatipg, and/or air conditioning for safety-related equipment/areas 3.2-5
 
DCPP UNITS 1 & 2 FSAR UPDATE (q)      Portions of the onsite electric power system, including the onsite electric power sources, that provide the emergency electric power needed for functioning of plant features included in Items (a) through (p) above (r)      Portions of the spent fuel pool cooling system used to remove spent fuel decay heat from the spent fuel pool; and portions of the refueling water purification system used to recirculate and cleanup the contents of the refueling water storage tank Notes:
(i) A system boundary includes those portions of the system required to accomplish the specified safety function and connected piping up to and including the first valve (including a safety or relief valve) that is either normally closed or capable of automatic closure when the safety function is required.
(ii) For purposes of these criteria, the protection system encompasses all electrical and mechanical devices andcircuitry (from sensors to actuation devices input terminals) involved in generating those signals associated with the protective function. These signals include those that actuate reactor trip and, in the event of a serious reactor accident, that actuate ESFs such as containment isolation, safety injection, pressure reduction, and air cleaning.
(iii) SSCs that form intcrfaccs between Design Class and Design Class !l or M features a`c dcsigned to Design    Class I
                                                  ;equiFem*ents..Not              Used.
(iv) Certain valves in these systems that are used for accident mitigation only, and do not support dafe shutdown following an HE, were qualified for active function for an HE to provide increased conservatism in accordance with Reference 7.
All plant fcaturcs designated as Design Class are also Seismi, Categ        ...
(2)    Design Class II: Plant features S&Gs important to reactor operation but not essential to safe shutdown and isolatioR of the reactor, ard failure of which would not Fesult in therFe I acs of substantial amoeunts of radioactivity, a.. classified as DeSigRn lass W,  . safety, including plant features not required to be Design Class I.
In general, plant features designated as Design Class II correspond to SSCs not identified as Non-Seismic Category I features, as identified in SG 29 and are not designed to withstand the effects of the design basis earthquakes. However, based on specific licensing requirements, certain 3.2-6
 
DCPP UNITS 1 & 2 FSAR UPDATE Design Class II plant features, as indentified in the Q-List, have been designed to withstand one or more of the desiqn basis earthquakes and form a subset of Seismic Category I features. These licensing requirements are addressed in Sections 3.2.3, 3.2.4, and/or 3.2.5. as applicable., are rcr      to by th guid,,    Non.ciem.c Categ... I feat.res. Under the DCPP classificati.n system, Design Class  -. features Mayo                  eismic C"g' ..      Seismically gualified Desigan Class II features include, but are not limited to, the following:
(a) Architectural Platforms supporting Design Class I components (b) Spent Fuel Pool Liner (c) Turbine Building (d) Turbine Pedestals (e) Intake Structure (f) Pipe Vaults at Outdoor Water Storage Tanks (g) Reactor Coolant Pump Motors (h) Reactor Coolant Pump Oil Collection Tank and Pans (i) Reactor Vessel Support Coolers (j) Firewater Pumps (k) Containment Penetration Overcurrent Protection fl) Main and Remote Annunciator Cabinets (m)Seismic Monitoring System (n) Containment Fan Cooler Ductwork and Annular Ring Duct (o) Post-LOCA Sampling Room Ventilation System (p) Technical Support Center Ventilation System (3)  Design Class IIl: Plant featuresSSCs not related to reactor operation or safety. are classified as Desigpn lass 111.
In general, plant features designated as Design Class III correspond to Non-Seismic Category I. as identified in SG 29 and are not designed to 3.2-7
 
DCPP UNITS 1 & 2 FSAR UPDATE withstand the effects of the desiqn basis earthquakes. However, based on specific licensing requirements, certain Design Class III plant features, as indentified in the Q-List, have been designed to withstand one or more of the design basis earthquakes. These licensing requirements are addressed in Sections 3.2.3, 3.2.4, and/or 3.2.5, as applicable.
Seismically qualified Design Class III features include, but are not limited to, the following:
(a) Containment Dome Service Crane (b) New Fuel Elevator Power and auxiliary service piping systems (as defined in ANSI B31.1, Paragraph 100.1), which might otherwise be considered as Design Class Ill, are classified as Design Class II (i.e., Design Class III is not used for power and auxiliary service piping systems).
3.2.3 QUALITY ASSURANCE CLASSIFICATION T, additi*e*.,,Appendix B to 10 CFR 50, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants (Reference 13)0'), requires that SSCs important to safety be designed and constructed in accordance with the quality assurance requirements described in Appendix B. Therefore, as described in Chapter 17, the requirements of the DCPP Quality Assurance (QA) Program apply to all SSCs classified as Design Class I. This ensures that plant features important to safety have met the requirements of Appendix B. Specific quality assurance requirements may also be applied to selected Design Class II and III features, described as the "graded" QA Program.
Thc gcneFal applicability and req*ir*ements of the design lass, quality/code Glass ThI c-la--Sifi-ation Of*.peific SSCv are p..vided in the DCPP List (sec Reference              8).
The DCPP- Q List is co-ntrolled by a written PG&E procedure. The procedure require that all non edite0ial cng to. the contents of the Q List be rcvIewed pursuant to the requ. ients of 10 CFR 50.59. Access to the p List is available through hard copy or elec-tronically at PG&E-.
The QA classification of individual SSCs is identified in the Q-List. The following QA classes are used at DCPP:
QA Class                                        Description Q        Equipment  and structures  to which the QA provisions of Appendix B to
_          10 CFR 50 apply for design, procurement, and constrUction.
        "Blank"      Design Class IIor III equipment that is not subiect to nuclear quality assurance requirements.
3.2-8
 
DCPP UNITS 1 & 2 FSAR UPDATE QA Class                                      Description R        Those radioactive waste management items which require application of graded quality assurance requirements including Regulatory Guide 1.143 (Reference 14). See Section 2.2.2 of the Q-List for further details.
G        Those portions of the fire protection systems and emergency lighting and communication equipment which require application of a quality pro-gram as described in Appendix A to NRC Branch Technical Position APCSB 9.5-1 (Reference 15). See Section 2.2.2 of the Q-List for further details.'
S        Design Class IIand III equipment that requires seismic qualification to satisfy license or FSAR Update commitments or to assure the functionality of Design Class I components. Thisincludes, but is not limited to equipment in the foilowing categories:
* SSCs required to achieve Mode 5 for both units following a 1977 HE, assuming a single failure and the loss of offsite power (Section 5.1 and Appendix J of the Hosqri Report (Reference 12), Section 3.2 of SSER-7 (Reference 17) and Section 3.2 of SSER-8 (Reference 18))
* SSCs associated with electrical isolation in certain 120 VAC power circuits a SSCs required for compliance with the requirements of RG 1.97.
* SSCs associated with certain inputs to the Solid State Protection        I System.
T        Regulatory Guide 1.97 (Reference 16) Category 2 and 3 instrumentation which requires application of a graded Quality Assurance Program. (Note: Other Category 2 and 3 instrumentation which is within the Environmental Qualification (EQ) Program, is part of the pressure boundary of a Design Class I System, or is treated as a Class 1E electrical devices, is QA Class Q.)
3.2.4 PIPING CLASSIFICATION SYMBOLS The piping schematic drawings arei-Ilustrated in-(see Figures 3.2-1 through 3.2-27)_
employ a system of symbols The p*iPig symbol syst, m that appears on all piping schematics and draw44gs. to indicate piping fabrication, erection, and test criteria. Their -
ea,-be-correlationed to the design class (Section 3.2.2) and quality group/code classes (Section 3.2.5) is as follows:
PiDinq Schematic Correlation Piping            Design            Quality GrouM/Code Symbol            Class            Classw A                I                  I 3.2-9
 
DCPP UNITS 1 & 2 FSAR UPDATE Pipinq Schematic Correlation Piping          Design          Quality Group/Code Symbol          Class            Classc B              1                II
                        @(a)              1/11            II/None C                I                III D                I                III E              II              None F              II              None G                II              None G1              II              None H                II              None J              I                Ill
_(b)            I                Not Applicable
_(b)            II or III        None Notes:
(a) The symbol '@' is referred to in the FSAR Update and the Q-List. However, this symbol is not used on the piping schematics for Code Class designation; the line is bubbled (i.e., 0-) and the notes describe the applicable code(s).
(b) For HVAC system ductwork symbols, see Figures 3.2-1A and 3.2-2A.
(c) See Section 3.2.5 for Quality Group/Code Classification system 3.2.25 SYSTEM QUALITY GROUP/CODE CLASSIFICATIONS FOR FLUID SYSTEMS AND FLUID SYSTEM COMPONENTS GDC 1 requires that systems and componehts essential to the prevention of accidents be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed. This section describes the quality classification system that has been used to implement quality standards that satisfy Criterion 1 for DCPP fluid systems and fluid system components. The discussion also shows the relationship of this classification system to fluid system and fluid system components classification systems in ANSI N18.2, Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants (Reference 1) , and SG 26.
DCPP SSCs are classified as Design Class 1,11, or III (Section 3.2.2). Design Class I is-ScISM, , Ct.Gor. I "and fluid systems and fluid system components areis further categorized as PG&E Quality Group/Code Class I, II,or III.
Design Classes II or III fluid systems and fluid system components are .uualy" Nos*ns.i.mG Catego*y 1 and have no PG&E quality_group/code class designation.
3.2-10
 
DCPP UNITS 1 & 2 FSAR UPDATE Specific requirements as dictated by the quality standards applicable to the respective commercial (ASME, ANSI, or ASA)code classes are also applicable. However, some Design Class II and III components have been seismically designed, e.g., items in the Seismically Induced Systems Interaction Program (Section 3.7.3.13), specific components required for post-HE shutdown, CCW header C components, and items that were designed for the DE pursuant to RG 1.143 (Reference 14). Forthis reason, there is not a direct correlation between design class and seismic category (except that all Design Class I features are Seismic Category I). In addition, the design class_
ificatien of Seismic Categ.ry I does not indicate which of the three design basis earthquakes a feature has been qualified for, nor whether that qualification is for passive or active function (except that all electrical Class 1E and Instrument Class IA components are qualified to remain operable for all three design basis earthquakes).
The design basis function of the equipment determines the type of seismic qualification required. These classifications and their relationships are illustrated in Table 3.2-2 and discussed below.
3.2.25.1 Design Class I, Quality Group/Code Class I Fluid Systems and Fluid System Components 10 CFR 50.55a requires that certain components of the reactor coolant pressure boundary be designed, fabricated, erected, and tested in accordance with the requirements for Class A(a) components of Section III of the ASME Boiler and Pressure Vessel Code, or the most recently available industry codes and standards. Code Class I has been applied to those components of the reactor coolant pressure boundary and implerrients the quality standards that satisfy the requirements of Section 50.55a, 10 CFR 50. DCPP Code Class I components of the reactor coolant pressure boundary are listed in the DCPP Q-List (Reference 8), along with the industry codes and standards used for their design, fabrication, erection, and test. The Code Class I classification includes the components of the reactor coolant pressure boundary identified as Safety Class I in ANSI N18.2 and Quality Group A in SG 26.
3.2.25.2 Design Class I, QualityGroup/Code Class IIFluid Systems and Fluid System Components Generally, Code Class II has been applied to include fluid systems and fluid system components that are either:
(1)    Part of the reactor coolant boundary, but excluded from Code Class I requirements by Section 50.55a of 10 CFR 50 (2)    Not part of the reactor coolant pressure boundary, but part of:
(a) The 1971 edition of the ASME Boiler and Pressure Vessel Code, Section Ii1,Nuclear Power Plant Components, uses the term Class I in lieu of Class A.
3.2-11
 
DCPP UNITS 1 & 2 FSAR UPDATE (a)      Systems or po'rtions of systems(b) that are required for emergency core cooling, postaccident containment heat removal, or postaccident containment atmosphere cleanup (b)      Systems or portions of systems that are required for reactor shutdown and residual heat removal (c)      Those portions of the main steam, feedwater, and steam generator blowdown systems extending from and including the secondary side of steam generators up to and including the outermost containment isolation valves, and connected piping up to and including the first valve (including a safety or relief valve) that are either normally closed or capable of automatic closure during all modes of normal reactor operation (d)      Systems or portions of systems that are connected to the reactor coolant pressure boundary and are not capable of being isolated from the boundary during all modes of normal reactor operation by two valves, each of which is either normally closed or capable of automatic closure Code Class IIfluid systems and fluid system components are listed in the DCPP Q-List (see Reference 8), along with the industry codes and standards used for their design, fabrication, erection, and testing.
3.2.25.3 Design Class I, QualityGroup/Code Class III Fluid Systems and Fluid System Components Generally, Code Class III has been applied to include fluid systems and fluid system components not part of the reactor coolant pressure boundary, nor included in Code Class II, but part of:
(1)      Auxiliary saltwater, component cooling water, and auxiliary feedwater systems, or portions of these systems that are required for (a) emergency
            -    core cooling, (b) postaccident containment heat removal, (c) postaccident containment atmosphere cleanup, and (d) residual heat removal from the reactor (2)      Systems or portions of systems that are connected to the reactor coolant pressure boundary and are capable of being isolated from the boundary during all modes of normal reactor operation by two valves, each of which is either normally closed or capable of automatic closure (b) The system boundary includes those portions of the system required to accomplish the specified safety function and connected piping up to and including the first valve (including a safety or relief valve) that is either normally closed or capable of automatic closure when the safety function is required.
3.2-12
 
DCPP UNITS 1 & 2 FSAR UPDATE (3) . Those portions of systems other than radioactive waste management systems that contain or may contain radiqactive material, and whose postulated failure could result in conservatively calculated potential offsite exposures in excess of 0.5 rem whole body (or its equivalent to parts of the body) at the site boundary or beyond (4)    Component cooling water system and seal water systems, or portions of these systems, that are required for functioning of other systems or components important to safety (5)    Portions of the spent fuel pool cooling system required for spent fuel cooling, and the refueling water purification system whose postulated failure could result in a loss of refueling water storage tank inventory Code Class III fluid systems and fluid system components are listed in the DCPP Q-List (see Reference 8), along with the industry codes and standards used for their design, fabrication, erection, and testing.
3.2.25.4 Other Fluid Systems and Fluid System Components Fluid systems and fluid system components that are not part of the reactor coolant pressure boundary, not essential to shut down the reactor and maintain it in a safe condition, and not essential to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures of 10 CFR 100, are not included in the Design Class I classification..
These other systems and components are classified as Design Class II or III and are listed in the DCPP Q-List (see Reference 8), along with the industry codes and standards used for their design, fabrication, erection, and testing. They comprise a design class, but have not been assigned a code class. Design Class II includes the fluid systems and fluid system components identified as Quality Group D in SG 26 and as radioactive waste management system in RG 1.143, i.e., those fluid systems and fluid system components that contain or may contain radioactive material, but whose failure would not result in calculated potential exposures in excess of 0.5 rem whole body (or its equivalent to parts of the body) at the site boundary. These fluid systems and fluid system components are in conformance with the accepted industry codes and standards in effect during the design and construction of DCPP. If they were designed and constructed to codes and standards outside of the requirements of SG 26 or RG 1.143, additional quality standards have normally been applied so that the intent has been met.
3.2.25.5 Summary of System Quality Group/Code Classifications 3.2-13
 
DCPP UNITS 1 & 2 FSAR UPDATE Table 3.2-2 summarizes the design and quality group classifications applied to the DCPP SSGs-fluid systems and fluid system components, and their relationships to the other methods of classification.
Generally, codes and standards were applied prior to issuance of the latest codes and standards, such as the 1971 edition of the ASME Boiler and Pressure Vessel Code, Section III, Nuclear Power Plant Components. In some cases, fluid systems and components were designed and built to codes and standards outside the requirements of SG 26, ANSI N18.2, and RG 1.143 definitions. The classification for those fluid systems and fluid system components that do not fall within the strict definition of SG 26, ANSI N18.2, and RG 1.143 were established prior to ANSI N18.2, SG 26, RG 1.143, and the issuance of revised industry codes and standards. For these fluid systems and fluid system components, the design specifications specified the accepted industry codes and standards in effect during the design and construction of DCPP.
While some portions of the fire protection system components are designated Design Class I, the system is not required to ensure the integrity of the reactor coolant pressure boundary or to shut down the reactor and maintain it in a safe shutdown condition. Fire protection features meet the requirements defined in BTP APCSB 9.5-1 (Reference 5) after 1979 and, where designated Design Class I, are designed to withstand the effects of an HE.
3.2.36 REFERENCES
: 1.      Nuclear Safety Criteria for the Desiqn of Stationary Pressurized Water Reactor Plants. N18.2 American Nuclear Society, August 1970 Draft.
: 2. Quality Group Classifications and Standards for Water, Steam, and Radioactive Waste Containing Components of Nuclear Power Plants, SG 26, Atomic Energy Commission.
: 3.      Seismic Design Classification, SG 29, US Atomic Energy Commission.,
June 7, 1972.
: 4.      Spent Fuel Storage Facility Design Basis, RG 1.13, Nuclear Regulatory Commission.
: 5.      Guidelines for Fire Protection for Nuclear Power Plants, BTP APCSP 9.5-1, Nuclear Regulatory Commission.
: 6.      Design Guidance for Radioactive Waste Management Systems, Structures, and Components Installed in Light-Water-Cooled Nuclear Power Plants, RG 1.143, Nuclear Regulatory Commission.
: 7.      PG&E Letter to the NRC, "Inadequate Maintenance of Hosgri Report Commitments," DCL-92-198 (LER 1-92-015), September 11, 1992.
3.2-14
 
DCPP UNITS 1 & 2 FSAR UPDATE
: 8. Classification of Structures, Systems, and Components for Diablo Canyon Power Plant Units 1 and 2 (Q-List), PG&E.
: 9. L.-ter from, NRC (L. F ille-r'F) to PG&E (G. M. Rueger), datd De-rn.berF , 1993, Subj:*,;.      NRC lnsphcti9n* f Diablo Canyon Units 1 and 2 (Repor- N~o. 50 275, 50 323/93-31) [pages I"and 2]Deleted in revision xx.
: 10. LcftcrFfrom NRC (A.W. Bcach) to PG&E= (G. M. Rucgcr), dated August 15, 1994, SubjeGct NRC lnspIctio; Rcport 50-275i94 18.; 50-323194 18 (,tlee-e of Violation) [pages 14 and I 5]Deleted in revision xx.
: 11. Seismic and Geologic Siting Criteria for Nuclear Power Plants, Appendix A to 10 CFR 100.
: 12. Seismic Evaluation for Postulated 7.5M Hosgri Earthquake, DCPP Units 1&2, PG&E, (Amendment Nos. 50, 53, 54, 56, 59, 60, 62, 64, 66, 68, 70, 72, 75, 76, 77, 79, 82, and 83 to the DCPP Final Safety Analysis Report dated September 28, 1973)
: 13. Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants, Appendix B to 10 CFR 50.
: 14. Design Guidance for Radioactive Waste Management Systems, Structures, and Components Installed in Light-Water-Cooled Nuclear Power Plants, RG 1.143, Nuclear Regulatory Commission, Revision 1 (October 1979)
: 15. Guidelines for Fire Protection for Nuclear Power Plants Docketed prior to July 1, 1976, NRC Branch Technical Position APCSB9.5-1, Appendix A, (August 23, 1976)
: 16. Criteria for Accident Monitoring Instrumentation for Nuclear Power Plants, RG 1.97, Nuclear Regulatory Commission
: 17. Supplement No. 7 to the Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units I and 2, NUREG-0675, Nuclear Regulatory Commission, May 1978.
: 18. Supplement No. 8 to the Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2, NUREG-0675, Nuclear Regulatory Commission, November 1978.
3.2.74 REFERENCE DRAWINGS 3.2-15
 
DCPP UNITS I & 2 FSAR UPDATE Figures representing controlled engineering drawings are incorporated by reference and are identified in Table 1.6-1. The contents of the drawings are controlled by DCPP procedures.
3.2-16
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7      SEISMIC DESIGN 3.7.1 SEISMIC INPUT This section describes the three design basis earthquakes, the Design Earthquake (DE), the Double Design Earthquake (DDE), and the postulated 7.5M Hosqi Earthquake (HE).
In addition to the above three earthquakes, in response to Unit i Operating License Condition No. 2.C.(7), PG&E conducted, as described in Sections 2.5.2.9.4and 2.5.2.10.4 below, a program to reevaluate the seismic design basis for DCPP.-Qn-No.ember 2, 1984, the NRC issued the DCPP UnitI Facility Op-r.ating Licenc DPR
: 80. In Li-,ene Condition 2.G(7) of DPR 80, the NRC stated, in part; "PG&E sh'll develop and implement a program to r.cevaluat. the seiSMic design bases used for the Diable Canyon Power P.ant." This reevaluation effort was titled the "Long Term Seismic Proqram".
PG&.'S                  effort.in response to the license cndition was titled the "Long
              .e.va.uation Term Seismic Progaram" (LTSP). PG&E prepared and submitted to the NRC the "Final Report of the Diablo Canyon Long Tc" Seismic Program" in July 1988 (Reference 19).
The NRC reviewed the Final Report betweecn 1088 and 1901, and PG&E prepared and submitted written responses to NRC queStions resulting fromI that review.,l' In Febrluar' 1991,' PG&E issued the ",Addendum to the 19Q8-8 Final Report of the Diable Canyon Long Term Seismic Program." (Refere*ne 20), In June 1991, the NRC Issued Supplement 34 to the Diable Canyon Safety Evaluation Report (SSER) (Reference 21), in W..hich the NRC ceonluded that PG&E= had satisfied License Condition 2.C(7) of DPR 80. In the SSER the NRC requested certain.onfirmato..          analyses from PG&E=, and PG&E subsequently submitted the requested -,Ralys*s. The NRC's f*in*a a          .ep*tanceof the LTSP is documented in a le.,er to PG&E dated April 17, 1992 (Reference 22).
The LT-SP contains extensive databases and analyses that update the basic geologic and seismic nformation in this FSAR Update. However,        the LTSP material does not alter-the design bases for DCPP. in SSER 34 (Reference 21), the NR states, ,"The Staff notes that the seismic qualification basis for Diablo Canyon will continue to be the original design basis plus the HeSgri evaluation basis, along with associated a nalo4ial methods, initial condkitins, etG."
As a condition of the NRC's final acceptance of the LTSP. PG&E committed to ongoing activities in support of the LTSP, as follows:
(1)    The "Framework for the Future," per letter to the NRC, dated April 17, 1991 (Reference 32). These on-going activities include the following (Reference 21, and Section 2.5.6.1):
(a)    To continue to maintain a strong qeosciences and engineering staff to keep abreast of new geological, seismic, and seismic 3.7-1
 
DCPP UNITS 1 & 2 FSAR UPDATE engineering information and evaluate it with respect to its significance to Diablo Canyon. See Section 2.5.6 for additional details.
(b)    To continue to operate a strong-motion accelerometer array and the coastal seismic network, although likely with fewer stations than currently operating. See Section 3.7.4 for additional details.
(2)    "Future Plant Additions and Modifications," per letterPG&E co..mittcd to the NRC,. in a !ett  dated July 16, 1991 (Reference 23). This commitment requires7 that certain plant additions and modifications, as identified in that letter, would be checked against insights and knowledge gained from the LTSP to verify that the plant margins remain acceptable. See Section 3.7.6 for additional details.
A completed listing of bibliographic references to the LTSP reports and other documents are provided in References 19, 20, and 21.
3.7.1.1 Design Response Spectra Section 2.5.2 provides a discussion of the earthquakes postulated for the DCPP site and the effects of these earthquakes in terms of maximum free-field ground motion accelerations and corresponding response spectra at the plant site. The ground motion response spectra associated with each of these earthquakes are described in the following sections.
3.7.1.1.1 Design Earthquake (DE)
The original (pre-construction permit) -geological and seismological investigations determined that the maximum vibratory accelerations at the plant site would result from either Earthquake B (a magnitude 7.5 earthquake on the Nacimiento fault) or Earthquake D-modified (a magnitude 6.75 aftershock, on an unknown fault directly below DCPP, associated with a magnitude 8.5 earthquake on the San Andreas fault),
depending on the natural period of the vibrating body (See Section 2.5.2.9.1).
Response acceleration spectra curves for horizontal free-field ground motion at the plant site from Earthquake B and- Earthquake D-modified, and HE are presented in Figures 2.5-20T and 2.5-21, and 2.5 29 through 32, r.spe.tively.
For design purposes, the response spectra for each damping value from Earthquake B and Earthquake D-modified a:e-were combined to produce an envelope spectrum. The acceleration value for any period on the envelope spectrum is equal to the larger of the two values from the Earthquake B spectrum and the Earthquake D-modified spectrum.
Vertical free field ground accelerations, and the vertical free-field ground motion response spectra are-were assumed to be two-thirds of the corresponding horizontal spectra.
3.7-2
 
DCPP UNITS 1 & 2 FSAR UPDATE The DE is the hypothetical earthquake that would produce these horizontal and vertical vibratory accelerations. As discussed in Section 3.2.1, theThe DE corresponds to the operating basis earthquake (OBE), as described in Appendix A to 10 CFR 100 (Reference 7) (SSER 7, Section 2.5.2, "Operatinq Basis Earthquake").
Note that the DE is a hypothetical earthquake that is not to be revised based on any insights from new geotechnical information from the Long Term Seismic Program (LTSP). The process for the evaluation of updated LTSP ground motions is described in Section 2.5.6.2. Updated ground motions are compared to the 1991 LTSP spectra, which is bounded by the 1977 HE spectra. The HE is the SSE.
3.7.1.1.2 Double Design Earthquake (DDE)
To ensure adequate reserve energy capacity, Design Class I structures and equipment are Feviewed-also designed for the DDE. The DDE is the hypothetical earthquake that would produce accelerations twice those of the DE. The DDE Go-nrsponds to the SSE, as deScribed in Appendix A to 10 CFR 100 (RefccRnc. 7). The horizontal free-field response spectra for the DDE correspond to twice the envelope of the spectra shown in Figures 2.5-20 and 2.5-21. The vertical free field ground accelerations and the vertical free-field ground motion response spectra are assumed to be two-thirds of the corresponding horizontal spectra.
Note that the DDE is a hypothetical earthquake that is not to be revised based on any insights from new geotechnical information from the Long Term Seismic Program. The process for the evaluation of updated LTSP ground motions is described in Section 2.5.6.2. Updated ground motions are compared to the 1991 LTSP spectra, which is bounded by the 1977 HE spectra. The HE is the SSE.
3.7.1.1.3 1977 Hos-gri Earthquake (HE)
PG&E was requested by the NRC to evaluate the plant's capability to withstand a postulated Richter magnitude 7:5 earthquake centered along an offshore zone of geologic faulting, generally referred to as the Hosgri Fault. This evaluation is discussed in the various chapters when it is specifically referred to as the Hosgri evaluation or Hosgri event evaluation.
Acceleration response spectra curves for horizontal and vertical free field ground motion at the plant site from the HE in 1977 are the Newmark and Blume spectra described in Section 2.5. The vertical free field response spectra are two-thirds of the corresponding horizontal spectra. As discussed in Section 3.2.1, the 1977 HE spectrum corresponds to the SSE, as described in Appendix A to 10 CFR 100 (Reference 7). The horizontal free-field ground motion response spectra for the HE (Blume) and HE (Newmark) are shown in Figures 2.5-29 and 2.5-30, respectively. The vertical free-field ground motion response spectra for the HE are shown in Figures 2.5-31 and 2.5-32.
3.7.1.1.4 1991 Long Term Seismic Program Earthquake (LTSP) 3.7-3
 
DCPP UNITS 1 & 2 FSAR UPDATE As discussed in Sections 2.5 and 3.7, the Long Term Seismic Program was developed in response to Unit 1 Operating License Condition 2.C.(7). The acceleration response spectra curves for horizontal and vertical free field ground motion at the plant site are the 84th percentile ground motion response spectrum, as modified per SSER-34 (Reference 21), as described in Section 2.5.2.10.4, are shown in Figures 2.5-33 and 2.5-34. Note that, unlike the DE, DDE, or 1977 HE, the vertical free field response spectrum is not based on a scale factor times the corresponding horizontal spectrum.
The ongoing activities in support of the LTSP, described in Section 2.5.6, may result in changes to the 84th percentile ground motion response spectrum for the LTSP. The methods for the evaluation of the significance of any changes are described in Section 2.5.6.
3.7.1.2 Design Response Spectra Derivation 3.7.1.2.1 Design Earthquake (DE) and Double Design Earthquake (DDE)
Derivation The free-field ground motion acceleration time-histories used in the dynamic analyses of the containment structure, auxiliary building, turbine building, and intake structure are developed by the following procedure: The response spectra for 2 percent damping for Earthquake B and Earthquake D-modified are enveloped to produce a single response spectrum (DE intensity). A time-history is then developed that produces a spectrum with no significant deviation from the smooth DE-envelope spectrum. This procedure eliminates undesirable peaks and valleys that exist in the response spectrum calculated directly from Earthquake B and Earthquake D-modified records.
A similar procedure is used to obtain a free-field ground motion acceleration time-history for the DDE. The free-field ground motion acceleration time-histories for the DE and DDE are shown in Figures 3.7-1 and 3.7-2, respectively. Comparison of the response spectrum computed from the time-history with the smoothed envelope spectrum is shown in Figure 3.7-3 (2 percent damping) and in Figure 3.7-4 (5 percent damping).
These spectra are calculated at period intervals of 0.01 seconds, which adequately define the spectra.
The dynamic analyses of the containment structures and auxiliary building consider the interactions between their embedded foundations and the surrounding soil through the inclusion of soil-structure interaction effects in the finite element models (see Section 3.7.2.1.7.1). As a result, the calculated response at ground level is not the same as the free-field ground motion. Soil-structure interaction effects are not considered in the dynamic analysis of the turbine building and intake structure.
3.7.1.2.2 1977 Hosgri Earthquake (HE) Derivation 3.7-4
 
DCPP UNITS 1 & 2 FSAR UPDATE For the HE evaluation of containment structure, auxiliary building, turbine building, and intake structure, the horizontal input motions are reduced from free-field motions to account for the presence of the structures that have large foundations. These reduced inputs have been derived by spatial averaging of acceleration across the foundations of each structure by the Tau filtering procedure (Reference 12). The resulting horizontal response spectra for these structures are shown in Figures 3.7-4A through 3.7-4F.
For the HE evaluation of outdoor water storage tanks and smaller structures, the horizontal design response spectra are the free-field horizontal response spectra. HE vertical design response spectra are the free-field vertical response spectra. For-design purpo)se&,th-e--N'e-wmark spectra aro used, orAltcratcly the Bluine 6pectr-a are used, with adjustIment in eertain frequency ranges as necessar; so that they do not fall beow the correspending Newmark spectra.
For the design of structures, the seismic response parameters (e.g., forces, moments, displacements, accelerations) are determined based on either of the following methods:
(1) The response to the Newmark and Blume ground motions are developed separately, and then the response parameters are enveloped.
(2) The response to an envelope of the Newmark and Blume -groundmotions is developed Acceleration time-histories used in the analysis of the containment and intake structures, auxiliary building, and turbine building are shown in Figures 3.7-4G through 3.7-4M. Comparison of the response spectrum computed from each time-history with the corresponding design response spectrum for 7 percent damping is shown in Figures 3.7-4N through 3.7-4T.
3.7.1.2.3 1991 Long Term Seismic Program Earthquake (LTSP)
The free-field ground motion acceleration time-histories used in the dynamic analyses of the containment structure, auxiliary building, and turbine building are developed by the following procedure (Reference 19, Chapter 5, and Reference 33, Question DE-2):
(1)    Two sets of strong-motion recordings of three-component actual earthquakes were selected.
(2)    The original recorded motions were adjusted to conform to source-specific and site-specific conditions, such as the maximum earthquake magnitude, source-to-site distance, and site conditions.
(3)    The two horizontal components of the motions were transformed, as necessary, into longitudinal and transverse horizontal components to provide motions in the directions normal and parallel to the strike of the causative fault.
3.7-5
 
DCPP UNITS 1 & 2 FSAR UPDATE (4)  The lonqitudinal and transverse time histories were both modified by adiusting the Fourier amplitudes, but keeping the Fourier phase-angles unchanged, so that the resulting time history response spectra closely matched the median site-specific target spectra at several damping ratios.
Likewise, the vertical component time histories were modified to match the median site-specific target vertical spectra at several damping values.
(5)  The three-component time histories were scaled upwards by a constant scaling factor common to all three components to envelop the LTSP 84th percentile ground motion response spectrum (Figures 2.5-33 and 2.5-34)
Sample free-field ground motion acceleration time-histories for the LTSP 84th percentile ground motion response spectrum are shown in Figures 3.7-29 and 3.7-30.
Comparison of the response spectrum computed from the time-history with the target spectrum is shown in Figures 3.7-31 and 3.7-32 (5 percent damping).
The dynamic analyses of the containment structures, auxiliary building, and turbine building consider the interaction between their embedded foundations and surrounding soil theouqh the inclusion of soil-structure interaction effects in the finite element models (see Chapter 5 of Reference 19). As a result, the calculated response at ground level is not the same as the free-field ground motion. A dynamic analysis of the intake structure was not performed for the LTSP earthguake.
3.7-6
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7.3.15.3 Control Rod Drive Mechanism Evaluation The replacement CRDMs were evaluated using a combination of linear and nonlinear finite element models which included the CRDM housings, RPV head adapters, and the integrated head assembly. The following models and analysis methods were employed for the specified earthquakes:
(1)    DE and DDE: The horizontal analyses for the DE and DDE were based on a nonlinear model. The horizontal DE and DDE acceleration time-histories at the seismic plate elevation and the reactor vessel support elevation were used as inputs to the model. The vertical analyses for the DE and DDE were based on a linear model. The vertical DE and DDE response spectra at the reactor vessel head elevation were used as input to the model.
(2)    HE: The horizontal and vertical analyses for the HE were based on a linear model. The horizontal and vertical HE response spectra at the seismic plate elevation and the reactor vessel head elevation were used as input to the model.
The DDE and the HE seismic loads were combined by the square root sum of the squares (SRSS) methodoloqy with the LOCA loads. The resulting stress levels satisfied the code requirements.
3.7-7
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7.3.15.4 CRDM Support System Evaluation The integrated head assembly CRDM seismic support structure, tie rods, and head lifting legs were evaluated using linear elastic 3-D finite element models of the support system. Tension-only capability of the tie rods was modeled. The loading from the CRDMs was addressed through the inclusion of a simplified representation of the pressure housings, including the appropriate lumped masses.
In general, the qualification was based on the response spectrum superposition method using the envelope of the spectra at the 140 foot elevation of the containment interior concrete (attachment point for the tie rods for the tie rods to the reactor cavity walls) and on the reactor vessel lifting lugs and pads (attachment point for the integrated head assembly ring beam to the head) for the DE, DDE, HE, and LOCA load cases. These analyses were supplemented with the time history modal superposition method for the determination of DDE loads for selected connections.
The DDE and the HE seismic loads were combined by the square root sum of the squares (SRSS) methodology with the LOCA loads. The resulting stress levels satisfied the code requirements.
3.7-8
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7.4 SEISMIC INSTRUMENTATION PROGRAM The seismic instrumentation program for DCPP includes two independent systems, the Seismic Monitoring System and the Central CoastSeismic Network. Descriptions of these systems are provided in the following sections.
3.7.4.1 Seismic Monitoring System 3.7.4.1.1 Comparison With NRC Regulatory Guide 1.12, Revision 2 The seismic monitoring system instrumentation consists of strong motion triaxial accelerometers that sense and record ground motions. The licensing basis for the seismic monitoring system instrumentation is Safety Guide 12, "Instrumentation for Earthquakes," dated March 10, 1971. T-hisThe seismic monitoring system instrumentation consists of a Basic and Supplemental System., meets the intent of RG 1.12, Reviskon 2. The Basic System is consistent with, but not committed to, RG 1.12 Revision 2. Enhancements to the Basic seismic instrumentation monitoring system have been made to improve the system effectiveness. The enhancements,..
described as the Supplemental System, include supplemental accelerometers and rapid processing of the ground motion data. The enhancements exceed the int&erecommendations of RG 1.12, Revision 2, and are not considered part of the licensing basis. However, as discussed in Section 3.7, one of the ongoing commitments associated with the LTSP requires that the entire system, including both the basic and supplemental accelerometers, be maintained.
3.7.4.1.2 Location and Description of Instrumentation Seismic instrumentation is provided in accordance with RG 1.12, Revision 2, paragraph 1.2. All instruments are rigidly mounted so their records can be related to movement of the structures and ground motion. All are accessible for periodic servicing and for obtaining readings.
3.7.4.1.2.1 Strong Motion Triaxial Accelerometers Strong motion triaxial accelerometers provide time-histories of acceleration for each of three orthogonal directions. These histories are recorded in the accelerometer housings. The instruments start recording upon actuation of a seismic trigger which has an adjustable threshold. Six strong motion triaxial accelerometers are provided in accordance with RG 1.12. Revision 2, paragraph 1.2. Supplemental accelerometers provide ground motion data beyond the regulatory guidance and are not part of the licensing commitment, 3.7.4.1.3 Control Room Operator Notification Operation of the strong motion triaxial accelerometers (ESTA01 or ESTA28) will activate an annunciator in the control room and provide indications on the earthquake 3.7-9
 
DCPP UNITS I & 2 FSAR UPDATE force monitor (EFM) in the R54-seismic instrumentation panel. The EFM will display the acceleration levels for all areas of both the Unit 1 containment base sensor (ESTA01) and the free field sensor (ESTA28). For the Emergency Plan event classification, it also provides a status of level exceedance for any axis on both sensors within a few minutes. The setpoint thresholds are set in accordance with Emergency Plan Action Levels.
3.7.4.1.4 Comparison of Measured and Predicted Responses In the event of an earthquake that produces significant ground motions, all seismic instruments are read and the readings compared to the corresponding design values.
This comparison, together with information provided by other plant instrumentation and an inspection of safety-related systems, forms the basis for a judgment on severity, level, and the effects of the earthquake.
In addition, the recorded time histories, and the associated response spectra, are used by the PG&E Geosciences Department, as input to the ongoing LTSP activities. See Section 2.5.6.
3.7.4.2 Central Coast Seismic Network The PG&E Geosciences Department operates and maintains an array of seismometers located primarily along the south-central California coast, between Ragged Point and Point Sal, and the recording equipment located at the PG&E Geosciences Department office in San Francisco. The Central Coast Seismic Network (CCSN) was installed in 1987 as part of the LTSP to provide continuous real-time monitoring of earthquake activity in the vicinity of DCPP. Data from the CCSN are transmitted directly to the PG&E Geosciences Department, where it is stored, processed, and archived, and to the United State Geological Survey in Menlo Park, CA.
These data are used by the PG&E Geosciences Department, as input to the ongoing LTSP activities. See Section 2.5.6.
3.7-10
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7.6 SEISMIC EVALUATION TO DEMONSTRATE COMPLIANCE WITH THE HOSGRI EARTHQUAKE REQUIREMENTS UTILIZING A DEDICATEr SHUTDOWN FLOWPATH 3.7.6.1 Post HQsgri Shutdown Rcurmnts and Assumed Conditions in response to -a requcet from the NRC, PG&E evaluated the ability of DCPP to shut down folloi thc1ocurrenco of a 7.5M ealthquake duo to a seiimic event On Hoegr"i fault. This ovaluati.. is presented in Rferenco 1-5, whi-h was am..ndod SeVeral times -#te it WaS firSt issued in order torlespnd to questions by thc NRC and rF** t* 1 agrecements made at meetings with the NRC. The final dGcumcn~t deGcribcs thc method propsedby-G& E to shut down the plant after the earthquake, assuming a loss of all offeite        %power, but no concurrent accident, using onRly equipmqent qualified to remain
*r.'*l*l*
operable- foil OW!R'ig such an earthquake.
For thiS*pUr*pse, valves that are required to operate to a.hieVo shutdown following the earthqu--ake wore qualified for active funcation to the HoSgri paramneters, whereas other valves, which might have an active function for. postaccident mitigation, but were not required to operate to- a.hieve shutdown following the earthquake, were qualified for psiefunction (pressure boundiry iqtegrity) to the Hoer pa        ete~s. This I-&
conistntwith the DC PP design basis stated in ESAR Sec-Ption 3.7.1.1 that the DEis the SSE for [)CPP, and that the guidelines presented in RG 1.29 apply to~thc DDE.
in addi4tion, pursuant to the NRC request, it was necessar' to demonstrate that DCPP co.uld be shut dowR fo-liowing an HE in o4rder to poftect the health and safety of the public. The Hosgri evaluation presented in Reference 15 demont*rated this. To-pro~vide increased E;Onservatismn, PG&E has subsequently qualified all actiVe valveS for active function for an HE pursuant to a commitment mnade in Referenc~e 17.-
3.7 .. 2 Post-Hosgri Safe Shutdowvn F..wpath The flowpath qualified to eRable shutdown of th plant following an HE i=s defined            in Chapter 5 of Reference 15. For this purpose, safe shutdoewn was defined as col shutdown. it assumes concurrent loss of offsitc power, a single active failure, but no Gencufrent accident Or fire. LocGa! manual oprto o f equipment fromF outside the control room i- aceptable for takinRg the pla* t from hot standby to cold shutdown.
3.7.6.2.1 Hot Standby Hot stnndhv OE;        iche'ved b- feedino the steam obneratos usina the au'iliar' feedwater system -and      byrelease of steam t. the atmoper. through the 10 percent steam d4ump valves. Although other long term cooling waterso                s may be available, onlythe1 seismnically qualified condensate storage tank and firewater storage tank are assumfed tobeavailable.
3.7-11
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7.6.2.2 Cold Shutdown Cold  shutdow-4Afn is -ahiev;dby use of the normal charging system fIow path.
Depro-Ssurization is pe~fGrmed using auxiliary Spray (alternatively, the PORVs mnay be used). Boration to cold shutdo)wn concRentratio~n is accomrplished using boric acid ferom the boric acid Storage tanks via the emergency borate valve 8104 and uJsing a cent~fugal charging PUMP (CCP1 Or CCP2) charging through valves FCGV 1.28, HGV 142, 8108, 8107, and 8146 or 8117. Sampling capability to erfbon cOncontration is availaible. Whilo reactorF coolant PUMP seal injection flA woldb AOw' available, the seal water return flow path and the normal letdown flow path arc assumed not to be available. Calculations have shown that even with. letdown unavailable, by taking credit for shrinkage of the roactorF coolant during cOOld own, sufficident voxlume is available in the reactor Goolant system to borate to cold shutdown using 4 percent boric Once the RCS is less than or equal to 390 psig and 350 0 F, the normnal RHR system is placed into service, alpng with the pO~tiGRS of the co)mponent cooling water and auxiliary salt water systems which suppo~t RHR operation.
3.7.6.2.3 Single Arativc Failurc Systems and comnponents used tpcomthe post Hosgri shutdown described above have redundant Gounterpa~ts except for-components along the normal charging-flOWpath, which lacks redundancy since its redundant flow path for emergency boration is the high preEssure safety injection flo)w path. Use of that redundant flow path isnot postulated for post Hesgri shutdown, however, so adequate redundancy had tob incorporated into the norFmal charging flewpath to enable cold shutdown following the HE. For this purpose, the Hosgri cvaluatien assumed that manual bypass valves 83878 or 8387C; would be used in the event that fail open valve FCGV 128 was to fail closed.
Manual bypass valve 8103 would be used in the event that fail closed valve HCV 142 was to fail closed. Fail-open valve FCV 11 OA and manual bypass valve 8471 would be used in the event that motor operated valve 8101 was to fail closed. Valves 8116 and 814 7 were assumed Fedun~dant for nrm)Fal charging anaves6 81145 anRd 8118 werFe assumed redundant for pressurizer auxiliar' spray. Valves with pneumnatic operators, which arc required to o~perate to achieve shutdown, were fitted with seismically qualified air-or nitrogen accumulatorFs to enable their operation in spite of thc loss of their instrument air or nitrogcn- supply. Although some of these valves do not have sfet elated operators since they are not required for accident mnitigation, they are seismAically qualified to ensure their operability for post Hosgri shutdown.
3.7-.6.2.4 Equipment ReqUircd for Post HoISgri Shutdown The equipment determined to be required to achiove post Hosgri coold shutdown in the manner described above is prese-nted in Sections 7.3 and 9.2 of Refe-rence. 15. Som~e mnrrvisionRs to the list of valves required have been made, -andarc rflecr-ted in the latest revision of the active valve list, FSAR Table 3.9 9. instrument Class 1A, 3.7-12
 
DCPP UNITS 1 & 2 FSAR UPDATE
.. St.Um.nt Class I13, .ategorv  1, and on a case by case basis, Inst.um.nt Class Q ainStrumcntation arc qualified to the Ho)Sgri parametcrs,, and assumed to be operable following an HE. Additional inStrumentation dctcrMined to be required is presented i Section 7.3 of Rcference 15. Some revisions have been mflade to that list; the rovised list ef required instrumentation is presented in Reference 16. The electrical ClasS 1E system is also qualified to the Hoogri parameters, and is assumned to be operabl foloieng a-nHE.
3.7-13
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.7.6 APPLICATION OF THE LTSP TO MODIFICATIONS AND ADDITIONS As indicated in Section 3.7.1, one of the on-going commitments associated with the LTSP requires that certain plant additions and modifications, as identified in Reference 23, would be checked against insights and knowledge gained from the LTSP to verify that the plant seismic margins remain acceptable (Reference 23).
The LTSP findings have demonstrated that the use of the original DCPP design criteria and methodology for DE, DDE, and 1977 HE consistently produces an adequately conservative design. Therefore, future additions and modifications to DCPP will be designed and constructed in accordance with the existing seismic qualification basis.
This includes the following:
(1)    The earthquake motions defined for the DE,-DDE, and 1977 HE.
(2)    The acceptance criteria and methodology corresponding to each of these earthquakes.
In addition, in order to take advantage of the insights and knowledge gained from the LTSP, certain additions and modifications will be evaluated under the LTSP, to verify that the seismic margins remain acceptable. The basis for this selection process is described in Section 3.7.6.1.
3.7.6.1 Basis for Selection of LTSP Evaluation Scope 3.7.6.1.1 Modifications and Additions in the LTSP Evaluation Scope The additions and/or modifications of plant structures and components that will be evaluated under the LTSP are selected based on the following:
(1)    The seismic probabilistic risk assessment studies have identified certain structures and components that are significant contributors to the Plant seismic risk (e.g., turbine building and diesel control panel. The seismic capacities are defined in terms of average spectral acceleration in 3 to 8.5 hertz frequency range of the 5 percent damped horizontal ground response spectrum having the same spectral shape as the 1991 LTSP spectrum shown in Figure 2.5-33.
(2)    Maior modifications to structures particularly important to plant safety are included (e.g., the containment structures and auxiliary building). Maior modifications are defined as those chantges that significantly affect the dynamic properties (such as mass, stiffness) and strengths of the structures.
3.7-14
 
DCPP UNITS 1 & 2 FSAR UPDATE (3)    New/unique structures (such as non-safety related structures which could interact with safety related structures) that significantly impact the seismic margins of the existing safety-related structures.
(4)    Masonry walls (all new construction and significant modifications to' existing walls).
(5)    Specific issues determined to be important in the LTSP margins evaluation (e.-g. relay chatter and electrical panel anchorage).
(6)    New maior safety related equipment that may significantly impact seismic risk (e.g., diesel generator no. 2-3).
Tables 3.7-25 and 3.7-26, list all structures, systems, and components (SSCs) that have the potential to impact SCDF and were evaluated under the 1991 LTSP. The tables also indicate which of the listed SSCs require LTSP evaluations for the impact of additions or modifications. The original (1991) scope of these tables, as listed in References 19 and 20, was developed based on the methods and evaluations described in Reference 39, which identified the SSCs that were the dominant contributors to the overall seismic risk. Based on estimates of the fragilities for these SSCs, a subset were modeled in the seismic PRA, while the remainder were not modeled, based on their relatively high seismic capacities.
SSCs have been, and will continue to be, added to Tables 3.7-25 and 3.7-26 if the SSC meets the criteria for requiring an LTSP evaluation, described above.
3.7.6.1.2 Modifications and Additions Excluded from LTSP Evaluation Scope Specific categories of additions and/or modifications to the structures, equipment, and components need not be evaluated under the LTSP. These categories are as follows:
(1)    Seismic like-for-like replacement-of structures, equipment, and components. These replacements will not change the SSC's seismic margin.
(2)    Minor additions or modification to structures (such as access platforms, typical core drills, modifications to nonstructural elements, etc.). These additions and modifications will not significantly affect the structure's seismic margin.
(3)    Additions or modifications to electrical raceways and supports. These commodities have high seismic margins due to redundancies in design and high damping.
(4)    Additions or modifications to HVAC ducts and duct supports. These commodities have high seismic margins due to redundancies in design.
3.7-15
 
DCPP UNITS 1 & 2 FSAR UPDATE (5)    Additions or modifications to pipingq and supports. These commodities have high seismic margins due to redundancies in design.
(6)    Additions or modifications to hand-operated valves, relief valves, solenoid valves and check valves and air- and motor-operated valves, due to their high seismic margins. Specific exceptions are noted in Table 3.7-26.
(7)    Other additions and modifications not meeting the criteria defined in Section 3.7.6.1.1 3.7.6.2 LTSP Evaluation Process The following provides a summary of the key steps of the LTSP evaluation process applied to additions and modifications to DCPP structures, systems, and components.
An overview of the LTSP evaluation process is shown in Figure 3.7-33.
(1)    Additions and modifications are designed in accordance with the DCPP design change process, considering the applicable seismic qualification bases (e.g., DE, DDE, HE, as applicable), and reviewed under the Licensing Basis Impact Evaluation process.
(2)    The scope of the addition or modification is checked against the criteria defined in Section 3.7.6.1 to determine if an LTSP evaluation is required.
If an LTSP evaluation is required, proceed to Step (3), otherwise, the process is complete at this stage.
(3)    Calculate the 84th percentile ground motion response spectrum High-Confidence-Low-Probability-of-Failure capacity (HCLPF84) capacities for the in-scope items using either the Fragility Analysis method (see Section 3.7.6.2.1), the Conservative Deterministic Failure Margin (CDFM) method (see Section 3.7.6.2.2), or the earthquake experience data method (see Section 3.7.6.2.3).
(4)    If the in-scope item is a new SSC, skip to Step (6). Otherwise, for modifications to existing SSCs, proceed to Step (5).
(5)    If the revised capacity for a modified SSC is.greater than or equal to the value listed in Tables 3.7-25 or 3.7-26, skip to Step (9). Otherwise proceed to Step (6).
(6)    Calculate the seismic margin (ratio of the HCLPF capacity to the seismic demand associated with the 1991 LTSP ground motion spectrum) for the SSC. If the seismic margin is greater than or equal to 1.3*, skip to Step (8). Otherwise, proceed to Step (7).
3.7-16
 
DCPP UNITS 1 & 2 FSAR UPDATE
* A seismic margin of less than 1.3 is acceptable for certain SSCs (see Section 2.5.6.2.1.1). For these SSCs, skip to Step (8).
(7)    Determine if a license amendment request will be pursued to allow a seismic margin below 1.3 for SSC. If a license amendment reguest is submitted, hold design pending receipt of license amendment, then proceed to Step (8). Otherwise, redesign the new/modified SSC to increase the seismic margin and return to Step (1).
(8)    Calculate the fragility curve for the new/modified SSC (see Section 3.7.6.2.1) and conduct a seismic probabilistic risk assessment, in accordance with ASME/ANS RA-Sa-2009 and RG 1.200, Rev. 2, to determine the seismic core damage frequency.
(9)    The LTSP evaluation for the new/modified SSC is complete.
Note that the process for the LTSP evaluation, described above, is in terms of the horizontal ground motion and the fragility/capacity of the SSC relative to horizontal input motion. A similar approach can be applied to the vertical ground motion and the fragility/capacity of the SSC relative to vertical input motion. However, as discussed in Chapter 6 of Reference 19, the fragilities of most SSCs are dominated by their response to horizontal input motion, and the contribution due to vertical input motion is generally small. Therefore, the consideration of the impact of vertical input motion on the LTSP evaluation of a specific SSC will be addressed on a case-by-case basis.
3.7.6.2.1    Fragility Analysis Method During the initial implementation of the LTSP (1985 through 1991), the HCLPF capacities of most SSCs were developed using the fragility analysis method. Details of the fragility analysis method are described in Chapter 6 of the 1988 LTSP Final Report (Reference 19). The fragility curves (see Figure 2.5-39 for sample curve) are tied to the 5% damped spectral acceleration value, averaged between 3 and 8.5 Hz.
The computation of fragilities for new components, modifications to existing components, or as inputs to the evaluation of updated LTSP sei-SMi hazards ,Ru*-
probabilistic risk assessment and/or deterministic seismic margin evaluation (See Section 2.5.6) shall be based on the methods described in ASME/ANS RA-Sa-2009 (Reference 36), as modified by Regulatory Guide 1.200, Revision 2 (Reference 37).
3.7.6.2.2 Conservative Deterministic Failure Margins Method During the initial implementation of the LTSP (1985 through 1991), the HCLPF capacities of certain SSCs were developed using the CDFM method, and compared to the HCLPF capacities developed based on the fragility method. This comparison validated the approximate equivalency of the two methods. General guidelines of the application of the CFDM method are provided in EPRI NP-6041-SL (Reference 35).
3.7-17
 
DCPP UNITS 1 & 2 FSAR UPDATE Details of the application of the CDFM method at DCPP are described in PG&E report "Additional Deterministic Evaluations Performed to Assess Seismic Margins of the Diablo Canyon Power Plant" (Reference 38).
The HCLPF capacities are tied to the 5% damped spectral acceleration value, averaged between 3 and 8.5 Hz. The same methodology may be used for the computation of HCLPF capacities for new components, modifications to existing components, or as input to the evaluation of updated LTSP seismic hazards input (See Section 2.5.6).
3.7.6.2.3 Earthquake Experience Data Method Durinq the initial implementatio.n of the LTSP (1985 through 1991), the HCLPF capacities of components associated with the 230kV switchyard (e.g., transformers, breakers, switches) were developed using the earthquake experience data method.
General guidelines of the application of the earthquake experience data method are provided in Appendix A to EPRI NP-6041-SL (Reference 35). Details of the application of the earthguake experience data method at DCPP are described in PG&E report "Long Term Seismic Program - Seismic Capacity of the 230 kV Switchyard" (Reference 34).
The HCLPF capacities are tied to the 5% damped spectral acceleration value, averaged between 3 and 8.5 Hz. The same methodology may be used for the computation.of HCLPF capacities for new components, modifications to existing components, or as input to the evaluation of updated LTSP seismic hazards input (See Section 2.5.6).
3.7-18
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.
 
==7.7 REFERENCES==
: 1. Deleted in Revision 4.
: 2. Lawrence Livermore Laboratory, Soil-Structure Interaction: The Status of Current Analysis Methods and Research, NUREG/CR-1780, January 1981.
(Section by J. M. Roesset.)
: 3. J. E. Luco, Independence Functions for a Rigid Foundation on a Layered Medium, Nuclear Engineering and Design, Vol. 31, 1974.
: 4. R. V. Whitman and F. E. Richardt, Design Procedures for Dynamically Loaded Foundations, Journal of Soil Mechanics and Foundations Division, SM6, Nov. 1967.
: 5. G. Bohm, Seismic Analysis of Reactor Internals for Pressurized Water Reactors, First National Congress of Pressure Vessel and Piping Technology, ASME Panel on Seismic Analysis & Design of Pressure Vessel and Piping Components, San Francisco, May 10-12, 1971.
: 6. U.S. Atomic Energy Commission (Division of Reactor Development) Publication TID - 7024, Nuclear Reactors and Earthquakes.
: 7. Appendix A to 10 CFR 100, Seismic and Geologic Siting Criteria for Nuclear Power Plants.
: 8. Damping Values of Nuclear Power Plant Components, WCAP-7921-AR, May 1974.
: 9. Stress Evaluation of Piping Systems Assuming Single Snubber Failures, Letter dated January 24, 1978, from P.A. Crane (PG&E) to J.F. Stolz (NRC).
: 10. Description of the Systems Interaction Program for Seismically Induced Events, Revision 4, August 29, 1980.
: 11. Answer to the NRC Staff Questions on the Westinghouse Evaluation of the Effect of Grid Deformation on ECCS Performance, transmitted via letter May 11, 1978, P.A. Crane to J.F. Stolz.
: 12. Supplement No. 5 to the Safety Evaluation of the Diablo Canyon Nuclear Power Station, Units 1 and 2, Nuclear Regulatory Commission, Division of Reactor Licensing, Washington, DC, September 1976.
: 13.  "Dynamics of Fixed-Base Liquid Storage Tanks," Velestsos, A.S. and T.Y. Yang; Proceedings of U.S.-Japan Seminar on Earthquake Engineering Research with Emphasis on Lifeline Systems, Tokyo, November 1976.
3.7-19
 
DCPP UNITS 1 & 2 FSAR UPDATE
: 14. Westinghouse 1981 ECCS Evaluation Model Using the BASH Code, WCAP-10266-P-A, Rev. 2, March 1987.
15, Seism,  Eva-*
uation for P,.÷tulatcd 7.5M Hesqri Earthgua"l,  DCPP  Wnit  4-&2, PG&E.Deleted in Revision 21 16, PG&E Dcsign Change Packa..        N
                              ,7546.Deleted          in Revision 21 17, PG&E= Letter to thc NIRC, DCL- *2*    98 (LER 1 92 015).Deleted in Revision 21
: 18. Phase I Final Report - Design Verification Program, Diablo Canyon Power Plant, Revision 14, transmitted via letter dated October 14, 1983, J. 0. Schuyler (PG&E) to D. G. Eisenhut (NRC).
: 19. Final Report of the Diablo Canyon Long Term Seismic Program, July 1988, PG&E.
: 20. Addendum to the 1988 Final Report of the Diablo Canyon Long Term Seismic Program, February 1991, PG&E.
: 21. NUREG-0675, Supplement Number 34, Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2, NRC, June 1991.
: 22. NRC letter to PG&E, "Transmittal of Safety Evaluation Closing Out Diablo Canyon Long-Term Seismic Program," April 17i 1992.
: 23. PG&E letter to the NRC, "Long Term Seismic Program - Future Plant Modifications," DCL-91-178, July 16, 1991.
: 24. Supplement No. 7 to the Safety Evaluation of the Diablo Canyon Nuclear Power Station, Units 1 and 2, Nuclear Regulatory Commission, Division of Reactor Licensing, Washington, DC, May 1978.
: 25. Supplement No. 8 to the Safety Evaluation of the Diablo Canyon Nuclear Power Station, Units 1 and 2, Nuclear Regulatory Commission, Division of Reactor Licensing, Washington, DC, November 1978.
: 26. Damping Values for Seismic Design of Nuclear Power Plants, Regulatory Guide 1.61, USAEC, October 1973.
: 27. PG&E Licensing Basis Impact Evaluation 2005-03, "Replacement Steam Generator Seismic Damping Values," May 25, 2005.
: 28. Deleted 3.7-20
 
DCPP UNITS 1 & 2 FSAR UPDATE
: 29. SFAD-07-168, Revision 1, Diablo Canyon Unit 2 Seismic and LOCA Analysis for Reactor Vessel Head Project, Staub, D. E. and Jiang, J. X., January 24, 2008 (Located in PG&E Document 6023227-139).
: 30. PG&E Document 6023227-19, "Damping Values for Use in the Integrated Head Assembly Seismic Response Analysis at Diablo Canyon Power Plant (DCPP)
Units 1 and 2."
: 31. Damping Values for Seismic Design of Nuclear Power Plants, Regulatory Guide 1.61, Revision 1, USNRC, for the Seismic Analyses for the IHA and Unit 2 CRDMs.
: 32. PG&E letter to the NRC, "Benefits and Insights of the Long Term Seismic Program," DCL-91-091, April 17, 1991
: 33. PG&E letter to the NRC, "Long Term Seismic Program - Additional Deterministic Evaluations," DCL-90-226, September 18, 1990
: 34. PG&E letter to the NRC, "Long Term Seismic Program - Seismic Capacity of the 230 kV Switchyard," DCL-90-205, October 8. 1990
: 35. Electric Power Research Institute, "A Methodology for the Assessment of Nuclear Power Plant Seismic Maroins." Repnort No. NP-6041-SL. Revision 1. Aunust 1991
: 36. American Society of Mechanical Engineers/American Nuclear Society, "Addenda to ASME/ANS RA-Sa-2008, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment of Nuclear Power Plant Applications," Standard No. ASME/ANS RA-Sa-2009.
: 37. United States Nuclear Regulatory Commission, "An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Resutls for Risk-Informed Activities," Regulatory Guide 1.200, Revision 2, March 2009.
: 38. PG&E letter to. the NRC, "Long Term Seismic Program - Additional Deterministic Evaluations," DCL-90-226. September 18, 1990.
: 39. PG&E Letter to the NRC, "Long Term Seismic Program - Results of Phase II Scoping Study," DCL-86-022, January 30, 1986.
3.7-21
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 3.7-25 HIGH CONFIDENCE LOW PROBABILITY OF FAILURE (HCLPF 84 )CAPACITIES AND SEISMIC MARGINS FOR CIVIL STRUCTURES(e)
HCLPF.M          Seismic        In Scope for LTSP Review of Structure                  Caoacitv ((        Margin(b              Modifications(*-?
Containment Structures                  4.30            2.22                        Y Containment Interior Structures              3.58            1.85                        Y Intake Structure                    3.88            2.00                        Y Auxiliary Building                  3.19            1.64                        Y Turbine Building                    2.21            1 .1 4 (dI                  Y (includinq Turbine Pedestals)
Refiuelin9 Water Storage Tanks            . 4.21            2.17 Condensate Storaoe Tank                    >5            >2.58 Diesel Generator Fuel Oil Storage Tanks          >5            >2.58 Safety Related Masonry Walls                2.83            1.46                        Y Notes:
(a) The HCLPF84capacity is equal to 1.20 times the HCLPF      (median) capacity (b) The seismic margin equals HCLPF. 4 capacity divided by 1.94 q (applicable to horizontal input motion).
(c) Per Reference 23. See Section 3.7.6.1.1.
(d) Seismic margin of less than 1.3 acceptable for Turbine Building, see Section 2.5.6.2.1.1.
(e) The HCLPF84 capacities and seismic margin value provided in this table are associated with horizontal input motion. The corresponding values' associated with vertical input motion are not reported, and must be evaluated on a case-by-case basis, if required, as discussed in Section 3.7.9.2.
3.7-22
 
DCPP UNITS I & 2 FSAR UPDATE TABLE 3.7-26                                  Sheet        of 4 HIGH CONFIDENCE LOW PROBABILITY OF FAILURE (HCLPF8 4)CAPACITIES AND SEISMIC MARGINS FOR EQUIPMENT AND COMPONENTS(')
HCLPF        Seismic    In Scope for LTSP Review System/Component        Capacity (q)(a
* of Modifications(C)?
Nuclear Steam Supply System Reactor Pressure Vessel                        4.01        2.07 Reactor Internals                              4.85        2.50
    - Integrated Head Assemblil                                1.24(d__))
2.40                                Y Steam Generators                              3.16        1.63                  Y Pressurizer                                    4.00        2.06 Pressurizer Safety Valves                      >3        >1t55 Power Operated Relief Valves                  2.78        1.43                  Y_
Reactor Coolant Pumps                          3.40        1.75                  y Control Rod Drives                            4.08        2.10 NSSS Piping                                    >3        >1.55 Residual Heat Removal RHR Pumos                                      4.02        2.07 RHR Heat Exchangers                            4.18        2,15 Safety Injection SI Accumulators                                5.44        2.80 St Pumps                                      5.57        2.87 Boron Injection Tank                          4.75        2.45 Component Cooling Water CCW Pumps                                      4.49        2.31 CCW Heat Exchangers                            3.06        1.58                  Y CCW Surge Tank                                3.31        1.71                  Y Chemical and Volume Control ECCS Centrifugal Charging Pumps                5.34        2.75 Auxiliary Saltwater ASW Pumps                                      >3        >1.55 ASW Piping                                    5.45        2.81 Containment Spray CS Pumps                                      4.62        2.38 Spray Additive Tank                            3.68        1.90 3.7-23
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 3.7-26                                Sheet 2 of 4 HCLPF,        Seismic  In Scope for LTSP Review System/Component            Capacity (g)(8)      n        of Modificationst'l?
Main Steam MS Isolation Valves                                >3          >1.55 MS Safety Valves                                    >3          >1.55 MS PORVs                                          4.21          2.17 Auxiliary Feedwater AFW Pumps (Motor Driven)                            >3          >1.55 AFW Pumps (Turbine Driven)                          4.06          2.09 Diesel Generator DG Fuel Oil Day Tank                                >3          >1.55 DG Fuel Oil Pumps/Filters                          4.39          226 DG Fuel Off Shutoff Valve                          >3          >1,55 DG Air Start Compressor                            >3          >1t55 DG Air Start Receiver                              >3          >1.55 Diesel Generators                                  4.37          2.25 DG RadiatorNWater Pump                            4.39          2.26 DG Inlet Silencer/Air Filter                        >3          >1.55 DG Excitation Cubical                              3.08          1.59                y DG Control Panel
    - Chatter                                          5.51          2.84                Y
    - Structural                                      2.69.        1.39                Y DG Main Lead Terminal/Box                            >3        >1.55 Containment Building Ventilation Containment Fan Cooler                            3.38          1.74              Y Control Room Ventilation Supply Fans                                        4.58          2.36 AC Units/Compressor                                  >3        >1.55 Control Cabinets                                    >3        >1.55 480V Switchgear/Inverter/DC Switchgear/Spreading Room Ventilation Supply/Retum Fans                                  4.74          2.44 Backdraft and Shutoff Dampers                        >3        >1.55 4160V (Vital) Electric Power Switchgear
    - Chatter                                          1.57        0.81(d)              y
    - Structural                                      3.84          1.98              Y Potential Transformers
    - Bus F                                            4.16          2.14 Buses G & H                                        >3          >1,55 3.7-24
 
DCPP UNITS 1 & 2'FSAR UPDATE TABLE 3.7-26                                Sheet 3 of 4 HCLPF.A      Seismic In Scope for LTSP Review System/Component          Capacity (d,(Ol              of Modifications(q?
Safeguard Relay Panel                            4,07        2.10 125V DC Electric Power Batteries                                        3.29        1.70                Y Battery Racks                                    6.48        3,34 Battery Chargers                                  3.52        1.81                Y_
Switchqear/Breaker Panels                        2.83        1,46                Y_
120V AC Electric Power Instrument Breaker Panels                        >3          >1.55 Inverters                                        3.30          1.70              Y 480-V (Vital) Electric Power 4160-V/480-V Transformers                        2.90        1.49                Y_
Breaker Cabinets (Load Centers)                    >3          >1.55 Auxiliary Relay Panel                            4.28        2.21 Control Room Main Control Boards                                                              Y
    -  Switch Function                                >3          >1.55
    - Structural                                    3.58          1.85 Hot Shutdown Panel
    - Switch Function                                4.36        2.25
    - Structural                                    4,.22        2.18 Auxiliary Safeguards Cabinet                      >3          >1,55 NSSS Control Process Control and Protection System            4.28          2.21 Solid State Protection System                    5,18          2.67 Reactor Trip Switchgear                          3.77          1.94 Resistance and Temperature Detectors              >3          >1.55 Pressure and DP Transmitters                    4.93          2.54 Miscellaneous Components Auxiliary Relay Rack                              >3          >1.55 Local Starter Boards                              >3          >1.55 Mnldrisl      Circuit Breakmre                  >3          >1.55 Valve Limit Switches                              >3          >1.55 Impulse Lines (which affect LOCA)              3.16          1.63              Y Containment Purge Valves                          >3        >1.55 3.7-25
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 3.7-26                                      Sheet 4 of 4 HCLPF,        Seismic      In Scope for LTSP Review System/Component              Capacity (qoP          n            of Modificatlonsýcý?
Generic Components 230 kV Off-Site Power
        - Circuit Breakers                                  0.84          0.43(d)                  Y
        - Switches                                          0.84          0 .4 3 "d)              y
        - Transformers                                      0.84          0 .4 3 (d)              Y Penetrations. Penetration Boxes                    3.40            1.75 BOP Pinincg and Supports                            3.60            1.86 Hand, Relief, Solenoid, and Check Valves            >3          >1.55 Air and Motor Operated Valves                      4.28          2.21 Cable Trays and Supports                            >3          >1.55 HVAC Ducting and Supports                          2.99            1.55 Notes:
(a) The HCLPFS4 capacity is equal to 1.20 times the HCLPFa0 (median) capacity (b) The seismic marqin equals HCLPF capacity divided by 1.94 q.
(c) Per Reference 23. See Section 3.7.6.1.1.
(d Seismic margin of less than 1.3 acceptable for this component, see Section 2.5.6.2.1.1.
(e) The inteqrated head assembly (IHA) provides lateral support to the control rod drive mechanisms.
Seismically induced failure of the IHA could impair control rod drop required for reactor trip. Since the reactor trip function is modeled as part of the reactor internals in the seismic PRA, the IHA is treated as a subcomponent of the reactor internals.
(f  The HCLPF84 capacities and seismic margin value provided in this table are associated with horizontal input motion. The corresponding values associated with vertical input motion are not reported, and must be evaluated on a case-by-case basis, if required, as discussed in Section 3.7.9.2.
3.7-26
 
DCPP UNITS 1 & 2 FSAR UPDATE Unmodified (transformed and scaled up by 1.6) 1.2 a
4-0      0 S
      -1.2 Modified 1.2
.2 0      0
.2 S
0 0
    -1.2 0              3'          6            9            12          .15          18 Time (sec)
Notes:
1, This figure is reproduced from Reference 19, Figure 5-23 2,      This figure is for comparison purposes only and shall not be used for design FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 3.7-29 SAMPLE FREE FIELD GROUND MOTION LTSP ANALYSIS LONGITUDINAL COMPONENT 3.7-27
 
DCPP UNITS 1 & 2 FSAR UPDATE Unmodified (transformed and scaled up by 1.6) 1.2 02 0
I-02  0 02 03 a
    -1.2 Modified S
02 0              3            6            9            12            15          18  21 Time (sec)
Notes:
: 1. This figure is reproduced from Reference 19, Figure 5-24
: 2. This figure is for comparison purposes only and shall not be used for design FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 3.7-30 SAMPLE FREE FIELD GROUND MOTION LTSP ANALYSIS TRANSVERSE COMPONENT 3.7-28
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.0 2.5 2.0 1.5 CL V) 1.0 Frequency (Hz)
Notes:
: 1. This figure is reproduced from Reference 33. Figure DE Q2-3
: 2. This figure is for comparison purposes only and shall not be used for design FSAR UPDATE UNITS I AND 2 DIABLO CANYON SITE FIGURE 3.7-31 SAMPLE FREE FIELD GROUND MOTION COMPARISON TO TARGET SPECTRUM LTSP ANALYSIS LONGITUDINAL COMPONENT
                                                                      .5% DAMPING RATIO 3.7-29
 
DCPP UNITS 1 & 2 FSAR UPDATE S~  2.0 o                L0,"  -,,              '
  .*    1.5/
      . 1.0o                                                            -
          .5 01                      I I  I. i  )    I  I.                              .
10                              100 Frequency (Hz)
Notes:
: 1. This figure is reproduced from Reference 33, Figure DE Q2-4
: 2. This figure is for comparison purposes only and shall not be used for design FSAR UPDATE UNITS 1 AND 2 DIABLO CANYON SITE FIGURE 3.7-32 SAMPLE FREE FIELD GROUND MOTION COMPARISON TO TARGET SPECTRUM LTSP ANALYSIS TRANSVERSE COMPONENT 5% DAMPING RATIO 3.7-30
 
Design Change For Plant Modifications or Additions
                                          . ...... -[ ...  .            S Design.
or C617l6.nt    StctI,ue DE.
n(SSC)'.for  staem, Sit  n and HE ODE, (as Applicable)
Hih6ýnfidh e: Lo
                                                                'O:.Does Probability of Failur.6 (HCLPF) 4Yes          SSC Require                      -    No--
                                                ýCapact                      Rview for LTSP Of NeMdiffi dSSC?'-
Is Is                        HC      Ca*tCpacity SSC dValue New        No-  N                in.Tabl
: 7.                  72or3.7-26 No Caiculae 'Seismic Yes-                Ma in for SSC.
Is Seismic Margin' No, Rvis Designi to                                        Licensýeý Amedent t CapaPcity                                                      7 ree Yes                    Yes Receipt of License":
Develop New/Revised Fmgility IiCurse forSSC;-
Cn*d"ct Seisrnic Piobabillstic Risk Assessment to Determine Seismic SCo°re .Da-mageF'requency Notes:                                                                                                        FSAR UPDATE
: 1. A seismic margin below 1.3 is acceptable for certain SSCs                                                  UNITS I AND 2 (see Section 2.5.6.2.1.1). Therefore, redesign or a License                                          ...        .
Amendment Request is not required for these SSCs.                                                  UIRALU koArNTUN Zo1I I:
FIGURE 3.7-33 LTSP Evaluation Process for Plant Additions and Modifications
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.8.1  CONTAINMENT STRUCTURE 3.8.1.1 Description of the Containment The reactor containment for each unit is a steel-lined, reinforced concrete building of cylindrical shape with a dome roof that completely encloses the reactor and RCS. It ensures that essentially no leakage of radioactive materials to the environment would result even if gross failure of the RCS were to occur simultaneously with an earthquake of intensity twice the maximum postulated.
The containment structures for Units 1 and 2 are essentially identical, as mirror images.
The following discussion applies to either unit:
The concrete outline and equipment locations are shown in Chapter 1. The exterior shell consists of a 142-foot-high cylinder, topped with a hemispherical dome. The minimum thickness of the concretewalls is 3.6 feet, and the minimum thickness of the concrete roof is 2.5 feet. Both have a nominal inside diameter of 140 feet and a nominal inside height of 212 feet. The concrete floor pad is 153 feet in diameter with a minimum thickness of 14.5 feet, with the reactor cavity near the center. The inside of the dome, cylinder, and base slab is lined with welded steel plate, which forms a leaktight membrane. The nominal thickness of the steel liner is 3/8-inch on the wall and dome and the nominal thickness of the steel lineron the base slab is 1/4-inch.
The containment is designed and will be maintained for a maximum internal pressure of 47 psig and a temperature of 271 OF, coincident with a Double Design Earthquake or Hosgri Earthquake.
The internal concrete structure approximates a 106-foot-diameter, 51-foot-high cylinder, with a slab on top. However, there are multiple openings and walls, such as the reactor support and the stainless steel lined refueling canal, which complicate the shape. The walls and top slab are generally 3. feet thick. This structure provides support for the reactor and components of the RCS, provides radiation shielding, and provides protection for the liner from postulated missiles originating from the RCS.
A polar crane is mounted on top of the internal concrete cylinder wall. The support of the polar crane, its connection to the concrete, and provisions to resist seismic forces are shown in Figure 3.8-23 and described in Section 9.1.4. Seismic analysis for the polar crane is discussed in Section 3.7.
The piping and electrical connections between equipment inside the containment structure and other parts of the plant are made through specially designed, leaktight penetrations. In addition to the piping and electrical penetrations, other penetrations are the 18-foot 6-inch diameter equipment hatch, the 9-foot 7-inch diameter personnel hatch, the 5-foot 6-inch diameter personnel emergency hatch, and the fuel transfer tube.
3.8-1
 
DCPP UNITS 1 & 2 FSAR UPDATE The 6-foot 7-inch by 13-foot ventilation duct is attached to the outside of the structure, extending from an elevation 25 feet above the base slab to the top of the dome. The duct is fabricated from steel plate with stiffeners.
A system of lightning rods is installed on the dome to protect against lightning damage.
The following paragraphs describe the various parts of the structure:
3.8-2
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.9.3 CORE AND REACTOR INTERNALS 3.9.3.1 Core and Internals Integrity Analysis (Mechanical Analysis)
Stainless steel clad silver-indium-cadmium alloy absorber rods are resistant to radiation and thermal damage, thereby ensuring their effectiveness under all operating conditions.
Rods of similar design have been successfully used in the original and reload cores of San Onofre, Connecticut Yankee, and others.
Two burnable poison rods (Reference 6) of smaller length but similar in design to those used in DCPP were exposed to in-pile test conditions in the Saxton Test Reactor in October 1967. A visual examination of the rods was made in early June 1968 and a visual and profilometer examination was made on July 30, 1968, after an exposure of 1900 effective full power hours (approximately 25 percent B10 depletion). The rods were found to be inexcellent condition and profilometry results showed no dimensional variation from the initial condition.
An experimental verification of the reactivity worth calculations for borosilicate glass tubing has been accomplished. Similar rods have been successfully operated in the Ginna Reactor (Reference 7) with no evidence of deficiency.
Manufacturing defects did not appear during the hot functional tests because any manufacturing defects were detected in the shop or during the assembly period. The basic program that is currently being used to ensure adequacy of manufacturing practices consists of:
(1)    Extremely thorough nil ductility temperature and quality assurance programs at the internals vendors (2)    Extensive visual examination at the plant site prior to hot functional testing of the primary system (3)    Running the hot functional test with full flow for 240 hours that accumulates approximately 107 cycles on the majority of the core structure components (4)    Reexamining all areas of the internals after the 240-hour hot functional test The response of the reactor core and vessel internals under excitation produced by a simultaneous complete severance of a reactor coolant pipe and seismic excitation for a typical Westinghouse pressurized water reactor plant internals was determined. The following mechanical functional performance requirements applied:
(1)    Following the DBA, the basic operational or functional requirement to be met for the reactor internals is that the plant shall be shut down and cooled in an orderly fashion so that fuel cladding temperature is kept within 3.9-1
 
DCPP UNITS 1 & 2 FSAR UPDATE specified limits. This implies that the deformation of certain critical reactor internals must be kept sufficiently small to allow core cooling.
(2)    For large breaks, the reduction in water density greatly reduces the reactivity of the core, thereby shutting down the core whether the rods are tripped or not. The subsequent reflooding of the core by the ECCS with borated water maintains the core in a subcritical state. Therefore, the main requirement is to ensure effectiveness of the ECCS. Insertion of the control rods, although not needed, gives further assurance of the ability to shut the plant down and keep it in a safe shutdown condition.
(3)  The functional requirements for the core structures during the DBA are shown in Table 3.9-10. The inward upper barrel deflections are controlled to ensure no contacting of the nearest rod cluster control guide tube. The outward upper barrel deflections are controlled in order to maintain an adequate annulus for the coolant between the vessel inner diameter and core barrel outer diameter.
(4)  The rod cluster control guide tube deflections are limited to ensure operability of the control rods.
(5)  To ensure no column loading of rod cluster control guide tubes, the upper core plate deflection is limited to the value shown in Table 3.9-10.
(6)  The reactor has mechanical provisions that are sufficient to maintain the design core and intemals and to ensure that the core is intact with acceptable heat transfer geometry following transients arising from the DBA operating conditions (References 2, 8, and 13).
(7)  The core internals are designed to withstand mechanical loads arising from DE, DDE, HE, and pipe ruptures (References 2, 4, 8, and 13).
While these performance requirements originally had to be met for load combinations that included the contribution from a main RCS loop line break, with the acceptanc6 of the DCPP leak-before-break analysis by the NRC (Reference 14), dynamic loads resulting from pipe rupture events in the main reactor coolant loop piping no longer have to be considered in the design basis structural analyses and included in the loading combinations; only the much smaller loads from RCS branch line breaks have to be considered (see Section 3.6.2.1,1.1).
3.9-2
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.9.3.5.1 Blowdown Forces Due to Cold and Hot Leg Break A USNRC approved FORTRAN-IV computer program called MULTIFLEX (Reference 3) is used to calculate the local fluid pressure, flow, and density transientsthat occur during a LOCA. MULTIFLEX is an extension of the BLODOWN-2 computer code and includes mechanical structure models and their interaction with the thermal-hydraulic system.
The analysis is performed for the subcooled decompression period of.the transient, where the hydraulic loads are the greatest. These loads are used for the structural evaluation of the reactor pressure vessel support system, in conjunction with other loads associated with a LOCA and with the Hosqri earthquake (HE). (Previous calculations usingq LOCA and DDE loads that bound the LOCA and HE loads would be conservative.)
3.9-3
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 3.9-9                                                                      Page 24 of 25 Failure Valve                                              Size          Actuator        Valve Position    Position for Safe    Analysis System or Service Description              Identification  - FSAR Fig. No. Body-Type            in.            Type          On Failure        Shutdown(a)      Comments MAIN STEAM LEAD FOUR 10%                    MS-4015            3.2-4            Gate              8            Manual              NA                Closed STEAM DUMP ISOLATION                                                                                                                                  Note 24 (a)  The valves whose positions are listed in this column are those valves whose operability is relied on to perform an active function such as safe shutdown of the reactor or mitigation of the consequences of a Design Basis Accident coincidental with loss of offsite power. An entry of "functional" or equivalently "operable" means that the valve must be capable of being opened and/or closed to perform its active function. For DCPP, safe shutdown is defined as Mode 3 following an accident (SSER 7 and SSER 22), Mode 5 following a Hosgd earthquake ........ 3.7.64), and Mode 3, followed by Mode 5 within 72 hours, following an Appendix R fire (10 CFR 50, Appendix R).
Failure Analysis Comment Notes:
: 1. Deleted in Revision 9.
: 2. Deleted in Revision 9.
: 3. Deleted in Revision 9.
: 4. Valve is provided for control. Failure, open or close, is remedied by redundant train and EOP RNO actions.
: 5. Valve provides isolation. Failure to close is remedied by valve in series.
: 6. Deleted in Revision 9.
: 7. Locally mounted air accumulators protected against compressed air system failure by check valves can hold open the main steam isolation valves for a short duration of time after the compressed air system is lost. In the event of loss of all air to the main steam isolation valves, the valves will fail closed.
: 8. These valves are provided for controlled steam release. Failure to open is remedied by redundant valves. Failure to close is remedied by closure of series valve or system shutdown.
: 9. These valves provide vessel protection. Failure to open is remedied by redundant valves in parallel. Valve size limits flow on failure to close.
    ,10. Valve provides isolation. Failure to close (or stay closed) is remedied by a redundant valve in series. Failure to open (or stay open) is remedied by a redundant line (or system).
: 11. Valve opens to start device. Failure to open is remedied by use of redundant system.
: 12. Air-operated valve operation is not required for safe shutdown.
: 13. Used during recirculation mode.
 
                                                                  .DCPP UNITS I & 2 FSAR UPDATE TABLE 3.9-9                                                                Page 25 of 25 Failure Analysis Comment Notes (continued)
: 14. Valve provides isolation. Failure to stay open could defeat system function. "Hot" short could close valve, but is not considered credible.
: 15. Deleted in Revision 9.
: 16. Deleted in Revision 9.
: 17. Deleted in Revision 9.
: 18. Deleted in Revision 9.
: 19. Valves operated (opened) during changeover from cold leg recirculation to hot leg injection. Failure to stay closed during cold leg injection or cold leg recirculation could defeat system function. "Hot" short could open valve but is not considered credible.
: 20. Valve 8809A operated (closed) during the changeover from cold leg injection to cold leg recirculation. Valve 8809B operated (closed) during the changeover from cold leg recirculation to hot leg recirculation. Failure of one valve to stay open during cold leg injection remedied by redundant system.
: 21. Air operated valves required to operate or maintain position after a loss of the compressed air system are supplied with compressed gas from the backup air/nitrogen supply system. See Section 9.3.1.6 for details.
: 22. If one of the CCW heat exchangers is valved out-of-service, then backup air is supplied to the respective CCW heat exchanger saltwater inlet valve to maintain the valve closed. This ensures all ASW flow is directed to in-service CCW heat exchangers.
: 23. Valve does not have an active safety function to support accident mitigation or Mode 3-safe-shutdown. Valve is active to support achieving Mode 5 following a Hospri earthquake and mustepest HesgreGold shutdown iA the -n Ar-4eefined4n the Wcsgrl Report. Valve needse4o be seismically qualified for active function for Hosgri earthquake loadingenly.
: 24. Valve has an active safety function to support accident mitigation or Mode 3-safe-shutdown. Valve is passive to support achieving Mode 5 following a Hosqri earthauake.post H        .cgrI cGld shutdown in tho mannor defined ii the HosgrWRepo).
: 25. Normal position for Safe Shutdown is Open. For Containment Isolation and the condition described in section 6.5.3.4, valve must be Operable.
Abbreviations:
FCV    =    Flow control valve            RCP        =    Reactor coolant pump    B'fly      Butterfly LCV    =    Level control valve            FAI        =    Fail as is              RC      =  Reactor coolant PCV    =    Pressure control valve        PP & PPS    =    Pump(s)                  CCW    =  Component cooling water HCV    =    Hand control valve            CNT        =    Containment              RHR    =  Residual heat removal RV    =    Relief valve                  CHG        =    Charging                AFW    =  Auxiliary feedwater TCV    =    Temperature control valve      DSL FO      =    Diesel fuel oil          NA      =  Not applicable
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.10.2.7,1 4160 V Metal-Clad Switchgear The original 4160 V metal-clad switchgear with General Electric (GE) 250 mVA 4.16 kV magneblast circuit breakers was seismically qualified by a combination of testing and analyses.
Later, it was discovered that 350 mVA circuit breakers should be used in place of the GE 250 mVA 4.16 kV magneblast circuit breakers. GE could not supply such breakers to the same switchgear. Consequently, PG&E decided to procure 350 mVA 4.16 kV breakers from NTS/PDS, which converted Japanese-made Yaskawa SF6 circuit breakers to fit the existing 4 kV switchgear. The new circuit breakers were installed during refueling outages 1R8 and 2R7.
New circuit breakers were seismically qualified by shake table testing (NTS report No. TR60431-95N-FR). The shake table testing was intended to achieve the following objectives.
(1)    Demonstrate the structural integrity and functionality of the Yaskawa breakers.
(2)    Demonstrate the structural integrity of as-installed 4 kV switchgear cubicles at DCPP with the Yaskawa breakers.
(3)    Demonstrate the functional performance of the existing components (i.e.,
various relays and switches) installed in the existing 4 kV switchgear cubicles with replacement Yaskawa breakers.
(4)    Instrument the test 4 kV switchgear cubicles with sufficient number of accelerometers to obtain accurate information on the dynamic response (response frequencies, test response spectra) at various cubicle locations.
This information is to be used for further/future testing and analyses.
(5)    Take immediate corrective actions to address significant anomalies observed during the test.
The initial seismic testing was performed at Wyle Laboratories in Huntsville, Alabama.
Three seismic mock-up 4 kV switchgear cubicles were built to duplicate the design, material, and construction of cubicles G-5, G-12, and G-13 of Unit 1. A total of 18 OBE-DE and SSE-DDE/HE (envelope of the applicable DDE and HE response spectra) test runs were performed, including three runs of resonance search. Test results showed that the new breakers and mock-up cubicles successfully passed the minimum required 5 OBE-DE tests.
For the SSE-DDE/HE tests performed at Wyle Laboratories, excessive relay chatter at certain frequencies were noted. The excessive chatter was due to over-testing the equipment, which in turn was a result of Wyle Laboratories being unable to accurately 3.10-1
 
DCPP UNITS 1 & 2 FSAR UPDATE control the test table response at 10 Hz and above due to resonance of the table. The over-test produced a significant amount of relay chatter, which caused the tripping and closing of breakers. The post test functional check showed that the breakers were functioning properly and had no structural damage.
To properly test the relays, supplemental SSE-DDE/HE testing was performed at Farwell and Hendricks (F&H) Laboratories. The upper front doors of the G-1 2 and G-1 3 cubicles, where a majority of relays are mounted, were mounted on the F&H rigid test fixture. One 1200A breaker and one 2000A breaker, located adjacent to the test table, were fed by the relays. The SSE--DDE/HE RRS obtained at relay locations on the G-12 and G-1 3 cubicles from the previous Wyle testing were reduced with the appropriate scaling factor to eliminate unnecessary over-testing. The supplemental SE--DDE/HE testing was successful. However, certain modifications (such as adding chokes to the breakers and removing the seal-ins from certain relays) were made when the new breakers were installed in the 4-kV switchgear.
Based on the above, the switchgear and its contents are qualified for the DE, DDE, and HEHosgri, and -LTSPp*.stuat-4 seismic events at DCPP.
3.10-2
 
DCPP UNITS 1 & 2 FSAR UPDATE 3.10.2.32.1 RVLIS/Incore Thermocouple Cabinets Two RVLIS/incore thermocouple cabinets (PAMs 3 and 4) are provided for DCPP application. Located within each cabinet are the microprocessor electronics, reactor coolant pump (RCP) status panel, and a remote display. The above RVLIS instrumentation is only required to operate normally before and after seismic excitation.
The RCP status panel assembly is shown to be operational by the signals recorded during testing and the functional checks made after each simulated SSE DDE/HE (envelope of the applicable DDE and HE response spectra). The remote display electronics must function normally by providing microprocessor output display formatted information.
The results of seismic testing of the original RVLIS/incore thermocouple cabinets are provided in Reference 27. The original remote display was not included in the cabinet tested. The original remote display was tested later to worst-case (maximum) in-cabinet response for the RVLIS/incore thermoncouple cabinets. The seismic testing of the original remote display is documented in Reference 28.
Because the original Westinghouse-supplied system is obsolete and due to the lack of availability of replacement components, the obsolete RVLIS/incore thermocouple
.systems were replaced. The replacement processors, signal conditioners, and displays are seismically qualified by testing and analysis as documented in References 47 and 48 and PG&E Calculation IS-66.
3.10-3
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 4.1-3 DESIGN LOADING CONDITIONS FOR REACTOR CORE COMPONENTS (1)    Fuel assembly weight (2)    Fuel assembly spring forces (3)    Internals weight (4)    Control rod scram (equivalent static load)
(5)    Differential pressure (6)    Spring preloads (7)    Coolant flow forces (static)
(8)    Temperature gradients (9)    Differences in thermal expansions (a)  Due to temperature differences (b) Due to expansion of different materials (10)    Interference between components (11)    Vibration (mechanically or hydraulically induced)
(12)    One or more loops out of service (13)    All operational transients listed in Table 5.2-4 (14)    Pump overspeed (15)    Seismic loads (DE 1 aid-DDE, and HE)
(16)    Blowdown forces (due to RCS branch line breaks)(a)
(a)  In the original analysis, the blowdown forces used were those resulting from breaks in the RCS cold and hot legs. However, with the acceptance of the DCPP leak-before-break analysis by the NRC, the blowdown forces resulting from pipe rupture events in the main reactor coolant loop piping no longer have to be considered in the design basis structural analyses and included in the loading combinations. Only the much smaller forces from RCS branch line breaks have to be considered (see Section 3.6.2.1.1.1).
 
DCPP UNITS 1 & 2 FSAR UPDATE 5.2.1.5.4 Faulted Conditions The following transients are considered faulted conditions:
(1)    RCS Boundary Pipe Break
            -This accident involves the postulated rupture of a pipe belonging to the RCS boundary. It is conservatively assumed that system pressure is reduced rapidly and the emergency core cooling system (ECCS) is initiated to introduce water into the RCS. The safety injection signal will also initiate a turbine and reactor trip.
The criteria for locating design basis pipe ruptures for the design of RCS supports and restraints, thus ensuring continued integrity of vital components and engineered safety features (ESF), are presented in Section 3.6. They are analyzed in Reference 7. With the acceptance of the DCPP leak-before-break analysis by the NRC (Reference 31), the dynamic effects of breaks in the main reactor coolant loop piping no longer have to be considered in the design basis analyses. Only the dynamic effects from RCS branch line breaks have to be considered (see Section 3.6.2.1.1.1).
(2)    Steam Line Break For RCS component evaluation, the following conservative conditions are considered:
(a)      The reactor is initially in hot, zero power subcritical condition assuming all rods in, except the most reactive rod, which is assumed to be stuck in its fully withdrawn position.
(b)      A steam line break occurs inside the containment.
(c)    Subsequent to the break, there is no return to power and the reactor coolant temperature cools down to 212 0 F.
(d)    The ECCS pumps restore the reactor coolant pressure.
The above conditions result in the most severe temperature and pressure variations that the component will encounter during a steam break accident.
The dynamic reaction forces associated with circumferential steam line breaks are considered in the design of supports and restraints to ensure continued integrity of vital components and ESFs. Criteria for protection 5.2-1
 
DCPP UNITS 1 & 2 FSAR UPDATE against dynamic effects associated with pipe breaks are covered in Section 3.6.
(3)    Double Design Earthquake (DDE)
The mechanical stress resulting from the DDE is considered on a component basis. As discussed in Sections 2.5.2.9.2 and 3.2.1, the DDE is part of the oriqinal The design basis for the plant-i-he4DQE and is still applicable to the desiqn of the reactor coolant system. The seismic analysis is described in Section.3.7.
(4)    Hosgri Earthquake As discussed in Sections 2.5.2.9.3 and 2.5.2.10.3, studies subsequent to the original seismological survey of the site region have resulted in the development of the Hosqri earthquake, producinq qround motions at DCCP .qreater than those associated with the DDE. a postulated-earthqUak, of greate. magnitude. The characteristics and consequences of theis peostulated Hosgri earthquake are discussed in Section 5.2.1.15.
The design transients and the number of cycles of each are shown in Table 5.2-4.
5.2-2
 
DCPP UNITS 1 & 2 FSAR UPDATE 5.2.1.7 Design of Active Pumps and Valves The design criteria for active safety-related pumps outside the RCS boundary are discussed in Section 3.9.2. All these safety-related pumps are designated either ASME B&PV Code Class IIor Ill.
Active pumps were qualified for operability by first being subjected to rigid tests both prior to installation in the plant and after installation in the plant. The in-shop test included (a) hydrostatic tests of pressure-retaining parts to 150 percent of the product of the design pressure times the ratio of materialý allowable stress at room temperature to the allowable stress value at the design temperature, (b) seal leakage tests, and (c) performance tests to determine total developed head, minimum and maximum head, net positive suction head (NPSH) requirements and other pump parameters. Bearing temperature and vibration levels were monitored during these operating tests. Bearing temperature limits and vibration levels were established by the manufacturer based on bearing materials, clearances, oil type and rotational speed. After a pump was installed in the plant, it underwent cold hydrostatic tests, and hot functional tests, and will undergo the required periodic inservice inspection operation. These tests demonstrated that a pump will function as required during all normal operating conditions for the design life of the plant.
In addition to these tests, the active pumps were qualified for operability by assuring that they will start, continue operating and not be damaged during the pEstu!ated Hosgri earthquake.
It was shown that the pumps will perform their design functions when subjected to loads imposed by the maximum seismic accelerations and maximum nozzle loads. It was required that test or analysis be used to show that the lowest natural frequency of each pump was greater than 33 Hz. A pump having a natural frequency above 33 Hz was considered rigid. This consideration avoids amplification between the component and structure for all seismic areas. A static shaft deflection analysis of rotors was performed with horizontal and vertical accelerations acting simultaneously. The deflections, determined from the static shaft analyses, were compared to the allowable rotor clearances. Pump and motor bearing loads were determined and shown to be below the manufacturer's specified levels.
To avoid damage during the postulated earthquake, the stresses caused by the combination of normal operating loads, earthquake, and dynamic system loads were limited to the limits indicated in Section 3.9.2. Pump casing stresses caused by the maximum nozzle loads were limited to the stresses outlined in Section 3.9.2. The maximum seismic nozzle loads combined with the loads imposed by the seismic accelerations were considered in the analysis of pump supports. Furthermore, calculated misalignment was shown to be less than that which could hinder pump operation. The stresses in the supports were below those of Section 3.9.2. Therefore, support distortion is elastic and of short duration (no longer than the duration of the seismic event).
5.2-3
 
DCPP UNITS 1 & 2 FSAR UPDATE Performing these analyses with the loads and the stress limits of Section 3.9.2, assures that critical parts of pumps will not be damaged during the postulated earthquake.
Ifthe naturalifrequency was found to be below 33 Hz, an analysis was performed to determine the amplified input accelerations necessary to perform the static analysis.
The adjusted accelerations were determined with the same conservatisms used for rigid structures. The static analysis was performed using the adjusted accelerations; the stress limits stated in Section 3.9.2 were satisfied.
To complete the seismic qualifications procedures, the pump motors were qualified for operation during the maximum seismic event. Any auxiliary equipment which is vital to the operation of the pump or pump motor, and which was not qualified for operation with the pump or motor was qualified separately.
The above program gives assurance that the active pumps and motors would not be damaged and would continue operating under seismic loadings. These requirements demonstrate that the active pumps will perform their intended functions.
Since it has been demonstrated that the pumps would not be damaged during the earthquake, the functional ability of the active pumps after the earthquake is assured.
Normal operating loads and steady state nozzle loads are the most probable conditions following an earthquake. The ability of the pumps to function under these loads is demonstrated during normal plant operation.
The valves were designed to function at normal operating conditions, maximum design conditions, and DDE/Hosgri conditions. Active valves that serve a post-earthquake safe shutdown and/or aFe-use4d-fF an accident mitigation functiononly, and do not scv-c to support safe shutdown following a Hesgri ca.thquak.,      were qualified for active function for a Hosgri earthquake to p..vid. inceasd
                                      .    .      nse..atism in acco..danc. with (Reference 30). The design meets the requirements of the ANSI B31.1, ANSI B16.5, and MSS-SP-66 codes.
The stress limits for the valves in the RCS pressure boundary are indicated in Table 5.2-5. The design criteria and allowable stress limits for safety-related valves outside the RCS pressure boundary (i.e., valves considered to be ASME B&PV Code Class II or IIl components) are indicated in Section 3.9.2.
In addition, all valves 1 inch and larger within the RCPB were checked for wall thickness to ANSI B16.5, MSS-SP-66, or ASME B&PV Code, Section 111 (1968, some 1974) requirements, as applicable, and subjected to nondestructive tests in accordance with ASME and ASTM codes.
The valves were designed to the requirements of ANSI 816.5 or MSS-SP-66 pertaining to minimum wall thickness for pressure containing components. Analyses were performed to qualify active valves. These valves were subjected to a series of stringent tests prior to service and during the plant life. Prior to installation, the following tests 5.2-4
 
DCPP UNITS 1 & 2 FSAR UPDATE were performed: shell hydrostatic tests to MSS-SP-61 requirements, backseat and main seat leakage tests. Cold hydrostatic tests, hot functional qualification tests, periodic inservice inspections and operability tests have been and are performed to verify and assure the functional ability of the valves. These tests assure reliability of the valves for the design life of the plant.
On all active valves, an analysis of the extended structure was performed for static equivalent seismic loads applied at the center of gravity of the extended structure. The minimum stress limits allowed in'these analyses will assure that no significant permanent damage occurs in the extended structures during the earthquake.
Motor operators and other electrical appurtenances necessary for operation were qualified.
The natural frequencies of all active valves were determined by test or by analysis. If the natural frequencies of the valves were shown to be less than 33 Hz, one of the following options was employed:
(1)    The valve was qualified by dynamic testing.
(2)    The valve was modified to increase the minimum frequency to greater than 33 Hz.
(3)    The valve was qualified conservatively using static accelerations that are sufficiently in excess of accelerations it might experience in the plant to take into account any effect due to both multifrequency excitation and, multi-mode response (a factor of 1.5 times peak acceleration is generally accepted, although lower coefficients can be used when shown to yield conservative results).
(4)    A dynamic analysis of the valve was performed to determine the equivalent acceleration to be applied during the static analysis. The analysis provided the amplification of the input acceleration considering the natural frequency of the valve and the frequency content of the applicable plant floor response spectra. The adjusted accelerations were then used in the static analysis and the valve operability was assured by the methods outlined above, using the modified acceleration input.
Swing check valves are characteristically simple in design and their operation is not affected by seismic accelerations or applied nozzle loads. The check valve design is compact and there are no extended structures or masses whose motion could cause distortions which could restrict operation of the valve. The nozzle loads due to seismic excitation do not affect the functional ability of the'valve since the valve disc is typically designed to be isolated from the casing wall. The clearance available around the disc prevents the disc from becoming bound or restricted due to any casing distortions caused by nozzle loads. Therefore, the design of these valves is such that once the 5.2-5
 
DCPP UNITS 1 & 2 FSAR UPDATE structural integrity of the valve is assured using standard design or analysis methods, the ability of the valve to operate is assured by the design features. For the faulted condition evaluations, since piping stresses are shown to be acceptable, the check valves are qualified.
The valves have undergone the following tests: (a) in-shop hydrostatic test, (b) in-shop seat leakage test, and (c) periodic in-plant exercising and inspection to assure functional ability.
By the above methods, all active valves are qualified for operability for the faulted condition seismic loads. These methods simulate the seismic event and assure that the active valves will perform their safety-related functions when necessary.
5.2-6
 
DCPP UNITS 1 & 2 FSAR UPDATE 5.2.1.11 Analysis Method for Faulted Condition The analysis of the RCLs and support systems for blowdown loads resulting from a LOCA is based on the time-history response of simultaneously applied blowdown forcing functions on a broken and unbroken loop dynamic model. The forcing functions are defined at points in the system loop where changes in cross section or direction of flow occur such that differential loads are generated during the blowdown transient.
Stresses and loads are checked and compared to the corresponding allowable stress.
The stresses in components resulting from normal sustained loads and the worst case blowdown analysis are combined with the DDE seismic analysis (see Section 5.2.1.15 for a discussion of the Hosgri seismic analysis) to determine the maximum stress for the combined loading case. This is considered a very conservative method since it is highly improbable that both maxima will occur at the same instant. These stresses are combined to ensure that the main reactor coolant piping loops and connected primary equipment support system will not lose their intended functions under this highly improbable situation.
For faulted conditions, the limits are provided in Table 5.2-7.
Further details of the stress analysis for faulted conditions are presented in Section 5.2.1.14. With the acceptance of the DCPP leak-before-break analysis by the NRC (Reference 31), the dynamic thrust forces and blowdown loads resulting from pipe rupture events in the main reactor coolant loop piping no longer have to be considered 'in the design basis analyses. Only the thrust forces and blowdown loads resulting from RCS branch line breaks have to be considered (see Section 3.6.2.1.1.1). For the RCL reanalysis performed for the RSGs, thrust forces and blowdown loads were determined for RCS branch line breaks identified in Section 5.2.1.10.1. Details of the stress analyses performed to evaluate the effects of the postulated Hosgri earthquake are presented in Section 5.2.1.15.
Protection criteria against dynamic effects associated with pipe breaks are covered in Section 3.6. With the acceptance of the DCPP leak-before-break analysis by the NRC (Reference 31), the dynamic effects of breaks in the main reactor coolant loop piping no longer have to be considered in the design basis analyses. Only the dynamic effects from RCS branch line breaks have to be considered (see Section 3.6.2.1.1.1).
5.2-7
 
DCPP UNITS 1 & 2 FSAR UPDATE 5.2.1.14 Stress Analysis for Faulted Condition Loadings (DDE and LOCA)
Stress analyses of the RCS for faulted conditions employ the displacement (stiffness) matrix method and lumped-parameter, multimass representation of the system. The analyses are based on adequate and accurate representation of the system using an idealized, mathematical model. See Section 5.2.1.15 for a discussion of the faulted condition loadinq associated with HosQri and LOCA.
5.2-8
 
DCPP UNITS 1 &2 FSAR UPDATE 5.2.1.15 Stress Analysis for Faulted Condition Loadings (Hosgri and LOCA)
This section describes the supplemental analyses of the faulted condition load combination to address the Hosgri earthquake. Differences between this analysis, and the faulted condition load combination evaluation for DDE and LOCA described in Section 5.2.1.14 are discussed.
5.2.1.15.1 Integrated Reactor Coolant Loop Analysis Analysis of the reactor coolant loop piping was performed using the response spectra method. The RCL model was constructed for the WESTDYN computer program.
The horizontal response spectrum at 140 feet in the inner containment structure, corresponding to the steam generator upper support elevation, and the horizontal spectrum at 114 feet inthe inner containment structure, corresponding to the reactor coolant pump support and reactor vessel elevation, was used in the analysis. A vertical response spectrum envelope from elevation 114 ft to the base slab of elevation 87 ft was used in the analysis. With mode, the results due to the vertical shock were combined by direct addition with the results of the horizontal shock directions. The modal contributions were then added by the square-root-sum-of-the-squares (SRSS) method.
Two seismic cases were considered; north-south plus vertical and east-west plus vertical. Each horizontal shock was combined with the vertical shock and the worst combined response was used in the evaluation of the system.
The stresses and loads associated with the LOCA loading case are taken from the analysis described in Section 5.2.1.14.1.
The results of the analysis are as follows: The results of the Hoscqri seismic evaluation were combined with the pressure, and-deadweight, and LOCA stresses. The fevised-combined piping stresses were all under the allowable of 2.4 Sh, or, for loop piping, 3.6 Sh.
5.2.1.15.2 Steam Generator Evaluation The seismic spectra at the elevations of the steam generator upper support and vertical support were used as the seismic input. The horizontal spectra at the upper support and the vertical spectra at the vertical support were used as input. The model was used to evaluate the shell, tube bundles, upper and lower internals, and other pressure boundary components.
The nozzles and support feet of the steam generator were analyzed using static stress analysis methods with externally applied design loads. Loadings on the inlet and outlet nozzles of the steam generator for the Hosgri earthquake were calculated as part of the reactor coolant loop piping analysis. The stresses and loads associated with the LOCA 5.2-9
 
DCPP UNITS 1 & 2 FSAR UPDATE loading case are taken from the analysis described in Section 5.2.1.14.1. The results of the Hosgri seismic evaluation were combined with the pressure, deadweight, and LOCA stresses. The combined loadings calculated by this analysis were compared with p-e-vius-faulted condition loads associated with the DDE and LOCA combination. The new-Hosqd and LOCA faulted condition loads were shown to be lower than the loads that were used initially to evaluate the nozzles or was shown to be less than the applicable stress allowable. Therefore, the stresses eaused-abyssociated with the Hosgri speGtFearthquake are within the design basis of these nozzles.
The loads on the steam generator support feet and upper seismic support were supplied    taken from the Hosgri evaluation by the reactor coolant loop analysis. The LOCA loads were taken from the analysis described in Section 5.2.1.14.1. The results of the Hosgri seismic evaluation were combined with the deadweight, pressure, and LOCA loads. These combined loadings are below the loading originally calculated for the DDE and LOCA faulted condition analysis or was shown to be less than the applicable stress allowable.
A long tr            prgram (LTSP) seismic margin assessment was peifoicd by Westinghouse fOr the DCPP RSGs and associated, suppo.,ts. Thc assessment shows that the limitirg LTSP scismni, margin foRG  the      ,OMPnGntS affted by tho RSGs is gr.eater than the Conollntug value of 3.06 contained in the LTSP final report (Rdfynamic 34). in addition, th a-  -e- lment confirms a minimum elasti seismic mare        gin greate thta 1665 for spctra oeresp(oFniE)g                              m ponents. A lowecr Ya'rueof FS&
r e co was calcusated for the RSG vertical support; however, the resulting 81 perccnt Tenonzzleedande high confideet,      loW pterbability of failure is greater than 3.06 (ice.
3.22 g), when the standard ductility factor Of 1d.2 is applied. Details Of the mfarginlt assessment are provided  Oi Supplement 1 to Reference 33.
AnLTSP seismic mnai a              ment was also peuformed for the cnit 2 RSG support anchorages. An Fgm o-f 1.321 co-nrresponding to an LTSP seIc capaity of 2.6 gwa s determined for the RS.G veirticsal support anchorages. Higher L=TSP seism~ic capacities were calc-ulated for the RSG upper and lower support anchorages.
5.2.1.15.3 Reactor Coolant Pump Evaluation The Hospri seismic analyses of the reactor coolant pump were performed using dynamic modal methods with a finite element computer program. The seismic response spectra corresponding to the elevation of the reactor coolant pump support structure were used. The LOCA loads were taken from the analysis described in Section 5.2.1.14.1. The results of the Hospri seismic evaluation were combined with the-deadweight, pressur6, and LOCA loads.
The nozzles and support feet of the reactor coolant pump were analyzed by static stress analysis methods with externally applied design loads. For the Holsgii-spec'faTulted condition including Hosgri seismic loads, the combined external loads appli.ed to the inlet and outlet nozzles of the reactor coolant pump by the reactor coolant loop piping 5.2-10
 
DCPP UNITS 1 & 2 FSAR UPDATE are all below the load for which the nozzles preViously were shown acceptable. NO futhe-a-nay.. is was necessay for the nozzl..resulted in the code stress allowables being met.
The loads resulting from piping reactions for the *,,esg-,,+peerHosciri and LOCA faulted load combination resulted in the code stress allowables being met. were lower than the DDE loads for which the reactor coolant pump suppo. t feet were analyzed. NO futher analysis was necessa r; for the support feet-.
5.2.1.15.4 Reactor Vessel Evaluation Several portions of the reactor vessel were evaluated using static stress analysis methods with externally applied design loads. The control rod drive mechanism head adapter, closure head flange, vessel flange, closure studs, inlet nozzle, outlet nozzle, vessel support, vessel wall transition, core barrel support pads, bottom head shell juncture and bottom head instrumentation penetrations were analyzed by this method.
The design loads for all areas evaluated except the inlet and outlet nozzles and vessel supports were chosen to be more conservative than any actual load the component would ever experience. The design loads for the inlet and outlet nozzles and vessel supports were umbrellas of loads experienced by past plants. In cases where the actual plant loads exceed the design loads, separate analyses were performed to assure adequacy. All stresses and fatigue usage factors were found to be acceptable The LOCA loads were taken from the analysis described in Section 5.2.1.14.1. The results of the Hosgri seismic evaluation of the reactor coolant loop were combined with the deadweight, pressure, and LOCA loads and code stress allowables were met.
The Hesgý loads calculated by the reactor coolant loop analysis were compared with the DDE seismic loads and arc lower. Thus, the previouG reactor vessel analysi 5.2.1.15.5 Reactor Vessel Internals Evaluation The reactor Vessel internals evaluation is presented in Section 3.7.3.15.
5.2.1.15.6 Fuel Assembly Evaluation The fuel assembly evaluation is presented in Section 3.7.3.15.
5.2.1.15.7 Control Rod Drive Mechanism and Support System Evaluation The evaluation of the control rod drive mechanism and its support system is presented in Section 3.7.3.15.
5.2-11
 
DCPP UNITS 1 & 2 FSAR UPDATE.
5.2.1.15.8 Primary Equipment Support Evaluation Reactor coolant system component supports were shown adequate for the Hosgri seismic event by evaluating the supports for the loads determined in the integrated reactor coolant loops seismic analysis.
The STASYS and NASTRAN computer programs were used to obtain support stiffness matrices and member influence coefficients for the equipment supports.
Loads acting on the supports obtained from the reactor coolant loop analysis; support structure member properties, and influence coefficients at each end of each member were input to the THESSE program. The LOCA loads were taken from the analysis described in Section 5.2.1.14.1. The results of the Hosgri seismic evaluation of the integrated reactor cool loop analyses were combined with the deadweight, pressure, and LOCA loads.
A finite element stress analysis of the steam generator upper support structure was performed with the WECAN (Reference 18) computer program. The STRUDL program was used to analyze the pressurizer support frame.
In summary, stresses in all reactor coolant system component support members are below yield and buckling values for the Hosgri seiemie-eveintand LOCA faulted load condition. The integrity of the supports has therefore been demonstrated for this postulated.evcn.Ioading combination.
5.2.1.15.9 Pressurizer Evaluation Hosgri seismic loading on the pressurizer is based on 4 percent damped Hosqri response spectra at elevation 140 ft. on the containment interior concrete structure.
When the Hosgri seismic loads are combined with the deadweight, pressure, and LOCA loads, the total loading met code allowable stresses.The HOsgr, response sp,-t-a for 4
...... t da* npi; at
                  *t he, 140 ft. eley... i-n ha a. pea
                                                      . of 5  ,,--,-.,o ... , kwell below the*
value used to qual~if' the pressurizer. Therefore, the o~iginal pressurizer analysis is-conservative for the Hosgri earthquake.
A dynamic reactor coolant loop analysis, which included a surge line model and was performed with the Hosgri response spectra, produced total loads (forces and moments). when combined with deadweight, pressure, and LOCA loads, on the support skirt, surge nozzle, and upper seismic lug which met code allowable stresses.weFe eIs-than these proeduced by tho original surge line analy~sis. Therefore, the loads On these compo9nents are acepetable.
5.2-12
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 5.2-6 LOAD COMBINATIONS AND STRESS CRITERIA FOR WESTINGHOUSE PRIMARY EQUIPMENT (a)
CONDITION            LOAD COMBINATION                                                      STRESS CRITERIA(e)
Design                Deadweight + Pressure +/- DE                                            Pm<* Sm PL + Pb*< 1.5 Sm Normal                Deadweight + Pressure + Thermal                                        PL + Pb + Pe + Q0< 3 Sm(b)
Upset- 1              Deadweight + Pressure + Thermal +/- DE                                  UT *5  1.0(b)
PL + Pb + Pe + Q <*3 Sm UT -<1.0*b)
Deadweight + Pressure + Thermal PL + Pb + Pe + Q-5 3 Sm Faulted - 1          Deadweight + Pressure +/- DDE                                            Table 5.2-7 Faulted - 2          Deadweight + Pressure +/- DDE + LPR(c' d, g)                            Table 5.2-7 Faulted - 3          Deadweight + Pressure +/- Hosgri + LPR(c' d.,g)                          Table 5.2-7 Faulted - 4          Deadweight + Pressure + Other Pipe Rupture(f)                          Table 5.2-7 (a)    Steam generators, reactor coolant pumps, pressurizer.
(b)    Based on elastic analysis. For simplified elastic-plastic analysis, the stress limits of the 1971 ASME Code Section III, NB-3228.3 apply.
(c)    LPR = reactor coolant loop pipe rupture (d)    DDE or Hosqri and LPR combined by SRSS method (e)    For definition of stress criteria terms, see Additional Notes.
(f)    Pipe rupture other than LPR.
(g)    While the original stress analysis considered this load combination, with the acceptance of the DCPP leak-before-break analysis by the NRC, loads resulting from ruptures in the main reactor coolant loop no longer have to be considered in the design basis structural analyses and included in the loading combinations, only the loads resulting from RCS branch line breaks have to be considered.
P,    =    General membrane; average primary stress across solid section. Excludes discontinuities and concentrations. Produced only by mechanical loads.
PL    =    Local membrane; average stress across any solid section. Considers discontinuities, but not concentrations. Produced only by mechanical loads.
Pb    =    Bending; component of primary stress proportional to distance from centroid of solid section. Excludes discontinuities and concentrations. Produced only by mechanical loads.
Pe  =    Expansions; stresses which result from the constraint of "free end displacement" and the effect of anchor point motions resulting from earthquakes. Considers effects of discontinuities, but not local stress concentration. (Not applicable to vessels).
0    =    Membrane Plus Bending; self-equilibrating stress necessary to satisfy continuity of structure. Occurs at structural discontinuities. Can be caused by mechanical loads or by differential thermal expansion.
Excludes local stress concentrations.
UT  =    Cumulative usage factor.
5.2-13
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 5.2-8 LOADING COMBINATIONS AND ACCEPTANCE CRITERIA FOR PRIMARY EQUIPMENT SUPPORTS CONDITION            LOADING COMBINATIONS                                            STRESS LIMITS Normal          Deadweight + Temperature + Pressure                    1969 AISC Specification, Part 1 Upset          Deadweight + Temperature + Pressure +/- DE                1969 AISC Specification, Part 1 Faulted - 1    Deadweight + Pressure +/- DDE + LPR(a'    b,0)            1969 AISC Specification, Part 2(c) or Sy after load redistribution, whichever is higher Faulted - 2    Deadweight + Pressure +/- HOSGRI + LPR(a. b,f)            1969 AISC Specification, Part 2(c) or Sy(e) after load redistribution, whichever is higher Faulted - 3    DeadweiMht + Pressure + Other Pipe                      1969 AISC Specification, Part 2(c)
Rtr          upture                                    or Sy after load redistribution, whichever is higher (a)  LPR = Reactor coolant loop pipe rupture.
(b)  DDE or HOSGRI and LPR combinedby SRSS method (or more conservative method).
'(c)  For supports qualified by load test, allowable loads = 0.8 times Lt per Table 5.2-7.
(d)  Pipe rupture other than LPR.
(e)  For the pressurizer upper lateral supports and the reactor vessel supports, the allowable Sy is based on average value of actual yield stress of the material.
(f)  While the original stress analysis considered this load combination, with the acceptance of the DCPP leak-before-break analysis by the NRC, loads resulting from ruptures in the main reactor coolant loop no longer have to be considered in the design basis structural analyses and included in the loading combinations, only the loads resulting from RCS branch line breaks have to be considered.
5.2-14
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 5.2-16                                                Sheet 1 of 4 REACTOR COOLANT BOUNDARY LEAKAGE DETECTION SYSTEMS Radioactivity Detection Systems Indicator Detector Location                                                  Approximate Time to    Identified(c)  Instrument  in Control or Process          Medium Type        Range                      Detect 1-clpm Leak      Leak Detection Class(a)    Room Containment        Air    G-M          10-1 to 104 mR/hr          Less responsive than          No                    Yes other detection systems Incore inst area    Air    G-M          10.1 to 104 mR/hr          Less responsive than          No                    Yes other detection systems Containment air    Air    Nal          10 to 106 cpm              See Fig. 5.2-9                No                    Yes particulate                Scintillator                                                                        11(b)
Containment        Air    G-M          10 to 106 cpm              See Fig. 5.2-9                No                    Yes radiogas Plant vent radiogas Air    Beta        10 to 5E6 cpm              Less responsive than          No          IM        Yes Scintillator                            other detection systems Condenser air      Air    Beta        10 to 5E6 cpm              See Fig. 5.2-10              Yes                    Yes ejector                    Scintillator Component cooling  Liquid Nal          10 to Ior cpm              See Fig. 5.2-12              No          IC        Yes liquid                    Scintillator Steam generator    Liquid Nal          10 to 10? cpm              See Fig. 5.2-11              Yes          it        Yes blowdown                  Scintillator 5.2-1
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 5.2-16                                                Sheet 2 of 4 Other Detection Systems Indicator Detector Location                                                      Approximate Time to  Identified(c)  Instrument  in Control or Process        Medium Type            Rangqe and Repeatabilitv(e)  Detect 1-qpm Leak (qT Leak Detection Class(a)    Room
                                                                                                            ,sei-s&#xfd;M*
Containment(d)    Liquid Change in time  see note (m)                  1 hjr (g)(h)(1)      No            II          Yes condensation              required to accumulate fixed volume Containment sumps  Liquid Liquid level    1 to 48 in. W.C. In)          <1 hr(h)              No            II          Yes and quantity of 1 to 35 in. W.C. (P) liquid          +/-1 in.
Reactor vessel    Liquid Temperature    50 to 300 OF                  <30 sec (            Yes            II          Yes flange leakoff                            +/-5 OF Reactor coolant    Liquid Liquid level    0-100%                        <20 min (h)          Yes            II          No drain tank                and quantity of +/-2%
liquid Pressurizer relief Liquid Temperature    50 to 400 OF                  <30 sec (f)          Yes            II          Yes valve discharge                          +/-7 OF Pressurizer relief Liquid                                                                    Yes            11          Yes tank Liquid level    0 to 100 %                    <12 hrs (h)
                                          +/-2%
5.2-2
 
DCPP UNITS I & 2 FSAR UPDATE TABLE 5.2-16                                                              Sheet 3 of 4 Systems Used to Quantify Leakage W)
Indicated in Detector System                    Medium                Type                    Range/Sensitivity                  Instrument              Control Room Class(a)
Pressurizer level                  Liquid                Liquid level            o to 100% (91)0                                                  Yes
                                                                                  -125 gal/% level Volume control tank level          Liquid                Liquid level            0 to 100% (g9)                          II                      Yes
                                                                                  -19 gal/% level Charging pump flow                Liquid                Flow                    0 to 200 gpm (k)                        II                      Yes
                                                                                  +/- 10% span when flow >60 gpm (channel uncertainty value)
Pressurizer relief tank level      Liquid                Liquid level            0 to 100% (h)                            II                      Yes min. 127, max. 154 gal/% level (20 < % level < 80)
(a)  See Section 7.1 for the definition of Instrument Class. Instrument Class SeismiG Categry I systems are designed to perform required safety functions following a DDE or HE(whichever is larger). Instrument Class ,ategeY-I1 instrument systems were designed to function under conditions up to DE. Instrument Class IC instrument systems refer to maintenance of pressure boundary integrity of Category I fluid systems. Also refer to Section 3.2.
(b)  These units were not constructed to withstand DDE accelerations; however, they will be housed in a Seimi-G                  Desicqn Class I structure and protected from external damage associated with a seismic event. Therefore, it is considered that these units can be returned to operational status within 36 hours of a DDE or HE.
(c)  Leakage is defined as identified or unidentified in accordance with Regulatory Guide 1.45.
(d)  Containment condensation measures moisture condensed by the fan cooler drip collection system.
(e)  Repeatability, including the operators ability to read the same value at another time, is included in this column; this is a true measure of ability to detect a change in system conditions over a period of time.
(f)  Automatically alarmed.
5.2-3
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 5.2-16                                                        Sheet 4 of 4 (g) Requires operator action - (i.e., close valve, start-stop pump, etc., and operator monitoring and logging).
(h) Requires operator monitoring and logging to note changes in rate, level, flow, etc.
(i) Systems listed here would be used to quantify true leakage rate in the event systems listed on Sheets 1 &2 above detected an unidentified leak.
These systems also provide additional capability for detecting leak rates of 1-gpm within short periods of time.
(j) Normal variations in process variable or automatic control systems will mask this change. Operator must take action as in (g) above to detect leakage.
(k) Insufficient accuracy/repeatability to ever detect a 1.-gpm change in flowrate.
(I) Dependent on initial conditions. May take longer for fan cooler drip level if humidity is initially low.
(m) Level switches (HI and HI-HI) are provided in each CFCU drain line. The level switches have a fixed location in each drain line providing a repeatable alarm. The time intervals between the receipt of the HI level and HI-HI level alarms are monitored and logged by the operator. Alarm intervals less than a conservative pre-defined value directs the operator to perform an RCS water inventory balance to quantify the RCS leakage rate.
(n) This range refers to the containment structure sumps.
(o) Not used.
(p) This range refers to the reactor cavity sump.
(q) This column refers to the capability of the detection system to sense a leak.
5.2-4
 
DCPP UNITS 1 & 2 FSAR UPDATE 6.3.1.4.3 Seismic Requirements The ECCS is designed to perform its function of ensuring core cooling and providing shutdown capability following an accident under-with simultaneous seismic (lamer of DDE and HE) loading. ECCS p*..ability during and fo,.,.G.i. a H,-gri .,e.t  has been "riticl. The seismic requirements are defined in Sections 3.7 and 3.10.
6.3-1
 
DCPP UNITS 1 & 2 FSAR UPDATE 9.1.1.2 Facilities Description There are two new fuel storage racks for each unit. A rack is approximately 9 feet 6 inches wide, 13 feet long, and 13 feet 6 inches high (excluding centering cones). It is built from Type 304 stainless steel.
The storage cells in the racks are in seven rows, five deep, and are spaced to have a nominal center-to-center distance of 22 inches. They are of Type 304 stainless steel and have a cone shaped top entrance to facilitate loading of fuel elements. They are shaped in a 9-inch square (cross section) hollow beam configuration, standing upright.
At the base, they have a 1-inch thick bearing plate made of neoprene-impregnated fabric.
The new fuel storage racks and the anchorage of racks to the floor are designed for the design earthquake (DE).,-a_ double design earthquake (DDE), and Hoscqri Earthquake (HE) loading conditions and checked for a postulated Hoesgr ei*smi*c e..t (RefeFencG
-14with the racks containing fuel assemblies at the corners.
The racks are designed to withstand a vertical (uplift) force of 4000 pounds in the unlikely event that an assembly would bind in the rack while being lifted by the spent fuel bridge crane.
9.1-1
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE B-1 COMPARISON OF DCPP TO APPENDIX A OF BTP APCSB 9.5-1 A. OVERALL REQUIREMENTS OF NUCLEAR PLANT FIRE PROTECTION PROGRAM Guideline Statement                                                      DCPP Compliance to Commitment
: 2. Design Bases The overall fire protection program should be based upon                The overall fire protection program is based on the evaluation of evaluation of potential fire hazards throughout the plant and the        potential fire hazards throughout the plant. The Appendix R effect of postulated design basis fires relative to maintaining          Reports for DCPP Units 1 and 2 analyze the effect of a postulated ability to perform safety shutdown functions and minimize                design basis fire relative to safe shutdown functions and minimize radioactive releases to the environment.                                radioactive releases to the environment.
: 3. Backup Total reliance should not be placed on a single automatic fire          In areas of the plant where automatic fire suppression systems are suppression system. Appropriate backup fire suppression                  employed, appropriate backup fire suppression capability is capability should be provided.                                          provided by installation of manual hose stations, portable fire extinguishers and portable fire pumps. Each backup method is surveilled as per procedure to ensure equipment availability so total reliance is not dependent upon a single automatic fire suppression system.
: 4. Single Failure Criterion A single failure in the fire suppression system should not impair        A single failure in the fire suppression system will not impair both both the primary and backup fire suppression capability. For            the primary and backup suppression capability due to the nature of example, redundant fire water pumps with the independent                the primary and backup water supplies, the independence of power supplies and controls should be provided. Postulated fires        power supplies for the associated pumps and valves, and the or fire protection system failures need not be considered                provision for portable backup fire pumps.
concurrent with other plant accidents or the most severe natural phenomena. The effects of lightning strikes should be included          Portions of the fire water system have been analyzed in regard to in the overall plant fire protection program                            the design basis earthquake and are seismically qualified so that all hose-reels in safety-related areas of the plant will be available following a safe- shutdow-IDDE/Hosdri earthquake. The seismically qualified portion of the fire system can be readily isolated from the rest of the fire system. Other than those areas required to be available after the design basis earthquake, postulated fires or fire protection system failures are not considered concurrent with other plant accidents or the most severe natural phenomena.
Lightning rods are installed at the high points of the containment, and lightning arrestors are installed on each of the phases of the main and auxiliary transformers. The effects of lightning strikes are included in the overall plant fire protection program 9.5B-3
 
DCPP UNITS 1 & 2 FSAR UPDATE F.2 Basis for Deviation Request (Unit 1)
: a. The RCP lube oil collection tank overflow pipe discharges downward to a recessed trench in the elevation 91 feet floor, along the outside of the shield wall. This trench is sloped so that an RCP lube oil overflow would flow to the containment drain sump.
: b. The overflow pipe of the oil collection tank has pickup from 3 inches above the tank bottom. Thus, in the remote likelihood of a multiple RCP motor lube oil spill and fire propagation to the oil collection tank, such a fire would not be extended to the oil discharges to the floor trench.
: c. The Westinghouse RCP CS VSS motor currently utilizes a high flash point lubricating oil (425 0 F). The fire point of this oil is 5200&deg;F. Therefore, a high-energy ignition source would be necessary to sustain combustion in the unlikely event that a multiple RCP lube oil spill occurs and oil is discharged through the overflow pipe. An additional evaluation on the impact of the flash point temperature is included in FHARE 115.
: d. Because an oil-to-water heat exchanger serves each bearing assembly, and the heat exchanger discharge water and bearing temperatures are monitored and alarm in the continuously manned control room, it is not deemed credible for the RCP lube oil to reach temperatures within 50 percent of its flash point.
: e. There are various components and circuits necessary for safe shutdown in the vicinity of this floor trench. Power cable is routed in conduit. Other circuits are not considered to present a high-energy ignition source.
F.3 Basis for Deviation Request (Unit 2)
: a. The RCP oil collection system, including the oil collection tank and overflow piping, has been designed to withstand the safe shutdo DDEHos.-ri earthquake.
: b. The RCP lube oil collection tank overflow pipe discharges downward to a recessed trench in the floor at elevation 91 feet, along the outside of the shield wall. This trench is sloped so that any RCP lube oil overflow would flow to the containment drain sump.
: c. The inlet of the overflow pipe of the oil collection tank, located 3 inches above the tank bottom, will drain water off the bottom of the tank while containing the entire oil inventory of one RCP. The discharge is piped to the containment annulus trench such that splashing of the tank overflow in the trench is precluded.
9.5C-4
 
DCPP UNITS 1 & 2 FSAR UPDATE Chapter 15 ACCIDENT ANALYSES Since 1970, the ANS classification of plant conditions has been used to divide plant conditions into four categories in accordance with anticipated frequency of occurrence and potential radiological consequences to the public. The four categories are as follows:
(1)    Condition I:        Normal Operation and Operational Transients (2)    Condition I1:      Faults of Moderate Frequency (3)    Condition III:      Infrequent Faults (4)    Condition IV:      Limiting Faults The basic principle applied in relating design requirements to each of the conditions is that the most frequent occurrences must yield little or no radiological risk to the public, and those extreme situations having the potential for the greatest risk to the public shall be those least likely to occur. Where applicable, reactor trip system and engineered safety features functioning is assumed, to the extent allowed by considerations such as the single failure criterion, in fulfilling this principle.
In the evaluation of the radiological consequences associated with initiation of a spectrum of accident conditions, numerous assumptions must be postulated. In many instances these assumptions are a product of extremely conservative judgments. This is due to the fact that many physical phenomena, in particular fission product transport under accident conditions, are not understood to the extent that accurate predictions can be made. Therefore, the set of assumptions postulated would predominantly determine the accident classification.
The specific accident sequences analyzed in this chapter include those required by Revision I of Regulatory Guide 1.70, Standard Format and Content of Safety Analysis Reports for Nuclear Power Plants, and others considered significant for the Diablo Canyon Power Plant (DCPP). Because the DCPP design differs from other plants, some of the accidents identified in Table 15-1 of Regulatory Guide 1.70, Revision 1, are not applicable to this plant; some comments on these items are as follows:
(Item 10) - There are no pressure regulators or regulating instruments in the Westinghouse pressurized water reactor (PWR) design whose failure could cause heat removal greater than heat generation.
(Item 11) - Reactor coolant flow controller is not a feature of the Westinghouse PWR design. Treatment of the performance of the reactivity controller in a number of accident conditions is offered in this chapter.
15-1
 
DCPP UNITS 1 & 2 FSAR UPDATE (Item 12) - The reactor coolant system (RCS) components whose failure could cause a Condition Ill or Condition IV loss-of-coolant accident (LOCA) are Design Class I components, that is, they are designed to withstand consequences of the safe-shutdown ca.thquak. .. , (SSE) ,,,hih is equivalent to thc double design earthquake (DDE) and the Hosgri earthquake (HE) OGcUrrcncc. In addition, the analysc. of thc dcg*n" L A in.........
        ..                    of the desiqn LOCA include the assumption of unavailability of offsite power.
(Item 22) - No instrument lines from the RCS boundary in the DCPP design penetrate the containment(a).
(Item 24) - The analysis of the consequences of such small spills and leaks is included within the cases evaluated in Chapter 11, and larger leaks and spills are analyzed in Section 15.5.
(Item 25) - The radiological consequences of this event are analyzed in Chapter 11, for the case of "Anticipated Operational Occurrences."
(Item 26) - Habitability of the control room following accident conditions is discussed in Chapter 6, and potential radiological exposures are reported in Section 15.5. In addition, Chapter 7 contains an analysis showing that the plant can be brought to, and maintained in, the hot shutdown condition from outsidethe control room.
(Item 27) - Overpressurization of the residual heat removal system (RHRS) is considered extremely unlikely. PG&E reviewed possible RHRS overpressure scenarios and qualified the system for all credible high pressure transients in DCPP design change package N-049118.
(Item 28) - This event is covered by the analyses of Section 15.2.7.
(Item 29) - Same as Item 28 above.
(Item 30) - Malfunctions of auxiliary saltwater system and component cooling water system (CCWS) are discussed in Chapter 9, Sections 9.2.7 and 9.2.2 respectively.
(Item 31) - There are no significant safety-related consequences of this event.
(Item 33) - The effects of turbine trip on the RCS are presented in Section 15.2.7.
(Item 34) - Malfunctions of this system are discussed in Section 9.3.2.
(Item 35) - The radiological effects of this event are not significant for PWR plants.
Minor leakages are within the scope of the analysis cases presented in Chapter 11.
(a) For definition of the RCS boundary, refer to the 1972 issue of ANS N18.2, Nuclear Safety Criteria for the Design of Stationary PWR Plants.
15-2
 
DCPP UNITS 1 & 2 FSAR UPDATE 15.4.5.1.2 Probability of Activity Release In the above operations, there exists the remote possibility that one or more fuel assemblies will sustain some mechanical damage. There exists an even more remote possibility that this damage will be severe enough to breach the cladding and release some of the radioactive fission products contained therein.
Both the fuel handling procedure and the fuel handling equipment design adhere to the following safety criteria:
(1)    Fuel handling operations must not commence before short-lived core activity has decayed, leaving only relatively long-lived activity. Equipment Control Guidelines for refueling operations specify the minimum waiting time.
(2)    Fuel handling operations must preclude any critical configuration of the core, spent fuel, or new fuel.
(3)    The fuel handling system design must ensure an adequate water depth for radiation shielding of operating personnel.
(4)    Active components of the fuel handling systems must be designed such that loss-of-function failures will terminate in stable modes.
(5)    The design of fuel handling equipment must minimize the possibility of accidental impact of a moving fuel assembly with any structure.
(6)    The design of fuel handling equipment and procedures must minimize the possibility of any massive object damaging a stationary fuel assembly.
(7)    Fuel assembly design must minimize the possibility of damage in the event that portable or hand tools come into contact with a fuel assembly.
(8)    The design of structures around the fuel handling system must minimize the possibility of the structures themselves failing in the event of a double design earthquake (DDE) or Hosciri earthquake (HE)., '.-hich is the safe shutdoWn earthqu.k . Furthermore, the structures must minimize the possibility of any external missile from reaching fuel assemblies.
(9)    Fuel handling equipment must be capable of supporting maximum loads under seismic conditions. Furthermore, fuel handling equipment must not generate missiles during seismic conditions. The earthquake loading of the fuel handling equipment is evaluated in accordance with the seismic considerations addressed in Section 9.1.4.3.2.
15.4-1
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 15.4.1-7A                                          Sheet 1 of 3 UNIT 1 PLANT*OPERATING RANGE ALLOWED BY THE BEST-ESTIMATE LARGE BREAK LOCA ANALYSIS Parameter                                          Operating Range 1.0    Plant Physical Description
: a. Dimensions                            No in-board assembly grid deformation assumed duo teduring LOCA + DDE or LOCA + HESSE (which ever is more limitingq
: b. Flow resistance                        N/A
: c. Pressurizer location                  N/A
: d. Hot assembly location                  Anywhere in core
: e. Hot assembly type                      Fresh 17X1 7 V5, ZIRLO, or Zircaloy cladding, 1.5X IFBA or non-IFBA
: f. SG tube plugging level                <15%
: g. Fuel assembly type                    Vantage 5, ZIRLO, or Zircaloy cladding, 1.5X IFBA or non-IFBA 2.0    Plant Initial Operating Conditions 2.1  Reactor Power
: a. Core average linear heat rate Core power_< 102% of 3411 MWt
: b. Peak linear heat rate        FQ_< 2.7
: c. Hot rod average linear heat  FaH 5 1.7 rate
: d. Hot assembly average linear    "P HA< 1.57 heat rate
: e. Hot assembly peak linear      FQHA < 2.7/1.04 heat rate 15.4-3
 
DCPP UNITS 1 & 2 FSAR UPDATE TABLE 15.4.1-7B                                        Sheet 1 of 2 UNIT 2 PLANT OPERATING RANGE ALLOWED BY THE BEST-ESTIMATE LARGE BREAK LOCA ANALYSIS Parameter                                              Operating Range 1.0    Plant Physical Description a)    Dimensions                          No in-board assembly grid deformation during LOCA + DDE or LOCA + HE (which ever is more limitinqS b)  Flow resistance                      N/A c)    Pressurizer location                N/A d)    Hot assembly location              Anywhere in core interior (149 locations)(a) e)    Hot assembly type                    Fresh 17x17 V5+ fuel with ZIRLOTM cladding f) Steam generator tube plugging          < 15%
level g) Fuel assembly type                      17x17 V5+ fuel with ZIRLOTM cladding, non-IFBA or IFBA 2.0    Plant Initial Operating Conditions 2.1 Reactor Power a)  Core average linear heat rate  Core power _<100.3% of 3,468 MWt b) - Peak linear heat rate          FQ *2.7 c)  Hot rod average linear heat    FAH  !51.7 rate d)  Hot assembly average linear    PHA < 1.7/1.04 heat rate e)  Hot assembly peak linear heat  FQHA_<  2.7/1.04 rate f)  Axial power distribution (PBOT, PMID)                  See Figure 15.4.1-15B.
g)  Low power region relative power (PLOW)                  0.3 _5PLOW -*0.8 h)  Hot assembly bumup              -*75,000 MWD/MTU, lead rod(a) i)  Prior operating history        All normal operating histories j)  Moderator temperature coefficient                    _*0at HFP k)  HFP boron (minimum)            800 ppm (at BOL) 2.2 Fluid Conditions a)  Tavg                            565 - 5&deg;F  -<Tavg *<577.6 + 5&deg;F b)  Pressurizer pressure            2250 - 60 psia --PRcs *<2250 + 60 psia 15.4-4
 
Enclosure Attachment 4 PG&E Letter DCL-1 1-097 Summary of Regulatory Commitments New Commitment:
: 1) Any outstanding gaps in the probabilistic risk assessment model when compared to the Capability Category II of ASME/ANS RA-Sa-2009 will be addressed as part of any seismic probabilistic risk assessment (SPRA) update. The SPRA update will be completed within 2 years following issuance of (currently draft)
NRC Generic Letter 2011-XX, Seismic Risk Evaluations for Operating Reactors.
Revision to Existing Commitment:
In PG&E Letter DCL-91-178, PG&E made the following commitment:
Future additions and modifications to the plant will be designed and constructed in accordance with this existing seismic qualification basis. In addition, certain future plant additions and modifications as specified in enclosed Table 1 will be checked against insights and knowledge gained from the LTSP to verify that the plant "high-confidence-of-low-probability-of-failure" values remain acceptable.
DCL-91-178 included an implementing procedure which stated that in order to take advantage of the insights and knowledge gained from the
[LTSP], certain future additions and modifications will be checked against the [LTSP] spectra described in the U. S. Nuclear.Regulatory Commission's Supplemental Safety Evaluation Report (SSER) No. 34, June 1991, to verify that the [DCPP] high-confidence-of-low-probability-of-failure (HCLPF) values remain acceptable.
PG&E is revising the commitment above to the following:
This commitment is being revised to be consistent with the proposed evaluation process for new seismic information. The evaluation process proposed in this license amendment request (LAR) requires that the seismic margin for plant additions and plant modifications be maintained at or above 1.3, unless the minimum seismic margin below 1.3 is identified in Final Safety Analysis Report Update (FSARU) Tables 3.7-25 or 3.7-26 due to previous review and approval by the NRC.
1
 
Enclosure Attachment 5 PG&E Letter DCL-1 1-097 Chapter 5 of the 1988 Long Term Seismic Program Final Report 1
 
Chapter 5 SOULSTRUCTURE INTERACTION ANALYSIS To Partially Address Element 4 of the License Condition ELEMENT 4 OF THE LICENSE                                Regulatory Commission (NRC) Staff and its CONDITION                                              consultants through several NRC/PG&E meetings, three , specific      NRC/PG&E        workshops        on PG&E shall assess the significance of            soil/structure interaction analyses, and one NRC conclusions drawn from the seismic                audit on soil/structure        interaction analysis reevaluationstudies in Elements 1, 2, and 3,      calculations. The schedule and milestones of the utilizing a probabilistic risk analysis and      soil/structure analysis program are summarized in deterministic studies, as necessary, to assure    Figure 5-1. Comments received to date from the adequacy of seismic margins.                      NRC at various stages of review have been incorporated        into    the  program wherever applicable, and they are reflected in the final OBJECTIVES                                            results of the analysis.
The objectives of the soil/structure interaction      The scope of the soil/structure interaction analysis analysis conducted for the Diablo Canyon Power        that has been carried out for the Long Term Plant Long Term Seismic Program were to                Seismic Program consists of the following major examine the effects of dynamic interaction            activities:
between the Plant structures and the supporting rock medium on the seismic response of the              "    Assemble, review, and determine appropriate structures, and to generate seismic responses for            site rock profiles and properties.
the Plant structures required for the seismic
* Develop suitable three-dimensional dynamic fragility evaluation and seismic margin assessment.
models for the power block structures.
This analysis was conducted in response to Element 4 of the license condition.
* Implement, modify, and validate dual soil/structure interaction analysis computer SCOPE                                                      programs, CLASSI and SASSI.
* Perform parametric studies to assess', the The soil/structure interaction analysis started in sensitivities    of soil/structure      interaction late 1984 and continued through mid-1988. The response and identify significant parameters to analysis was carried out in three phases, namely, be considered for modeling and analysis.
Phase I: Program Plan development; Phase IL:
preparatory work and Scoping Study; Phase III:          4    Perform      analyses of on-site recorded method development,              implementation,  and      earthquake data and extract information verification; preliminary results; and final analysis        useful for correlation and calibration of model and results.                                                parameters..
The progress and results of the soil/structure
* Perform soil/structure interaction analyses to interaction analysis obtained in various phases            generate the responses for the power block were reviewed and discussed with the Nuclear                structures subjected to coherent, vertically Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                                        Page 5-2 Work Phases                  Description              1984.      1985            1986        1987            1988 e                                  I        a
* I Phase I          Program Plan Development                                                          a
:(2) (3)
Phase    1      Preparatory and Scoping Studies Phase I          Development PrA              of Methods,                                        (4)
Verification, and Preliminary Studies                              I      S II                aI    I        Ia a    Ia                                a S
a a1 a  a  , a a    ,    ,      . .      .a.            .
Phase IIB        FnalAnalysis
_a_eii and Results n Pelain ien      ,      a  *a    a    a          ,
a ,*  ,            a
                                                                                                              ,    a  ,
a Stdi    s                      a    a    a    a    a,  y                  a    a  a Ph sai                n                        a    a,  ,    a    a    a      .  ..
Milestones:
: 1. NRC approval of the Long Term Seismic Program Plan, January 31, 1985
: 2. NRC/PG&E meeting on Long Term Seismic Program, October 21, 1985
: 3. First NRC/PG&E soil/structure interaction workshop, April 14-16, 1986
: 4. NRC/PG&E ground-motion workshop to review soil/structure interaction work, October 24, 1986
: 5. Second NRC/PG&E soil/structure interaction workshop, December 10-12, 1986
: 6. NRC audit of PG&E soil/structure interaction calculations, June 9-11, 1987
: 7. Third NRC/PG&E soil/structure interaction workshop, November 4-6, 1987
: 8. PG&E submittal of Long Term Seismic Program Final Report to NRC, July 31, 1988 Figure 5-1 Soil/structure interaction assessment schedule and milestones.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                          Long Term Seismic Program
 
Chapter 5                                                                                              Page 5--3 Chapter 5                                                                                              Page 5~-3
"    Develop and validate the method and                "    The effect of spatial variation of free-field computer programs for incorporating the                seismic ground motion, including the apparent spatial incoherence of seismic ground motions          wave passage effect, has been properly for soil/structure interaction analysis; perform        evaluated.
analyses to develop the soil/structure interaction response adjustment factors to account for the spatial incoherence of ground
* The effect of nonlinear base uplifting behavior motions.                                                on the seismic response of the most critical containment structure under the fragility
* Modify and validate the method and                      evaluation strong ground motion input has computer program for nonlinear soil/structure          been assessed.
interaction analysis, taking into account the nonlinear base-uplifting response behavior,
* Recorded      earthquake    data at the Diablo and perform analyses for the containment                Canyon site and on the power block structures structure to assess the effect on soil/structure        have been utilized to the extent practicable to interaction response due to partial uplifting of        assist in calibrating the low amplitude dynamic the containment base from the rock                      characteristics of the site rock and dynamic foundation.                                            models.
METHOD OF ANALYSIS AND The free-field seismic ground-motion inputs for
 
==SUMMARY==
OF RESULTS                                      the soil/structure interaction analyses were obtained from the ground-motion studies, as The general configuration of the Plant powver          summarized in Chapter 4. The results of the block structures, which include the containment        soil/structure interaction analyses provided the structures of both units, the auxiliary building, and  Plant responses required for the probabilistic Plant the turbine building, is shown schematically'in        fragility evaluation and the deterministic seismic Figure 5-2. An elevation view of a section              margin assessment. The overall soil/structure through the Plant is shown in Figure 5-3. To            interaction analysis method, from the ground-achieve the objective of the soil/structure            motion input to the generation of Plant response interaction analysis, a complete reevaluation of        output, is shown schematically in Figure 5-4.
the seismic soil/structure interaction effects on the power block structures was carried out, using state-of-the-art analysis techniques. The analysis    Prior to performing the soil/structure interaction has also incorporated all available relevant new      analysis, an extensive effort was conducted to information that became available -after 1978.        characterize the soil/structure interaction systems This includes the additional site investigation data  for the power block structures and to prepare the obtained during 1977 to 1978, and the on-site          appropriate analytical methods and computer recorded actual earthquake data available since        programs required by various phases of analysis.
1980.                                                The effort spent on the characterization of the systems includes: (a) the characterization of site As stipulated in the Program Plan, the Long Term      rock profile and properties; (b) the development Seismic Program soil/structure interaction analyses    of suitable three-dimensional dynamic models for have specifically included the following elements:    the' power block structures; and (c) parametric studies to evaluate the sensitivities of soil/structure
* Three-dimensional soil/structure        analysis  interaction response and identify important methods have been used.                            soil/structure interaction parameters to be considered. The effort on preparation of
* All components of free-field ground motions        appropriate analytical tools for the soil/structure at the site have been- considered in the          interaction      analysis    includes:        (a)      the determination of seismic response of interest. implementation and validation of the CLASSI and Diablo Canyon Power Plant r    Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 5                                                                                          Page 5-4 Paee 5-4 Chapter 5 PLANT NORTH 1                                              748 ft                I AJ        Notes:
* All elevations are at top of mat
                                                                                        " See figure 5-3 for Elevation of Section A-A Figure 5-2 Foundation configuration of power block structures.
Diablo Canyon Power Plant R-1 Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-5 I
Road)Structure    % Containment            .
Road      -400
                                                                                                            -3So Buidin                          -300 Auiir
                                                                                                          -250 Turbine                                          200 Elevation (ft)
Figure 5-3 Elevation view of section A-A of Figure 5-2.
Diablo Canyon Power Plant Pacific Gas and Electric Company-                                              Long TernmSeismic Program
 
Chapter 5                                                                                                          Page 5-6 Chapter 5                                                                                                          Page 5-6 Ground Motion Studies (Empirical and Numerical)
Ground Motion Power Spectral Density                    Site-Specific Spatial Site-Specific                    Function Compatible with                        Incoherence Response Spectrum                      Site-Specific Response                        Functions I Select  2 sets of Time HistoriesI Spectrum i
I
* Vertically Propagating Plane Waves
* Time History Adjus:tments            e Time History Scaling to to Match Site-Spec ific                Target Intens Ity Level for Response Specinrn                      Evaluation Time History                                                                Random Vibrational Soil/Structure                        Containment Uplift                        Soil/Structure Interaction Analysis                      Nonlinear Analysis                      Interaction Analysis Using SASSI                                                                      Using CLASSI Plant Responses to                      Modification Factors                    Modification Factors Coherent Ground                      Due to Base Uplifting                        Due to Spatial Motions                              for Containment                            Variation
                                                              &~                                          r Plant Fragility Evaluation and Capacity Margin Assessment Figure 5-4 Overall soil/structure interaction analysis method.
Dlablo Canyon Power Plant In  Pacific Gas and Electric Company                                                                  Long Term Seismic Program
 
Chpe-                                                                                            Page 5-7 Chapter 5                                                                                            Page 5-7 SASSI computer programs for three-dimensional        rock conditions and the test results are marked analysis; (b) the development, implementation,      with uncertainties resulting from the specimen and validation of analysis method and computer      saturation procedures used and the test equipment programs for soil/structure interaction analysis      flexibilities. Thus, in deriving the low-strain rock incorporating the spatial incoherence of seismic    property profiles for soil/structure interaction ground motions; and (c) the modification and        analysis purposes, emphasis was placed                  on validation of the soil/structure analysis method    field-measured data, especially the data taken and computer program for analyzing the nonlinear    from the depth below El 50 feet, because the dynamic response due to base-uplifting.              foundations of the power block structures are located at elevations between 50 feet and 80 feet.
Characterization of Site Rock Properties Based on the review of rock data assembled, representative profiles and the ranges of variation Recognizing the importance of fixing the site rock  of rock shear wave velocity, Poisson's ratio, rock properties at the beginning of the Long Term          density, damping ratio at low-strain, and the Seismic Program, a priority task was performed to    strain-dependent variations of shear modulus and assemble and review all available site rock data    damping ratio, were derived. Figure,5-5 shows and, based on this review, to assess the            the mean shear wave velocity profile and the appropriate rock profile and properties for          upper-bound and lower-bound of data developed soil/structure interaction analysis. The rock data  from the assembled site rock data.
that have been assembled include two sets of data:
one set consists of data contained in the source references of the Diablo Canyon Power Plant          Because the rock shear wave velocity profiles FSAR Section 2.5, which were obtained from the      developed from the assembled data showed site investigations conducted from 1967 to 1973;    relatively large scattering, a study was carried out the second set consists of data obtained from the    to assess the sensitivity of soil/structure interaction additional site investigations conducted from 1977  response due to the variation of rock shear wave to 1978. Both sets of data have been reviewed in    velocity profile. The sensitivity study was detail.                                              performed using a simplified soil/structure interaction model for the containment structure The rock data available from the FSAR                and the CLASSI computer program for references consist of data obtained from both field  soil/structure interaction analyses. The results of geophysical surveys and laboratory tests of rock    this sensitivity study indicated that, as the samples. These data were applicable mainly for      foundation rock shear wave velocity profile varies rocks at shallow depths, that is, down to a depth    from the upper-bound to the mean and then to of about 40 feet below the finished grade at El 85 the lower-bound, the fundamental soil/structure feet. The rock data available from the 1977 to interaction frequency for the coupled horizontal 1978 site invettigations consist of data from translation and rocking mode of the containment borehole logging, field geophysical surveys, and shell shifts from 4.6 hertz to 4.0 hertz, and then laboratory tests of rock samples obtained from      to 3.3 hertz. Despite the relatively large variation four deep boreholes drilled around the Plant to a    in the rock shear wave velocity profile, the depth of approximately 300 feet below grade.        frequency variation was found to be within approximately +/-15 percent.
Review of data from both sets indicated that the data from field-measured shear and compression      To provide an independent confirmation of the wave velocities and rock densities are more          appropriateness of the rock property profiles mutually consistent and these data are considered    developed for soil/structure interaction analysis, to be more representative of the in situ properties the      fundamental      soillstructure      interaction of the rock mass below the plant foundation; the    frequency of the containment shell, which was laboratory test values represent only very local    sensitive to the variation of rock shear wave Diablo Canyon Power Plant in      Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                            Page 5-8 Page 5-8 Chapter 5 Shear Wave Velocity (fps in 1 000s) 1-      2        3        4          6      6    7
                                                                                      - 0 100                                                I      I I        I        I 80
                                          .%      +S%
60
                                              -33/4      +33%    I 40 II 20 I
II 0
                                                                  +30%
                                                      -30%
II
                    -20 II LowrMean                    -Upper
                    -40                                                      Bound Bound    I                            I
                    -60 1-
                    -80                            II I                  25 I
l      +2
                  -100                                  I II
                  -120                                  II II o440 II
                  -160 II
                  -160
                  -200 Figure S-S Site shear wave velocity profiles (based on 1978 downhole velocity measurements).
Oiabto Canyon Power Plant Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter    5                                                                                              Page 5-9
    &deg; Chapter 5                                                                                                  Page 5-9 velocity profile, was selected as the parameter for        In the early stages of the Long Term Seismic a correlation study using the available on-site            Program, both these computer programs (that is, recorded earthquake data in the free-field and on          CLASSI and SASSI) were obtained from the the Unit 1 containment structure for three very            program developers and they were implemerited low intensity earthquakes (the maximum ground              to test their suitability for Program applications.
accelerations recorded were between 0.01 to 0.03            As a result of these tests, desirable modifications g). The results of this correlation study showed            to both programs were identified to suit the that the analytical soil/structure interaction              Program        application requirements;            these frequency based on the mean shear wave velocity            modifications were subsequently implemented profile and the associated properties correlates            with the aid of the program developers. At this very well          (within +/-5 percent) with the            stage, an extensive code verification program was corresponding            soil/structure      interaction  performed to validate the modified versions of the frequencies determined from the analysis of                computer codes. The results of the program recorded data for all three earthquakes. This good          modifications and validation for both programs correlation confirms that t.he mean shear wave              have been fully documented in the Theoretical, velocity profile along with other associated elastic        User's, and Validation Manuals for CLASSI and properties of the rock as developed from the                SASSI (Bechtel, 1988).
assembled rock data provides an appropriate representation of the characteristics of the foundation rock at the Diablo Canyon site for              CLASSI (Continuum Linear Analysis for Soil/
strain levels (2 x 104 percent to 4 x 10-4 percent)        Structure Interaction)        is a linear three-consistent with the low-intensity earthquakes              dimensional seismic soil/structure interaction considered in the study. It can be concluded from          analysis computer code developed at the this result that values of shear wave velocity above        University of California, San Diego (Wong and those represented by the mean profile shown in              Luco, 1976). The analysis method used in Figure 5-5 need not be considered                      for CLASSI is based on the substructuring technique soil/structure interaction analyses with input              that separates the analysis of kinematic interaction seismic intensities higher than those considered in        (foundation scattering of seismic motions) from this correlation study.                                    that of inertial interaction (dynamic coupling of structure and foundation impedances), as shown schematically in Figure 5-6. The foundation medium is represented in CLASSI by a uniform Soil/Structure Interaction Analysis                        or a horizontally layered, elastic or viscoelastic Methods and Computer Programs                              continuum halfspace. The most significant limitation of the version of CLASSI implemented for our Program applications is that the structural To adequately address the issues relating to                foundation must be rigid, flat, and founded on the soil/structure interaction raised in the NRC SER            surface of the halfspace. Thus, the foundation Supplement No. 27, the analysis adopted the                embedment and basemat flexibility effect cannot newly developed three-dimensional soil/structure          be evaluated. This version of CLASSI has been interaction analysis methods and the associated            validated by benchmarking the CLASSI solutions computer programs, CLASSI and SASSI. Both                  against available published solutions for 18 these programs are capable                of handling      validation      test      problems,        and        by three-dimensional          soil/structure    interaction  cross-benchmarking with the SASSI solutions problems with seismic inputs in the form of                available for the common validation test general incidence plane wave fields. Although              problems.
some limitations still exist in the use of the individual computer codes, the effects of these limitations can be evaluated through the                    SASSI (Systems for Analysis of Soil/Structure concurrent use of both analysis techniques and              Interaction) is a finite-element computer program reconciliation of the results with each other.            for    two-    and    three-dimensional          linear Dlablo Canyon Power Plant Fa    Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 5                                                                                Page 5-10 I
le        e-Free-Field Motion          Foundation Input Motion
                                                                  ""    I                            !
I 0,
Interacton        IISail/Structure EXPLANATION M    Apply base moment F    Apply base shear                Structural Model Incidence wave                                      &#xfd; Figure 5-6 CLASSI substru/ing technique.
Diablo Canyon Power Plant In  Patilic Gas and Electric Company                                        Long lerm Seismic Program
 
Chapter 5                                                                                            Page 5-11 Chapter 5                                                                                            Page 5-11 soil/structure interaction analyses developed at the    multiple-stick model, as shown in Figure 5-8.
University of California, Berkeley (Lysmer and          The model consists of a 9-lumped-mass, single others, 1981). The program uses the complex              stick for representing the exterior containment response method and the flexible-volume                  shell and a 16-lumped-mass, multiple-branch substructuring technique as shown schematically          single-stick for representing the interior concrete in Figure 5-7. The soil material is modeled using        structure. An extra single degree-of-freedom complex moduli and -a hysteretic damping                vertical lumped-mass model was developed and mechanism.        The foundation medium is              attached to the containment shell stick at the represented, by a horizontally layered soil system      containment springline location to represent the overlaying an elastic halfspace. Due to the unique      fundamental vertical drumming mode of the flexible-volume          substructuring        technique containment hemispherical dome. Due to its employed and the use of finite-element models, asymmetric configuration, the three-dimensional SASSI can rigorously handle the soil/structure stick model for the interior concrete structure interaction effects due to foundation embedment includes both the mass eccentricities and the and basemat flexibility. However, because of the large number of degrees-of-freedom that usually          proper locations and orientations of the centers of result from the use of three-dimensional finite-        rigidity of the structure.
element models, the most significant limitation of the SASSI program is the soil/structure interaction model size and the computational costs. The              For the auxiliary building, two three-dimensional SASSI version implemented for Program                    dynamic models were developed for analysis applications has been validated by benchmarking          applications. One of these models was a SASSI solutions against available published              three-dimensional finite-element dynamic model, solutions for 20 validation test problems, and by        which was        developed by modifying the cross-benchmarking with the CLASSI solutions            three-dimensional finite-element static model that available for the common validation test                existed prior to the Program. The second model problems.                                                was a three-dimensional,          25-lumped-mass, five-stick model. The three-dimensional finite-element dynamic model was developed primarily for studying the dynamic characteristics of the Three-Dimensional Dynamic Models for                    building in relation to its irregular configuration.
Power Block Structures                                  The knowledge gained from this study provided a basis for developing the three-dimensional lumped-mass stick model. In addition to this For      the      purpose      of    three-dimensional application,, the three-dimensional finite-element soil/structure interaction analysis for the power        dynamic model was also used for soil/structure block structures using either CLASSI or SASSI,          interaction parametric studies to assess the effect three-dimensional          dynamic        models    were  of foundation basemat flexibility.
developed for the containment structure, auxiliary building, and turbine building including the turbine pedestal. The development of .these models used as much as possible the model data          The three-dimensional lumped-mass stick model available from the dynamic models used for              for the auxiliary building was developed with the seismic analysis prior to the Long Term Seismic          specific intent of CLASSI and SASSI analysis Program.                                                applications. The development was based on the conventional dynamic stick model development technique aided with the understanding of the For the containment structure, the three-                dynamic characteristics of the building obtained dimensional dynamic model developed for the              from    the  three-dimensional ' finite-element analysis is a three-dimensional lumped-mass,            dynamic model.
Diabla Canyon Power Plant In    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                                PaRe 5-12 Page    5-12 Chapter 5
          .*  \i        ~TI  7I  TI T I I I f
(a) Free-field soil medium f
(b) Excavated soil volume SI__                                                  _  _  _  _  _  _    _    _    _
EXPLANATION
                                              /\                      Interaction degrees of freedom S-    /                          at the structure / soil interface f Interaction degrees of freedom in excavated soil volume (c) Structure Figure 5-7 SASSI flexible-volume substructuring technique.
PDiablo InPacific Gas and Electric Company                            'Long                              Canyon Term    PoweiPrPlant Seismic rogram
 
Chapter 5                                                                                  Page 5-13 El 231' (a) Containment Shell
                                                                    -d (b) Internal Structure Figure S-8 Three-dimensional lumped-mass dynamic model for the containment structure.
Diable Canyon Power Plant I    Pacific Gas and Electric Company                                          Long Term Seismic Program
 
Chapter 5                                                                                          Page 5-14 Chapter 5                                                                                          Page 5-14 The configuration of the three-dimensional            multiple-structure-to-structure interaction effect, lumped-mass stick model developed for the            the effect of nonvertically incident seismic wave auxiliary building is shown in Figure 5-9. Modal      inputs, the foundation basemat flexibility effect, analysis performed using the. three-dimensional      and the sensitivity of results to the CLASSI/SASSI stick model and the three-dimensional finite-        solution techniques. In addition, a separate study element dynamic model, both with the same            was performed to assess the importance of fixed-base conditions, showed that they are          strain-dependency of the site rock shear modulus dynamically equivalent with each other in terms of    under high intensity earthquake conditions and providing comparable modal characteristics for        the effects of variations in Poisson's ratio and the significant response modes.                      material damping ratio for the foundation rock.
For the turbine building, because of the complexity of the building structural system and      For the purpose of the parametric studies, the the lack of continuous rigid diaphragm action due    horizontal soil/structure interaction responses of to the presence of turbine pedestal openings in the  the containment structure and the auxiliary floors, the three-dimensional dynamic model          building were analyzed using either CLASSI or selected for analysis            applications was a  SASSI, or both, for seven parametric cases, each three-dimensional finite-element dynamic model,      with a different combination of the following as shown in Figure 5-10 for the Unit 2 turbine        parameters: surface-supported versus embedded building. This model was developed by modifying      foundations; single versus multiple foundations; the detailed three-dimensional finite-element        rigid versus flexible foundation. The seismic input model used in studies prior to the Program. The      for the analysis considered three different type of three-dimensional dynamic model for the turbine      seismic wave fields, namely, vertical SV plane pedestal developed for Program applications is a      waves; SV plane waves inclined at a 30-degree single lumped-mass stick model. This simple          angle from the vertical; and horizontally model was considered adequate, because the            propagating SH plane waves. The seven dynamic characteristics of the turbine pedestal as    parametric cases with different types of seismic indicated by the existing refined model were          input analyzed for the parametric studies are found to be dominated by the fundamental modes        summarized in Table 5-1. Except the study for in each of the three directions.                      the foundation basemat flexibility effect, for which the analysis was based on the three-dimensional finite-element dynamic model of the auxiliary Soil/Structure Interaction Parametric                building coupled with a finite- element foundation Studies                                              model, all analyses for the parametric studies were based on simplified soil/structure interaction Prior to the development of suitable soil/structure  models of both the containment structure and the interaction models for the power block structures    auxiliary building. As- an example, the simplified and the selection of the more appropriate            model for the containment structure used for. the computer programs between CLASSI and SASSI          studies is shown in Figure 5-11. The seismic input to be applied for final soil/structure interaction    time history for the parametric studies was a analysis, a series of parametric studies were        horizontal acceleration time history with a carried out. The objectives of these parametric      maximum acceleration of either 0.75 g or 0.96 g, studies was to assess the soil/structure interaction prescribed at the rock surface of the Plant's response sensitivities as affected by various        finished grade at El 85 feet.
parameters and to identify those parameters which are important for the soil/structure interaction modeling and analysis for power block structures. Based on the assessment of the soil/structure interaction response sensitivities indicated by the The soil/structure interaction parameters studied    results of the parametric studies, the following included the foundation embedment effect, the        conclusions were made:
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 5                                                                                    Page 5-15 Page 5-15 Chapter 5 Fuel-Handling Structure
                                                                                      -Rigid El 140' cc EXPLANATION CW  Core West CC  Core Center CE Core East NW  North Wing SW  South Wing Figure S-9 Three-dimensional 25-lumped-mass, 5-stick model for auxiliary building.
OMablo Canyon Power Plant IsRPacific Gas and Electric Company                                            Long TernmSeismic Program
 
Chpe Chapter 5 Page 5-16 Page 5-16 AeaX N
Figure 5-10 Three-dimensional finite-element dynamic model for Unit 2 turbine building above El 85 feet.
In Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 5                                                                          Page 5-17 Chapter 5                                                                          Page 5-17 Table 5-1 PARAMETRIC CASES STUDIED AND COMPUTER PROGRAMS USED Ground Motion Input Parametric Cases            Vertical SV    SV-30 Degrees        Horizontal SH (1) Fixed-Base Condition for              Standard Containment and Auxiliary Building    Structural Dynamics Programs (2) Single Surface Rigid Foundation for CLASSI/SASSI    CLASSI/SASSI            CLASSI Containment and Auxiliary Building (3) Single Embedded Rigid Foundation        SASSI            SASSI for Containment and Auxiliary Building (4) Containment and Auxiliary Building  SASSI/CLASSI    SASSI/CLASSI            CLASSI Surface Rigid Foundation (5) Containment and Auxiliary Building      SASSI            SASSI Embedded Rigid Foundation (6) Auxiliary Building Embedded            SASSI Flexible Foundation (7) Containment with Embedded Rigid        SASSI Foundation and Rock Property Variations F    Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-18 Chapter 5                                                                                    Page 5-18 El 302.25'        1 0
El 274.37'      2 El 258.27'      3
                                                  -      Containment El 231.00'      4 Q
El 205.58'      5 Q
El 181.08'      6 El 138.5'  12    Interior El 155.83'      7                              Concrete
(*)      El 111.63', 11 El 130.58'      8 El 109.87'        9 El 91.00'        400" A      1023 153.0' Figure 5-11 Simplified lump-mass stick model of the containment structure used in the parametric studies.
Diablo Canyon Power Plant an Pacific Gas'and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                            Page 5-19 Chapter 5                                                                                            Page 5-19 CLASSI/SASSI Solution Techniques. CLASSI                and incorporated in the soil/structure interaction and SASSI produce solutions that are closely            analysis.
comparable with each other so that the choice of either solution method and computer program for        Basemat Flexibility Effect. The effect of a specific application can be based simply on the      foundation basemat flexibility was shown to be suitability of foundation model assumptions 'for        relatively important for the auxiliary building. This the      specific      application. Representative is demonstrated by the comparisons shown in comparisons of the floor response spectra              Figure 5-17 of the transfer function amplitudes at determined from CLASSI and SASSI analyses for          the core west location of the floor at El 140 feet of a common parametric case involving the response        the auxiliary building obtained from SASSI of the containment base and top of the interior        analysis assuming five different basemat flexibility structure to vertically propagating SV wave inputs      conditions as shown in Figure 5-18. Thus, for are shown in Figures 5-12 and 5-13, respectively.      those structures having basemats of large plan dimensions such as the auxiliary and turbine Foundation Embedment Effect. The foundation            buildings, the basemat flexibility should be embedment effect is relatively important and.          considered in the soil/structure interaction thus, should be considered in the final                models.
soil/structure interaction models for the power block structures. This is demonstrated by the          Rock Property Variation Effect. The effect of comparison shown in Figure 5-14 of floor                strain-dependency of site rock shear modulus was response spectra at El 140 feet of the auxiliary        found to be insignificant (maximum reduction of building obtained from SASSI analyses assuming          containment          fundamental          soil/structure surface-supported versus embedded foundation            interaction frequency was less than 8 percent) for conditions.                                            seismic input intensities involving            maximum ground acceleration as high as 1.0 g. The effects Structure-to-Structure Interaction Effect. The          of variations in the Poisson's ration and material through-rock,          multiple-structure-to-structure damping ration of the rock within the ranges of interaction effect is relatively unimportant; thus, it  values considered appropriate was found to be can be neglected in the soil/structure interaction      negligible.
analyses for the power block structures. This is demonstrated by the comparison shown in Figure          Based on the above conclusions, the SASSI 5-15 ot the floor response spectra at the top of        computer program was selected for the final containment interior concrete structure obtained        soil/structure interaction analysis application from SASSI analyses assuming single-embedded            because of its capability to include the effects of versus multiple-embedded foundation conditions.          foundation embedment and basemat flexibility.
The SASSI finite-element foundation models Non-Vertical Wave Propagation Effect. The use            developed for the power block structures for the of non-vertical seismic wave input motions was          final analysis are shown in Figure 5-19 for the found to generally result in reductions in the          containment structure, in Figure 5-20 for. the seismic response; thus, the use of vertical plane        auxiliary building, and in Figure 5-21 for the wave input for soil/structure interaction analysis is  turbine building.
conservative. This is demonstrated by the comparison shown in Figure 5-16 of the floor response spectra at El 140 feet of the auxiliary        Ground-Motion Input for Soil/Structure building obtained from SASSI analyses assuming          Interaction Analysis vertical SV wave versus inclined SV-30-degree wave inputs. Furthermore, the use of vertically        The basic data of seismic ground-motion input for propagating wave input precludes double counting        soil/structure interaction analysis were provided by of the effect of horizontal spatial variations of      the ground-motion studies (Chapter 4). These ground motions when such a variation is included        data consisted of the median and                    84th in the ground-motion spatial incoherence model          percentile, horizontal and vertical site-specific Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                  Page 5-20 2% Damping 6
S 0C Z      4                                                          A CL 2
0.10 SASSI ana 0        .,                                            I  I  I I  III    I      I    I    I  I 10                                    1001 Frequency (Hz)
Figure 5-12 Comparisons of floor response spectra obtained from CLASSI and SASSI analysis for the east/west response at the containment base.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                        Long Term Seismic Program
 
Chapter 5                                                                                                Page 5-21 Chapter 5                                                                                                Page 5-21 8                            1    L  I I                                                  Imi      I    1    9  . I 1 2% Damping 6
CLASSI analysis 4.'
2*
SASSI analysis 0        t                      i  i                U11        I  I I  I II          "          I    I    I  I  II  I 10-1                                    100                                101                                        102 Frequency (Hz)
Figure 5-13 Comparisons of floor response spectra obtained from CLASSI and SASSI analyses for the east/west response at the top of interior concrete structure.
EDiablo                                                                                            Canyon Power Plant Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-22 Chapter 5                                                                                        Page 5-22 2% Damping 6
foundation 0O                                                                                            surface kSingle 03 4
eS 2
Single embedded foundation--'-.
0 10-1                                100                              101                                  102 Frequency (Hz)
Figure 5-14 Comparison of floor response spectra obtained from SASSI analysis assuming surface-supported versus embedded foundation conditions for the auxiLiary building at El 140 feet.
Diablo Canyon Power Plant In    Pacific 4as and Electric Company                                              Long Term Seismic Program
 
Chanter      5                                                                                  .Page 5-23 Chanter 5                                                                                          Page 5-23 2% 1 6.
.                              ,    Single embedded foundation
.0.
CL Auxiliary building and containment embedded foundation 10-1                                    100                              101                                102 Frequency (Hz)
Figure 5-15 Comparison of floor response spectra obtained from SASSI analyses assuming single embedded foundation versus multiple-embedded foundations.
Diablo Can yon Power Plant Pacific Gas and Electric Company                                              Long Term, Seismic Program
 
Chapter 5                                                                                          Page 5-24 Chapter 5                                                                                          Page 5-24 8
6 0
4.
(U I-4 2
0 10-1                                  100                              10,                                102 Frequency (Hz)
Figure 5-16 Comparison of floor response spectra at El 140 feet of the auxiliary building obtained from SASSI analyses with vertical SV wave input versus inclined SV wave input.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 5                                                                                                  Page 5-25 12.0 EXPLANATION
                                                                    ........... Fixed-Base
                                                                      - - -    Fully Rigid Bass Partially Rigid Base, Rigid Embedded Walls 10.0                                                          ......... Partially Rigid Base, Flexible Embedded Walls Fully Flexible Base and Embedded Walls 8.0
.2  6.0 4.0 2.0 0
2.5          5.0 Frequency, (Hz)
Figure 5-17 Transfer functions for eastJwest response at core west El 140 feet of the auxiliary building for various conditions of foundation systems.
Diable Canyon Power Plant.
In    Pacific Gas and Electric Company                                                          Long Term Seismic Program
 
Chapter 8      5                                                                                      Page 5-26 Chapter  5                                                                                      Pane 5-26 CASE 1: Fixed Base                                                                -El 140ft (Rigid Base, Rigid Rock)                                                              El 85 ft El 60ft CASE 2: Fully Rigid Base, Flexible Rock CASE 3: Partially Rigid Base and Embedded Walls, Flexible Rock CASE 4: Partially Rigid Base, Flexible Embedded Walls and Rock CASE 5: Fully Flexible Base, Embedded Walls, and Rock Figure S-18 Various foundation basemat flexibility assumptions for the auxiliary building considered in the parametric studies.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                Long 7erm Seismic Program
 
Chapter 5                                                                                  Page 5-27 Chapter 5                                                                                  Page 5-27 N
Y X
Figure S-19 SASSI foundation model for containment structure.
Diablo Canyon Power Plant MI  Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-28 Page 5-28 Chapter 5 N
cov Figure 5-20 SASSI foundation half-model for auxiliary building.
Diablo Canyon Power Plant I  Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-29 Chapter 5                                                                                      Page 5-29 unitl N
0'1-&#xfd; Unit 2 turbine building foundation model Unit 2 turbine pedestal foundation model Figure 5-21 SASS! foundation model for Unit 2 turbine building.
Diable Canyon Powel Plant
*J  Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                          Page 5-30 Chaper                      5Page5-3 earthquake acceleration response spectra for the            amplitudes,    but keeping the            Fourier Diablo Canyon site. Both the median and the 84th            phase-angles unchanged,          so that the percentile spectra, normalized with respect to              resulting time history response spectra closely peak ground acceleration values, have almost the            matched the median site-specific horizontal same spectral shape. Thus, it is only necessary to          spectra of several damping values. Likewise, consider one set (median or 84th percentile) of            the vertical component time histories were these spectra for linear soil/structure interaction        modified to match the median site-specific analysis, because the responses so obtained can be          vertical spectra of several damping values.
linearly scaled up or down, based on the peak ground acceleration ratio, to obtain the soil/structure interaction responses for any desired  (4)  The three-component time histories were level of input.                                            scaled upward by a constant scaling factor common to all three components to Associated with the site-specific response spectra,        correspond to a reference seismic input level three sets of three-component actual earthquake            for Plant fragility evaluation purposes.
ground-motion time histories were selected and provided by the ground-motion study for soil/structure interaction analysis applications.    (5)  Because the Plant north/south direction is These three sets of ground-motion records are:              approximately parallel to the strike of the (a) the Pacoima Dam records of the 1971 San                Hosgri fault zone, the modified and scaled Fernando earthquake; (b) the Tabas records of              three-component time histories were applied the 1978 Tabas earthquake; and (c) the El Centro            as the. input for soil/structure interaction No. 4 records of the 1979 Imperial Valley                  analyses;    first,  with the longitudinal earthquake. Two of the three sets of ground-                component applied in the Plant north/south motion records provided (Pacoima and Tabas)                direction, and the transverse component in were actually used for final soil/structure                the plant east/west direction; then vice versa, interaction analyses.                                      the vertical component was applied in the Plant vertical direction. The interchanging of the two horizontal components for input was Before these motions were applied for done to allow for uncertainties in the time soil/structure interaction analysis, the following history phasing, because both the Pacoima step-by-step procedure was used to adjust the and Tabas motions were initiated by thrust motions:
events.
(1) The original recorded motions were adjusted to conform to site-specific conditions, such    For Plant fragility evaluation applications, the as the maximum earthquake magnitude,            constant scaling factor used in step (4) above, -was source-to-site distance, and site condition. derived in such manner that the average spectral value of the 5 percent damped site-specific (2) The two horizontal components of the            horizontal spectral acceleration in the frequency motions were transformed, as necessary, into    range from 4.8 hertz to 14.7 hertz, equal to the the longitudinal and transverse horizontal      fragility evaluation reference spectral acceleration components to provide motions in the            of 2 g. The frequency range was chosen directions normal and parallel to the strike of considering the fragility evaluations described in the causative fault.                            Chapter 6. This procedure is illustrated in Figure 5-22. The resulting scaling factor was 1.6, and the peak spectral acceleration of the resulting (3) The longitudinal and transverse time histories  horizontal spectrum was about 2.2 g. The fragility were both modified by adjusting the Fourier    evaluation reference spectra so obtained are Dlablo Canyon Power Plant Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 5                                                                                            Page 5-31
  -~      2
  .2 U
h.
S U
U S
S I..
4..
U S
0.1 Co 0
0.1                              1                              10                            100 Frequency (Hz)
EXPLANATION Median site-specific response spectrum scaled by 1.6
                                ----- Median site-specific response spectrum Figure S-22 Illustrative procedure for obtaining the 5 percent damped horizontal reference spectrum for soil/structure interaction analyses.
Diablo Canyon Power Plant IN    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-32 Chapter 5                                                                                      Page 5-32 slightly higher than the 84th'percentile response  horizontal responses (Chapter 6), only the spectra for the site.                              horizontal north/south and east/west responses of the power block structure were generated.
The final three-component Pacoima time histories, which have been modified to match the median spectra shapes and subsequently scaled up    For these        analyses, the final scaled-up by the 1.6 factor, are shown and compared with      three-component spectrum-compatible Pacoima the unmodified, time histories from step (2) above  and Tabas time histories, shown in Figures 5-23 (but scaled to the maximum acceleration of 0.96 g  through 5-25, and Figures 5-29 through 5-31, for the horizontal components) in Figures 5-23,    respectively, were directly used as inputs for 5-24, and 5-25, respectively for the longitudinal,  analyses. These input motions were assumed in transverse, and vertical components. The            the analyses to be the free-field surface motions comparisons of the 5 percent damped final          prescribed at the plant grade (El 85 feet). The Pacoima. time history response spectra with the    incident seismic wave field was assumed to be 5 percent damped fragility evaluation reference    coherent, vertically propagating plane seismic response spectra are shown in Figures 5-26,        shear and compression waves, respectively, for the 5-27, and 5-28. Similar comparisons for the        horizontal and vertical components of the three-component Tabas time histories are shown      free-field motion. Because only the horizontal in Figures 5-29, 5-30, and 5-31; and similar        north/south and east/west responses were comparisons for response spectra are shown in      generated, the coupling between the two Figures 5-32, 5-33, and 5-34.                      horizontal      responses      that        exists      for non-symmetrical structures was considered by combining the co-directional time history As shown in these comparisons, the modified final  responses or by combining the floor response time history response spectra closely match the    spectra using the rule of square-root-of-the-corresponding reference response spectra, which    sum-of-squares. Under the vertically propagating are about 10 percent higher than the 84th          plane wave assumption, the contributions to the percentile response spectra discussed previously. horizontal responses due to the vertical input Furthermore, as a result of keeping the time        motion are negligible; thus, they were not history Fourier phases unchanged during the time    considered in the response combinations to obtain history modifications for spectrum compatibility,  the    north/south    and east/west horizontal the final spectrum-compatible time histories        responses.
maintain realistic characteristics and appearances, and resemble the time histories of the motions before modifications.
The results of the sofi/structure interaction analyses were obtained and provided for us* in..
the Plant fragility evaluation in terms of 5 percent Generation of Soil/Structure Interaction            damped horizontal north/south and east/west Responses to Coherent Ground-Motion                floor response spectra at selected locations in the Inputs                                              power block structures. Floor response spectra for both sets of input motions, namely, the Pacoima and the Tabas          inputs, were generated.
To      generate the soil/structure interaction    Representative results obtained from both sets of responses required for the Plant fragility          input motions are shown in Figures 5-35 and evaluations, soil/structure interaction analyses    5-36 for the north/south response of the were performed using the SASSI computer            containment at the base (El 85 feet) and at the program, the soil/structure interaction models      top of the interior structure (El 138.5 feet),
developed for the power block structures, and the  respectively. Similarly, the results for the ground motions described previously. Because        north/south response of the auxiliary building at equipment fragilities are mostly dominated by      El 85 feet and El 140 feet of the core west liablo Canyon Power Plant In    Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                      Page  5-33 Chapter 5                                                                                      Page 5-33 Unmodified (transformed and scaled up by 1.6) 1.2 S
0
  -1.2 Modified 1.2 0
0
  -1.2 0                3                6            9            12            15              18 Time (sec)
Figure S-23 Comparisons of unmodified and modified Pacoima acceleration time histories, longitudinal component.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-34 Chapter 5                                                                                        Page 5-34 Unmodified (transformed and scaled up by 1.6) 1.2 Transverse component Peak ground acceleration = 0.96 g
.o_
4-*
  -      0 0)
      -1.2 Modified 1.2 C
.2 0
    -1.2 0                3                6            9            12            15              18            21 Time (sec)
Figure S-24 Comparisons of unmodified and modified Pacoima acceleration time histories, transverse component.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 5                                                                                    Page 5-35 Chapter 5                                                                                    Page 5-35 Unmodified (scaled by 1.6) 1.2
.2 9-a) 1~
0 S
S U
U
    -1.2 Modified 1.2 0
4..
cc    0
    .1.2 0                  3              6      9            12            15                18            21 Time (sec)
Figure 5-25 Comparisons of unmodified and modified Pacoima acceleration time histories, vertical component.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                            Page 5-36 Chapter 5                                                                                            Page 5-36 101                          ,        u              ,1  1 It I  I 1aaa          1    1  1iT 5 % damping 100-:
                                      ,/,-4-*Reference 4-U 1..
a) a)
U
'I U
U I-10-11,-
                            -o-- Modified Pacoima 10-2              I          UI    I    .        I      p  I  a  l  ,      Il 10.1                              100                            101                                  2 Frequency (Hz)
Figure 5-26 Comparisons of modified Pacoima time history response spectrum and fragility evaluation reference response spectrum, longitudinal component.
Diablo Canyon Power Plant IQ    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                      Page S-37 Chapter 5                                                                                      Page 5-37 10 100 0
U I-0 El Ia.
tj~
10-1 10          10.1                              100                        101                            102 Frequency (Hz)
Figure 5-27 Comparisons of modified Pacoima time history response spectrum and fragility evaluation reference response spectrum, transverse component.
Diablo Canyon Power Plant R    Pacific Gas and Electric Company  ,                                          Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-38 10T                                                                    1                              17 5 % damping 100 C
0                    Modified Pacoima 6
to)      r*    10"I/            .'*--Reference
        *,"10-                                100o                        10 t                              10 2 Frequency RHz)
Figure 5-28 Comparisons of modified Pacoima time history response spectrum and fragility evaluation reference response spectrum, vertical component.
Diablo Canyon Power Plant In  Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 5                                                                                      Page S-39 Chapter 5                                                                                      Page 5-39 A
Unmodified (transformed and scaled by 1.6)
    -1.2 0,
0
@2 U
U ci:
1.2 Modified
    -1.21                                                      I              I                  i Longitudinal component und acceleration = 1.01 g S,
C a
0 I                                              I 1.2 0                    5              10              15              20                25              30 Time (sec)
Figure 5-29 Comparisons of unmodified and modified Tabas acceleration time histories, longitudinal component.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                      Pae54 Page    5-40 Chapter 5 Unmodified (transformed and scaled by 1.6) 1.2                                      9 Transverse component 02 Peak ground acceleration = 0.96 g 0
0 i                I              I
    -1.2 Modified 1.2 Transverse component 02                                                                            Peak ground acceleration = 0.95 g C
0 41 I-      0 a) a)
a
(.2
    -1.2 0                    5            10              .15            20                25              30 Time (sec)
Figure S-30 Comparisons of unmodified and modified Tabas acceleration time histories, transverse component.
aDiablo                                                                          Canyon Power Plant Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-41 Unmodified (scaled by 1.6) 1.2                                                  I                      !                I Vertical component Peak ground acceleration = 0.79 g 00 1W. 0      A    -
Y440
      -1.2                      I Modified 1.2 01 C
-  0 4..
U I-0)
U 0
  'I
      -1.2 0                    5            10          15                20                  25                30 Time (sec)
Figure S-31 Comparisons of unmodified and modified Tabas acceleration time histories, vertical component.
Diablo Canyon Power Plant an Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                    Page 5-42 Chpe                                                                                          ae54
    "*m**.A--R1fereece 0e U )0"2            1      t  I  I I 1  11        1. 1  1  1 1 -t I I I, "1                            10 0                          101 Frequency (Hz)
Figure 5-32 Comparisons of modified Tabas time history response spectrum and fragility evaluation reference response spectrum, longitudinal component.
a  Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-43 Chne                                                                                            ae54 Reference        .
a s&deg;J                                ,
  @Modified                                            Tabas icY 10-2.j I          I]m I i  I              li I muI  I        ,    a  a  agI.
: 10.                              100                            1,01                        102 Frequency (Hz)
Figure 5-33 Comparisons of modified Tabas time history response spectrum and fragility evaluation reference response spectrum, transverse component.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                    Page 5-44 Chapter 5                                                                                    Page 5-44 101 0
CL C-102 Frequency (Hz)
Figure 5-34 Comparisons of modified Tabas time history response spectrum and fragility evaluation reference response spectrum, vertical component.
Diablo Canyon Power Plant a Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-45 HI" I    I,  I 5% Damping 3'
0 4-0O)
                                    -  I              *I. 9    4 S            p                  I 4-I WIV Modified Pacoima input Modified Tabas input A
mlI II .
i  I II I I I i      i 100                                                                  101                                  10zz 10 Frequency (Hz)
Figure 5-35 Floor response spectra for the north/south response of the containment at the base (El 85 feet) obtained from SASSI analyses with coherent ground motion input.
Diablo Canyon Power Plant a Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-46 Chapter S                                                                                      Page 5-46 1:  '                            ,1  ,    I I    3        I.        ,        ,    ,
5% Damping 9
.2 0
0      6                                                I    i U
U 0
1..
4.'
U 6)
: a.                                                                          Modified Pacoima input Modified Tabas input 0                                t            I  I  I              I        I        I      I    I      I I 10o                                                    101                                                  102 Frequency (Hz)
Figure 5-36 Floor response spectra for the northisouth response of the containment at the top of interior concrete structure (El 138.5 feet) obtained from SASSI analyses with coherent ground motion input.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                            Page 5-47 Chapter 5                                                                                            Page 5-47 location are shown in Figures 5-37 and 5-38,            site within the foundation region were represented respectively.                                          in the frequency domain, using a 3x3 ground-motion    covariance    matrix    in    which      the The soil/structure interaction responses resulting      on-diagonal elements represent the auto-power from the two sets of input motions (Pacoima and        spectral density and the off-diagonal elements Tabas) were found to be consistent with each            represent the cross-power spectral density for the other for all response locations, as shown in          three-components of the ground motions.
Figures 5-35 through 5-38. Thus, the use of
-more sets of such motions as input was                  The ground-motion covariance matrix for the considered unnecessary. It was also found that          Diablo Canyon site was derived from the time interchanging the directions of the horizontal          history    ensemble used        for deriving the motion components had no significant effect on          site-specific spectra. Thus, it is consistent with the structural responses. The soil/structure interaction    site-specific earthquake spectra. The amplitude of responses generated using the spectrum-                one element of the covariance matrix, scaled-up compatible input motions as used herein also can        by the factor of (1.6)2 to correspond to the be shown to be consistent with the responses that      fragility evaluation reference input, is shown in would be obtained from the ensemble averages of        Figure 5-4 1.
the responses to the individual inputs of the time history ensemble that forms the basis of the To incorporate the ground-motion covariance site-specific earthquake spectra.                      matrix in conjunction with the spatial incoherence functions for soil/structure interaction analyses, an Adjustment of Soil/Structure Interaction                analysis method was developed that is based on Responses Due to Spatial Incoherence                    the random vibration theory of structural dynamics and uses the covariance matrix of the of Ground Motions ground motions directly as the input.
The soil/structure interaction responses based on the assumption of vertical coherent plane wave          Because the site-specific spatial incoherence input do not consider the effects of horizontal        functions were developed only for free-field spatial variation of free-field ground motions.        surface motions, only the spatial variations of Thus, separate soil/structure interaction analyses      surface motions need be considered for were performed to develop the response                  soil/structure interaction analyses. Consequently, adjustment factors that could be used to adjust the    the analysis method developed to incorporate the soil/structure interaction responses obtained from      site-specific spatial incoherence functions used the coherent ground-motion input to account for        the CLASSI method of soil/structure interaction the effect of spatial variations.                      analysis, which is applicable for surface-supported rigid foundations. The total method, which The characterization of spatial variation of            inclddes applying the CLASSI computer code for free-field surface motions at the Diablo Canyon        generating the scattered foundation input motions site was achieved using a set of site-specific spatial  and soil/structure interaction response transfer incoherence functions, as described in Chapter 4.      functions, and the PROSPEC computer code Such functions consist of ground-motion                (Lilhanand and Tseng, 1983) for generating the coherency amplitudes (Figure 5-39), and the            probabilistic floor response spectra based on corresponding phase angles (Figure 5-40). These        random vibration theory, is shown schematically functions vary with the Fourier frequency of the        in Figure 5-42. Using this method, the spatial surface motions and the separation distance            incoherence functions are incorporated into the between two points on the ground surface.              ground-motion input at the step when the ground-motion covariance matrices for various points on To use such spatial incoherence functions for          the ground surface covered by the CLASSI soil/structure interaction analysis, the free-field    foundation model are calculated, and then ground surface motions at various points of the        integrated to generate the scattered foundation Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                                                        Page S-48 Chapter 5                                                                                        Page 5-48 6
4.5 Q
0    3 CL co 1.5 0                      I                I  I  I 100                                                  10ot                                                  102 Frequency (Hz)
Figure 5-37 Floor response spectra for the north/south response of the auxiliary building at the core west (El 85 feet) obtained from SASSI analyses with coherent ground motion input.
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Chapter 5                                                                                      Page 5-49 Chapter 5                                                                                      Page 5-49 W
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                                    *'4**C*.Modified                                  Pacoima input
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Frequency  (Hz)
Figure S-38 Floor response spectra for the north/south response of the auxiliary building at core west (El 140 feet) obtained from SASSI analyses with coherent ground motion input.
                                                                          -i--Diablo          CanMo n Power P
[lant INPacific Gas and Electric Company                                                Long Term Seismic Pro gram
 
Chanter 5                                                                                          Page 5-50 Chanter 5                                                                                          Page 5-50 1    0.50 x0 U'
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Figure 4-12 Horizontal coherence spectral amplitude functions.
Figure 5-39 Amplitudes of horizontal site-specific spatial incoherence functions.
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Chapter 5                                                                                          Page 5-51 Chapter 5                                                                                          Page 5-51 2.00 Vertical 300 OI 1.00-                                                                                    250
* so 0.00 0.00              4.00          8.00          12.00        16.00        20.00 Frequency (Hz) 2.00 Horizontal                                    300 250 200 1.00-100 50 50 0.00 0.00              4.00          8.00          12.00        16.00        20.00 Frequency (Hz) 2.00, Cross-term 300 CL        250      -
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50 0-Oc 4.d 0.00              4.00          8.00          12.00        16.00        20.00 Frequency (Hz)
Figure 5-40 Phase angle of site-specific spatial incoherence functions.
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Chapter 5                                                                                                          Page 5-52 Chapter 5                                                                                                          Page 5-52 100                        I        I ~    I    J l
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Figure 5-41 Amplitude of one element of the ground motion covariance matrix used for the soil/structure interaction analysis with incoherent ground motion input.
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Chapter 5                                                                                            Page 5-53 Chapter 5                                                                                            Page 5-53 r--    Floor response spectrum (Rul) 9 I
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                            .Ug)                              response spectrum QSite-specific incoherence functions V                                              /                          EXPLANATION Half space U Floor response motion for foundation muedium                                    m Mass Figure 5-42 Schematic diagram of random vibrational soil/structure interaction analysis for incoherence ground motion input.
Diablo Canyon Power Plant Ia  Pacilic Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 5                                                                                                Page 5-34 Chapter 5                                                                                                Page 3-54 input motions. This method and the associated              incorporating site-specific spatial incoherence computer programs have been benchmarked                    ground motion effects, indicate the following:
against the available published solutions (Luco and Wong, 1986; Mita and Luco, 1986).
(1) Spatial incoherence of ground motions generally results      in reductions in the Using this method and the CLASSI soil/structure                  foundation base translational motions as interaction models for the power block structures,              indicated by the floor response spectral ratios analyses were performed with input conforming to                for the basemat responses shown in the fragility evaluation reference average spectral              Figures 5-43, 5-45, 5-47, and 5-48, and acceleration of 2 g, as shown in Figure 5-22.                    such reductions are proportional to the plan Soil/structure interaction responses (including the              area of the foundation. For the basemats of effects of spatial incoherence) in terms of the power block structures, the magnitudes of 5 percent damped floor response spectra were these reductions increase gradually with developed for each of the locations in the power increasing frequency. For frequencies above block structures where the responses to the 10 hertz, these reductions, as indicated by coherent ground-motion inputs were generated the analytical studies, are about 6 percent for earlier. To isolate the effect of spatial incoherence using the same analysis method, soil/structurp                  the containment structure, 15 percent for the interaction analyses in which the spatial                        auxiliary building, and between 0 and 30 incoherence functions were set equal to unity,                  percent for the turbine building.
were also performed to generate the responses to the coherent ground motions at the same (2) Due to the accompanying 'rocking and locations. Values of the floor response spectral torsional motions induced as a result of ratio, which is the ratio of the 5 percent damped spatial incoherence, the reductions in floor response spectral value resulting from the incoherent      ground-motion        input      to    the      response are less at the locations within the corresponding spectral value resulting from the                  structures where the response is affected by coherent ground-motion input, were determined.                  rocking or torsional response motions, and in The floor response spectral ratios for various                  the specific frequency ranges of the rocking response locations, which represent only the effect              and torsional response modes of the on the soil/structure interaction response due to                structure. This is illustrated by comparing the the spatial incoherence of ground motions, were                  floor response spectral ratios for the then provided for' use in the Plant fragility                    north/south and east/west responses as evaluations.      Representative      results    of the        shown, respectively; in Figures 5-49 and 5 percent damped floor response spectra and the                  5-50 for the switchgear location near the corresponding floor response spectral ratios to be                south end of the Unit 2 turbine building. The used as the response adjustment factors, obtained                comparisons indicate that the spectral ratio from both the coherent and incoherent ground                      for the, north/south response, which is close motion inputs consistent with the fragility                      to the north/south centerline of the evaluation reference response spectra, are shown                  foundation mat and thus has little in Figures 5-43 and 5-44 for north/south                          contribution from the torsional response, is responses of the containment, in Figures 5-45 similar to the spectral ratio of the north/south and 5-46 for north/south responses of the response near the center of the basemat, as auxiliary building, and in Figures 5-47 through shown in Figure 5-47. The spectral ratio for 5-50 for north/south and east/west responses of the east/west response, which is away from the turbine building.
the east/west centerline and thus is sensitive to torsional response, is different from that of The      results    obtained      from      soil/structure      the east/west response of the basemat, as interaction analyses of the power block structure,              shown in Figure 5-48.
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Charter 5                                                                                              Page 5-55 Chamer 5 a
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Figure 5-43 Floor response spectra and floor response spectral ratio for the north/south response of the containment at the base, El 85 feet.
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Chanter 5                                                                                        Page 5-56 12                                                            I    1    S  I      I I I 5% Damping "9
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Figure 5-44 Floor response spectra and floor response spectral ratio for the north/south response of the containment at the top of interior concrete structure, El 138.5 feet.
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Chapter 5                                                                                            Page 5-57 Chapter 5                                                                                            Page 5-57 4.5
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Figure 5-45 Floor response spectra and floor response spectral ratio for the north/south response of the auxiliary building at El 85 feet..
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.... r" ....                                                                                                Page 5-58 Chantier 5                                                                                                    ae55 12                I          I    I  I  I  I  I        I  I !    I    i    I  I  I I 5% Damping 9
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Figure S-46 Floor response spectra and floor response spectral ratio for the north/south response of the auxiliary building at El 140 feet.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                        Long Term Seismic Program
 
Chapter 5                                                                                                Page 5-59 l    l  I    I        I          I I  I  v  1-r-r 5% Damping 4.'g                                                    A.
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Figure 5-47 Floor response spectra and floor response spectral ratio for the north/south response of
                    . the turbine building at CCW heat exchange location, El 85 feet.
Diable Canyon Power Plant Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-60 Chapter 5                                                                                        Page 5-60 0
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    .2 E.i                          I  I  I  I  jI lII          I      I    I  i  I    I I CL, 1I
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Figure 5-48 Floor response spectra and floor response spectral ratio for the eastJwest response of the turbine building at CCW heat exchange location, El 85 feet.
Diablo Canyon Power Plant 6" Pacific Gas and Electric Company                                                  Long lerm Seismic Program
 
Chapter 5                                                                                              a 5-61 Page Chanter S
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            .2 0I                        I    I  I  I                    I      l    l  l  I  II 10O                                          101                                      102 Frequency (Hz)
Figure 5-49 Floor response spectra and floor response spectral ratio for the north/south response of the turbine building at switchgear location, El 119 feet.
Dlablo Canyon Power Plant In    Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chaoter 5                                                                                                              Page 5-62 Chanter 5                                                                                                                ae56 12                          I        I  I      I I l  il                    I    I    l  I  I    II 5% Damping 9
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        .4
        .2 I          I      I    I  I  I    I          "    I      I  I  I        !I      II 102 100                                                          101                                            101 Frequency (Hz)
Figure 5-50 Floor response spectra and floor response spectral ratio for the east/west response of the turbine building at switchgear location, El 119 feet.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                                  Long Term Seismic Program
 
Chapter 5                                                                                              Page 5-63 Chapter 5                                                                                              Page 5-63 Assessment of Soil/Structure Interadtion              The ground motions that were used as the input for the containment base uplift response analysis Responses of the Containment Structure consisted of . three sets of three-component Due to Basemat Uplifting                              recorded motions as selected by the ground-motion studies, which are: (a) the Pacoima Dam The effect on the containment seismic response        records of the 1971 San Fernando earthquake; due to partial uplift of the containment basemat      (b) the 1978 Tabas records of the Tabas from the rock foundation under strong seismic          earthquake; and (c) the El Centro No. 4 records ground motions was investigated in a separate          of the 1979 Imperial Valley earthquake. Before study using a two-dimensional nonlinear time          applying these as-recorded motions for the history analysis method.                              analysis, the motions were adjusted in the following manner:
The analysis was based on a soil/structure interaction model for the containment formed by coupling the lumped-mass stick model for the            (1)  The original recorded motions were adjusted structure with a Winkler foundation model                    to conform with the site-specific conditions (uniformly distributed discrete foundation springs            such as the maximum earthquake magnitude, and dampers) which has no tension capability.                source-to-site distance, and site condition.
This    model      is    shown      schematically in Figure 5-51. For the Diablo Canyon Power Plant          (2) The two horizontal components of the containment which has foundation embedment,                  adjusted three-component motions were the Winkler foundation model was further                      transformed,      as    necessary,      into two extended to simulate the foundation embedment                longitudinal      and    transverse      horizontal effect by incorporating a set of Winkler-type                components      to  provide    motions      in the side-rock springs and dampers. Furthermore, a                directions normal and parallel to the strike of method was also developed to incorporate the                  the causative fault.
energy dissipation associated, with the base
'slapdown" which occurs following base uplift.        (3)  The three-component time histories were scaled by a constant scaling factor common The mechanism of energy dissipation was for all three components, to correspond to simulated using an equivalent viscous damping for the reference seismic Input level used for the foundation model which becomes effective fragility evaluation purposes.
when base uplift occurs.
(4)  The scaled three-component time histories The nonlinear base uplifting analysis methodology              were then applied as the input for the base and the associated UPLIFT computer program                    uplift response analyses, first, with the (Tseng and Wing, 1984) used for the analysis of              longitudinal component applied in the Plant containment have been benchmarked against                    north/south direction and the transverse available published solutions for the effects of              component in the Plant east/west direction, base uplifting in dynamic response problems                  and then vice versa; the vertical component (Psycharis, 1981).                                            was applied in the Plant vertical direction in each case.
The free-field input motions used for the containment base uplift response analyses were        To be conservative for the containment base uplift the rock surface motions assumed in the form of        response analyses, the constant scaling factor used coherent, vertically incident, plane waves. Since a    for step (3) above was derived such that the two-dimensional analysis was used, one horizontal      average value of the 5 percent damped component together with the vertical component        acceleration response spectral values of the two of the three-component prescribed earthquake          horizontal time histories in the frequency range of motions were simultaneously applied as the input        3 to 8.5 hertz, inclusively, was equal to 2.25 g.
for each analysis. Both horizontal components          This procedure is illustrated in Figure 5-52. The were used in this manner in two separate analyses. scaling factors -as derived for the three sets of Diablo Canyon Power Plant IQ  Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 5                                                                                        Pae&#xfd;6 Page    5-64 Chapter 5 2F?
EXPLANATION H - Containment Height R - Containment Radius D  - Contact Length 0  - Basemat Rotation a -  Static Displacement
                                                                          - Soil Spring Stiffness Figure S-51 Schematic configuration of containment on Winkler foundation with base uplift.
Diablo Canyon Power Plant In  Pacific Gas and Electric Company                                              Long Term Selsmit Program
 
Chapter 5                                                                                        Page 5-65 6
5% Damping 5+I 4 .-
0 C,
01
*13 a    3, U
01                      Longitudinal component U
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                                                  /-.
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                      - -        - -  . s .
I.    . . .I . 1 10-1                                  100                            10'                                    102 Frequency (Hz)
Figure 5-52 Illustration of the procedure used to derive the constant scaling factor for the input motions using the Pacoima motions for containment base uplift analyses.
Ian Pacific Gas and Electric Company                                                Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-66 Chapter 5                                                                                          Page 5-66 ground motion inputs considered were: 1.2 for the    the response; and (c) consideration of the base Pacoima input; 0.9 for the Tabas. input; and 2.5      slapdown impact energy. dissipation, as proposed for the El Centro No. 4 input. The scaled final      by Psycharis (1981), resulted in further reductions time histories used for analyses of base uplift      in both horizontal and vertical response; however, effects are shown in Figures 5-53 through 5-55.      the effect was found to be relatively small. In view The 5 percent damped acceleration response            of these results, it was concluded that base uplift spectra of these time histories are shown in          had no significant effects on the dynamic response Figures 5-56 through 5-58.                            of the containment structure.
Containment base uplift analyses were performed for three foundation model assumptions: (a) a       
 
==SUMMARY==
AND CONCLUSIONS Winkler base foundation model with the full amount of side-rock impedances to simulate the        A complete reevaluation            of the seismic condition of full contact between the side rock      soil/structure interaction effect on the- power and the embedded containment basemat wall; (b)        block structures was carried out as part of the a Winkler base foundation model with one-half        Long Term Seismic Program. The conclusisons the side-rock impedances to simulate the partial      from these studies are described below.
loss of side-rock support up to one-half the basemat wall perimeter; and (c) a Winkler base        CLASSI/SASSI          Solution Techniques.            The foundation model with one-half the side-rock          reevaluation      used    state-of-the-art        three-impedances and with added viscous damping to          dimensional analysis techniques and computer simulate the base slapdown impact energy              programs, CLASSI and SASSI. An extensive dissipation. For comparison purposes, linear          effort was spent implementating, upgrading, response analyses, in which base uplift was          validating, and documenting these two programs suppressed, were also performed for all base uplift  for our Program's applications. Plant-specific analysis cases.                                      applications of these two programs have demonstrated that they produce essentially the Representative horizontal and vertical response      same solutions for the same soil/structure results obtained from the analyses for all three      interaction problems.
foundation model cases and all three sets of three-component time histories used as input          Soil/Structure Interaction Parametric Studies.
motions, are presented in Figures 5-59 through        Prior to performing the soil/structure interaction 5-64 in terms of the 5 percent damped floor          analysis, extensive studies were made to response spectra 'at the containment shell            characterize the soil/sthicture interaction systems springline location and at the top floor of the      for the power block structures. These studies containment interior structure.                      included      the    assemblage,      review,      and characterization of the foundation rock profile The results of the containment base uplift            and properties, the development of appropriate analyses, as presented in these figures, show that:  three-dimensional dynamic models for the power (a) allowance for base uplift generally leads to    block structures, and the performance of a series small reductions in the horizontal acceleration      of soil/structure interaction parametric studies. In response, shear, and overturning moment; and          these studies, the additional site investigation data small increases in the horizontal displacement and    that became available in 1978, and the on-site the vertical acceleration response in the high        earthquake recordings that became available after frequency range, as compared to the response          I98M have been used to assist in calibrating the obtained without including base uplift effects; (b)  dynamic characteristics of the site rock and the a reduction in the side-rock impedances to            soll/structure interaction systems for the power one-half the full values, to account for the partial  block structures.
separation of the embedded wall from the surrounding rock over one-half the basemat wall      The results of the soil/structure interaction perimeter, produced relatively small variations in    parametric studies indicated that the effects of Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-67 1.6 0
0
    -1.6 1.6 0)
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        -1 0                3                6              9            12      15                18            21 Time (sec)
Figure 5-53 Scaled Pacoima acceleration time histories used for containment base uplift analyses, longitudinal, transverse, and vertical components.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5,                                                                                      Page 5-68 I
C 0
(U I-  0                                                                            Logtuia copoen S
      -1 Pea grudaclrain=07 0
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      .1 0                3-              6              9            12        15                18            21 Time (sec)
Figure 5-54 Scaled Tabas acceleration time histories used for containment base uplift analyses, longitudinal, trans-verse, and vertical components.
Olablo Canyon Power Plant Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-69 Chapter 5                                                                                          Page 5-69 1.6I 1.6                                                                            Longitudinal corn ponent Peak ground acceleration 1.33g 0
0
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    -1.6                  I                I              I              I            I 1.6 Transverse coml Peak ground acceleration =
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    -1.6 1                  p              I              I              I            I                  I Vertical coml Peak ground acceleration :
.2 0I
      -1I                                                  I                          II 0              3                6              9              12          15                18            21 Time (sec)
Figure 5-5$
Scaled El Centro No. 4 acceleration time histories used for containment base uplift analyses, longitudinal, transverse, and vertical components.
                                                                                            'Diablo Canyon Power Plant In! Pacific Gas and Eletric Company                                                    Long Term Seismic Progpam
 
Chapter 5                                                                                    Page 5-70 Chapter 5                                                                                    Page 5-70 6
5 S
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1 0                                                                                                          -J4 100                                101                                102 Frequency (Hz)
Figure 5-56 Acceleration response spectra of scaled Pacoima time histories used for containment base uplift analyses.
EDiablo                                                                                  Canyon Power Plant 10 Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chaoter 5                                                                                      Page 5-71 Chanter 5Pae-7 6
5 4
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10.1                                100                                                                    102 Frequency (Hz)
Figure 5-57 Acceleration response spectra of scaled Tabas time histories used for containment base uplift analyses.
Diablo Canyon Power. Plant IQ  Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-72 6                                                1    4 "  1      4 1                          I        I I I 5% Damping 5
4 "u  3 Vertical component.t Longitudinal component                /moe o  2                        Transverse component
                                                      / ",'/      \ IV 101                                  100                            10'                                      102 Frequency (Hz)
Figure 5-58 Acceleration response spectra of scaled El Centro No. 4 time histories used for containment base uplift analyses.
Olablo Canyon Power Plant ral Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                      Page 5-73 Cha~,ter S                                                                                    Page 5-73 20                                                                                      I- I      I 1  1 1 1 EXPL AN A T IO N    I    I,      '.I.        I Without uplift (linear analysis)                                5% damping With uplift, full side-rock impact
              -----  With uplift, half side-rock impact
                - -  With uplift, half side-rock impact and with base impact damping 15 0,
10 5
0                    I      I      I    I    I  I      I  I        I                    I    I    I  I ,I 100                                                        101                                              102 Frequency (Hz)
Figure 5-59 Floor response spectra for the north/south response of containment shell at El 231 feet due to scaled Pacoima input.
Diablo Canyon Power Plant an Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-74 Chapter S                                                                                        Page 5-74 12                                                                                          I. I I EX PLA N A TIO N '.        .    . . . I                                            I  I. I Without uplift (linear analysis)                                  5% damping With uplift, full side-rock impact
              ..... With uplift, half side-rock impact
              -    --  With uplift, half side-rock impact and with base impact damping 9
02 0
C
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(U I-4.'
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                ,,        p              I        I  I I  I,            I    . I        I      I        I    I  I 0
100                                                      101                                                      102 Frequency (Hz)
Figure 5-60 Floor response spectra for the east/west response of containment interior structure at El 138.5 feet due to scaled El Centro 4 input.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                        Page 5-75 Chapter 5                                                                                        Page 5-75 1
2                  EXPLANAiION              . '          ,'1'1        I.        I      I    I a        I I I Without uplift (linear analysis)                                5% damping
              -----    With uplift, full side-rock impact
                    -. With uplift, half side-rock impact
            -    -    With uplift, half side-rock impact and with base impact damping.
CL 6
CO) 3.
0 100                                                      101                                                  102 Frequency (Hz)
Figure 5-61 Floor response spectra for the east/west response of containment interior structure at El 138.5 feet due to scaled Tabas input.
Diablo Canyon Power Plant 1,    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 5                                                                                        Pa*e 5-76 Chaper                    5Paae                                    5-76 12                        '  -      . I I  I                                              _            - 1 T EXPLANATION Without uplift (linear analysis)                                5% damping With uplift, full side-rock impact
                  ---    With uplift, half side-rock impact With uplift, half side-rock impact 9                  and with base impact damping 3
0C3 6                                                                                  D
.9 U                  mA 0                    "'  "          I              'I '
100                                                      101                                                  102 Frequency (Hz)
Figure 5-62 Floor response spectra for the vertical response of containment shell at El 231 feet due to scaled Pacoima input.
EUDlablo                                                                                  Canyon Power Plant
[I& Pacific Gas and Electric Company                                            Long Term Seismic Pronram
 
Chapter 5                                                                                        Page 5-77 Chapter 5                                                                                        Page 5-77 I
12 EXPLANATION Without uplift (linear analysis)                                  5% damping
              -----    With uplift, full side-rock impact With uplift, half side-rock impact With uplift, half side-rock impact and with base impact damping 9
S 6
CL CO) 3 II        I    I    I  I    I I                            I    I    I    I    I I' 0
100                                                          101                                                  102 Frequency (Hz)
Figure S-63 Floor response spectra for the vertical response of containment interior structure shell at El 138.5 feet due to scaled Pacoima input.
Dlablo Cpnyon Power Plant P    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
  .Chapter 5                                                                                        Page 5-78 Chapter 5                                                                                        Page 5-78 12 EXPLANA.ION          ,,
Without uplift (linear analysis)                                    5% damping
              ----    With uplift, full side-rock impact
              ..      With uplift, half side-rock impact
                -- -  With uplift, half side-rock impact and with base impact damping 9
03 6
CL W
3 II        I  I  I        I      I    . .. t            l "    I i    a 0
100                                                      101                                                  102 Frequency (Hz)
Figure 5-64 Floor response spectra for the vertical response of containment interior structure at El 231 feet due to scaled El Centro No. 4 input.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
.I Chapter 5                                                                                            Page 5-79 structure-to-structure interaction, degradation of      motions generally resulted in a reduction in the rock shear modulus, and variations of Poisson's          soil/structure interaction responses. However, the ratio and material damping ratio of the foundation      amount of reduction varied from point to point rock are relatively unimportant;however, the            within the structure. These variations resulted effects of foundation embedment and foundation          from rocking and torsional response motions basemat flexibility are relatively important for        induced by spatial incoherence. At the structural the power block structures. The important                base near the center region (which is not affected parameters, such as foundation embedment and            by rocking and torsion), in the frequency range basemat flexibility, were incorporated into the          above 10 hertz, such reductions are about 6 models of the power block structures for the final      percent for the containment, 15 percent for the soil/structure interaction analyses.                    auxiliary building, and 20 percent for the turbine building.
Soil/Structure          Interaction      Response    to Coherent Ground-Motion Inputs. The basic Containment Base Uplift Effects. The effect of soil/structure interaction responses of the power base uplift on the containment seismic response block structures required for the Plant fragility was investigated using a separate study that used a evaluations and seismic margin assessment were two-dimensional        nonlinear      time      history generated using the three-dimensional SASSI base-uplift response analysis procedure. This time history response analyses with coherent study considered the seismic input from three sets ground-motion inputs; the input motions were of      three-component        actual        earthquake consistent with the site-specific earthquake ground-motions adjusted to an intensity level response spectrum and at a level slightly higher higher than the site-specific 84th percentile than the site-specific 84th percentile response ground motion level. It              also considered spectum. The results of these analyses indicated foundation model parameter variations including substantial      soil/structure interaction effects, the partial loss of side rock support for embedded mainly due to inertial interaction, for the short, basemat wall and the base slapdown impact stiff containment interior structure and the energy dissipation. The results of the study auxiliary building. The soil/structure interaction indicated that base-uplift has no significant effect effects due to coherent ground-motion excitation on the dynamic response of the containment was, however, found to be relatively small for the structure, even under the strong input motions taller and more flexible containment shell and the considered in the study.
turbine building.
Adjustment of            Soil/Structure    Interaction REFERENCES Responses Due to Special Incoherence of Ground Motions. To account for the effect of spatial variations        of ground motions on Bechtel Power Corporation, 1988, "CLASSI" soil/structure      interaction response,      separate Computer Program: Theoretical Manual, analyses, using the CLASSI analysis technique User's Manual, and Validation Report, and and random vibration theory, were performed "SASSI" Computer Program: Theoretical incorporating site-specific spatial incoherence Manual, User's Manual, and Validation functions. Soil/structure interaction response Report.
adjustment factors, in the form of floor response spectral ratios applicable to specific response          Lilhanand, K., and Tseng, W. S., 1983, Direct directions and locations, were developed to adjust          generation of probabilistic floor response the floor response spectra resulting from the                spectra: Bechtel Power Corporation, Report coherent ground-motion analyses to give the final            No. SFPD-C/S-83-07.
soil/structure interaction responses for the Plant fragility evaluations. The results of these analyses    Luco, J. E., and Wong, H. L., 1986, Response of showed that spatial incoherence of ground                    a rigid foundation to a spatially random Dlablo Canyon Power Plant IN    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 5                                                            Page 5-80 ground motion: Earthquake Engineering and Structural Dynamics, v. 14.
Lysmer, J., Tabatabaie-Raissi, M., Tajirian, F.,
Vahdani, S., and Ostandan, F., 1981, SASSI-A system for analysis of soil-structure interaction:      University      of    California, Berkeley, Report No. UCB/GT/81-02.
Mita, A., and Luco, J. E., 1986, Response of structures to a spatially random ground motion: Third U.S. National Conference on Earthquake Engineering, Charleston, South Carolina.
Psycharis, 1. N., 1981, Dynamic behavior of rocking structures allowed to uplift: California Institute of Technology, Report No. EERL 81-02.
Tseng, W. S., and Wing, D. W., 1984, Seismic soil-structure      interaction    analysis  with basemat uplift: Bechtel Power Corporation, Theoretical Manual, Revision 1, Computer Program CE 444 (UPLIFT).
Wong, H. L., and Luco, J. E., 1976, Dynamic response of rigid foundations of arbitrary shape: Earthquake Engineering and Structural Dynamics, v. 4, p. 576-587.
Diablo Canyon Power Plant P    Pacific-Gas and Electric Company                  Long Term Seismic Program,
 
Enclosure Attachment 6 PG&E Letter DCL-1 1-097 Chapter 6 of the 1988 Long Term Seismic Program Final Report 1
 
Chapter 6 PROBABILISTIC RISK ANALYSIS To Partially Address Element 4 of the License Condition ELEMENT 4 OF THE LICENSE CONDITION PG&E shall assess the significance of                          L1                                      Core Plant Model              Damage conclusions drawn from            the seismic        Other        -Frequency External  f reevaluation studies in Elements 1, 2, and 3,        Events (Nonsetsmic) utilizing a probabilistic risk analysis and deterministic studies, as necessary, to assure adequacy of seismic margins.                    This chapter details the processes and results of each component of the probabilistic risk assessment and how these components are combined to produce the results. The Seismic Hazards Analysis is described first, followed by INTRODUCTION the Seismic Fragility Analysis. Finally, the remaining components are described in the Probabilistic Risk Assessment.
Element 4 of the license condition calls for an assessment of the significance of conclusions SEISMIC HAZARDS ANALYSIS drawn from the seismic studies in Elements 1, 2, and 3, utilizing a probabilistic risk analysis and deterministic studies, as necessary, to assure        Objectives adequacy of seismic margins. This chapter The objective of the seismic hazards analysis was summarizes our approach to and key findings to provide a probabilistic representation of the from the probabilistic risk analysis. The approach earthquake ground motions at the Diablo Canyon and findings related to deterministic studies are Power Plant site, in a format suitable for use i the summarized in Chapter 7.
probabilistic risk analysis. A secondary objective of the seismic hazards analysis was to calculate constant hazard spectra over the frequency range The results presented in the earlier chapters have    of interest to Plant structures and equipment.
been integrated to develop seismic hazard curves and fragilities of Plant structures and items of      Scope equipment that are important to evaluating probabilities of seismic risk. The seismic hazards    The        seismic    hazards        analysis      included and fragilities are combined to perform a systems    consideration of all seismic sources that can affect analysis on the Plant risk model as part of the      ground motions at the Diablo Canyon Power Plant probabilistic risk analysis.                          site. Logic trees were developed for the Hosgri, Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chante    6-..
Page 6-2 Chanter 6                                                                                            Page 6-2 Los Osos, San Luis Bay, Santa Lucia Bank, West        hazard curves, and in the form of aggregate Huasna,        offshore      Lompoc,  Rinconada,  hazard curves, which reduce the large number in Nacimiento, and San: Andreas faults. Seismic          the total family of hazard curves to a limited hazards calculations were performed and it was        number of curves (about 8 to 12) for input into shown that the Hosgri fault dominates the seismic    the probabilistic risk assessment.
hazard at the site, and that the Los Osos and San Luis Bay faults taken together add only a few        Method of Analysis percent to the total seismic hazard.        Relative contributions to the total hazard from the other      The procedures used to calculate seismic hazard faults are insignificant.                            for the case when faults can be identified as the potential sources of earthquakes are documented The seismic hazards analysis for the Hosgri, Los      in detail (for example, Der Kiureghian and Ang, Osos and San Luis Bay faults was performed in        1977; McGuire, 1978). The steps involved in a terms of response spectral acceleration, in order    seismic hazards analysis are illustrated in to provide consistency with the fragility estimates  Figure 6-1. The calculation of seismic hazard is of Plant structures and equipment.                    made with the following equation:
The development of ground-motion attenuation            V(e) =    V. J'GA  d() ).    *)f I D(ifd m) dm dd relationships applicable to the Diablo Canyon Power Plant site is described in Chapter 4. For      in which the summation is performed over all use in the seismic hazards analysis, attenuation      faults i that affect the site, vi is the mean annual relationships were          developed  for spectral  rate of damaging earthquakes for fault i. The acceleration at 5 percent damping, at frequencies    probability-density function of magnitude and of vibration of 33, 25, 14, 8, 4, and 2 hertz, and    distance for fault i are fM(fa) and .            mC4 (The i).
for average spectral acceleration in the ranges of 3  distance distribution depends on magnitude to 8.5 hertz and 5 to 14 hertz.              These  because the rupture length is explicitly taken into relationships include factors that represent the      account.)      The ground-motion or attenuation different styles of faulting included in the logic model allows calculation of, for a given magnitude tree representation (strike-slip, oblique-slip and    m and distance r, the probability GAI m. d(a') that thrust) based on results derived from the a ground motion amplitude a* is exceeded. The numerical modeling program, from the empirical hazard defined in equation 6-1 represents the ground-motion studies, and from review of annual rate v at which ground-motion amplitude available literature.                                a* is exceeded at the site; because it is much smaller than unity, this rate can be interpreted as Seismic hazards analyses for the Hosgri, Los Osos, the probability that ground-motion amplitude a*
and San Luis Bay faults were performed for each is exceeded in any one year. As is common in of the structural frequencies mentioned above probabilistic risk assessments, we refer to this rate (33, 25, 14, 8, 4, and 2 hertz), and for the as an "annual frequency of exceedance." The frequency ranges of 3 to 8.5 hertz, and 5 to calculation of equation (6-1) is performed for 14 hertz. From these multiple hazards analyses, several values of a* and the resulting values can the hazards curves representing the frequency be plotted as a "hazard curve," illustrated on range of 3 to 8.5 hertz were selected for use in the Figure 6-1 (D).
probabilistic risk assessment, and are presented herein. In addition, the analyses at individual      This is a standard formulation of seismic hazard; frequencies were used to construct constant          the application takes proper account of hazard response spectra as presented herein.          randomness in the following factors:
The results of, the seismic hazards analyses are
                                                      "    Fault geometry in three dimensions, presented in terms of fractile hazard curves, which show at each spectral acceleration amplitude the
* All possible locations of the rupture surface, distribution of hazard from the entire family of          both horizontally and vertically, Diablo Canyon Power Plant Pal Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 6                                                                                                Page 6-3 Chapter 6                                                                                                Page 6-3 (A)    Seismic source i                                                Rupture (earthquake locations in space lead to a distribution of epicentral distances fD(d I m)
Site                              Fault i 0
fD (dlm)
Distance d (B)    Magnitude distribution and                          fM(m) rate of occurrence for source i:
fM(m), V,                                                                    m max Magnitude m (C)    Ground motion estimation:                    Ground motion                m    7            GAjm,d (a*)
GAImd (a*)                              level m6.
I d
Distance (D)    Probability analysis:
P[A > a* in time t] It --
I v, ff GAId      (a*) fM(i)(m) fD(i)(d I m)dm dd = v (a*)
N P[A > a* in t]/t              N N,      \
(log scale)            N        \*
N Gr'ound motion level a*
Figure 6-1 Steps involved in seismic hazard analysis.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                        Long Term Seismic Program
 
Chanter 6                                                                                            Page 6-4 Chanter 6                                                                                              ae    -
* Sizes (magnitudes of earthquakes that might      hazard curves or by fractiles of hazard at all occur on the fault),                              ground-motion amplitudes. The uncertainties in input were represented using the logic tree format,
"    Size of rupture as a function of earthquake      an example of which is shown on Figure 6-2.
magnitude,                                        Each element in the logic tree consists of a set of nodes representing an uncertain state of nature,
"    Closest distance of the site to the rupture, as  and each branch represents discrete possible required by the ground-motion estimation          values for that state. Probabilities were assigned equations,                                        to each branch using subjective assessments, and the end branch probabilities were calculated as
* Ground motions at the site as a function of      the product of all the intermediate branch the earthquake magnitude and its location        probabilities. A single seismic hazard analysis was relative to the site, and                        performed for each end branch resulting in a single hazard curve for the set of assumptions that
"    Possible amplification        or reduction of the led to that end branch. The eight hazard curves ground motions as a result of the sense of        for the logic tree on Figure 6-2 are illustrated at fault slip and geometry of the fault.            the right side of the figure. The uncertainty in hazard is represented by this family of hazard Thus, for a given fault geometry and style of          curves, the size of the family being equal to the faulting, the calculation integrates over all possible number of end branches.
magnitudes of earthquakes, generates a rupture surface for each magnitude, and integrates over all possible locations of the rupture surface on the  Typically, large numbers (several thousand) of fault plane. For each possible rupture location,      hazard curves result from practical applications of the procedure calculates the distance to the Plant    the logic-tree concept.      This large number is site; estimates the distribution of site ground        reduced to summary curves, both for examination motions, accounting for any amplification or          and analysis and for input to other Plant reduction caused by faulting style and geometry;      evaluations. One simple representation of the and integrates over randomness in ground              uncertainty in hazard is gained through fractile motions, given the earthquake magnitude and            hazard      curves,    which      show,      at    each location with respect to the site. The result is a      ground-motion amplitude, the distribution of calculation of annual rates (probabilities) that        hazard from the family. A second representation specified levels of ground shaking will be              is through aggregate hazard curves,,which reduce exceeded.          The procedure accounts for          the large number in the total family of hazard randomness in the models used to represent              curves to a limited number of curves (about 8 to earthquake occurrences: earthquake magnitudes,          12) for input into a probabilistic risk assessment of rupture locations, times of occurrence, and            the Plant systems.
ground-motion levels given the occurrence of the event.                                                  The logic tree approach has several important advantages over others that might be pursued.
Uncertainties are distinct from randomness in the      First, the complete enumeration of all possible sense that they involve parameters and models          states of nature ensures that all hypotheses have that are chosen to describe earthquake                  been accounted for properly, with appropriate occurrences; in concept, uncertainties can be          weights assigned to each. As a result of the reduced as more data are collected and physical        efficient algorithms us.d to calculate seismic processes are better understood. Uncertainties          hazard, no compromises need be made to keep are' treated by performing separate hazard              the number of combinations small or to reduce calculations (equation 6-1) for different sets of      the number of hypotheses that can be considered.
models and parameter values. Hence, uncertainty        The procedure allows consideration of all in the input results in uncertainty in the hazard      suggestions made about tectonics, fault behavior, curve, which may be represented by a family of          seismicity, and ground-motion characteristics, Dlablo Canyon Power Plant 1J    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 6                                                                                          Page 6-5 ground motion seismicity                              end branch geoloIVY 112 0 9 .*
                                                ,      123 0                          .'.
00
* 145"
* C 13412 O rP 1 46 ground motion Figure. 6-2 Example of logic tree and resulting family of hazard curves.
Dilablo Canyon Power Plant Pacific Gas and Electric Company                                                  Long Term  Seismic Program
 
.... r" ....                                                                                          Page 6-6 Chanter 6                                                                                              ae      -
however unlikely, and puts them in the proper            For probabilistic risk analyses, it is necessary to context along with all other interpretations.            construct a sophisticated representation of the family of hazard curves. The reason is that Second, the procedure provides a logical means of        probabilistic risk assessment procedures treat identifying those elements that contribute              uncertainty by conditioning on alternative importantly to uncertainty in seismic hazard and        interpretations (in this case seismic hazard those that do not. This allows priorities for            curves),    convolving these      with alternative investigations on appropriate input models and          representations of Plant response, and calculating parameters to be established on a logical basis.        the resulting uncertainty in Plant state frequency.
Therefore, if several hazard curves represent the Third, the entire procedure is documentable and          uncertainty in geological and seismological trackable, so that decisions (for example, which        interpretations, and these curves have different faults to investigate further can be justified and      slopes, the character of the curves (slopes) must defended.                                                be maintained for probabilistic risk assessment input. Fractile hazard curves do not transmit this The analyses considered here calculated hazard          information.
from each fault separately. Although several faults To derive hazard results appropriate for are currently active in south-central coastal probabilistic risk assessment, an aggregation California, the Hosgri fault dominates the seismic process is employed that reduces the large number hazard at the Diablo Canyon site (as will be of hazard curves (20,700) to a few (typically 8 to demonstrated below), so that consideration of 12), using a procedure that optimally determines multiple faults acting simultaneously is not how to combine pairs of curves sequentially so required. The total hazard can be accurately that the character of the original curves will be calculated          by      considering      each  fault maintained, and the set of aggregate curves will characterization          separately,    and combining represent as mu.h -of the original uncertainty in hazards to evaluate the total hazard.
hazard as possible for each ground-motion amplitude. The procedure uses the following The logic tree used to represent input for the steps:
Hosgri, Los Osos, and San Luis Bay faults is shown on Figure 6-3.                                      1) A contribution to variance analysis is used to select nodes on the logic tree that do not A total of 20,700 end branches of the logic tree              contribute significantly to uncertainty in resulted from the input specification. The                    hazard. The logic tree is then restructured to resulting family of hazard curves is too numerous            reduce the number of end branches by to interpret, or even to illustrate on a single plot.        combining hazard results for end branches As described above, one summary of this family                that are identical except for branches at nodes can be constructed by determining, at            each      that contribute little to the uncertainty in ground motion amplitude, the distribution of                hazard. By this mechanism the family of annual frequency of exceedance, and identifying              hazard curves is reduced to several hundred the frequencies that are associated with certain              in number. These hazard curves typically preselected fractiles. For example, at each                  represent greater than 96 percent of the total ground-motion amplitude the median frequency                uncertainty in hazard.
of exceedance can be determined, meaning that curves below that frequency have 50 percent of          2) The hazard curves are characterized by the the total weight. Constructing a plot of frequency        - frequency      of    exceedance        at    three of exceedance versus ground-motion, and                      ground-motion amplitudes, chosen as those drawing these medians, gives an indication of the            most critical to the determination of Plant median seismic hazard for all ground motions.                response and system state. The total variance This procedure can be applied to other fractiles as          in frequency of exceedance at these three well.                                                        amplitudes is calculated.
Diablo Canyon Power Plant 1        Pacific Gas and Electric Company                                                Long Teri Seismic Program
 
Chapter A
6                                                                                              Page 6-7 Chapter 6                                                                                                Page 6-7 Ground Motion Source Characterization                                Characterization
: 1.            2.                3.        4.          5.        6.        7.          8.                9.
sense          dip            depth of  length    maximum    seismicity rate of      median        site reduction/
of slip        angle          seismogenic of fault    magnitude    model    activity  attenuation      amplification zone                                                  equation I
Figure 6-3 Elements in logic tree used for Hosgri. Los Osos, and San Luis Bay faults.
Diablo Canyon Power Plant V      Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter    6                                                                                            Page 6-8 Chapter 6                                                                                                Page 6-8
: 3)  A small number of possible aggregate curves          for Step 1). Typically, 8 to 12 aggregate curves (for example, 64) is estimated by dividing the      can be constructed with this algorithm that ranges of frequencies of exceedance into              replicate about 90 percent of the total variance of intervals and constructing *a first set of          the original data set, for all ground-motion aggregates at the centers of these intervals.        amplitudes (that is, the standard deviation of frequency of exceedance is 95 percent of the
: 4) Each of the hazard curves is assigned to a            original). Figure 6-4 illustrates how this procedure tentative aggregate curve, based on its              would work for the case of reducing nine hazard proximity in frequency-of-exceedance for the          curves. Three aggregate curves adequately three amplitudes.                                    represent the amplitude and slope of the original nine curves.
: 5) The        tentative      aggregate    curves    are recomputed as the conditional mean or the assigned curves.                                    Input Data
: 6) Steps 4 and 5 are repeated, because step 5            As illustrated schematically on Figure 6-1, input may change the assignments based on                  data for the seismic hazards analysis consisted of proximity, until the tentative aggregate curves      seismic source characteristics (location and are stable (that is, until there are no changes      recurrence) and ground-motion attenuation in assignments). A weight for each tentative          relationships.
aggregate curve is calculated as the sum of weights of the assigned curves.                      SEISMIC SOURCE CHARACTERISTICS
: 7)  All possible pairs of tentative aggregate curves    The logic trees for the Hosgri, Los Osos, and San are examined as candidates for combination;          Luis Bay faults are given in Chapter 3. The range the pair that, when combined, will result in          of parameters and associated probabilities provide the minimum reduction in variance is selected        a description of the uncertainties associated with and combined by computing the weighted                the characteristics of each earthquake source.
average frequency of exceedance for all three        Included in the analysis of the logic tree are amplitudes. The combined curve is assigned a          calculations of the distribution of maximum weight equal to the sum of the weights of the        magnitudes and recurrence relationships for each two curves used to calculate it.                      source. In addition, the calculations of seismic hazard include the ranges of fault geometries
: 8)  Steps 4 through 7 are repeated to reduce            given in the logic trees in defining source sequentially the number of tentative aggregate        locations.
curves. The process ends when the desired number of aggregate curves is reached.                The input data for the Hosgri, Los Osos, and San Luis Bay faults are summarized as follows:
: 9)  The curve assignments are used to calculate aggregate hazard curves for all ground-motion        Hosgri Fault. Geologic data, were provided for amplitudes; the weight given to each aggregate      the first four nodes of the Hosgri fault logic tree is the sum of the weights of the assigned            (Figure 6-3). These are summarized as follows:
curves.
There are no general solution techniques for              Style of        Dip        Depth              Fault Faulting      (Degrees)      (kim)        Length (kin) aggregating        a      discrete,      multidimensional distribution, but the above algorithm has been            Strike-slip  , 90, 70        9, 12, 15      410 tested for a number of seismic hazard problems Oblique        90, 60, 45    9, 12, 15      110, 250, 410 and works well. It is efficient for up to several hundred initial hazard curves (which is the reason        Thrust        60, 30, 15    9, 12, 15      110, 160, 250 Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 6                                                                                        Page 6-9 Weight W1 + W2 + W3 W4 + W5 W6 + W7
                                                                                            + W8 + W9 0
    =.
Hazard curve 6, Hazard  curve 7,
                                                                    ,  Hazard  curve 8,
                                                                    ,  Hazard  curve 9, Hazard curve 4, Weight W4*
Hazard curve 5, Weight W5*
Ground motion Figure 6-4 Example of aggregation of nine hazard curves to obtain three curves.
                        ~Diab Pacific Gas and Electric Company                                                Lou!Ilo Canyon Power Plant gTerm Seismic Program
 
Chapter M      6                                                                                              Page 6-10 Charter 6                                                                                                  Page 6-10 Weights assigned to the style of faulting                      the Rinconada fault, the Naciniento fault, the interpretations are as follows: strike-slip = 0.65;            offshore Lompoc fault, and the West Huasna oblique = 0.30; thrust = 0.05. Weights assigned to              fault. Input for these faults was specified using the the subsequent interpretations are conditional on              logic tree format. The hazard from these faults is style of faulting.                                            several orders of magnitude lower than for the Hosgri, as will be documented below. Thus, the Seismological input constituted the next three sets            total seismic hazard at the Plant can accurately be of nodes on the logic tree of Figure 6-3. The                  calculated by considering only the Hosgri, the Los assessments of maximum magnitudes (the fifth                    Osos, and the San Luis Bay faults.
element of the logic tree) and their probabilities are conditional on previous branches; values                    GROUND-MOTION CHARACTERISTICS chosen for maximum magnitude range from 6.5 to I.        .*  I~  o&#xa5;&#xa3; 'e*
s    U, iUty  ULaUoe  kgic,. Ut&#xa9; Ground-motion input constitutes the last two element 6)          were use d, exponential              and elements of the logic tree. Three median characteristic; these were weighted 0.4 and 0.6,                ground-motion          attenuation        relationships respectively, for all faultt. The rate of seismic              (element 8) were used for all faults. The activity (element 7) was dLiscretized and estimated            attenuation equations for the eight frequencies from interpretations of faault slip rate; the values            and frequency bands investigated are listed in and their probabilities are conditional on previous            Table 6-1. Note that for use in probabilistic branches of the logic tree                                    seismic hazard analyses, the nonlinear magnitude ologic input for the Los  scaling of spectral ordinates (presented in Los Osos Fault, The ge( as follows:                            Chapter 4) was simplified into a bilinear form to Osos fault is summarized                                      provide linear magnitude scaling within two magnitude ranges, Mw < 6.5 and Mw > 6.5. The Style of              Dip Faulting          (Degrees)          (kD )    Length (kl    coefficients for this bilinear form provide essentially , identical spectral values in the Oblique            75, 45            9, 12, 15    16. 24, 36,  magnitude range Mw 5.5 to 7.5, which is the 44, 49, 57  range of interest to the seismic hazard analysis.
Thrust              60, 30          9, 12, 15    16, 24, 36, 44, 49, 57  The coefficients given in Table 6-1 represent the average      amplitudes      for    two      horizontal Weights assigned to the style of faulting                      components. The variability in amplitude was interpretations are as follows: oblique = 0.1;                expressed as the standard deviation of In (spectral thrust = 0.9. Weights assigned to the subsequent              acceleration) = 0.36 for magnitude greater than or interpretations are conditional on the style of                equal to 6.5, and 1.27 - 0.14M for magnitude less faulting.                                                      than 6.5. This is the variability specified for the frequency bands 3 to, 8.5 hertz and 5 to 14 hertz, San Luis Bay Fault. The geologic input for the                and does not include frequency-to-frequency San Luis Bay fault is summarized as follows:                  variations (these variations have been averaged by calculating the average spectral acceleration for a Style of              Dip .          Depth          Fault    frequency band). Because the amplitudes desired Faulting          (Degrees)          (km)      Length (km) for the probabilistic risk assessment are spectral
---Thrust            70, 40          9, 12, 15      6, 12, 19  accelerations      (average    of    two      horizontal components, without peak-to-valley variability from frequency to frequency),                the above In this case a weight of unity was assigned to the            variability was used for all frequencies.
thrust, interpretation.
The site factor (element 9) represents the portion Other Faults. Other faults considered in the                  of empirical ground-motion variability that can be hazard analysis are the Santa Lucia Bank fault,                attributed to variability in site characteristics. As K      Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Fhant*r fi                                                                                            Page 6-11 Table 6-1 ATTINUATION EQUATIONS* FOR SPECTRAL ACCELERATION (5% DAMPING)
FOR THRUST FAULTING**
In(S a [f]) = co + cM + c2 ln[D + c3 exp(c 4 M)]
c2= -2.1 for all frequencies and magnitudes.
c 3 = 3.656 and c4 = 0.25 for M<6.5 c3 = 0.616 and c 4 = 0.524 for M>6.5 f(Hz)              co(for M&#x17d;6.5)                c0 (for M<6.5)        c 1(for Mg>6.5)      c, (for M<6.5) 33                      -1.092                        -0.442                  1.1                  1.0 25                      -0.943                        -0.293                  1.1                  1.0 14                      -0.280                        +0.695                  1.05                  0.90 8                        -0.327                        +0.323                  1.1                  1.0 4                        -0.872                        -0.840                  1.184                1.179 2                        -1.902                        -21624                  1.286                1.397 3-8.5                    -0.537                        -0.154                  1.136                1.077
                        -0.374 5-14                                                    +0.276                  1.1                  1.0
    " Coefficients above representthe best-estimate equation, which is assigned a weight of 0.5; alternative equations, which were assigned weights of 0.25 each, provide acceleration values 1.15 times the above values, and 111.15 times the above values.
Equationsfor strike-slipfaulting are obtained by multiplying the reverselthrust amplitudes by 0.833.
Equationsfor oblique faulting are obtained by multiplying the reverse(thrust amplitudes by 0.913.
Note: M is moment magnitude, D is closest distance to rupture surface, in kilometers.
Diablo Canyon Power Plant r      Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
(*hant*r    f*                                                                                  Page 6-12 Chanter 6 such, this variability is treated as an uncertainty  ratios to the current mean Hosgri hazard curve for any specific site. The variance representing    that uses the most current ground-motion total ground-motion variability discussed above      assumptions. This approximation is justified in (represented. by the variance of In [spectral        light of the low hazards that these curves indicate, acceleration]) was divided into two parts:          compared to the Hosgri fault. It is clear that the Hosgri fault zone is the dominant contributor to 2        2        2                          the seismic hazard, with the Los Osos and San a ot--r        +    site                  (6-2)
Luis Bay faults contributing a minor fraction of this hazard (about 3 to 5 percent in aggregate) and the remaining faults contributing hazards that where 2o is the total variance of ground-motion    are several orders of magnitude lower.
amplitude (that is, of response spectral amplitude at a given frequency), o 2 is variance attributed to To calculate aggregate hazard curves for input to r&#xfd; randomness and o 2site is variance attributed to    probabilistic assessment, the family of 20,700 uncertainty in site conditions. As discussed        Hosgri hazard        curves based on spectral above, 0 tot was specified as 0.36 for magnitude    acceleration for 3 to 8.5 hertz were aggregated to greater than 6.5. We divide the total variance      eight curves, using the method presented in the equally between Crr and qite , so that both are    previous section. For this aggregation process, equal to 0.255. As aslte is treated as uncertainty, hazards at 1.5 g, 2.0 g, and 3.0 g spectral we represent it with element 10 of the logic tree  acceleration were used, as these levels of ground (Figure 6-3) and use five discrete factors of      motions contribute most to Plant seismic risk 0.682, 0.869, 1.00, 1.15, and 1.47, weighted        studied in probabilistic risk assessments and equally, to represent this uncertainty in site      therefore are the most important to represent response. The total variability in ground motions    accurately. To these eight aggregate curves were was truncated at three standard deviations, but      added the mean hazards from the Los Osos and this truncation has almost no influence on the      San Luis Bay faults. This procedure preserves the final hazard results.                              mean total-hazard from all three faults, and incurs almost no loss of accuracy in representing the uncertainty in hazard, because of the low Results of Analysis contribution of these faults relative to the Hosgri.
Figure 6-7 shows the resulting eight aggregate Results of the hazard calculations are shown for hazard curves. The seismic hazard is highly the Hosgri fault on Figure 6-5 in the form of skewed, with a high probability at relatively low fractile hazard curves for spectral acceleration in hazards and a small probability of relatively high the frequency range 3 to 8.5 hertz (5 percent hazards. This characteristic is properly portrayed damping). These fractile curves illustrate the range of uncertainty in hazard that results from      by the aggregate hazard curves. As discussed in uncertainty in the geologic, seismologic, and        the previous section, the amplitudes presented on Figure 6-7 are spectral accelerations for the ground-motion input.
average of two components, with frequency--to-Figure 6-6 compares the mean hazard from the        frequency (peak and valley) variation removed.
Hosgri fault to mean hazards from the Los Osos fault and the San Luis Bay faults (for spectral      A second set of hazard curves is presented on acceleration in the same frequency range of 3 to    Figure 6-8 as fractile curves of total hazard.
8.5 hertz), and to approximate mean hazards          These curves were obtained in a manner similar to from the Nacimiento, West Huasna, Rinconada,        the aggregate curves; that is, fractile curves were offshore Lompoc, and Santa Lucia Bank faults.        calculated for the Hosgri fault, and mean hazards The approximate mean curves were constructed        were added to represent the Los Osos and San by determining the ratios of hazards from these      Luis Bay faults. Thus, these fractile curves are faults to that of the Hosgri under the same          approximate for the lower fractiles; they are very ground-motion assumptions, and applying these        accurate for fractiles above the median.
Diablo Canyon Power Plant I"    Pachlic Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 6                                                                                          Page 6-13 0
Ur
*0 3
0.25    0.50      0.75    1.00    1.25  1.50    1.75    2.00    2.25 2.50    2.75      3.00 Spectral acceleration, 3 to 8.5 hertz (g)
Figure 6-5 Fracifle seismic hazard curves for Hosgri fault zone.
Diablo Canyon Power Plant In  Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 6                                                                                                Page 6-14 Chapter 6                                                                                                Page 6-14 a
C 0
0 C
Ur 100          1.2      1.5    1      2      2.2i.        2 5 ..      . 32    3        3.7    4.0 1.00        1.25      1.50    1.75  2.00    2.25    2.50 2.75 3.00        3.25  3.50      3.75 4.00 Special acceleration (g) or peak ground acceleration Explanation Hosgri fault zone            ................ West Huasna fault zone
                .....        -      Los Osos fault zone                            .Rinconada fault
                      ........... San Luis Bay fault                            Offshore Lompoc fault              ----------
              ...........          Nacimiento fault                              Santa Lucia fault Figure 6-6 Comparison of mean hazard from-Hosgri fault zone to mean hazards from Los Osos and San Luis Bay faults, and to approximate mean hazards from other faults.
Diablo Canyon Power Plant In  Pacific Gas and Electric Company                                                        Long Term Seismic Program
 
Chapter 6                                                                                          Page 6-15 Page 6-15 Chapter 6 C
W C) cr10-s"                          Explanation
          '.-                          -Curve 1 (WT=0.342)
"M                                      Curve 2 (WT=0.196)
C    10-6 .          ................ Curve 3 (w'r=0.217)
      =,-----------.Curve 4 (WT=0.1 11)
                              ......... Curve 5 (WT=0.036) 10.7.            -* *-------.. Curve 6 (WT=O.043)
                        ---------- Curve 7 (WT=O.032)
                          ----            Curve 8 (WT=O.023) 0.25    0.50      0.75    1.00    1.25    1.50 1.75 2.00 2.25          2.50      2.75      3.00 Spectral acceleration, 3 to 8
                                                                          .5 hertz (g)
Figure 6-7 Total aggregate hazard curves.
aS Pacific      and Electric Company            aas Olablo Canyon Power Plant Long Term Seismic Program
 
Chapter 6                                                                                              Page 6-16 Chapter 6                                                                                              Page 6-16 0                      -.
                                                            -. o o
Explanation 0*
S10..            . ....      ........ 0.9 Fractile 10                                      8 Fractile
                                ---------    0.7 Fractile
                          ....            . 0.6 Fractile
                          . .........        0.5 Fractile
                                    --- -    0.4 Fractile
                            .........        0.3 Fractile 10                  .----              0.2 Fractile 0.1 Fractile 10  -8                                1 0.25    0.50        0.75    1.00    1.25  1.50    1.75    2.00    2.25 2.50      2.75 3.00 Spectral acceleration, 3 to 8.5 hertz (g)
Figure 6-8 Curves representing approximate fractiles of total hazard.
J  Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 6                                                                                                Page 6-17 The final set of results was obtained from the            The fragility description of structures consisted of hazard calculations at all six frequencies shown in        the identification and evaluation of controlling Table 6-1. For each frequency, total fractile              failure modes associated with the important hazard results were prepared (as illustrated on            structures (Table 6-2). Similarly, the fragility Figure 6-8 for the frequency range 3 to                    description      of  mechanical        and      electrical 8.5 hertz) and spectra were calculated for 10-3,          equipment consisted of the identification and 10-1.      and      10-5 annual        frequencies    of evaluation of controlling failure modes related to exceedance, for median results. These spectra are elements of the major safe shutdown reactor plant shown on Figure 6-9.                                      systems (Table 6-3). In every case, the fragility analyses were based upon Plant-specific structure or component seismic qualification analyses SEISMIC FRAGILITY ANALYSIS directly related to elements in place at the Diablo Canyon Plant.        Even the fragility &#xfd;for generic component categories, whose elements are too Objectives                                                numerous to evaluate individually, were based upon a sampling of Plant-specific seismic As part of the probabilistic risk assessment, a            qualification analyses for components in the seismic fragility evaluation of key safety related        category. Typical generic component categories structures and equipment was conducted. The                are listed in Table 6-4.
seismic fragility evaluation consisted of a probabilistic definition of seismic capacity which, together with a probabilistic definition of the seismic hazard and an event-tree and fault-tree            Method Of Analysis characterization of the operating system, provided the necessary data for the probabilistic risk assessment. The objective of the fragility analysis        The definition of failure is vitally important to the was to carefully evaluate each of the structures          development of median fragilities for structures and components which are included in the risk and equipment. For purposes of this study, model to define those failure modes that have the Category I structure failure was defined in terms lowest seismic capacities and which, therefore, of inelastic lateral drifts generally corresponding to may constitute the most important or dominant contributors to Plant seismic risk.                        the onset of significant strength degradation of major structural elements. The exception is the containment building where lateral drifts were Scope                                                      limited to lower levels consistent with the need of the      containment      building      to      remain pressure-tight.      Equipment      housed in the The Diablo Canyon seismic fragility evaluation            important structures was assumed to fail when the studies were conducted over a period of structure reached lateral drifts corresponding to approximately 3 years in a phased approach the onset of significant strength degradation or designe'd to clearly identify and reevaluate those severe distress. The fragility estimates for components whose failure most substantially contribute to plant risk. Appropriate aspects of          structures correspond to distress levels short of the variouf Diablo Canyon Long Term Seismic                partial or total collapse, but are treated as total Program studies, including the site-specific                collapse in the 'probabilistic risk assessment. The geotechnical        and soil/structure      interaction  degree of margin between the onset of significant investigations, the median in-structure response            strength degradation and total collapse is spectra evaluation, and the structural response            uncertain and difficult to estimate. However, the variability investigation were incorporated into the        benefits of this margin, which in most cases is fragility evaluations.                                    likely to be large, has been conservatively ignored.
Diablo Canyon Power Plant IN    Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
.... A,-....                                                                                          Page 6-18 Chanter 6Pae68 12                          I    k  a  I  I I I            I    I  I    I    I    I    I  I I          I    I  I      i ,4I.-                            .        .
2.-
0 0        1.-                                                                  Hazard        10 '5 Hazard        10 -4 Hazard        10 -3
: 0.                                                                    I    . I    I
* 0 10                                          10                                            10.
Frequency (hertz)
Figure 6-9 Median constant-hazard spectra (5 percent damping).
Diablo Canyon Power Plant an Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chanter 6                                                                                            Page 6-19 Chanter 6                                                                                              ae61 Table 6-2 IMPORTANT STRUCTURES Containment Building Concrete Internal Structure Auxiliary Building Turbine Building Intake Structure Refueling Water and Condensate Storage Tanks Diesel Generator Fuel Oil Storage Tank (Buried)
Auxiliary Saltwater System Piping (Buried)
Table 6-3 MAJOR REACTOR PLANT SYSTEMS Nuclear Steam Supply System (NSSS)                      Containment Building Ventilation System Residual Heat Removal System                            Control Room Ventilation System Safety Injection System                                  Vital Electrical Room Ventilation System Component Cooling Water System                          4160 V (Vital) Electrical System Chemical and Volume Control System                      480 V (Vital) Electrical System Auxiliary Saltwater System                              125 V DC Electrical System Containment Spray System                                120 V AC Electrical System Main Steam System                                        Operator Instrumentation and Control System Auxiliary Feedwater System                              NSSS Instrumentation and Control System-Diesel Generator and Auxiliaries                        Off-Site Power System Table 6-4 TYPICAL GENERIC COMPONENT CATEGORIES Electrical Penetrations Balance-of-Plant Piping and Supports Air- and Motor-Operated Valves Cable Tray, Conduits, and Supports HVAC Ducting and Supports Diablo Canyon Power Plant I  Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chanter 6                                                                                        Page 6-20 Chapter 6Pae60 Piping, electrical, mechanical, and electro-          distributed with logarithmic standard deviations of mechanical equipment vital to safe shutdown of        OR and PU, respectively.
the Plant or mitigation of an accident were considered to fail when it was judged they were no longer able to perform their designated functions.              v Therefore, for mechanical equipment, the fragility          9a= 9a CR 6U                                  (6-3) definition represents failure to function, loss of anchorage, or rupture of the pressure boundary.      The spectral ground acceleration capacity, a, is For electrical equipment, the fragility represents    computed as:
loss of function due to acceleration-sensitive failure (for example, relay chatter) or loss of function due to structural failure of the cabinet,        Sa-= F ' SaRef                                  (6-4) anchorage, or internals. For ductile systems such as piping, HVAC ducting, and electrical conduits,    where F equals the overall factor of safety based fragility represents crimping, choking of flow, or    on response to the reference earthquake, and rupture due to failure of the supports, as it has    'kRef equals the average spectral ground been shown that failure of these systems is          acceleration of the reference earthquakeV The virtually impossible apart from failure of the        overall factor of safety has a median value, F, and supports.                                            randomness      and      uncertainty      variabilities (OR and PU). In contrast, the average reference spectral acceleration is a deterministic quantity Fragility of a structure or a component is defined    determined over a specified frequency range of as the conditional frequency of its failure for a    .the reference ground spectrum. Thus, the product given value of the ground-motion parameter (for      of these terms, shown in equation (6-4). results in example, spectral acceleration).          Thus, the  a spectral acceleration capacity which has a fragility evaluation is based on the estimation of    median value,        . , and randomness                and the median ground spectral acceleration value for    uncertainty variabilities which are equal to the which the seismic response of a given structure or    corresponding variabilities associated with the component        exceeds its capacity, resulting in  overall factor of safety (Figure 6-10). As a result, failure. Because there are many sources of        the spectral acceleration capacity at any point variability in the estimation of the median ground    within the family of fragility curves is computed spectral acceleration capacity, the component        as:
fragility is described by means of a family of                  v fragility curves. Figure 6-10 depicts such curves,                                                        (6-5)
                                                              %= sa e(CIPR+C2U) showing the best                estimate (50 percent where C, and C2 are the statistical constants confidence, C2 = 0) curve with its shape governed associated with the failure fraction and confidence by randomness variability, (OR), and showing the level of interest (Figure 6-10).
relative position of the curve for other confidence levels greater than or less than 50 percent. The It must be noted then, that the term Sa as used in properties of the fragility curves and the general this chapter refers to an average spectral approach to their development are defined in acceleration capacity defined over the same previous works (Kennedy, 1980; Kennedy, 1984).
frequency range as Ref. This is in contrast to Employing the characteristics of the lognormal the normal usage of the term Sa, which refers to a distribution as described in these references, the spectral acceleration at a specific frequency.
entire family of fragility curves for any mode of failure is defined in terms of a median estimate pf  The    Diablo Canyon        site-specific median the ground spectral acceleration capacity, Sa        horizontal and vertical ground spectra were (Figure 6-10), times the product of randomness        established as part of the ground-motion studies and uncertainty variables, eR and eu, which have      documented in Chapter 4. These are shown on unit median          values and are lognormally      Figure 6-11 and define the median spectral shape Diablo Canyon Power Plant IM    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 6                                                                                            Page 6-21 ChaDter 6                                                                                            Page 6-21 Best estimate fragility curve 1.00-0.75                                          o; ooWo I"It Fragility curves having I                                          different confidence levels 0.250      c1                                              /
0.25  -                                      .
0.05    -              -
ground spectral acceleration C.= -160 IICLF GrundMedia Sa Grudspectral acceleration (Sal cc      Paii Gsad50cc opn Figure 6-10 Fragility- curve representations.
Diablo Canyon Power Plant SPacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 6                                                                                                                                                Page 6-22 Chainer 6                                                                                                                                                Page 6-22 5% Damping
: 2. 5 ......................................................                                                                            .............                .......
2    .................                  o............................................................ .....................-
0 I.0 5 . .............. I ...........                  ................. ..... ...................................................
Horizontal component                                                                                *                .....
Vertical
                                                                      .      . .  .  . .  . ,0.. . . .  . . . .    . o.&deg;S... . . . . . . .o. . o.  &deg;...
                                                                                                                                                            .  . .. . o.. . . . ...
5 . . .. . . .. . .. .. . "-" "" . . .. . . . ... . .. .. .. . .. . . .. . . .. .. ."... .. ... .. . . . . . . .. . . .. . .. . . . .          -'      - - -
100                                                                              101                                                                                      102 Frequency (Hz)
Figure 6-11 Diablo Canyon site-specific median ground-motion acceleration response spectra.
Olablo Canyon Power Plant I      Pacific Gas and Electric Company                                                                                                  Long Term Seismic Program
 
v=.*ybv*  v                                                                                      Page 6-23 C~hanter 6                                                                                        ae62 2
WU
'U CL CA 102 Frequency (Hz)
Figure 6-12 Reference horizontal ground-motion response spectrum.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chaoter 6                                                                                      Page 6-24 Chanter 6                                                                                      Page 6-24 and relative amplitude between the horizontal and      and many structures and components are vertical components on a frequency-by-frequency        capable of absorbing substantial amounts of basis. For use in the fragility evaluation of the      energy beyond yield without loss of function.
Diablo Canyon structures and equipment, the reference        horizontal      ground  spectrum  3) The Qualification Method factor, FOM, (Figure 6-12) was established by scaling the            comparing the acceleration values used in the median horizontal ground spectrum such that the        equipment design analysis (when Fs is based average spectral acceleration, -SaRf over the          on the design seismic event) to those obtained frequency range between 4.8 and 12.7 hertz was          from the reference floor response spectrum.
several      key variables together with the randomness and uncertainty variability associated    4) The Damping factor, FD, comparing response with each. The key factors involved are listed          accelerations from the reference floor spectra below and were appropriately applied for                at structure or equipment design damping to structures and/or components.                          that associated with the damping level expected at or near failure.
Because seismically induced fragility data are generally unavailable for most Plant components      5) The Modeling factor, FM, assessing the ability and all structures, fragility curves were developed    of the design mathematical model to primarily from design analysis data, equipment          accurately    determine    the fundamental qualification test data, and engineering judgment.      frequencies and mode shapes of the structures The overall median factor of safety. F, based on        or    equipment    modeled;        for    tested these data sources, was established by considering      components, assessing the similarity of the dynamic test boundary conditions to the
: 1)  The Strength factor, Fs. comparing the            in-Plant anchorage.
median 'strength available to resist seismic motion (or strength at loss of function) to the 6) The Mode Combination factor, FMc, assessing response level due to either the reference        the conservatism or unconservatism in the seismic event or the design seismic event.        mode combination method used in the design Where possible, based upon the form of the        process; for components qualified by test, available seismic qualification data, the          assessing the ability of the test method to Strength factor was based upon a revised          simultaneously excite all dynamic modes.
calculation of the critical response using the reference spectra, median-centered property    7) The Earthquake Component Combination values, and median-centered combination            factor, FEcc, evaluating the conservatism or methods. For such cases the response factors      unconservatism in the method used to discussed below were unity and only the            combine the responses from the various associated variabilities were evaluated. This      earthquake component directions during the was done to minimize the uncertainty              design analysis; for tested equipment, variabilities associated with the various          evaluating the unconservatism in the use of response parameters. Where the form of the        unlaxial or biaxial tests to duplicate actual available data did not permit recomputation        earthquake response.
of the median-centered response, the responses from the design event (usually        8) The Spectral Shape factor, Fss, evaluating the Hosgri reevaluation data) were used to            randomness and uncertainty associated with evaluate the Strength factor of safety. For        peaks and valleys in the reference giound such cases, the response factors were              spectra.
evaluated as necessary.
: 9) The Ground Motion Incoherency factor,
: 2) The Inelastic Energy Absorption factor, Fp.          Faoa, evaluating the conservatism in assuming (ductility), accounting for the fact that an      coherent ground motion in establishing the earthquake represents a limited energy source      reference floor spectra.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 6                                                                                              Page 6-25 Chapter 6                                                                                              Page 6-25
: 10) The Inelastic Structural Response factor, Fut,      the structure and equipment than it is a function evaluating the potential for increased high        of the peak ground acceleration. For nearly all of frequency floor acceleration response due to        the structures (except the turbine building) and nonlinear structural behavior. This factor is      the equipment, the frequency range of primary applicable to equipment fragility evaluation        interest was from about 3.5 hertz to about only.                                              35 hertz. From the 38 sets of time histories defined in Chapter 4 and used for the fragility The median overall factor of safety and its              evaluations, it was found that the ratio of spectral variabilities are computed as:                            acceleration, at any specific frequency of interest in the 3.5 hertz to 35 hertz frequency range, to v      V    v      V      -v    v    v          the average spectral acceleration over the 4.8 to F= Fs" FA *FOM'              FD" FM"  FMC        14.7 hertz range, showed lesser and more consistent variability than did the ratio of spectral (6-6)  acceleration at any specific frequency to peak.
ground acceleration. Over'the entire frequency range of 3.5 hertz to 35 hertz, the ratio of 2        2          2I          +Q 02it M] 1/2 spectral acceleration at any specific frequency to.
the average spectral acceleration over 4.8 to 14.7 hertz had a nearly constant logarithmic
    =          +2  2    +
                        ++                        2]1/2  standard deviation that averaged about OR = 0.18.
s                                    IOM      However, the ratio of spectral acceleration at a specific frequency to the peak ground acceleration Although the Diablo Canyon fragility evaluation of      was highly variable over this important frequency safety-related structures and equipment essentially      range. The logarithmic standard deviation of this followed the basic approach used for previous            ratio ranged from close to zero at 35 hertz to seismic probabilistic risk assessments of nuclear        more      than    0.25    below        5 hertz.      The power plants, substantial work went into the more        frequency-dependent        nature        of    spectral rigorous determination of certain factors and their      peak-and-valley or spectral shape variability is variabilities. This was accomplished with the intent    difficult to accommodate in the fragility analysis of of minimizing the variabilities associated with the      a large number of components and equipment so various parameters. A discussion of the important        that seismic fragility estimates anchored to peak differences between previous fragility estimation        ground acceleration have tended to use a efforts and the approaches used for the Diablo            conservative, frequency-independent spectral Canyon evaluation is included in the following          shape randomness variability of 0.25 or greater.
sections.                                                Anchoring the fragility estimates to the average spectral acceleration from 4.8 to 14.7 hertz eliminates this difficulty and has enabled the use Reference Ground-Motion Parameter of a lesser OR for peak-and-valley or. spectral shape variability for frequencies equal or greater The fragilities for all Diablo Canyon structures and than about 3.5 hertz.
equipment, except the turbine building, were estimated as a function of the 5 percent damped average spectral acceleration of the horizontal          As will be noted later,. the turbine building fragility ground-motion components averaged over the                was initially estimated to be sensitive to spectral frequency range of 4.8 to 14.7 hertz. Most                accelerations in the 3 to 8.5 hertz frequency previous seismic probabilistic risk assessments of        range, and was later found to be sensitive to nuclear plants have defined fragilities as a              spectral accelerations in the 1.7 to 9.5 hertz function of the peak ground acceleration.                frequency range. To enable a better incorporation However, damage to structures and equipment is            of spectral shape variability within the frequency more a function of the spectral accelerations            range of interest for the turbine building, its within the elastic and inelastic frequency ranges of      fragility estimate was developed as a function of Olablo Canyon Power Plant Long Term Seismic Program F      Pacific Gas and Electric Company
 
Chapter 6                                                                                          Page 6-26 Chapter 6                                                                                          Page 6-26 the average spectral acceleration in the 3 to          differences between the design and median 8.5 hertz range.                                        site-specific    ground    spectra,      effects      of soil/structure interaction, and differences between When convolving the seismic hazard and fragilities      design structural damping and structural damping together in the seismic probabilistic risk              expected at or near failure. In contrast, as assessment, it is desirable for all fragilities and the discussed in Chapter 5, reference median seismic hazard to be expressed in terms of one          horizontal floor spectra were generated for common ground-motion parameter. Because the            selected elevations of the Diablo Canyon median      and      84 percent      nonexceedance  safety-related structures corresponding to the probability site-specific spectra, the probabilistic    location of important safety-related equipment.
seismic hazard spectra with the annual probability      These floor spectra were generated using the range of interest, and the median horizontal            reference ground motion, together with median spectrum shape used in the fragility evaluations all    soil/structure interaction and building structural showed essentially the same ratio of average            parameters. Thus, the Strength factor of safety, spectral accelerat1dn in the 3 to 8.5 hertz range to    Fs, is generally based upon the reference median average spectral acceleration in the 4.8 to            horizontal floor spectra, together with a clear 14.7 hertz frequency range, it was immaterial          understanding of the associated variabilities.
which average spectral acceleration frequency range was used for the common ground-motion parameter. The ratio between these average              Relationship Between Horizontal and 5 percent damped spectral, accelerations was:          Vertical Ground Spectra The vertical ground spectrum used in the design
                              -- 1.125                of most nuclear plants is usually based upon some specified factor (for example, 2/3 or 1) times the a 4.8-  14.7 design horizontal spectrum evaluated on a frequency-by-frequency        basis.      For      the probabilistic risk assessments for such plants, the Because 3 to 8.5 hertz is the frequency range over potential for higher than the designed-for vertical which spectral accelerations are maximum, it was to horizontal ground-motion ratio is either ignored judged to be most descriptive to define the or included as a randomness variability based average spectral acceleration over the 3 to upon the vertical direction contribution to the 8.5 hertz range as the common ground motion response of interest. The Diablo Canyon parameter for convolving hazard and fragility site-specific horizontal and vertical 5 percent estimates.      All      fragility    median      and damped median ground spectra are shown on high-confidence-of-low-probability-of-failure es-Figure 6-11. As discussed earlier, the reference timates included in this report were converted so horizontal ground spectrum for use in the fragility as to be defined in terms of the average spectral evaluations was established by scaling the median acceleration in the 3 to 8.5 hertz frequency range horizontal spectrum such that the average spectral using the above defined conversion ratio.
acceleration over the 4.8 to 14.7 hertz range was equal to 2.0 g (Figure 6-12). This same scale Median Horizontal Floor Spectra                        factor was applied to the median vertical ground response spectrum to establish a reference vertical In many previous probabilistic risk assessments,        ground resporne spectrum              that properly the factors, for equipment capacities and                corresponded to the reference horizontal equipment responses were based upon the floor            spectrum. The resulting 5 percent damped spectra used during the Plant design phases.            reference vertical ground response spectrum is Various factors were then generated in an attempt        depicted on Figure 6-13 and is shown in to account for conservatism or unconservatism in        comparison with the Hosgri reevaluation vertical the generation of the design floor spectra due to      ground spectrum.
Diablo Canyon Power Plant IN Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 6                                                                                              Page 6-27 Chapter 6                                                                                              Page 6-27 From Figure 6-11 it can be seen that the vertical          of equipment fragilities, which affect the ground acceleration exceeds the horizontal                generation of in-structure floor spectra include:
acceleration over the frequency range of about 9.5 to 30 hertz. In addition, Figure 6-13 shows                  1)  Ground-motion spectral shape that the reference vertical ground spectrum exceeds the Hosgri reevaluation vertical spectrum              2)    Structural damping for frequencies greater than about 4.5 hertz. The
: 3)  Structural frequency effects of this reference vertical spectrum were included in the evaluation of equipment fragilities.
: 4)    Structural mode combination Equipment fragilities are mostly dominated by                    5)    Earthquake directional combination horizontal reponses.            As discussed      above, reference median horizontal floor spectra were                  6)    Soil/structure interaction developed for the safety-related                structures (Chapter 5). Reference median vertical floor                    7)    Structural mode shape spectra were not similarly generated. Reference
: 8)    Ground-motion incoherency vertical floor spectra were developed by scaling the    Hosgri      reevaluation      vertical  spectral
: 9)    Inelastic structural response acceleration at the floor by the ratio of the reference vertical ground spectrum to the Hosgri          The first six variables, which constitute the reevaluation        vertical      ground        spectrum  majority of the randomness and uncertainty (Figure 6-13). Since the vertical direction              variability, were included in the structural contribution to seismic fragilities of components is      response variability study described herein; the generally small, this approach for the generation        last three variables were added to the structure of reference vertical floor spectra was considered        and component fragility analyses based on the adequate.                                                normal separation-of-variables approach.
The variables associated with ground-motion Structural Response Variability                          spectral shape (peaks and valleys), structural mode *combination, and earthquake directional combination were represented in the variability In most previous seismic probabilistic risk study using a large suite of 38 sets of two assessments of nuclear power plants, the orthogonal horizontal components of earthquake evaluation of the Structural Response factor used time      histories    that    provided      a      broad in developing fragility descriptions for structures characterization of the ground motions which and equipment has employed simplified methods might occur at the Plant site in the event of a very using the separation-of-variables              approach.
large earthquake. The 38 sets of earthquake time Because of the significant variabilities associated histories used in the variability study consisted of a with each of the factors that would make up the set of 24 empirical earthquake time histories and Structural Response factor and the uncertainties 14    numerically      simulated    acceleration-time associated with the simplified approach (how the records. The variables associated with structural individual variabilities combine), a more rigorous damping, structural frequency, and rock modulus approach was undertaken to establish structural are model parameters that characterize -the response variability, as part of the Diablo Canyon behavior of the soil/structure system under a given Long Term Seismic Program.
ground      motion.      These    parameters        were represented by employing a random selection The Structural Response factor is a measure of the        procedure (Latin Hypercube simulation) to select conservatism introduced in the development of            model parameter values which were then the reference in-structure floor response spectra.        randomly mixed for use with the suite of The important variables used in the development            earthquake time history input ground motions.
Olablo Canyon Power Plant I    Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 6                                                                                                              Page 6-28 Chapter 6                                                                                                              Page 6-28
        *12 J
I  I    I 1        4    1  1  4    1    1 .
5% Damping 2.5-S
.2 4.-                                                                                                        Reference vertical spectrum Ua Hosgri reevaluation......................-.--..-----
FI                                                I    I  S  I                                                          D    m  i a    I.
10                                                        101                                                                      102 Frequency (Hz)
Figure 6-13 Diablo Canyon reference vertical ground spectrum.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                                    Long Term Seismic Program
 
Chpe Page 6-29 Chapter 6                                                                                        Page 6-29 Each set of randomly selected and mixed model          north/south stiffness of the core east stick.
parameter values and its associated north/south        Comparison of fixed-base modal properties and east/west earthquake time histories were input    between the two models, both fixed at El 85 feet, into a simplified soil/structure interaction system    showed close agreement at the lower modes. The model of -the auxiliary building, which was            embedded portion of the auxiliary building, the analyzed using the CLASSI computer code to            foundation, basement, and the underlying rock generate 38 sets of deterministic floor response      medium, were        represented    by equivalent spectra at various elevations. The floor response      foundation base mass, mass moments of inertia, spectra from the 38 earthquake runs were then          and impedances in the simplified model. The statistically analyzed to generate median and 84th    frequency-dependent      foundation      impedances percentile probabilistic floor spectra. At any        associated with the rigid rectangular base were frequency, the        combined variability,      pe,  calculated using the CLASSI code, based on the associated with the six variables included in the      same rock profile and properties used for the study was estimated from the ratio of the 50th and    soil/structure interaction study (Chapter 5). The 84th percentile spectral accelerations                frequency-dependent soil spring stiffnesses and damping coefficients were taken as the CLASSI ANALYSIS MODEL                                        calculated impedance functions at about 8 hertz, which closely corresponds to the fundamental As noted above, a simplified soil/structure            north/south and east/west frequencies from the interaction model of the auxiliary building was        soil/structure interaction model. These parameters used in this study. This structure was chosen          were then adjusted for the embedment effect of because it is a large structure that houses a          the core structure. The simplified soil/strUcture substantial portion of the important Plant            interaction model was formed by coupling the equipment. Emphasis in this study was placed          3-stick core structure model, the foundation base upon assessing the response variability of the        mass properties, and the soil spring and damping western core of.the auxiliary building because a      coefficients into the soil/structure interaction majority of the Plant safety-related equipment is      system.
located in the western core.
To validate the simplified CLASSI soil/structure As discussed in Chapter 5, detailed soil/structure interaction analyses of the auxiliary building were    interaction model, two response parameters were compared with results from the more detailed conducted using the SASSI computer code based upon a three-dimensional, 5-stick representation      SASSI model. The comparison of the north/south and east/west horizontal seismic response transfer of the structure above El 85 feet and a functions at El 140 feet is shown on Figure 6-16 three-dimensional        finite    element    plate representation below El 85 feet (Figure 6-14,          and the comparison of the 2 percent damped north/south and east/west floor response spectra SASSI model). A large number of time-history at El 140 feet (core west) for the same free-field soil/structure interaction response analyses and ground-motion time-history input is shown on varying model parameters were required in the Figure 6-17. Both show very good agreement.
structural response variability study; thus, it was desired that the model be simple and easily amendable to model parameter adjustment. The          The effect of conrete cracking on structural SASSI 5-stick model was considered too detailed      response was considered by adjusting the for the structural response variability study, and as frequencies of the fixed base model by a factor of a result, a simplified CLASSI model was              0.9 (stiffness reduction of approximately 0.8).
developed (Figure 6-15). The transformation to the simplified 3-stick model of the auxiliary          The median fundamental frequencies of the building superstructure was accomplished by            simplified soil/structure interaction model, for deleting the stick representation of the north and    both the north/south and east/west directions, south wings. The north/south stiffnesses of the      were approximately 8 hertz taking concrete deleted wings were accounted for by adjusting the    cracking into account.
Diablo Canyon Power Plant Pal Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 6                                                                                                Page 6-30 t
EXPANOlON CW Core West CC Core Center NW  Nort-Wing SW  South Wing IL      8W      =--        ---
Rii
                      -~~~~~~ii  Eemn            - --  = --
CE                      [ E l. 14 0 '
c% I
                            - -  - -                    -      -                        'Ers Figure 6-14 SASSI structural model for the auxilary building.
an Pacific Gas and Electric Company LongloTermyoeismic Long Term Seismic Program Progamt
 
Chapter 6                                                                                    Page 6-31 Chapter 6                                                                                    Page  6-31 EXPLANATION CE Core east CC Core center CW Core west
[* Node number El 164'
                                                                                  '51 El 140' 1151 CC Figure 6-15 Configuration of the simplified CLASSI model for the auxiliary building core structure.
an Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chante    6I                                                                                      Page 6-32 Chat~ter 6                                                                                        Page 6-32 5
4 3
E 2
1 0
0        2.5    5    7.5  10    12.5  15    17.5    20  22.5      25 Frequency (Hz) 5 4
a 3
E 2
1 0
0        2.5    5    7.5  10    12.5    15    17.5    20  22.5        25 Frequency (Hz)
Figure 6-16 Comparison of transfer functions from the simplified CLASSI soil/structure interaction model with those from the SASSI model at El 140 feet (core west).
a  Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 6                                                                                                                                Page 6-33 ChaDter 6                                                                                                                                Page 6-33 10                    ,_ISIS.                                              . 
                                                                                        .        5          .      .        . L  .  .
2% Damping North/south translation Simplified S
(,      . CLASSI model
              ..............                            ..              .    .....        .    .        .....................      *&deg;*
4-
              *..=.        ..
                            &deg;...  ..      ....
SASSI
                                                            ...............  =
4 0L ca 2 _......                                          .        ..
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10                                                      10    Frequency (hz)            10                                        ic In                                .        ..          . .            ....                . I            ..                .    .
2% Damping East/west translation SASSI model 0I
              .........................                              %...........i i ..                .....t; .......
m'iti 'i ed CL
      .2
                                        ...........                          .. ...... i......
CLASSI model
* Sim 10                                                      10    Frequency (hz)          10                                        10 Figure 6-17 Comparison of 2 percent damped response spectra from the simplified CLASSI soil/structure interaction model with those from the SASSI model at El 140 feet (core west).
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                                                      Long Term Seismic Program
 
Chapter 6                                                                                          Page 6-34 Chapter 6                                                                                          Page 6-34 INPUT MOTION                                          soil/structure system frequency (about 8 hertz) plus        or      minus      two          logarithmic Acceleration time histories used in the structural    standard deviations. Tables 6-5 and 6-6 present response variability study were developed to          details of each of the empirical and numerical represent ground motions that might be expected        time-history records, respectively, including fault at a rock site within 10 kilometers of the fault      type, scaling factor to achieve an average spectral rupture surface due to shallow crustal earthquakes    acceleration of 2.0 g, and the nature of having magnitudes in the range of 6.5 to 7.5 and      adjustments to the empirical records necessary so having strike-slip, oblique, or reverse faulting      that they would be appropriate for the Diablo mechanisms.                                            Canyon site.
A total of 52 horizontal ground-motion                VARIABLE MODEL PARAMETERS time-history records were used in this study.
Twelve pairs of orthogonal empirical time histories    Variability in structural response due to variation derived from actual recordings of eight past          in structural damping, structural frequency, and earthquakes were selected and are shown in            rock modulus were included in the auxiliary Table 6-5. Because directions of ground motions        building variability study. A Latin Hypercube for the suite of empirical time histories are          simulation was used to select the random variables random with respect to the north/south and            (model parameter values) used in the analysis.
east/west directions of the Plant, the two            Since the earthquake time histories selected were components of each of the 12 empirical records        assumed to be equally likely, the sample size was were interchanged to produce 24 empirical              set equal to the number of earthquake records earthquake time-history sets. To provide a more        provided. The damping ratios, frequencies, and balanced representation of potential fault              rock modulus values were assumed to be mechanisms at the site, and to increase the size of    lognormally distributed with medians and the suite of time histories for a better overall      variabilities as shown in Table 6-7. Two sets of distribution, 14 pairs of orthogonal numerically      model parameter samples were created: one for simulated time histories were also generated.          the set of 24 empirical earthquakes, and one for Because the numerical set of earthquake histories      the set of 14 numerically simulated earthquakes.
(Table 6-6) were specifically generated to correspond to the Plant north/south and east/west                            Table 6-7 directions respectively, they were applied in accordance with their specified directions.                    MEDIANS AND VARIABILITIES FOR MODEL PARAMETERS As discussed earlier, average spectral acceleration Parameter              .Median              .
over a broad frequency range is a substantially better descriptor of damage than is peak ground Structure Frequency Ratio.        1.0                0.25 acceleration. To maintain an approximately uniform variability over the entire frequency range    Structure Damping                0.07              0.35 of interest in the earthquake ground motion, each      Rock Modulus Ratio                1.00              0.45 time-history pair was scaled such that the average 5 percent damped spectral acceleration over the        The domain of each model parameter was divided.
frequency range of 4.8 to 14.7 hertz was 2.0 g for    into N + 2 strata (where N is equal to the number the average of the two horizontal components.          of sample points to be selected, that is, the This scaling method is identical to that used in the  number of earthquakes) such that each of the detailed      soil/structure    interaction analyses strata is of equal probability (Figure 6-18).
described in Chapter 5. The scaling factors used      Parameter values within the first and (N + 2)th are shown in Table 6-5 and Table 6-6. The              strata (that is, the tails of the probability frequency range of 4.8 to 14.7 hertz covers            distribution function) were considered to be approximately the median auxiliary building            extreme, unrealistic values; thus sampling was Dliablo Canyon Power Plant I      Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Table 6-5
-3                                                                                                                                                                          53 EARTHQUAKE RECORDS USED TO DEVELOP TIME HISTORIES FOR a
FRAGILITY STUDIES a'
Time History                                    Recording                Record          Magnitude        Distance        Style of                            Scaling Number          Earthquake                  Station                  Name              Used              (km)          Faulting        Adjustment          Factor' 1      1978 Tabas                Tabas                    Tabas N74B              7.4                3        Thrust          None                    0.98 2                                                          Tabas N16W 3      1971 San Fernando        Pacolma Dam              SFPAC S16E              6.6                3          Thrust          None                    1.12 4                                                          SFPAC S74W 1971 San Fernando        Lake Huges No. 12        SFLH12 N21E              6.6              20          Thrust          Distance                1.07 SFLH12 N69W 7      1971 San Fernando        Castalc                  CAS N69W                6.6              25          Thrust          Distance                1.25 8                                                          CAS N21E 9      1979 Imperial Valley      Differential Array        IVDA NOW0                6.5                5          Strike-slip      Site response          1.46 as        10 15                                                          IVDA N90W 16 11        1979 Imperial Valley      El Centro No. 4          IVEC S50W                6.5                4          Strike-slip      Site response          1.80 0    12                                                            IVEC S40E X59                                                                                              6.2                0.1        Strike-slip      Magnitude 0
13        1984 Morgan Hill          Coyote Lake Dam          CLD N75W                                                                                        1.21 14                                                            CLD SI5W is        1983 Coalinga            Pleasant Valley Pump      PVPP 045                6.5              10          Reverse          Distance                1.31 16                                  Station (Switchyard)      PVPP 135 17        1985 Nahanni              Site I                    NAHI 010                6.8                6          Thrust          None                    0.84 18                                                            NAHI 280 19        1976 Gazli                Karakyr Point            GazEl EAS                6.8                3          Reverse          None                    1.24 20                                                            Gazli NOR 21        1966 Parkfield            Temblor                  TEM N65W                6.1              10          Strike-sUp      Distance and            2.13 22                                                            TEM S25W                                                                magnitude
        .23        1978 Tabas                Dayhook                  Daybook N10E            7.4              17          Thrust          Distance                1.45 24                                                            Daybook N80W en Ca 0~o
      'This scaling factor was used to bring the empirical records to an average 5 percent damped spectral acceleration of 2.0 g in the 4.8 to 14.7 hertz range and is in      !.
addition to the scaling necessary to make the records appropriate for the Diablo Canyon site (Chapter 4).
 
Chapter 6                                                                                      Page 6-36 Chapter 6                                                                                      Page 6-36 Table 6-6 FAULT MODELS USED TO GENERATE SIMULATED TIME HISTORIES FOR FRAGILITY STUDIES Time History                                Style of      Rupture                                      Scaling Number          Record Name            Faulting        Mode          Source Functions              Factor 25            FILE1-C2E          Strike-slip  Bilateral    Coalinga aftershock                  1.38 26            FILE1-C2N 27            FILEI-13N            Strike-slip  Bilateral    Imperial Valley aftershock            2.06 28            FILEI-13E 29            FILE2-19N          Strike-slip  Unilateral-N Imperial Valley aftershock            2.53 30            FILE2-I9E 31            FILE3-C6N          Strike-slip  Unilateral-S Coalinga aftershock                  1.68 32            FILE3-C6E 33            FILE3-16N            Strike-slip  Unilateral-S Imperial Valley aftershock            2.33 34            FILE3-I6E 35            FILE4-C4N            Oblique      Bilateral    Coalinga aftershock                  1.09 36            FILE4-C4E 37            FILE4-CSN            Oblique      Bilateral    Coalinga aftershock                  1.33 38            FILE4-C5E 39            FILE4-17N            Oblique      Bilateral    Imperial Valley aftershock            2.63 40            FILE4-I7E 41            FILE5-C5N            Oblique      Unilateral-N Coalinga aftershock                  1.39 42            FILE5-CSE 43            FILES-16N            Oblique      Unilateral-N Imperial Valley aftershock            2.25 44            FILE5-16E 45            FILE6-C4N            Oblique      Unilateral-S Coalinga aftershock                  1.12 46            FILE6-C4E 47            FILE6-I1N            Oblique      Unilateral-S Imperial Valley aftershock            1.96 48            FILE6-I1E 49            FILE7-C1N          Thrust      Bilateral    Coalinga aftershock                  1.23 50            FILE7-C1E 51            FILE8-C2N          Thrust      Unilateral-N Coalinga aftershock                  1.05 52            FILE8-C2E Diablo Canyon Power Plant
'  Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 6                                                                                      Page 6-37 Chapter 6                                                                                      Page 6-37 Structure                              Structure                      Rock Damping                              Frequency                  Modulus N + 2 equal probability strata (that is, equal -
areas)
V D
D                    v F            F                                  oG D-1        D  .i
                  ..                            F, ... F  ... FN      G    ... G, .I.GN N random samples of                        N random samples of          N random samples of damping ratio, from                        frequency ratio, from        rock modulus ratio, N different strata                        N different strata          from N different strata GN Figure 6-18 Sampling of model parameter values.
Diablo Canyon Power Plant IM    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
.... &#xa3;-- ....                                                                                      Page .6-38 Chanter 6Pae-8 limited to the N strata lying between the first and      rock modulus ratio was also used to compute the last strata. For each model parameter, one sample        corresponding    shear  wave    velocity    for each value was chosen at random within each of the N          analysis.
strata (by using the model parameter medians and                                                      interaction One    deterministic    soil/structure variabilities given in Table 6-7) based on the          analysis was then performed for each of the 38 properties of the lognormal distribution. The earthquake/model parameter value sets.
result is a set of model parameter values consisting of N values of damping ratio, N values of                RESULTS frequency, and, N values of rock modulus as The time-history output from each of the 38 illustrated schematically on Figure 6-18. The deterministic analyses was obtained for both three sets of model parameter values were then horizontal directions for six selected locations in randomly mixed.' This might be visualized core west of the auxiliary building. Referring to asplacing the N damping values, N frequency Figure 6-15, the selected locations included El values, and N rock modulus values into three 164 feet (node 1), El 154 feet (node 50), El 140 separate bins, then drawing one damping, feet (node 2),        El 115 feet (node 4),
frequency, and rock modulus value at random, El 100 feet (node 5), and El 85 feet (structure without replacement, until all values have been base). From the floor response time histories, chosen. As a result, N sets of model parameter floor response spectra were generated for four values, each containing a damping, frequency, specified damping ratios (3, 5, 7, and 15 rock modulus value are obtained as shown on percent). As an illustration of the results of the 38 Figure 6-19. Each of the N equally likely CLASSI runs, the 5 percent damped north/south parameter values were assigned to one of the N response spectra from all 38 runs, at El 140 feet equally likely earthquake pairs; the resulting sets of the core west stick, were plotted on the same are given in Tables 6-8 and 6-9 for the frame on Figure 6-20. The spectral accelerations 24 empirical          and      14    numerical records, were arranged in descending order at each of the respectively.
selected frequency points and the median and The dynamic properties of the superstructure            84th percentile values were extracted. The portion of the simplified soil/structure interaction    resulting median (50th percentile) and 84th model were input in each CLASSI run in the form          percentile floor spectra were then plotted and of modal masses, structure damping. and mode            digitized for use in the fragility evaluations. The shapes and frequencies. A frequency cut-off point        north/south and east/west median and 84th of 33 hertz for the superstructure resulted in a        percentile spectra for El 140 feet are depicted on total of 56 modes, with cumulative effective modal      Figures 6-21 through 6-24.--.
masses of 87 percent and 95 percent in the              APPLICATION OF RESULTS north/south and east/west directions, respectively.
The balance of the modal masses were treated by          The combined variability associated with variation the CLASSI program as rigid masses.                    of the six parameters included in the auxiliary building variability study was determined by From the given set of model parameters, the            comparing the 5 percent damped median and sampled structure damping was applied to all 56        84th percentile floor spectra..-
modes. The frequency ratios, along with the 0.9 concrete cracking factor, were used to scale each            N= in  (%8a4 /%60)                          (6-7) of the 56 fixed base frequencies. The rock modulus ratio was applied to the median rock            In a comparison of the 50th and 84th percentile modulus value (that is, the value at the top layer      floor spectra for the various auxiliary building core of the soil profile, to which all other layers have    west elevations, it was found that the variabilities been normalized) to determine the input value for        tended to be consistent over certain frequency each analysis. The shear wave velocity, which is        bands. The resulting combined variabilities are not independent of the rock modulus, must also          shown in Tables 6-10 and 6-11, respectively, for be specified for the CLASSI program; thus the          the north/south and east/west directions.
Diablo Canyon Power Plant r        Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 6                                                                                                      Page 6-39 Chavter 6 v
Page 6-39 Structure                  Structure                    Rock Damping                  Frequency                    Modulus                      Earthquake Parameter selected at random.
without replacement I i;    &#xfd;        Assign          D D{1 I F I (3k, E}  I    ~              IFJ              Deterministic Ok        Analysis I N boxes Deterministic                      for Analysis 2                  N deterministic Continue until N boxes have D                                            soil/structure interaction analyses been filled.                          0 Deterministic Analysis N
  *The earthquake time histories were randomly mixed by virtue of the random selection of the other three parameters.
Figure 6-19 Random mixing of model parameters.
Diablo Canyon Power Plant
                                        ~2 In    Pacific Gas and Electric Company                                                            Long Term Seismic Program
 
Chanter 6                                                                                  Page 6-40 Chanter 6Pae64 Table 6-8 MODEL PARAMETER VALUES AND SCALING FACTORS FOR THE EMPIRICAL RECORDS Input Time History          Structure          Structure        Rock            Time History Analysis        Number            Damping          Frequency        Modulus              Scaling Number        NS      EW            (%)              Ratiol          Ratio              Factor 2 1            1        2          6.80      0.950 x  0.9 = 0.855  1.335                0.98 2            2        1          4.71      0.915 x  0.9 = 0.824  1.124                0.98 3            3        4          9.46      0.983 x  0.9 = 0.885  0.771                1.12 4            4        3        12.45      0.801 x  0.9 = 0.721  1.737                1.12 5            5        6          4.34      0.903 x  0.9 = 0.813  1.081                1.07 6            6        5          5.10      1.174 x  0.9 = 1.057  1.238                1.07 7            7        8          5.82      0.814 x  0.9 = 0.733  1.486                1.25 8            8        7          6.33      1.009 x 0.9 = 0.908  0.618                1.25 9            9        10        10.09      1.217 x  0.9 = 1.095  2.187                1.46 10          10        9        10.11      1.509 x  0.9 = 1.358  0.986                1.46 11          11        12          4.05      0.644 x  0.9 = 0.580  1.434                1.80 12          12        11          8.07      0.871 x  0.9 = 0.784  0.900                1.80 13          13        14          6.28      0.855 x 0.9 = 0.770  0.540                1.21 14          14        13          9.97      1.344 x 0.9 = 1.210  1.033                  1.21 15          15        16          7.29      1.068 x 0.9 = 0.961  1.651                1.31 16          16        15          7.68      0.750 x  0.9 = 0.675  0.853                1.31 17          17        is          5.49      1.428 x  0.9 = 1.285  0.934                0.84 18          18        17          8.02      1.134 x  0.9 = 1.021  0.672                0.84 19          19      20          5.33      0.957 x  0.9 = 0.861  1.167                1.24 20          20        19          7.01      1.121 x 0.9 =  1.009  0.512                1.24 21            21      22          6.08      1.047 x 0.9 =  0.942  0.697                2.13 22            22      21          8.57      0.734 x 0.9 =  0.661  0.738                2.13 23            23      24          8.73      1.264 x 0.9 =  1.138  1.311                1.45 24            24      23          6.72      1.097 x 0.9 =  0.987  0.830                1.45 10.9 factor accounts for concrete cracking (typical).
2 For both north/south and east/west time histories.
Diablo Canyon Power Plant Ian Pacific Gas and Electric Company                                            Long Term Seismic Program
 
rh  *t~tpr  t*                                                                              Page 6-41 Ch _r, er A                                                                                -
Table 6-9 MODEL PARAMETER VALUES AND SCALING FACTORS FOR THE NUMERICAL RECORDS Input Time History                            Structure                      Time History Structure                          Rock Analysis            Number            Damping          Frequency      Modulus              Scaling Number            NS      EW                            Ratio'        Ratio              Factor 2 25              26      25          9.28      0.892 x 0.9 = 0.803  0.954                1.38 26              27      28          5.42      0.865 x 0.9 = 0.779  0.566                2.06 27              29      30          8.77      1.061 x 0.9 = 0.955  0.669                2.53 28              31      32          7.90      1.218 x 0.9 = 1.096  1.510                1.68 29              33      34          5.08      1.265 x 0.9 = 1.139  1.693                2.33 30              35      36        10.57      0.801 x 0.9 = 0.721  0.924                1.09 31              37        38          5.56      0.928 x 0.9 = 0.835  1.016                1.33 32              39        40          7.0.8    0.811 x 0.9 = 0.730  1.190                2.63 33              41        42          9.77      1.025 x 0.9 = 0.923  1.470                1.39 34              43        44          6.05      1.180 x 0.9 = 1.062  0.747                2.25 35              45        46          7.56      0.712 x 0.9 = 0.641  1.299                1.12 36              47        48          6.58      1.430 x 0.9 = 1.287  1.098                1.96 37              49        50          6.75      0.986 x 0.9 = 0.887  0.701                1.23 38              51        52          4.35      1.129 x 0.9 = 1.016  0.864                1.05 10.9 factor accounts for concrete cracking (typical).
2 For both north/south and east/west time histories.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                          Long Term Seismic Program
 
Chapter 6                                                                                        Page 6-42 Chapter 6                                                                                      Page 6-42 I\
0 CO Frequency (Hz)
Figure 6-20 North/south response spectra at El 140 feet from all 38 deterministic analyses.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 6                                                                                                                  Page 6-43 Chapter 6                                                                                                                  Page 6-43 1                I          i  '      I      I      I  I    i I  I                I            I      I    I    I    I  I    i 10 . ....................        ....................                      .. ...............................................              -
8............................................                              ..........................................                    -
3% Damping Lo 6 .................................................................................                                                        -
CL                            5% Damping                    "-        '
                                                                  * /'\7%              Damnping CO)
                                                        *-~          \    \~        15% Damping 2 ................                  ............ .......                      7              .................................
4*I                          !  '                  I            I  I it  I  I          i      !    !      i  I i 100                                                                  10                                                                102 Frequency (Hz)
Figure 6-21 50th percentile north/south response spectra for El 140 feet.
Dlablo Canyon Power Plant I    Pacific Gas and Electric Company                                                                        Long Term Seismic Program
 
Chapter 6                                                                                                                                  Page 6-44 12                                                                                      I                                                                '
10 10  . . .........  . ...........................                          . .. .....
3% Damping S 8 ...............                                      ....                A................................
o                                                                                      t*
                      *                                                        /                          51ADamping M                      7%Damping U) 4 ....................                                                                              .......... ......          ........                .
                                            ' .      *#o a-,.          u-"        15% Damping                :
2 -.                ,.        - .a................................................
010101                                                                                                                            102 Frequency (Hz)
Figure 6-22 84th percentile north/south response spectra for El 140 feet.
In    Pacific Gas and Electric Company Dlablo Canyon Power Plant Long Term Seismic Program
 
Chapter 6                                                                                                        Page 6-45 12                                            ...... . . . ... I...
10 ...................................................            :...................................................
_*=j        -          .3%                    Damping    --
S 5% Damping
                                                              ,                7% Damping W      4                .........
                            . . . . . . . . . . . .1                  1.. . . . . . . . . . . . . . . . . . . . . . . . .
2 ...............................                                                        ................................
                        .. *-    -t    -----      15% Damping 01                                    10 ,1i0                        1                          2 Frequency (Hz)
Figure 6-23 50th percentile east/west response spectra for El 140 feet.
Diablo Canyon Power Plant 1,    Pacific Gas and Electric Company                                                                Long Term Seismic Program
 
Chapter 6                                                                                                                                              Page 6-46 Chapter 6                                                                                                                                              Page 6-46 12                                              I        I      I    l    l    l    II  I                      e
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  *~ 6                      ........ ...... ......    ....    .1... .,: '.. .z'          .... ...................................................
7% Damping                              "'  /            \
t;                                                            /...../    ...
CAP    4
                            *          ,                  1_5%Damping 2                                                                                ..      .    .      ........... ..
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: 10.                                                                                  1I                                                                              10O Frequency (Hz)
Figure 6-24 84th percentile east/west response spectra for El 140 feet.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                                                                  Long Term Seismic Program
 
Chaoter 6                                                                                        Page 6-47 Chanter 6Pae64 At El 85 feet, corresponding to the basemat of the    As noted earlier, the factors and variabilities structure, the entire combined variability over        associated with the remaining three structural each frequency band is taken to be due to              response parameters not included in the auxiliary randomness, that is, p,. It can be seen that the      building variability study were applied in combined variability is relatively insensitive to      accordance with the normal separation-of-changes in floor level in the low and high            variables approach.
frequency ranges, and thus, in these frequency ranges, the combined variability is also virtually all due to randomness. However, in the frequency          As part of the soil/structure interactions analysis bands near the fundamental frequency of the            described in Chapter 5, median reference floor auxiliary building, it can be seen that at higher      response spectra were developed for various elevations, the combined variability increases        locations of the containment, auxiliary, and substantially. The majority of the increase in the    turbine building structures. The 5 percent damped combined variability is due to the uncertainty        median reference floor spectra developed for associated with the structural property values and    selected locations in the west core of the auxiliary is assigned to flu.                                    building from the soil/structure interaction deterministic study were compared with those Specific structural response variabilities were not    developed in the structural response variability conducted for the containment building, concrete      study. It was found from the comparisons that the internal structure and the turbine building. The      spectra showed good agreement. A representative structural response variabilities for equipment        comparison is depicted on Figure 6-25. The peak located in structures other than the auxiliary        frequencies of the two spectra were found to be building were based upon a conservative                approximately the same, and the spectral application of the result of the auxiliary building    accelerations from the soil/structure interaction evaluation. Referring again to Tables 6-10 and        spectra were found to be only slightly higher than 6-11, the structural variabilities at the basemat (El  those from the response variability study in the 85 feet) and high in the structures (approximately    frequency range of interest. Thus, it was judged El 164 feet) were taken to be as shown below:          that the median reference spectra developed in the soil/structure interaction deterministic study FREQUENCY RANGE              were adequate for use in estimating equipment fragilities.
ELEVATION        Low            Mid        High
                  <0.6f,      0.6 fato 1.4fn >1.4fn 0.24            0.26      0.24    As noted above, the auxiliary building variability BASEMAT study results were used as the basis for the HIGH IN          0.34            0.41      0.26    structural response variabilities for the other STRUCTURE structures. The median reference floor spectra where f, is the median frequency of the                from the soil/structure interaction study for the appropriate structure, and the low, mid, and high      containment building, concrete internal structure, frequency range correspond to the ranges given in      and turbine building tended to be somewhat Tables 6-10 and 6-11.                                  sharply peaked. Therefore, to be certain that the equipment response near the peak of the reference    floor    spectra    was      adequately Values for other floor levels were interpolated        represented for structures other than the auxiliary accordingly. The variabilities for equipment          building, an additional uncertainty variability on located in these other structures were applied as      the fundamental frequency of the structures was shown above in terms of the ratio of the              introduced. This additional uncertainty variability equipment fundamental              frequency  to the  of 0.15 was combined with the equipment fundamental      frequency of the appropriate        frequency uncertainty variability in the assessment structure.                                            of the equipment modeling factor.
Diablo Canyon Power Plant I"  Pacific Gas and Electric Company                                                Long Term Seismic Program _
 
Chapter 6                                                                                              Page 6-48 Chanter 6Pae64 Table 6-10 NORTH/SOUTH RESPONSE COMBINED VARIABILITY (PC)
Frequency Band Floor Elevation                              (Hz)
(feet) 3.5 to 5      5 to 7      7 to 11      11 to 30 85            0.24                0.24                0.18 100            0.24                0.27                0.18 115            0.24        0.32          0.27          0.18 140            0.24        0.37          0.29          0.18 154            0.25        0.40          0.29          0.18 164            0.26        0.41          0.30          0.18 Table 6-11 EAST/WEST RESPONSE COMBINED VARIABILITY (PC)
Frequency Band Floor Elevation                      (Hz)
(feet) 3.5 to 6    6 to 11      11 to 30 85            0.24        0.28          0.25 100            0.24        0.30          0.25 115            0.24        0.30          0.25 140                  0.31                0.25 154                  0.32                0.26 164                  0.35
* 0.26
'Except for 6.9 to 7.5 hertz, where Oc = 0.47 Diablo Canyon Power Plant Ian Pacific Gas and Electric Company                                                        Long Term Seismic Program
 
Chapter      6'                                                                                                                                                                            Page 6-49
          =
ChaDter 6                                                                                                                                                                                  Page 6-49 12                                I            I          I          I            li      I      I  I    jI
* I          I          I      I      I "  I
                                                  .  .  . ,,,.  .  .....        , ..... ... a  o        ...  .      .  .  .  .  . ..      .      .      .  .  .  .  .    .  .  .  .  .    .  .  .  .  .
10        n.. ...    ..... , ,.,,    ... .  .
8 CL 6
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                                                                                                                      -        Soil/structure interaction studies 4,
Variability      studies 2.
fl U
100                                                                                                    10'                                                                                                      10; Freguency (Hz)
Figure 6-25 Representative comparison of median reference response spectra from the soil/structure interaction and structural response variability studies.
Diablo Canyon Power Plant I        Pacific Gas and Electric Company                                                                                                                                Long Term Seismic Program
 
Chapter 6                                                                                            Page 6-50 Chapter 6                                                                                            Page 6-SO Turbine Building Nonlinear Analysis                      In a manner similar to that used for the auxiliary building variability study, the variables associated with ground motions spectral shape were In the Diablo Canyon Long Term Seismic                  represented using a suite of 25 earthquake time Program, the fragilities (probabilistic seismic          histories that provide a broad characterization of capacities) of all major structures (Table 6-2)          the ground motions which might occur at the were        obtained          using    the    standard Diablo Canyon site. Further, the variables separation-of-variables          approach    (Kennedy,  associated with structural damping, stiffness, and 1980;      Kennedy and Ravindra, 1984) as              strength were represented by randomly selecting summarized earlier. From these analyses, it was          model parameters for use with the suite of found that the turbine building has the lowest          earthquake time-history ground motions.
seismic capacity of the structures and is the only one that could possibly .be a significant contributor    The 25 earthquake time histories used in the turbine building nonlinear analysis consisted of to the seismically induced risk of core damage.
21 actual recorded ground motions, some of Thus, it was determined that a probabilistically which have been scaled and modified to based, nonlinear evaluation of the turbine correspond to Diablo Canyon magnitude, building would be extremely valuable for the source-to-site distance, and site conditions, and purposes of:
four semi-numerically generated ground-motion records developed to simulate the magnitude of
"    Improving the probabilistic seismic capacity        a strike-slip earthquake on the Hosgri fault.
(fragility) estimates for severe overall distress of the turbine building for use in the seismic      A total of 200 deterministic nonlinear analyses probabilistic risk assessment.                      (25 each at average spectral accelerations of 3.0 g and 6.0 g with median structural properties, and
* Comparing the fragility estimate based upon        50 each at average spectral accelerations of 3.0 g, multiple nonlinear analyses with the estimate      4.0 g, and 6.0 g using variable structural extrapolated from a single median-centered          properties) was performed using a simplified elastic response spectrum analysis obtained        model of the turbine building, which was analyzed using the standard separation-of-variables          using the DRAIN-2D computer code (Kanaan fragility evaluation method.                        and Powell, 1975), The resulting inelastic structure drift from each deterministic run was compared with a criterion relating inelastic drift to As a by-product, it was found that the nonlinear the probability of severe distress and strength analysis provided an understanding of the degradation. The probabilities of severe distress relationship betweeW turbine building shear wall were then statistically evaluated as a function of distress and various earthquake ground-motion the three average spectral acceleration levels and characteristics.
the median seismic capacity and variabilities were estimated. The structural response variables It should be noted that the nonlinear evaluation of      associated with structural modeling, earthquake the Diablo Canyon turbine building provided both        directional      effects,    and      ground-motion probabilistic and determiniitic estimates of the        incoherency were then added using the normal turbine building capacity. It is the intention of this  separation-of-variables approach.
portion of the report to only briefly summarize those aspects of the study lerding to the                It should be emphasized again that this study is development of the fragility parameters. Details        concerned with the prediction of ground-motion are included in the full report entitled                levels associated with the onset of severe structural "Probabilistic Evaluation of the Diablo Canyon          distress and significant strength degradation of the Turbine _ Building          Seismic    Capacity Using  turbine building and not the prediction of failure Nonlinear Time-History Analysis" (Kennedy and          capacity. In the
* Diablo Canyon seismic others, 1988).                                          probabilistic risk assessment, the onset of severe I    Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
  .... r ....                                                                                              Page 6-51 Chan~ter 6Pae65 structural distress was conservatively used as a            height. Thus, these walls are long relative to their surrogate for a structure-induced failure of all            height and are rather thick.
safety equipment housed in the turbine building.            The operating floor consists of a 12-inch concrete slab supported on a steel beam framing system. It ANALYSIS MODEL                                              is 139 feet wide and 267 feet long between Walls 19 and 31. plus a 77-foot overhang beyond During'Phase II of the Long Term Seismic                    Wall 31. The slab contains a cutout for the Program, several possible failure modes that could          independently supported turbine pedestal which is lead to overall severe distress of the turbine              approximately 59 feet wide by 212 feet long.
building were investigated' using the standard              Thus, for east/west lateral forces, the operating fragility evaluation method. It was concluded that          floor was treated as two independent 267-foot-the most probable cause of overall severe distress          long by about 40-foot-deep beams between Walls was substantial inelastic drift and strength                19 and 31.
degradation        of the two major east/west              A minimum gap of 3.375-inch exists between the load-carrying shear walls spanning from -the                turbine pedestal and the operating floor. This gap foundation level (El 85 feet) to the operating floor        is insufficient to preclude impact between the (El 140 feet). Thus, the nonlinear analyses turbine pedestal and the operating floor at the consisted of an assessment of the east/west                high ground-motion levels of interest in the response of the Unit 2 turbine building, with              fragility evaluation. Furthermore, the effective emphasis          on    the      two    major    east/west inertial mass to be lumped at the top of the load-carrying shear walls below the operating turbine pedestal exceeds the entire inertial mass floor.                                                      supported by wall 19 plus wall 31; therefore, impact of the turbine pedestal potentially could Figure 6-26 shows a plan view of the Unit 2 lead to additional distress in the shear walls. Thus,
" turbine building;            Figure 6-27    presents    a the turbine pedestal was included in the nonlinear schematic elevation view, emphasizing the major model      together    with    a      gap    element east/west shear walls at column lines 19 and 31 interconnecting it to the operating floor beam (herein called wall 19 and wall 31), which support elements on each side.
the heavy operating floor at El 140 feet.
Essentially, walls 19 and 31 are the only two              Due to their relative ductility, severe distress of major walls available to resist east/west drift of the      the shear walls was expected to occur well before heavy operating floor. In turn, nearly all the              failure of either the operating floor beam elements in-plane lateral loads imposed on these two walls          or the turbine pedestal. For this reason, walls 19 come from the east/west inertial loads of the              and 31 were modeled in more detail than either operating floor, plus their own weight. Although          the operating floor beam elements or the turbine some additional in-plane loads enter due to                pedestal. The operating floor and turbine pedestal east/west inertial loads from the intermediate            were only modeled in sufficient detail to floors, these floor masses are small compared with        approximate their potential for distributing inertial that of the operating floor, and much of their              loads to the shear walls. The shear walls were east/west inertial load is carried by external            modeled into three segments each along their buttresses added to the turbine building. The              height, corresponding to points where both the inertial loads transferred into Walls 19 and 31            stiffness and strength of the walls greatly change.
from the superstructure above the operating floor          Because of the low height-to-length ratio, the wall are also small; they were approximated by a slight          shear stiffness is generally greater than the flexural increase in the weight at the operating floor level.        stiffness and the shear capacity is generally less Each wall is 55 feet high by approximately 137              than the flexural capacity.        Each shear wall feet long, and contains several openings                  segment was modeled with both a nonlinear shear (particularly wall 19). The thickness of wall 19          element and a nonlinear flexural element varies from 20 inches to about 36 inches over its            combined in series, because each element has height. Wall 31 is 24 inches thick over its entire        different nonlinear properties.
Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
.... Jr" ....                                                                                          Page 6-52 CThanter 6Pae-2 EXPLANATION
          ---    -  Continuous chord beams
          .....      Shear wall Figure 6-26 Turbine building Unit 2 concrete outline at El 140 feet.
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Page 6-53 Chapter 6~Pge65 N
31 Z/5
                                                                    /-Operating floor
                                        /a          19 z/Gap x    \ \\""17\
X\ NN '\ Nl&#xfd;                  'N\- X I
i
- i--                                                                          f I            -Wall      31 Wall 19-
                                            /
JI
                                                    /  ~~2]
I  --
                                        /Turbine Pedestal Figure 6-27 Schematic illustration of turbine building nonlinear model.
Diablo Canyon Power Plant VN Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 6                                                                                      Page 6-54 Chanter 6                                                                                      Page 6-54 The analysis was concerned only with east/west      to the shear resistance. The opening and closing response due to an east/west input; therefore, the  of cracks under load reversals causes a pinching schematic model (Figure 6-27) was simplified        behavior to be noted in the hysteresis loops. Also, into a two-dimensional model (Figure 6-28).          as shear cracks open wider and damage to the This model consists of the two shear walls          concrete increases, the contribution of concrete, subdivided into three segments (stories) each, two  through aggregate interlock, to shear resistance operating-floor beam elements, and the turbine      decreases. This effect causes strength degradation pedestal with a 3.375-inch separation gap            under large displacement cycles. A typical shear between the pedestal and the operating floor        force-shear distortion diagram obtained during a beam elements. Model properties, including          structural wail test is shown on Figure 6-29 (Wang, 1975), which illustrates the reverse-cycle masses, element strengths, and stiffnesses are      loading behavior characterized by stiffness summarized in Tables 6-12 through 6-14,              degradation and pinching of the hysteresis loops.
respectively. Elastic modal characteristics of this  This behavior was approximated by the 10 Rule model are summarized in Table 6-15.                  hysteretic model shown on Figure 6-30. The shear force-deformation curves used for the FORCE-DEFLECTION DIAGRAM FOR                        operating floor beams and the turbine pedestal are SHEAR DRIFT                                          shown on Figures 6-31 and 6-32, respectively.
Reinforced concrete walls resist shear through      VARIABLE STRUCTURE PROPERTIES various mechanisms. Initially, the wall is elastic and shear resistance is developed according to      To study the dispersion in the response due to elastic beam theory. Inclined shear cracks develop  uncertainty in structure properties, a Monte Carlo when the principal tensile stresses exceed the      technique was used in the turbine building concrete tensile strength. Once shear cracks open. nonlinear analysis. Important structure variables the shear force is resisted mainly by the            affecting structure response (damping, stiffness, reinforcing bars and aggregate interlock. Other      and strength), were assumed to be lognormally mechanisms such as dowel action, truss action,      distributed with median and logarithmic standard and the flexural compression zone also contribute    deviations as shown below:
Median              Logarithmic Standard Deviation Variable                      Value      Random            Uncertainty              Composite Damping                                7%          0                    0.35                    0.35 Stiffness Ratio                        1.0        0                    0.50                    0.50
,i  Strength Ratio                        1.0        0                    0.25                  0.25 Note that the stiffness and strength ratios were    simultaneously have a high stiffness ratio and a used to scale the median stiffnesses and median      low strehgth ratio. Similarly, shear walls could strengths of each of the structural elements of the  have a low strength ratio and the operating floor nonlinear model. For each nonlinear analysis, the    have a high strength ratio. However, all six shear median stiffnesses and strengths of the shear        wall elements in shear and flexure had the same walls, operating floor, and turbine pedestal were    stiffness and strength ratios in a given analysis.
multipled by a probabilistically defined stiffness  Similarly, the four operating floor elements had and strength ratio. Stiffness and strength ratios    the same stiffness and strength factors in a given were independently defined for each element type    analysis. The 50 sets of stiffness ratios, strength (shear walls, operating floors, and turbine        ratios and damping shown in Table 6-16 were pedestals). Thus, a given element could              independently selected.
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Chapter 6                                                                                      Page 6-55 Chapter 6                                                                                      Page 6-55 4010- AW                A1                                      I"T7 -11MAA 20          22  -      x Operating Floor 17Flexural 18            Stiffness Only r Inelastic 19 Shear 19 /        Element 20 TIFTAIL-A Q    -  Inelastic Shear Elements (Shear Def6rmation Only)
        - Inelastic Flexural Beam Element (Flexural Deformation Only)
El    - Operating Floor Element
        - Turbine Pedestal
        - Gap Element Figure 6-28 Turbine building DRAIN-2D model.
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Chamer 6                                                                                                  Page 6-56 Chanter 6Pae-6 Table 6-12 NODAL MASSES OF TURBINE BUILDING NONLINEAR MODEL Weight 1Nooe NO.
3              1,573              Wall 19 and Floor at El 104 5                  832          .Wall 19 and Floor at'El 123 7,            .4,219              Wall 19 and Operating Floor 10              2,256              Operating Floor 11              2,250              Operating Floor 12              25,000            Turbine Pedestal 16              6,331              Wall 31 and Operating Floor 18              2,130            Wall 31 and Floor at El 119 20                2,460              Wall 31 and Floor at El 107 Table 6-13 MEDIAN CAPACITIES OF SHEAR WALL ELEMENTS Flexural Capacities Shear Capacities                                              Equivalent Concrete Only          Ultimate            Yield Moment            Yield Shear Concrete                          Vc                  Vu                    M                        VM Shear Wall                        (kips)              (kips)                (klp,-yt)                (kis)
WALL 19 El 140 to El 123                  10,600                12,800            0.23 x 106                13,700 El 123 to El 104                  11,000                13,300            0.39 x 108                11,200 El 104 to El 85                      9,200                13,500            0.71 x 106                14,100 WALL 31 El 140 to El 119                  13,200                16,600            0.64 x 108                30,700 El 119 to El 107                  17,000                21,700            0.72 x 106                24,800 El 107 to El 85                    15,000                19,200            1.04 x 108                22,300 Table 6-14 EFFECTIVE ELASTIC SHEAR AND FLEXURAL STIFFNESS OF SHEAR WALLS Concrete                          Effective Shear Stiffness                  Effective Flexural Stiffness Shear Wall                                  (kips/ft)                                    (kips/ft)
WALL 19 El 140 to El 123                              1.14 x 106                                  6.13 x 107 El 123 to El 104                              1.22 x 100                                  7.55 x 107 El 104 to El 85                                2.25 x 10e                                  5.05 x 107 WALL 31 El 140 to El 119                              1.71 x 106                                24.2    x 101 El 119 to El 107                              3.10 x 106                                99.0    x 107 El 107 to El 85                              1.60 x 106                                16.0    x 107' Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                        Long Term Seismic Program
 
Chapter 6                                                                                                  Page 6-57 Table 6-15 ELASTIC MODAL PROPERTIES OF THE TURBINE BUILDING MODEL WITH MEDIAN STRUCTURE PROPERTIES (A) MODAL FREQUENCIES Natural Frequency Mode                                                  (Hz)                                              Remarks 1                                                  3.1                                          Turbine Pedestal 2                                                  4.0                                          Operating Floor 3                                                  8.6                                          Wall at Line 31 4                                                  9.5                                          Wall at Line 19 (B) MODAL SHEARS. AND MOMENTS Modal Shears (klpsl/)                        Modal Moments (kin-ftle)
Total                                                Total Mode      Mode. Mode    Mode    Higher        Mode    Mode    Mode      Mode      Higher Element                  1        2      3        4    Modes            1      2        3        4      Modes Turbine Pedestal        25,000        .      .          .      .
WALL 19 Operating Floor          -      1,410    -20    -260        0 (Per Beam)
EJl 123+                          3,470  -390    3,820    -420          -    59,000 -7,000 65,000          -7,000 El 104+                          3,550  -430    4,360    -160          -    126,000 -15,000 148,000        -i0,000 El 85+                            3,600  -460    4,740    1,010          -    195,000 -24,000 238,000          9,000 WALL 31 Operating Floor          -      1,460  -310        -40        0          -      -        -        -            -
(Per Beam)
El 119+                          3,660  5,580        160    -840                77,000 117,000      4,000    -18,000 El 107+                          3,820  7,020        230    -380                123,000 201,000      6,000    -22,000 El 85+                          3,950  8,190        280    740                210,000 381,000    12,000      -6,000 (C)    MODAL DISPLACEMENTS Drifts (inches/g)
Location                            Mode 1              Mode 2              Mode 3                Mode 4 Top of Turbine Pedestal                        1.040 Center of Operating Floor                                          0.768                -0.019                  -0.015 WALL 19 El 140                                                            0.098                -0.011                    0.111 El 123                                                            0.056                -0.007                  0.070 El 104                                                          0.020                -0.003                  0.026 WALL 31 El 140                                                          0.071                  0.129                  0.004 El 119                                                          0.044                  0.090                  0.003 El 107                                                          0.030                  0.062                  0.002 I      Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic PKogram
 
Chnnter                                                                                        Page 6-58 Cha-~tr 6                                                                                        ae65 Figure 6-29 Cyclic load-deflection behavior of concrete shear walls (Wang, 1975).
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Chapter 6                                                                                      Page 6-59 V
B      sK J V, 88 0    Model rul es Figure 6-30 Shear deformation hysteretic behavior.
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Chapter 6                                                                                    Page 6-60 Page 6-60 Chapter 6 Best estimate                  3000
    -  -  -  DRAIN input a._t singe near midspan P 2000                                ! at to ca                          3520 k/ft 1210 1000
    -6                -4              -2                          2          4                6 Deformation (inches)
                                                        -1000
                                                        -1210
                                                        -2000 Hinge at                          -3000 Line 31 Hinge near midspan Figure 6-31 Shear deformation curve of the beam-like portion of the operating diaphragm at the midspan for each of four beam elements.
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r*h~,torn Page 6-61 rt- Fter A Total                                                                                  DRAIN input base                                                                          ...  -  Best estimate shear (k) 80,000
                                  ~ 2.8" 1
                                        -Expected 40,000                                Elasto-perfectly plastic approximation K = 2.88 x 105 k/ft 20,000 2              4              6            8          10    Displacement (in) at top of model Figure 6-32 Shear-deformation curve of the turbine pedestal.
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Table 6-16                                                0 U
VARIABLES OF MODEL STRUCTURE PROPERTIES (0
.5                                                                                                      ~1 0'
0 System              stiurness Ratio                              Strength Ratio C-ID  Trial Damping                  Operating          Turbine                  Operating  Turbine a
a-  Number  Value                    Floor          Pedestal  Shear Walls      Floor    Pedestal m                    Shear Walls a
a I    .0601      .9343          .8421            1.4495    1.1481          .9319    1.1148
  -a    2    .0793    1.0607            .9839              .6679    1.0732          .9263    1.2484 C.
3    .1155      .9275        1.0205                .4355    .9692        1.8888    1.0005 4    .1009    1.0914        1.7003                .7948    .8729        1.2734    1.0282 5    .1023    2.1317        1.5155              1.2248    1.4069        1.1721    1.1336 6    .0582    3.0935          .6578            1.3189      .6618        1.3248    1.4670 7    .0585    1.0504        1.1815                .5977    1.0734          .7686    1.4773 8    .0568      .9974        1.5550            1.0877      1.2396          .7181    .7032 9    .0684    1.5548            .5104              .8385    1.3007        1.2217    1.5525 10    .0698    1.1254        1.3876            2.2731      1.4946          .8750    .7939 11    .0704      .4634        1.1817                *4356    .7953        1.0006    1.1623 12    .1493    1.4327        1.3365              1.3245      .9122        1.0389    1.5407 13    .0572      .6004        1.3288              1.0898      .7238          .8229    1.1988 14    .0927    1.5996          .9293            2.1709      .9210        1.3397    1.3248 15    .1123      .4682        1.0784                .6464    .8982          .6652    .8286 16    .0652    1.2137        1.0849            1.1087      .7419        1.4439      .8299 17    .1053    1.1349        1.7651            2.0897      .6416        1.1718      .9177 18    .0609    2.1395          .9588              .5845    1.0878          .8770    .9039 19    .1096    1.2604        1.6396            2.5241      1.1662        1.6452    1.1995 20    .1074    1.6790          .8242            2.5171      .8942          .8675    1.0032 21    .0596      .6275            .7439              .6320    .8245          .7250    .7423 22    .0760    1.0896        1.0855                .5099    .8584        1.4128    1.0756 23    .1369    3.5920          .8568            1.3599    1.2019          .9804    1.1332 24    .0831    1.0797          .9291              .6403    1.5220          .5480    1.0474 25    .1240    1.0087          .9222            1.8344      .6911          .6206    1.0911 26    .0772      .5653          .8310              .8607    1.0071          .8561    .8499 27    .1136    1.3648          .5680              .6208    1.3277          .7726    1.3637 28    .0910      .6796        1.1320              1.4513      .9571        1.0147      .7058 29    .0496    2.2296          1.8930              1.1704    1.0630        1.1235    1.3609 30    .0486      .9323        3.7765            2.3605      1.4893          .6491    1.6148 31    .053B      .4250          .5502            2.0228      1.1503          .6496      .9712 32    .1009    1.1350          .5983            2.5905      .8772          .8909      .6511 33    .0949      .8769        2.0427                .9961    .7191        1.2164      .6773 34    .0365    1.1243        1.9010                .7875    1.5064          .7779    1.0995 35    .1507    1.6397        3.7699              1.4291      .9167        1.0773    1.2275 36    .0334      .8274          .9919              .5106    .9336        1.0267      .6908 37    .0523      .6222        1.4331                .9317    .9753          .8322    1.2863
=3    38    .0357      .6568        1.4558              1.4051      .9462        1.0556    1.5023 39    .0603    1.0507        1.2858              1.2992    1.0741          .6953    .8159  0(
00 40    .0753      .9401        1.7601            1.0112      .7298          .7261    1.5294  (0 41    .0637    1.2890          .8582              .8481      .8885          .7238    .8793  a' 42    .0391      .5772          ,8199              .9413      .5133          .8863    1.2748 a'
(.3
 
Table 6-16 (Continued)
Di
*0                      VARIABLES OF MODEL STRUCTURE PROPERTIES flu                                                                                                C,
                                                                                                  ~1 C) 0~
C) a, ma C',          System            Stiffness Ratio                          Strength Ratio ma          Damping                Operating      Turbine                  Operating  Turbine U      Trial U. Number  Value Shear Walls      Floor        Pedestal  Shear Walls      Floor    Pedestal 0U C,
43    .1107    1.1182        1.3084            .4553      .9878        1.1935    1.1383 K. 44    .1180  2.6135          .8649          1.0102      .7662        1.1832      .9608 C,    45,    .1142  3.3185          1.5687            .8905    1.1715          .9960      .9420 a
46    .1162    .8227        1.1182            .7581    .8490        1.6054      .7599 ma    47    .0783    1.0485        3.6193            .9812    1.0399        1.2617      .8452 U                                                                .8526        1.0049      .9262 48    .0538    1.3866          .6226            .5341 49    .0403    .6810        1.2759            .5473    1.1852        1.0856    1.2072 50    .0616    .3445          .4155            .8854    1.1008        1.1917    1.2165 r;  s CA
=a 0 Di go El-
 
Chapter 6                                                                                          Page 6-64 Chaoter 6                                                                                          Page 6-64 INPUT MOTION                                            Even after modification, only a few of the empirical records met Criterion 4; it was assumed A single ground-motion parameter was used to            the records could be further modified by define the fragilities of Diablo Canyon structures      frequency-independent upward scaling to achieve and equipment. The 5 percent damped average            desired values of average spectral acceleration.
spectral acceleration over the 3 to 8.5 hertz range    Due to the paucity of near-source, strong-motion was chosen to convolve the seismic hazard and          records    from    rock sites        for magnitude seismic fragilities for use in the probabilistic risk  approximately      7.0  strike-slip      earthquakes, assessment.                                            records 22 through 25 were added (Criterion 3).
These are, simulated ground-motion records Twenty-one earthquake time-history records              generated. by semi-numerical            methods to (Table 6-17) representing actual recorded events        represent a magnitude 7.0 Ms strike-slip were selected for use in this study based upon the      earthquake on the Hosgri fault.
following selection criteria:
To study the randomness variability of the ground
: 1) The records should be appropriate for shallow      motions on the shear wall drifts, each of the 25 crustal earthquakes in the magnitude range        modified earthquake ground-motion time histories from 6.5 to 7.5 with recording distances          listed in Table 6-17 were constant-amplitude appropriate for the Hosgri fault zone.            (frequency-independent) scaled to obtain the same average spectral acceleration in the
: 2)  The records should            be appropriate  for frequency range of 3 to 8.5 hertz. Using median rock-site conditions.                              structural properties, shear wall drifts were computed from the nonlinear analyses for average
: 3)  The records should represent, in the              spectral acceleration values of 3.0 g and 6.0 g (25 aggregate, about a 50-50 mixture of thrust        trials each). Figure 6-33 presents the 5 percent and strike-slip faulting.                          damped response spectra for three of the records, each scaled to an average spectral acceleration of
: 4)  The records should be appropriate for ground      3.0 g to illustrate the diversity of spectral shapes motions having very high average spectral          included. Figure 6-34 depicts the mean, median, accelerations      (defined as the        average  84 percent probability of non-exceedance, and 5 percent damped spectral acceleration in the upper-bound spectra for the ensemble of 25 3 to 8.5 hertz range), of 2.0 g or greater.        records scaled to an average spectral acceleration Ground motions with average spectral of 2.25 g.
acceleration less than about 2.0 g are undamaging to the turbine building and are        To study the combined influence of the thus of little interest.                          randomness variability associated with the ground motions and the uncertainty variability associated Only the Tabas and Pacoima Dam records                  with the structural properties, each of the 25 (Records 3 through 6) met the above criteria in        modified ground-motion records was scaled to their original unmodified form. Although average average spectral acceleration values of 3.0 g, spectral acceleration was too low, the Gazli 4.0 g, and 6.0 g, and each was used twice (Trials records (Records 1 and 2) clearly met Criteria 1        1 through 25 and Trials 26 through 50), in and 2. All other empirical records had to be            combination with the 50 sets of variable structural modified for distance (frequency-independent            properties shown in Table 6-16 (150 total trials).
scaling) and/or magnitude and site conditions (non-constant, frequency-dependent correction).        SHEAR WALL DRIFT LIMIT After modification, all 21 empirical records met Criteria 1 and 2. Table 6-17 lists the                  The drifts associated with Walls 19 and 31 were characteristics of both the original and the            established from each of the 200 nonlinear trials modified records and the average spectral              using median and variable structural properties.
acceleration for each record after modification.        To calculate the corresponding probability of Diablo Canyon Power Plant Pacilic Gas and Electric Company                                                  Long Term Seismic Program
 
Table 6-17                                                      0 Os ma                                                                                                                                          *0 V                                                                  EARTHQUAKE TIME HISTORIES                                                0 0                                                                                                                                            *1 0%
Time Earthquake                Style of      Recording Station    History                                  Time History  B.5 Hz 0c.            Date        Magnitude Faulting              Distance      Number      Component Site Conditions    Adlustments 15 Gazli, U.S.S.R.      6.8    Reverse      Xnrakyr Point                              Rock/stiff alluvium None            1.33 2      East May 17. 1976                              3 km                              North                                          1.31 Tabas, Iran          7.4    Thrust      Tabas                      4      NIW      Stiff alluviumlrock None            2.48 Sept. 16, 1978                            3 km                      3      N74E                                          2.27 San Fernando. CA      6.6    Thrust      Pacoima Dam              5      S16E      Rock                None            2.00 Feb. 9. 1971                              3 km                      6      S74W                                          1.89 Lake Huges No. 12          7      N21E      Rock                Distance        2.38 20 km                      1:      N69W                                          2.27 Castalc                          N69W      Stiff alluvium      Distance        1.69 25 km Imperial VafJey. CA    6.5    Strike-Slip Differential Array                NOOE      Deep alluvium      Site response    1.38 Oct. 15, 1979                              5 km                              N90W                                          1.55 El Centro No. 4          18      S50W      Deep alluvium      Site response    0.75 4 km                      19      S40E                                          1.16 Parkfield. CA        6.1      Strike-Slip Temblor                  10      N65W      Rock                Distance and    1.27 Jun. 27. 1966                              10 km                    i1      $25W                          Magnitude        1.33 Morgan Hill, CA      6.2      Strike-Slip Coyote Lake Dam          12      N75W      Rock                Magnitude        2.29 Apr. 24, 1984                              0.1 km                    13      SISW                                            1.95 Coalinga. CA          6.5      Reverse    Pleasant Valley Pump      18      N45E      Stiff alluvium/rock Distance        1.63 May 2, 1983                                Station (Switchyard)      19      S45E                                            2.38 10 km Tabas, Iran 7.4      Thrust      Dayhook                  20      NIOE      Rock                Distance        1.12 Sep. 16. 1978                              17 km                    21      N8OW                                            1.67 Hnsogl Simulations    7.0      Strike-Slip -                        22      North                                          1.16 Bilateral                            23      East                                            1.47 5-us Strike-Slip -                        24      North                                          0.98 Unilateral                            25      East                                            1.56 SE X MI D%
0%J
 
Chapter 6                                                                                            Page 6-66 Chapter 6                                                                                            Page 6-66 V I 5% Damping 8
7-6-                                                                  Gazli C
0 U    5-                                                              San Fernando a:
U U
U 4-4-
Parkf ield                      I-V a:
0.
3-                                                                        A %-
2-1-                                        \%A          t
                                                                /
I' i-
                                                    -ii u.Y.
I      I    I  I  I  I I  I            I      I  I  I11  1I1I
        .1.                                    1                                    10 100 Frequency (Hz)
Figure 6-33 Acceleration response spectra for three empirical records scaled to an average spectral acceleration of 3.0 g over the frequency range of 3.0 to 8.5 hertz.
Diablo Canyon Power Plant a Pacific Gas and Electric Company                                                      Loag Term Seismic Pmwram
 
Chapter 6                                                                                        Page 6-67 ChapLer 6                                                                                        Page 6-67 5
50% Damping 44 C  3+
4.,
0 4.,
U a,  2+
C.
I,,
                                              -I 1
M      t    I  I I I 0
0.1          I      i    11I  I  I 1        I    I  I      1 10                  . r  '  I" I  I    0 100 Frequency (Hz)
Figure 6-34 Mean, median, 84 percent probability of nonexceedance, and upper-bound spectra for 25 records scaled to an average spectral acceleration of 2.25 g over the frequency range of 3.0 to 8.5 hertz.
Diablo Canyon Power Plant IF    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 6                                                                                            Page 6-68 Chapter 6                                                                                            Page 6-68 severe distress, the onset of severe shear wall          damping was used in this analysis). The results of damage (significant strength degradation) was            this analysis are presented in Table 6-18. Based defined in terms of shear wall drift limits. Based      upon these results, it was concluded that the lower upon a study. of the results of a number of shear        segment of both wall 19 and wall 31 will yield wall strength investigations, both in the United        slightly in shear at an average spectral acceleration Stated and Japan, the median estimate of shear          of 2.25 g because the elastic demand to yield wall drift (expressed as a percentage of wall            capacity ratios (Vi/Vy) are slightly greater than height) corresponding to the onset of significant        unity. Based on the median ground spectrum strength      degradation      and    the  associated shape and median structural properties, inelastic logarithmic standard deviations were taken as:          behavior is expected to initiate at about an average spectral acceleration of 1.90 g and 2.05 g V                                                    for the lower segment of walls 19 and 31, D = 0.79o                      (median drift limit) respectively. However, at an average spectral Pit= 0.15                                            acceleration of 2.25 g, with median properties, yielding in the shear walls will be slight and limited Pu= 0.30                                            to the lowest segment of each'wall. With median PC = 0.335                                          properties, the turbine pedestal is expected to remain elastic up to an average spectral acceleration of 3.30 g. At an average spectral When treated on a composite basis (using 1c),            acceleration of 2.25 g, the median drift of the there is about a 16 percent probability of severe        turbine pedestal was estimated to be about distress at 0.5 percent drift and about an 84            1.9 inches; that for the operating floor was percent probability of severe distress at 1.0            estimated to be about 2.0 inches. Combining the percent drift. These estimates might be more              drift responses by square-root-sum-of-the-conservative than necessary.                            squares, the gap closure between the pedestal and operating floor was estimated to be about Both walls 19 and 31 were segmented into three            2.75 inches, which is less than the available gap of elements along their height because of changing 3.375 inches. Thus, at an average spectral capacities and stiffnesses. With the shear acceleration of 2.25 g, it is not expected that the capacities listed in Table 6-13, drift percentages      turbine pedestal will impact the operating floor for tend to be greatest within the lower element in the median spectrum shape case.
wall 19 or within the lower or upper element of wall 31. It was conservatively decided to limit the element having the greatest drift percentage to the      Each of the 25 modified time histories, scaled to limits specified above. Thus, the probability of          an average spectral acceleration of 3.0 g and severe distress was based upon the shear element          6.0 g, Were applied to the nonlinear structure having the largest drift percentage obtained as a        model with median strength, stiffness, and percent of the element height, such that the limit        damping properties. Tables 6-19 and 6-20 list the criterion was essentially treated as an element drift    maximum total drift at the top of both Walls 19-criterion. The total drift of either wall 19 or 31        and 31, and for the operating floor and turbine was less than the maximum element drift                  pedestal for the two acceleration levels. Also percentage times the total wall height of 55 feet        shown are the maximum story drifts for each wall (often substantially less).                              defined as a percentage of the wall segment (story) height. In nearly every case, the maximum ANALYSIS RESULTS                                          story drifts occurred in the lowest segment of each wall. These tables also indicate for which cases the First, an elastic response spectrum analysis was          turbine pedestal impacted the operating floor.
performed using the 5 percent damped median              Lastly, the probability of severe shear wall distress response spectrum scaled to an average spectral          is estimated for each trial using the random shear acceleration~of 2.25 g (Figure 6-34) and median          wall distress criteria defined above. Defining structural properties (note that 7 percent median        P., as the probability    PF of severe distress for Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 6                                                                                                          Page 6-69 Table 6-18 ELASTIC COMPUTED RESPONSE FOR FIGURE 6-28 MEDIAN SPECTRUM SCALED TO AN AVERAGE 5 PERCENT DAMPED SPECTRAL ACCELERATION OF 2.25 G (A) DRIFTS Location                                          Drifts (inches)
Top of pedestal                                              1.89 Center of operating floor                                    1.570  (2.00)
Wall 19 El 140                                                  0.26 El 123                                                  0.16 El 104                                                  0.06 Wall 31 El 140                                                0.27 El 119                                                  0.18 El 107                                                0.12
* The operating floor is actually highly inelastic, so this elastic computed drift is too small. Value in parenthesis is more realistic for the inelastic operating floor.
(B)    SHEARS AND MOMENTS Shear VR              VR                Moment MR                    MR Element                              (kips)              Vy                (kip-ft) x 106                My Turbine pedestal                                    45,400              0.68 Wall 19 Operating Floor (Per Beam)                        2,910              2.41 El 123+                                            9,520              0.90                    0.16                    0.70 El 104+                                          10,240              0.93                    0.36                    0.91 El 85+                                            10,820              1.18                    0.56                    0.79 Wall 31 Operating Floor (Per Beam)                        3,030              2.50 El 119+                                          12,330              0.93                    0.26                    0.40 El 107+                                          14,560              0.86                    0.43                    0.60 El 85+                                          16,460              1.10                    0.79                    0.76 Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                                Long Term Seismic Program
 
Ch:*nter 6                                                                                                      Page 6-70 Chanter 6P Table 6-19 NONLINEAR RESULTS FOR MEDIAN STRUCTURAL MODEL AT AN AVERAGE SPECTRAL ACCELERATION OF 3.0 G Wall 19                Wall 31 Probability.
Max                    Max        Operating        Turbine                          of Severe Top        Story        Top      Story          Floor          Pedestal        Pedestal            Wall Trial          Drift      Drift        Drift    Drift          Drift            Drift          Impact          Distress No.        (inches)      (96)    (inches)'    (%)        (inches)          (inches)          Cases,              (%)
I          0.58        0.18        0.60      0.18          3.06            3.22                              0 2          1.01        0.35        1.30      0.42          5.15            2.47                              0 3          0.36        0.09        0.61      0.18          2.29            1.86                              0 4          0.24        0.04        0.29      0.06          1.58            2.20                              0 5          0.52        0.17        0.83      0.26          3.54            2.35                              0 6          0.79        0.26        0.79      0.26          4.57            2.40                              0 7          0.22        0.04        0.43      0.11          1.98            1.58                              0 8          0.20        0.04        0.24      0.05            1.81            2.12                              0 9          0.89        0.30        1.18      0.38            4.00            2.70                              0 10          0.64        0.20        0.70      0.22          2.71              2.45                              0 11          0.54        0.16        0.74      0.24            1.70            1.37                              0 12            0.36        0.10        0.52      0.17          2.84              2.24                              0 13          0.59        0.18        0.58      0.18          3.78              2.81                              0 14          0.28        0.06          0.25      0.05          3.18              3.43                              0 15            1.39      0.43          1.81      0.61          7.03              4.80                              17.9 16            1.03      0.35          1.10      0.37          3.71              2.28                              0 17            0.65        0.20        0.89      0.28          5.39              3.50                              0 18          1.69        0.53        2.36      0.69          5.77            2.48                              46.0 19            0.24        0.04        0.25      0.05          2.57              3.47                              0 20            1.62        0.51        2.11      0.59          5.37              3.12                              12.7 21            0.25      0.03          0.48      0.15          1.66              1.86                              0 22          0.41        0.11          0.62      0.19          3.47              3.07                              0 23          0.65        0.21          0.97    '0.32          4.18              3.76                              0 24            1.13      0.43          0.90      0.29          2.95              1.88                              0 25          0.23        0.04          0.62      0.19          3.84              3.88                              0 P = 76.6
                                                                                                          =765 6 . 3.1%
'Y indicates that the turbine pedestal did impact the operating floor. For all other cases, no impact occurred.
Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                              Long Term Seismic Program
 
Cha*ter 6                                                                                                              Page 6-71 Chanter 6Pa6 Table 6-20 NONLINEAR RESULTS FOR MEDIAN STRUCTURAL MODEL AT AN AVERAGE SPECTRAL ACCELERATION OF 6.0 G Wall 19                Wall 31                                                                    Probability Max                      Max        Operating        Turbine                              of Severe Story        Top        Story            Floor        Pedestal          Pedestal            Wall Top Trial          Drift      Drift      Drift        Drift          Drift          Drift            Impact            Distress No.          (inches)      (%)      (inches)        (%)          (inches)        (inches)            Cases'              (1) 1            4.8        0.89          5.9        1.46            8.8              6.1                                    100 0.97                      2.05          14.00            10.6                                    100 2            6.4                      7.7 3            2.1        0.59          4.2        0.97            7.4              4.0                                    99 4            2.4        0o66          3.1        0.90            7.3              4.6                                    95 5              3.2      0.84          5.8        1.20            8.6              5.2                                    100 6              4.6      0.82          6.3        1.50          11.5'            8.1                                    100 7              1.5      0.48          2.0        0.65            4.4              3.1                                    31 8              1.3      0,43          1.9        0.64            3.6              3.5                N                  27 9            7.2        1.16          9.1        1.89          13.10            9.7                                    100 10            2.8        0.71          4.0        1.13            7.3              5.4                                    100 11              1.5      0.48          1.8        0.57            3.9              2.8                N                    9 12              3.6      0.81          5.9        1.45            9.30            5.9                                    100 13            3.8        0.74          5.6        1.41          10.70            7.3                                    100 14            3.0        0.73          4.2        1.21            8.80            6.3                                    100 15              6.6      1.05          9.4        2.08          11.8'            9.9                                    100 16            6.6        1.00          8.2        1.67          11.8'            8.4                                    100 17            6.1        1.09          8.1        1.72          10.3              8.3                                    100 18          .10.1        1.82        12.2        2.76          18.5'            15.1                                    100 19              1.6      0.55          2.8        0.95            5.6              5.3                N                  98 20            7.7        1.23          8.8        1.91          14.20            10.8                                    100 21              1.7      0.55          2.0        0.65          4.9              4.0                                    31 22              4.3      0.77          5.3        1.33          10.0'            6.6                                    100 23              3.8      0.82          5.2        1.45            9.6'            6.2                                    100 24            4.2        0.81          5.2        1.33            7.9              5.0                                    100.
25              2.2      0.68          5.0        1.28            8.0              6.8                                    100 2190 P =        A"    = 987.6%
PF  25    -25
'Relative diaphragm drift exceeds the limits of applicability of the bilinear force-deflection relationship used for the operating floor so that diaphragm drifts are likely to be underpredicted and wall drifts are likely to be overpredicted to some extent for these cases.
'N indicates that the turbine pedestal did not Impact the operating floor. For all other cases there was Impact.
Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                                    Long Term Seismic Program
 
Chapter 6                                                                                            Page 6-72 Page 6-72 Chapter 6 Trail i, the median estimate of the probability        Thus, the turbine      building    fragility    estimate each average spectral acceleration value is            becomes:
obtained from:
v=    4.59 g
:  PF Pc = 0.37 (from randomness      and uncertainly runs)
N                                (6-8) where N is the number of-trials.
Olt = 0.23            (from randomness only runs)
P = (0.372 - 0.232)    112 = 0.29 In a similar manner, 50 nonlinear analyses were conducted at average spectral acceleration values of 3.0 g, 4.0 g, and 6.0 g, incorporating the                            4.59 e                          = 1.95 g HCLPF    R =        -1.65 (.23 + .29) randomly selected structure damping, stiffness, and strength ratios shown in Table 6-16. These As noted earlier, three structural response factors analyses include both input motion randomness were not included in the nonlinear time-history variability and structural property uncertainty.
analyses'and their effects were added by means of Table 6-21 tabulates the maximum story drift as a the separation-of-variables approach.
percentage of the wall segment height for both walls 19 and 31. Again, in nearly every case, the maximum story drifts occurred in the lowest            1) Modeling: Only a single mathematical model segment of each wall and again the composite              was used. Structure properties were varied, probability of severe wall distress for each trial was      but the model was not varied. The model estimated based upon the median drift limit of 0.7        which was used is judged to be percent and composite Pc = 0.335. The overall              median-centered. It is further judged that composite probability of severe wall distress is          modeling uncertainty is about p3UM = 0.15, computed using equation (6-8) for each average            which is equivalent to stating that the spectral      acceleration      level  as shown in          95 percent    nonexceedance              probability Table 6-21. Those trials in which turbine pedestal        responses near the base of the shear walls are and operating floor impact occurred are also              estimated to be as much as 1.28 times those indicated.                                                reported herein if differing models had been used.
The overall probability, estimates for each case studied (randomness only at an average spectral        2) Earthquake Component Variation: Within this acceleration of 3.0 g and 6.0 g, and randomness            study, the fragility of east/west shear walls plus uncertainty          at an average spectral          were defined in terms of average spectral acceleration of 3.0 g, 4.0 g, and 6.0 g) are              acceleration associated with east/west ground presented in Tables 6-19 through 6-21. These              motions. However, in the seismic probabilistic results were then fit by a "best-fit" lognormally          risk assessment, the seismic hazard was distributed fragility estimate using linear regression    defined in terms of the average horizontal (least-square error fitting). The result is a              component (&sect; ). The east/west component is lognormally distributed fragllty estimate defined          expected to have the same median value as in terms of the median, *,, and logarithmic                the average horizontal component (Fnm
.standard deviations for randomness variability,              1.0); however, the random variability (PR3DI)
Oa, composite variability, Pc, and uncertainty            for the east/west component, given an average variability,    Pu. The high-confidence-low-              horizontal component spectral acceleration, is probability-of-failure (HCLPF) capacity, defined          estimated to be about 0.12.
as a 95 percent confidence of less than 5 percent probability of failure, is calculated from:            3) Incoherence of Ground Motion: At any v                                      instant in time, the ground acceleration is not HCLPF -9 = 9,e -"60 R 0+u,)                    (6-9)    the same at every location under the turbine building foundation.        The soil/structure Dlablo Canyon Power Plant i      Pacific Gas and Electric Company                                                  Long Yef n Seismic Program
 
Table 6-21                                                                                0 a
NONLINEAR RESULTS FOR UNCERTAIN STRUCTURAL PROPERTIES MODEL aV Average Spectral Acceleration 3.0 a                      Averae*e Spectral Acceleration 4.0 R                    Average Spectral Acceleration 6.0 g Max Story            Prob.                              Max Story            Prob.                              Max Story          Prob.
Drift (%)                                                Drift (%)                                              Drift (%)          Severe        Pedestal CD                                          Severe        Pedestal                                  Severe        Pedestal Wall      Wall        Distress        Impact          Wall        Well      Distress        Impact          Wall        Wall      Distress        Impact Trial C.,    No.                                    (%)            (1)            .19                      (%)            (1)            19        31          (%)              (1) 19        31                                                        31 Y              0.29        0.64          39.4            Y            0.94      1.27        96.20              Y 0                    0.19        0.15            0 1.10        0.65          91.1            Y            1.76      1.62        99.7*              Y 2          0.45        0.37            9.3 0.40        0.46          10.6            Y              1.23      0.99        95.4                Y
: 3.          0.19        0.23            0 0                            0.18        0.25            0                          0.63      0.86        72.9                Y 4          0.04        0.05 0.06        0.11            0                          0.37      0.60          67.4              Y 5          0.02        0.04            0 0.33            1.3                                                    18.7            Y            1.68      0.92        99.50              Y 6          0.19                                      Y              0.47        0.52                                                                57.1 0.09            0                            0.16        0.29            0.4                        0.42      0.66 7          0.03 0                                        0.09            0                          0.27      0.44          8.2 8          0.02        0.05                                          0.05 Y                          0.40            4.7          Y            1.15      1.09        93.1'              Y 9          0.06        0.31            0.8                          0.24 0                          0.47      0.66        42.9                Y 10          0.03        0.06            0                            0.06        0.20 0.35          58.3                          0.72      0.86          72.9              Y 11          0.22        0.19            0                            0.75 0.44            8.2                        0.53      0.97          83.4              Y 12          0.14        0.16            0                            0.29 95.6            Y              1.20      1.97          99.90              Y 13          0.42        0.71          51.6            Y              0.67        1.24 0.40            4.7          Y            0.53      0.90        77.3                Y 14          0.09        0.06          .0                              0.28 1.84          99.8                          1.97      2.81        100.0                Y 15          0.72        0.96          82.6                          1.18 84.8            Y              1.44      1.51          98.9              Y 16          0.45        0.63          37.8                          0.87        0.99 Y              0.73        0.96          82.6            Y              1.11      1.42          98.3              Y 17          0.51        0.83          69.5 63.78          Y              1.46      1.15          98.60              Y 18          0.45        0.26            9.3            Y              0.38        0.79 0.17            0                          0.45      0.71          51.6              Y 19          0.02        0.04            0                            0.20 Y              0.45        0.70          50.0            Y            0.80      1.21          94.8"              Y 20          0.40        0.46          10.6 0.45            9.3.          Y            0.69      1.02          86.9              Y 21          0.24        0.31            0.8                          0.45 0.74          56.8            Y            0.84      1.25          95.8              Y 22          0.33        0.52          18.7            Y              0.58 0                          0.24      0.35          2.0              Y 23          0.01        0.01            0                            0.02        0.03
                                                                                                          .2.3          Y            0.86      0.78          72.9"              Y 24          0.05        0.24            0                            0.32        0.36 68.1            Y            0.71      1.15          93.1              Y 25          0.31        0.43            7.4                          0.49        0.82 CID (1) Y Indicates Ihat turbine pedestal did Impact the operating floor. For all other cases, no impact occurred.
Relative diaphragm drift exceeds the limits of applicability of the bilinear force-deflection relationship used for the operating floor so that wall drifts and probability  -. 3 of severe wall distress are likely to be overpredicted to some extent for these cases.
 
Il*
Table 6-21 (Continued)
NONLINEAR RESULTS FOR UNCERTAIN STRUCTURAL PROPERTIES MODEL a-w C.5 0a                      Average Spectral Acceleration 3.0 g                      Average Spectral Acceleration 4.0 i                    Average Spectral Acceleration 6.0 2 CD Max Story              Prob.                              Max Story            Prob.                            Max Story            Prob.
Drift (%)            Severe        Pedestal              Drift (%)          Severe        Pedestal            Drift (%)          Severe        Pedestal Trial          Wall        Wall        Distress      Impact            Wall        Wall      Distress        Impact          Wall        Wall        Distress        Impact No.            19          31            (%)            (1)              19        31          (%)            (1)            19          31          (%)            (1) 26          0.17        0.41            5.6                          0.69        0.85        71.9                          1.36      1.76        99.7              Y 27          0.37        0.17            2.9                          0.30        0.40          4.7                          0.57      0.76          59.9              Y 28          0.18        0.20            0                            0.43        0.46        10.6                          0.79      1.12          65.5              Y 29          0.05        0.18            0                            0.06        0.13          0                            0.35      0.43          7.4              Y 30          0.06        0.11            0                            0.25        0.27          0.2*                          0.87      1.07        89.80              Y 31          0.14        0.45            9.3            Y            0.79        1.37        97.7                          1.71      2.54        100.00              Y 32          0.03        0.12            0                            0.17        0.29          0.4                          0.41      0.62          35.9 33            0.33        0.30            1.3                          0.40        0.51          17.1                          0.50      0.66        42.9 34            0.08        0.09            0              Y            0.35        0.40          4.7                          0.80      1.11        91.6*              Y 35          0.12        0.15            0                            0.27        0.39          4.0                          0.70      0.67          50.0 36          0.19        0.23            0                            0.30        0.35          2.0                          0.51      0.61          34.1 37            0.16        0.28            0.3                          0.51        0.90          77.3                          1.31      1.99          99.9*            Y 38          0.25        0.36            2.4            Y            0.51        0.99        84.8                          2.11      1.90        100.0.              Y 39            0.04        0.05            0                            0.13        0.27          0.2                          0.91      1.17          93.7'            Y 40            0.75        1.10          91.1            Y              1.20        1.70        99.6                          1.70      2.20        100.0'              Y 41            0.31        0.43            7.4            Y            0.53        0.90        77.3                          1.03      1.41          98.2*            Y 42            0.67        0.98          84.1            Y              1.50        1.72        99.6                          2.86      3.14        100.0.              Y 43            0.41        0.67          44.8            Y            0.74        1.20        94.6                          1.69      2.30        100.0'            Y 44            0.08        0.06            0                            0.14        0.20          0                            0.35      0.46          10.6              Y 45            0.11        0.13            0                            0.22        0.39          4.0                          0.51      0.67          44.8*
46            0.06        0.15            0                            0.22        0.32          1.0                          0.57      0.76          59.9 47            0.35        0.25            1.9                          0.80        0.92        79.4                          1.23      1.42          98.3'            Y 48            0.15        0.36            2.4                          0.51        0.79        63.7                          0.59      1.15          93.1'            Y 49            0.27        0.29            0.4            Y            0.58        0.51        28.8                          1.14      1.73          99.7*            Y 5o            0.11        0.22            0              Y            0.43        1.04        88.1                          1.49      2.00        100.0              Y
: g. s9                                          553.6                                        E      -1860.8                                              ==  3833.8 3
E cas                  PF= 553.6150 = 11.1%                                      FF= 1860.8/50 = 37.2%                                    PF= 3833.8/50 = 76.7%
u5 3 CM 33    (1)    Y indicates that turbine pedestal did impact the operating floor. For all other cases, no impact occurred.                                                                    50 Relative diaphragra drift exceeds the limits of applicability of the bilinear force-deflection relationship used for the operating floor so that wall drifts and probability of severe wall distress are likely to be overpredicted to some extent for these cases.                                              I
 
Chapter 6                                                                                              Page 6-75 Chanter 6                                                                                              Page 6-75 interaction analysis considered this aspect for      core damage, generally have high median seismic Diablo Canyon, and it was estimated that            capacities relative to the median reference ground east/west shear wall responses are reduced by        motion. In addition, the important structures and a median factor of FGW = 1.06, with estimated        equipment have HCLPF capacities that are randomness 0RGM = 0.02, and uncertainty              generally in excess of 2.25 g average spectral 0 uow = 0.06.                                        acceleration. (The exceptions are noted below.)
The following summarizes the findings of the fragility evaluation with regard to several Table 6-22 includes the effects of these three categories of structures and equipment, and additional parameters on the fragility estimate for highlights those items that may contribute to the turbine building. The final fragility estimate seismic risk due to relatively low demonstrated for the turbine building for use in the seismic capacity. Only the salient information that is probabilistic risk assessment is:
specific to the Diablo Canyon fragility evaluation V                                                    is summarized. Details are included in the
                = 4.87 g                                comprehensive technical reports (Kennedy, 1988;
                = 0.26                                  Kipp, 1988) where descriptions of the methods Pc used, example calculations, interpretation of the
                = 0.33                                  fragilities, and failure consequences are discussed.
HCLPF Ta= 1.84 g                                      Again, it should be noted that the reported v
median fragility capacities,      ' are in terms of the 5 percent damped average spectral acceleration The median and HCLPF capacities are in terms of            averaged over the 3 to 8.5 hertz range.
an average          5 percent        damped spectral acceleration averaged over the 3 to 8.5 hertz              STRUCTURAL FRAGILITY RESULTS range.
The fragility parameters associated with the Results and Conclusions                                    important        structures    are      presented        in Table 6-23. The fundamental frequency of the The fragility evaluation established that the Diablo      stpucture, failure mode, fragility parameters Canyon sifety-related structures and equipment            (S, OR, and Pu ), and          HCLPF capacity are that are important to evaluating the probability of        included in the table.
Table 6-22 TURBINE BUILDING FRAGILITY ESTIMATE INCORPORATING ADDITIONAL VARIABLE PARAMETERS Median
_.X V          Randomness              Uncertainty              HCLPF or F OR                    Ou                    S, (g)
Nonlinear Time History Results            4.59 g              0.23                  0.29                  1.95 g Modeling                                  1.0                                        0.15 Directional Effects                        1.0                  0.12 Incoherence of Ground Motion                1.06                0.02                  0.06 Fragility Estimate                        4.87 g                0.26                  0.33                  1.84 g Diabln Canyon Power Plant I n  Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 6                                                                                                Page 6-76 Chapter 6                                                                                                Page 6-76 Table 6-23 DIABLO CANYON STRUCTURE FRAGILITIES (Based on hazard defined over 3 to 8.5 hertz range.)
Fundamental                                Spectral Acceleration Capacity Frequency                                v Structure                    Hertz          Failure Mode              a_                    HCLPF (a)
Containment Building                      4.1    Exterior Shell Shear            8.42  0.26  0.30        3.34 Concrete Internal Structure              8.9    Internal Structure Shear        6.91  0.20  0.31        2.98 Intake Structure                        23.3    North Wall Shear                8.55  0.28  0.31        3.23 Auxiliary Building                        8.2    North/South Shearwalls          5.79  0.21  0.26        2.66 Turbine Building                          8.6    Shear Wall, Column 31            4.87  0.26  0.33        1.84 9.0    Block Wall                    >10.0 Refueling Water Storage Tank              7.6    Concrete/Bedrock Flexure        9.92  0.29  0.36        3.40 Condensate Storage Tank                          Comparison to RWST            >10.0 DG Fuel-Oil Storage Tank                Buried  Rupture                      >10.0      -      -            -
Auxiliary Saltwater Piping              Buried  Rupture                          9.23  0.18 0.21          4.85 The containment building, concrete internal                nonlinear analysis, very few were found that met structure and intake structure all have very high          Criterion 4 (see page 6-64), related to high median and HCLPF capacities, and thus                      spectral acceleration in the 3.0 to 8.5 hertz range.
contribute very little to overall Plant risk.              This fact alone demonstrates the lack of seismic The auxiliary building fragility evaluation shows          vulnerability of the Diablo Canyon turbine median and HCLPF capacities of 5.79 g and                  building. Two of strongest ground motions that 2.66 g, respectively, which, although not as high          have ever been recorded anywhere in the world as the three concrete structures identified above,          (Tabas and Pacoima Dam) only have a slight are sufficiently high so as not to contribute              potential of causing measureable damage to the significantly to Plant seismic risk.                      turbine building. It should be further noted that the fragility estimate of the turbine building was The turbine building has the lowest median                  heavily influenced by the selection and equal seismic capacity of all the civil structures. The          weighting of the 25 time histories used in the median spectral acceleration capacity for the              study. The highest probability of severe distress turbine building is estimated to be 4.87 g, based          was related to those records that required upon a shear-wall failure due to east/west                  substantial frequency-dependent modifications to response, with randomness and uncertainty                  scale them up to the level required for the Diablo variabilities of 0.26 and 0.33, respectively. The          Canyon site. In contrast, those very strong motion resulting HCLPF spectral acceleration capacity is          records          requiring          only            minor 1.84 g. Because the turbine building houses the            frequency-independent        scaling      resulted      in diesel generators, the component cooling water            relatively small potential for severe distress. Thus, heat exchanger, and the 4160 V (vital) electrical          the turbine building fragility estimate is likely to be system, the potential for severe distress of the            conservatively biased. Particularly, both Pit and turbine building is likely to be a significant              Pu are likely to be too large.
contributor to overall Plant risk. However, it should be noted that in searching for actual              The main outdoor storage tanks for refueling earthquake records for use in the turbine building        water and condensate, the buried diesel generator Diablo Canyon Power Plant F    Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Charter 6                                                                                          Page 6-77 Chanter 6                                                                                          Page 6-77 fuel oil storage tank, and buried piping all have    most critical component is the steam generator, very high seismic capacities, and thus are            which has a median spectral acceleration capacity negligible contributors to overall Plant risk.        of 6.96 g, based upon the failure of the upper lateral support due to the formation of a plastic EQUIPMENT FRAGILITY RESULTS                          hinge in the ring band. The fundamental frequency of the steam generator is 8.8 hertz, which corresponds closely to the frequency of the Table 6-24 contains fragility descriptions for all concrete internal structure. Excessive movement the equipment that was included in the of the steam generator after loss of the, upper probabilistic risk assessment. The table includes support is assumed to result in rupture of the main the component location, frequency, method of steam system piping and other attached lines.
seismic qualification, critical failure mode, sfurces of information, and fragility parameters (&sect;, pit,    The components for the major balance-of-Plant and flu). As a means of reference, the resulting      safety systems, such as the residual heat removal, HCLPF capacity is also listed. Fragility derivations  safety injection, and component cooling water were conducted for each of the components and        systems were found to have high capacities. The are reported for those items that have a median      failure modes for these components were spectral ground acceleration capacity less than      generally associated with anchorage.              Pumps, 10.0 g. Based upon a review of the seismic            piping, and valves are estimated to have median capacity of a sample of such equipment, it was        capacities greater than 7.7 g and HCLPF determined that equipment that possessed median      capacities greater than 3.4 g. Similarly, tanks and spectral ground acceleration capacities greater      vessels have high capacities, with median than about 10.0 g also possessed HCLPF                capacities and HCLPF values estimated to be capacities in excess of 3.0 g. Due to the fact that  greater than 6.7 g and 3.0 g, respectively. The there is an extremely low frequency of occurrence      component cooling water heat exchanger was of a 3.0 g. average spectral acceleration              found to be the weakest of all mechanical system earthquake at the Diablo Canyon site, and that        components, based upon the failure of the other lower capacity equipment would govern the        longitudinal strut anchor bolts.          The median Plant seismic risk, it was judged that the high        seismic capacity of the heat exchanger was capacity equipment would not contribute to the        estimated to be 6.31 g, with randomness and overall Plant risk. Therefore, detailed fragility    uncertainty variabilities of 0.27 and 0.28, descriptions were not included for components        respectively, providing a HCLPF capacity of having median capacities greater than 10.0 g          2.55 g.
based on the capacity factor alone. Equipment in this category are labeled with a ">10.0" in the      Components of the diesel generator system exhibit spectral acceleration capacity column.              -high seismic capacities. For the diesel generator itself, fragility is based upon failure of the skid The seismic capacity for most of the                  anchor bolts and seismic stays, which occur at a safety-related equipment items is relatively high    spectral acceleration of 7.79 g. The most critical with respect to the median reference ground          element of the diesel generator system is the diesel motion. In all cases, the equipment fragilities were  generator control panel which was computed to based upon Plant-specific component analyses or      have median and HCLPF capacities of 4.55 g and qualification test data and involved the use of very  2.24 g, respectively, based upon a generic little generic information. Even for generic          structural failure. This fragility is based upon the component categories, the fragilities were based      seismic qualification dynamic testing of the upon the review of sample calculations from          cabinet and, as such, is not based on actual specific Diablo Canyon qualification analyses. The    fragility testing leading to an actual failure state.
piping and major equipment components                Because the control panel is situated on the associated with the reactor coolant loop have        basemat of the turbine building, the demand generally high capacities with respect to the        acceleration for the seismic qualification test was reference ground-motion spectra demands. The          relatively low. Thus, the reported fragility may be Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Table 6-24 DIABLO CANYON EQUIPMENT FRAGILITIES OR                                        (Based on hazard defined over 3 to 8.5 hertz range.)
en Spectral Acceleration Capacity Cu Fundamental      Method of Seismic                                Information      X                        HCLPF Syatem and Component            Frequency          Qualification      Failure Mode              Source          sag      PR.~
2 1L      W
-        Reactar Presure Vessel        12-14 HZ (H)    Dynamic Analysts        Support Pie Shaer        WSuommary Data      8.71  0.25    0.33    3.34 Reactor Inlernast            16-20 He (91)    Dynamic Analysis        Lower Core Plate        W Summary Data    10.54    0.40    0.26    3.55 Steam OGenrators              9 Us(H)          Dynamic Analysis        Upper Lateral Support    WSummary Data        6.96  0.31    0.29    2.55 Pressurizer                  is Hz (H)        Dynamic Analysis        Seismic Support Lug      W Sommary Data    11.46    0.31    0.44 Pressurizer Safety Valves    Flexible Piping  Static Anayl~slaTtst    Ceneric Funclion        M397, 4401        >10.0        -
Power Opetated Reliel Valves  Flexible Piping  Static AsnaiyutiTest    Generic Functlon        M397. M401          7.62  0.30    0.42    2.32 Reactor Coolant Pumps        7 HS:(H          Dynamic Analysis        Lower Motor Stand        M.355, M442, M429    8.82  0.37    0.32    2.81 Control Rod Drives            7-10 He (H)      Dynamic Analysis      .Hel d Adapter Yield      W Summary Data    11.71    0.41    0.34    3.40 MaSSPiping                    7-9 Hz CH&V)    Dynamic Anailysi        Rupture                  W Summary Data    >10.0        -        -
hS'RPump,                    Flexible Piping  Dynamic Analysis        Pump Hold Down Bolts    WSummary Data        1.31  0.33    0. Z2    3.35 RHB Heat Bxchaonjer          12 Hrz (H)      Static Analysis        Anchor Boilt & Upper    W Summary Data.      8.09  0.24    0.27    3.48 Lateral Support          M462. M474 Si Accumulators              23-34 HZ (H)    Static Analysis        Anchor Studs            !WSummary Data. 10.01    0.29    0.19    4.53 St Pumps                      >33 Hz (H)      Static Analysis        Pump Hold Down Bolts    W Summary Data    10.94    0.34    0.18    4.64 Boirn incection Tank          1 S-17 Hz (H)    Static Analysis        Anchor Belts            W Summary Data      8.46  0.27    0.19    3.96 nOMPONENT COOLING WATMi
          .CcqePumps                    Flexible Piping  Static Analysis        Pump Hold Down Bolts    MOO6,MOO?, M318      2.53  0.29    0.21    3.74 c"W Heat Exchangers          13 Hx (H)        Dynamic Analysis        Longitudinal Strut Bolts MOOS, M336. M475    6.31  0.27    0.21    2.55 CCW Sueje Tank                  12Ha (H)      Static Analysis        Seismic Lateral Brace    M319                7.22  0.33    0.22    2.91
      *J5IlI'4kT Awn* VOtLUME C"ONITROL chatrlng Pumps (centrliugal)  >33 itZ (eH)    Static Analysis        Motor Hold Down Bolts    W*Summary Data    10.16    0.31    0.19    4.45
* Chttlng Pumps (reciprocal)    >33 liz (H)      Static Antlysis        Pump Held Down Bolts    W summary Data    >10.0        -          -
J .
0    Atxinllry Saltwater Pumps    43 Hz (H)        Static Analysis        Pump Mounting Bosll      M009              >10.0 7      C Pumps                      >33 Hlz (1)      Static Analysij        Foundatlon Soits        W Summary Data      8.65  0.29    0.20    3.05 ong      Spray Additive Tank                            Static Analyslis 24 liz (H)                              Support ?WdISheil        W Summary Dais      6.78  0.30    0.18    3.07
 
0                                                                      Table 6-24 (Continued)                                                                                C)
:3-09 DIABLO CANYON EQUIPMENT FRAGILITIES I                                                        (Based on hazard defined over 3 to 8.5 hertz range.)                                                                  a m                                                                                                                                                                              0%
19                                                                                                                                                            Spectral Acceleration Capacity Fundamental        Method of Seismic                                    Information      X_                  HCLPF
-        System and Component                            Frequency            Qualification            Failure Mode              Source      ______            F    (q)
U    MAIN STEAM 4        MS Isolation Valves                            Flexible Piping  Dynamic Analysti/Test        Actuator Support        W067. M463, M469  >10.0 MS Safety Valves                              Flexible Pipln    Dynamic ADnOAlyicslct        Genoric FUnction          1391            >10.0 us PORv*S                                                        Dynamic Anaslylsrfut        Oneetlc Funclton        U3397                      0.74  0.36    3.51 AIW Pumps (Motor Driven)
                                                      .42 Fi (H)        Stalic Analysis              lump Held Dowd Bolts    1132IA              710.0 APW Pumps (Turbine Driven)                    4S Its (H)        Static Analysts              Pump Hold Down Bolts    M320. M321          7.71  0.2*9  0.21    3.38 DI2-SMGTERAIQ D.O. Fuel Oil Day Tank                        10 Hz (V)        Static Analysts              Bottom Plate Rupture. 1323            >10.0 D.O. Pucl Oil Pumps*hullters                  Flexible Pipln    Static Analyst.              Filter Anchor Bolts    M324. 1326          8.33  0.27  0.23    3.65 Fuel OUl Shutoff Vat"                    Flexible Piping  None                        Fusible Link            Data Bale        .10.0 D.0.
D.G. Air Start Compretnor                    >33 He (H)        Oceneric Anchorage Analytlis Hold Down Bolts        M1323            >10.0 D.G. Air Star Receiver                        26 H2 (H)        Dynamic Analyasi            Hold Danr Bolts          ,2903            >10.0 Desel  OGenerators                            17 lz (")        Dynamic Analysis            Skid Adchar Bolts      M423-M426            7.79  0.26  0.10    3.64 D.0. Radilaorl*ater Pump                      17 Its (H)        Dynamic Analysis            Anchor Boitlng          11323                0.76  0.29  0.24    3.66 O.O. Itelt liceaoriAls Filter                Flexlble Piping  Dynamic Analyslh            Filter Suport Rod Weld  M271. M449        >10.0 13 H* (H)        Taill                        Structurat              M346, M364          7.40  0.29  0.35    2.57 D.O  Entelistou Cubical D,. Control Panel                                              Test                        Chatter                M347. M3641.M464. 7,77  0.25  6.14    4.08 M482 a0 Hz (H)        Test                        Structural                                  4.55  0.30  0.13    2.24 D.0. Main l:ad Terminal;Box                                      Static Analysts              Attach mcot-Ftllet Weld 10348            >10.0 Cool CONTAINn'ENT 1F1a711n1            TILATIOer Continent Fane Cooler                          23 HZ (H)        Dynamic Analysis            Foot Plate/Embed. Weld  M399. M490. M420. 8.10  0.31  0.33    2.02 M421. M448 C'ONTR*OL ROOM V1EN13iATnOx Supply Pans                                    >33 Hz (H)        Static Analysli              Support Bolting        11056                9.79  0.33  0.24    3.82 G7 ;    AC Ualls/Compreaaors                            >33 Hz (H)        Static Analysst              Anchor Dolt            MU2. M312        >10.0        -
Control Cablaots                              21 Hx (H)        Test                        Structural              M455              >10.0        -
600V            ntt~PARINVENlvnIDC A=IL~lUzIANISPWKADIN5Sl            NV    1  11' supplylflrturn Fans                            >33 liZ (K)        Ststl Analyst.              ENp-1n    Ancbor      M1310              11.1    0.33  0.30    3.95 Backdraft and Shut-Ofl Dampers                >33 Hz (H)        Static Analysis              Structural              wa30s            >10.0        -      -      -
                                                                                                                                                                                '-7
 
Table 6-24 (Continued)                                                                          (-3 01 DIABLO CANYON EQUIPMENT FRAGILITIES                                                                          13 (Based on hazard daeined over 3 to 8.5 hertz range.)                                                        en Spectral Acceleration Capacity Fundamental      Method of Seismic                          Inrormation          x                    HCLPF C'    System and Component            Fraguency          Qualification        Failure Mode        Source            SawZ    OR-P            JW.
        .~4190y tYITALI IrLHCDic POWERk 7HzK(H)        Test                    Chatter            M049, M    ,315.
h13$6,  3.53  0.33  0.23    1.31 Static Analysis        Guide Rod Sending  b1373, M377-380.      7.44  0.31  0.23    2.95 potential Transformer$ (But F)  21 Hz (an      Static A=aIysls        Support USl/Embed. M4049.14375. U4416,  10.83  0.31  0.3. 3.47 Weld 35 Hx (H        Static Analysia        Support Leg/Embed. M4049.M375. M4416. >10.0 Weld              M450 11 Hz (H)      Stati Analysts          Anchor Welds      M012. 14373. M414. 10.76                    3.39 Safeguard Relay ftnel                                                                                                    0.34  0.36 M430 1,23 flC PhPVCOP2C  poWHE
                                                >$3 He (H)      Test                                                                                    2.74 Haitery-Raki                                                            Structural        M010, 1,054. It)64    6.04  0.30  0.18
                                                >33 HE (1)      Static Analysis        Lonlitudinal PEd    4013, W4032.M010,    11.91  0.26  0.22    3.40 Restraint          M4207 Battery Charge"                  2I Hz (H)      Test                    Structural        M034, b4364. M433. 9.93  0.34  0.40    2.93 M462 SwllchearelBreaker fanels      7 Hz (H)        Test                    Structural        M014, U051. ld354      6.67  0.35  0.28    2.36 Instrusment Breaker ?sanel      >20 112(K      Static Analysis        Slip-Nut Faluten  MO$IA                >10.0 Z Hz(H)
Test                    Structural        Mo1s. M016. M355,      6,32  0.31  0,24    2.It Inverters                                                                                  M411, M436. U451, M467 610V. (VrTA1~ WI WCratC POWER 416OVI490V Transform~ers        3 Hz (H)        Static Analysis        Structural        M052, Waltdonwn        3.34  0.20  0.20    2.42 Breaker Cabinets (Load Centers) is Hi (H)      Static Analysis        Anchor Stitch Weld M017. M364          >10.0        -
Aux~l~ary Relay Panel          29 Hz (H)      Test                    Structural        M1I3, M364            7.25  0.21  3.15    3.57
=    at
-E                                                              Test                    Switch Function
-l    0        main Coatral Boards            >33 Hz (H)                                                W Summary Data,      >10.0 Dynamic Analyals        Structural        MO4S6. 4432            7.77  0.31    0.27    2.98 tIn 'a        Hot Shzutdown Panel            >31 Hz (H)      Test                    Switch fuanclon    b4317. M383. M342.      7.60  0.27    0.25    3.22 to 0                                                          Static Analysli        Structural        M479, 14482            7.27  0.30    0.14    3.5Z Asmiltiary Safeguards Cabinet  9-13 Hz: (H)    Test                    Structural        M317. 3534. M359 >10.0 rug                                                                                                                                                            ,01
.5 a sn o *~                                                                                                                                                          00 H-0.
 
"*                                                                    . Table 6-24 (Continued) 0e                                                  DIABLO CANYON EQUIPMENT FRAGILITIES ci                                                  (Based on hazard defined over 3 to 8.5 hertz range.)
CID                                                                                                                                                Spectral Acceleration Capacity S. System and Component                Fundamental            Method or Seismic                          Information                          lICLPF Frequency                Qualification    Failure Mode            Source H nS ce  CONTROL Proess Control and Pr'otection System 8-20 Hz (i)            Test                Structural            IWLI*. M3ss        10.78  0.39  0.28    3.07 Tan                  Stnrctornt              ut17, M355        12.63  0.37  0.28    4.32 Solid State Pretactin System                                Test Reactos Trip Switcbltar              8 He (in              Test                Stracturil            M6317,M3S5          7.90  0.30  0.26    3.14 4,A*
Reliltamce & Temperature Detectors    Not Given                                  Structural            U41S              >10.0 8Preuure & AP Translutter            >33 Hz (H)            Test                Structural            h041                8.93  0.27  0.20 Acexisay, Relay Rack                  12-20 z (HI)          Static Analysis      Anchor Bolts            M317, MISO. M359 >10.0 Local Starter Boards                  IS us (H)              Test                Strutural              M4S4            >10.0 Molded Case Cir*lut realke            >33 Hz 01)            Teat                Structural              M476            >10.0 Valve Uimit Switches                  >33 Hs (H&V)          Test                Generic Functlon      86344            >10.0 5-20 Hz (H&V)          None                Rupture Prom Impact    Data Baue          7.05          0.32    2.61 Implsb Lines Coatatomonl Purge Valves                    H*
                                                  >3) H{l&V)            Static Analysis      Actuator Attach. Boelt M432              >10.0 0t-SIte FPower 230CVL                  ilexible              None                Generic Failure        DatsaBae            1.69  0.24  0.20    0.n9 500KV                                                                                                        0.11  0.24  0.20 Van~tatleKinIUpestnne r tBa  l        24 HZ (t)              Test                Generic Structural    A1054              7.38  0.31  0.27    1.91 8OP Npln and  "Sapporru                Flexibie Piping        Dynamic Analasis      enecric Support      M0280. M3St        11.01  0.40  0.39    3.01 Hand, Relief. Solenoid. & Check        Flexible Piping        Dynamic Analysi      Generic Function      Data Bane        >10.0 Valves Air and Motor Operated Valves          Flexible Piping        Dynamic Analysib    Generic Punction      M07, M401        .17.10  0.3I  0.60    3.57 Cable Trays and Supports              Flexible Trays        Static AnalysI*s    Generic Support        M2094--1I23      >10.0 HVAC Dueting and Suppoert              Flexible Dunctinsg    Static Analysis      Generic Support        14214-M218          9.78  0.35  0.48    2.49
  - n 0s
 
Chapter 6                                                                                        Page 6-82 Chapter 6                                                                                        Page 6-82 excessively conservative; however, it is difficult to The main components of the various critical justify higher values based upon qualification test  safety-related ventilation supply systems have data alone.                                          relatively high seismic capacities. The failure of the heating, ventilating, and air conditioning (HVAC) ducting is based upon the generic failure The fragility description of electrical cabinets was  of the ducting supports. The supports have a based upon the documented results of their            median spectral acceleration capacity of 9.78 g.
corresponding seismic qualification tests. The loss  Bending or slight buckling of the HVAC ducts is of function due to acceleration-sensitive failures    likely at accelerations less than the support (for example, relay chatter), when important, and    capacity, but is not expected to result in failure of the loss of function due to generic structural        the ventilation systems.
failure were generally based upon a conservative factor applied to the qualification acceleration test The fragility of offsite power is based upon the level. The structural capacities of the important    failure of ceramic insulators, transformers, and electrical components are high, and have              circuit breakers, and is generated from a data adequate factors of safety. The weakest of the        base pertaining to the performance of power electrical    elements      is the    4160 V/480-V  transmission components for both nuclear and transformer which has median and HCLPF                non-nuclear power stations in real earthquakes.
capacities estimated to be 5.34 g and 2.42 g,        Review of these data shows clear evidence of respectively.                                        superior performance of the lighter 230-kV systems over the 500-kV systems. This is Loss of function due to acceleration-sensitive particularly true where live-tank, air-blast circuit failures were considered to be of sufficient          breakers are used in the 500-kV systems. The importance to warrant fragility estimates for the    median capacities for the 230-kV and 500-kV following electrical cabinets:
switchyards are 1.69 g and 0.81 g, respectively.
Several items were treated in a generic manner Diesel Generator Control Panel                        due to the quantity of such items in the Plant.
These included balance-of-Plant piping, air and 4-kV Switchgear motor-operated valves, cable trays, and heating.
4-kV Safeguard Relay Panel                            ventilating, and air conditioning ducting and supports. In general, these had relatively high Main Control Boards capacities, with median spectral acceleration Hot Shutdown Panel                                  capacities of approximately 6.0 g or greater. The basis for the fragility of balance-of-Plant piping is generic failure of the piping supports.
Except for the 4-kV switchgear, the chatter failure mode capacities, when evaluated by means      Conclusion of relay-specific Generic Equipment Ruggedness Spectra, are sufficiently high so as not to          In summary, based upon the estimated fragility contribute significantly to Plant seismic risk. The  capacities of the important safety-related 4-kV switchgear, however, contains a large            structures and equipment, it is judged that the number of overcurrent relays, which are primarily    largest individual contributor to seismic risk is the sensitive to vertical excitation. The median and      turbine building, because the probable loss of HCLPF chatter failure capacities were estimated      function of the 4-kV switchgear due to to be 3.53 g and 1.31 g, respectively. The 4-kV      acceleration-sensitive failure is recoverable by switchgear chatter failure mode is recoverable by    operator action. Several other componerits operator action, and the probabilities associated    constitute much lesser contributors to overall with operator action were included in the model      Plant risk, and no other structures contribute to of the system.                                        the seismic risk.
Diablo Canyon Power Plant
-V      Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Pages 6.83 through 6.220 of Attachment 6 to PG&E Letter DCL-1 1-097 have been redacted from public disclosure
 
Chapter 6                                                                                        Page 6.-221 Chapter 6                                                                                        Page 6-221 REFERENCES                                            Kennedy, R. P.. 1988, Seismic fragilities of structures and components at the Diablo Canyon power plant, July.
American Nuclear Society and Institute of Electrical and Electronic Engineers, 1983,        Kazarians, M., and Apostolakis,              G., 1982, Probabilistic risk assessment procedures              Modeling rare events: The frequencies of fires guide; a guide to the performance of                  in nuclear power plants: presented at the probabilistic risk assessments for nuclear            Workshop        on        Low-Probability/High-power plants: sponsored by the U.S. Nuclear            Consequence Risk Analysis, Society for Risk Regulatory Commission and the Electric                Analysis, Arlington, Virgina.
Power Research Institute, NUREG/CR-2300, April.                                            Kazarians, M., Siu, N., and Apostolakis, G.,
1985, Fire risk analysis for nuclear power Fleming, K. N., and Mosleh, A.,                1985,      plants: methodological developments and Classification and analysis of reactor operating      applications: Risk Analysis, v. 5, no. 1.
experience involving dependent events: EPRI Kipp, T. R., and others, 1988, Seismic fragilities NP-3967, Interim Report, June.                        of civil structures and equipment components at the Diablo Canyon Power Plant: NTS Institute of Electrical and Electronics Engineers,        Engineering Report 1643.02.
1972, IEEE guide for the statistical analysis of thermal life test data: IEEE Std. 101-1972.      Lindley, D. V., 1970, Introduction to probability and statistics. Part 1: Probability, Part 2:
Kaplan, S., Apostolakis, G., Garrick, B. J., Bley,        Interference: Cambridge University Press.
D. C., and Woodard, K., 1981, Methodology Mosleh, A., and others, 1987, A data base for for probabilistic risk assessment of nuclear probabilistic risk assessment of LWRs:
power plants: PLG-0209, June.
Pickard, Lowe and Garrick, Inc., PLG-0500.
Kanaan, A. E., and Powell, G. H., 1973,                Pacific Gas and Electric Company letter from DRAIN-2D, general purpose computer                    Mr. Bruce Smith, dated July 5, 1988.
program for the dynamic analysis of inelastic plane structures: EERC Report No. 73-6,          Pacific Gas and Electric Company Mechanical (Heating, Ventilating, and Air Conditioning)
Earthquake Engineering Research Center, University of California, Berkeley (Revised          Calculation 86-9.
1975).                                          Pickard, Lowe, and Garrick, Inc., 1986, Three Mile    Island    Unit 1    probabilistic        risk Kennedy, R. P., and others, 1980, Probabilistic            assessment prepared for GPU Nuclear seismic safety study of an existing nuclear          Corporation: PLG-0525, December.
power plant: Nuclear Engineering and Design,
: v. 59, no. 2, p. 315-318.                        Pickard, Lowe and Garrick, Inc., 1983, Seabrook Station    probabilistic  safety      assessment:
Kennedy, R. P. and Ravindra, M. K., 1984,                  Prepared for Public Service Company of New Seismic fragilities for nuclear power plant risk      Hampshire and Yankee Atomic Electric studies: Nuclear Engineering and Design, v.          Company: PLG-0300, December.
79, no. 1, p. 47-68.                              Pickard, Lowe, and Garrick, Inc., 1986, Beznau Nuclear Power Plant risk analysis: Prepared Kennedy, R. P., Wesley,, D. A., and Tong, W.                for Nordostschweizerische Kraftwerke AG, H., 1988, Probabilitic evaluation of the              PLO-0510, draft, October.
Diablo Canyon turbine building seismic capacity using nonlinear time history analyses:  Pickard, Lowe, and Garrick, Inc., User Manual NTS Engineering Report 1643.01.                      for BEST4 Module of RISKMAN4.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                Long lerm Seismic Program
 
Chapter 6                                                                                  Page 6-222 Chper6Pae6-2 Siu, N., 1982, Physical models for compartment      The U.S. Nuclear Regulatory Commission, 1985, fires,    Reliability      Engineering, v. 3,    Evaluation of station blackout accidents at
: p. 229-252, 1982.                                nuclear power plants, NUREG-1032, draft, May.
Siu, N., and Apostolakis, G., 1982, Probabilistic models for cable tray fires: Reliability      Wang, T. Y., Bertero, V. V., and Popov, E.P.,
Engineering, v. 3, p. 213-227.                    1975, Hysteretic behavior of reinforced concrete framed walls: Reporq No. EERC Smith, B.D., 1988, Battery Life: response to          75-23. Earthquake Engineering Research PG&E-1123-RPI-4.                                  Center, University of California, Berkeley.
Diablo Canyon Power Plant
: a. Pacific Gas and Electric Company                                          Long Term Seismic Program
 
Enclosure Attachment 7 PG&E Letter DCL-1 1-097 Chapter 7 of the 1988 Long Term Seismic Program Final Report 1
 
Chapter 7 DETERMINISTIC EVALUATIONS To Partially Address Element 4 of the License Condition ELEMENT 4 OF THE LICENSE                            earthquake magnitude was quantified, as CONDITION                                            described in Chapter 3. Step 2, which is described in Chapter 4, involved the development of the PG&E shall assess the significance of          site-specific ground motions for the 50 percent conclusions drawn from the seismic              and 84 percent probability of nonexceedance reevaluationstudies in Elements 1, 2, and 3,    levels. Step 3 used information from the utilizing a probabilistic risk analysis and    soil/structure interaction studies (Chapter 5) and deterministic studies, as necessary, to assure  applied it to develop Plant responses resulting adequacy of seismic margins.                    from the site-specific ground motions. Step 4 compared these responses with the seismic qualification basis responses for the Plant. It also OBJECTIVE                                            addressed the effects of responses due to the The objective of the deterministic evaluations was  site-specific ground motions that exceed those for to augment the probabilistic risk assessment to      the seismic qualification basis. Step 5 involved the assure the adequacy of Plant seismic margins, as    determination of the capacities for plant structures specified by Element 4 of the license condition. and components. These capacities were derived This objective was achieved by:                      from the fragility evaluations described in Chapter 6. Finally, in Step 6, the capacities were
* Comparing Plant responses as calculated from      compared with the demands (Plant responses) to the site-specific ground motions due to the    assess the seismic margin of the Plant above the maximum earthquake on the Hosgri fault          demand resulting from the 84th percentile ground zone with those used as the bases for Plant    motions due to the maximum magnitude design or for the earlier Hosgri evaluation, as earthquake.
appropriate (note that we will use the term "qualification basis" to mean the combination  DETERMINISTIC COMPARISONS of the 6riginal design basis and the subsequent Hosgri evaluation basis).
Plant Responses to Site-Specific Ground 0  Assessing the Plant capacity margins over the    Motions demands (Plant responses) resulting from the 84th percentile ground motions due to the maximum magnitude earthquake.                    DEVELOPMENT OF SITE-SPECIFIC GROUND MOTIONS SCOPE The confirmation of the controlling seismic source The deterministic evaluation of the Plant drew      and its tectonic environment are described in from essentially all activities of the Long Term    Chapter 2 of this report. The source was identified Seismic Program (Figure 7-1). The evaluation        as the Hosgrl fault located at a distance of about consisted of six steps. In Step 1, the maximum      4.5 kilometers from the Plant site. The maximum Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 7                                                                                                      Page 7-2 Page 7-2 Chapter 7 Deterministic Evaluation                                Probabilistic Risk Assessment Studies
  'Seismic qualification basis is a combination of original design and Hosgri evaluation basis.
Figure 7-1 Deterministic evaluation process.
Diable Canyon Power Plant In    Pacific Gas and Electric Company                                                            Long Term Seismic Program
 
Chapter 7                                                                                                Page 7-3 Chapter 7                                                                                                Page 7-3 magnitude earthquake              on this source, as    ground-motion spectral shape used for the established in Chapter 3, is an earthquake of.            deterministic evaluation was similar to that used magnitude 7.2 Mw.                                        in the probabilistic risk assessment. At the time the soil/structure interaction analyses were This earthquake was used in the ground-motion            performed, the site-specific ground-motion study to develop appropriate ground response              spectra had not been finalized. To support the spectra. Because there is a lack of agreement in          fragility analyses, a "best estimate" spectrum was the nuclear industry on the selection of the level        established, recognizing that the soil/structure of ground motions for Plant reevaluations, the            interaction analysis results could be adjusted for site-specific ground motions have been specified          compatibility with the site-specific ground spectra, at both the 50 percent and 84 percent probability        as appropriate, at a later stage in the Program.
of nonexceedance levels. The details of the development of those ground motions are Figure 7-3 shows a comparison of the provided In Chapter 4. Site-specific horizontal ground-motion spectral shape used in the and vertical ground-motion response spectra for 5 soil/structure interaction analyses with the percent damping corresponding to the maximum site-specific ground-motion spectrum at the 84 earthquake magnitude are shown in Figures 4-22 percent probability of nonexceedance level. To and 4-23, respectively.
permit a meaningful comparison of the shapes of these two ground-motion spectra, the ground A comparison of the site-specific response spectra        response spectrum used in the soil/structure (for 5 percent damping) corresponding to the            interaction analyses (Figure 5-22) has been horizontal ground motions due to the maximum              scaled uniformly (frequency-independent scaling) magnitude earthquake and the 1977 Hosgri                  such that the average spectral acceleration (Newmark) evaluation spectrum is shown in                between 3 and 8.5 hertz is the same as that of the Figure 7-2. It may be seen that the Hosgri                84 percent probability of nonexceedance evaluation spectrum envelops the site-specific            site-specific ground-motion spectrum (1.94 g). A 50th percentile spectrum at all frequencies and          comparison of these spectra shows that the the 84th percentile spectrum at all frequencies          site-specific    ground-motion spectrum closely less than about 15 hertz. The magnitude of the            matches the soil/structure interaction analysis exceedance at frequencies above 15 hertz is              input spectral shape. Because the soil/structure approximately 10 percent.                                interaction analyses are linear elastic, their results can be scaled uniformly. Accordingly, the soil/structure interaction analysis results can be DEVELOPMENT OF PLANT RESPONSES                            used with small adjustment factors, to obtain Plant responses to the selected final site-specific ground To generate in-structure response spectra for use        motions.
In the fragility evaluations for the probabilistic risk assessment, detailed soil/structure interaction analyses were performed, as described in                  The procedure used to convert the results of the Chapter 5.      These      s~oil/structure interaction  soillstructure interaction analyses into Plant analyses were performed deterministicaily, using          responses for the site-specific ground motions is the most current site-specific acceleration              illustrated in Figure 7-4. It requires the use of two response spectra available at the time.                  factors:
Although the primary purpose of these analyses            1) A spectral shape factor (F,) that accounts was to generate inputs to the fragility analysis and          for the minor variations between the the probabilistic risk assessment, it was recognized          site-specific ground-motion spectrum and the that they could also provide data useful in the                soil/structure interaction input spectrum. This Plant      deterministic        evaluation,  if    the      factor is determined from the ratio of the I    Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 7                                                                                        Page 7-4 Page 7-4 Chapter 7 3
S                                                    /1977                          Hosgri evaluatior 1.07                                                                                (Newmark) 1988 84th Percentile 1**
                                              .- 5-1988 Median
              .5.
0                      II    I    n n      I          .I      ,  I            n      n    I. I  i
        .1          .2              .5      1        2          5        10      20              50 Frequency (Hz)
Figure 7-2 Comparison of the 1988 site-specific median and 84th percentile horizontal response spectra with the 1977 Hosgri evaluation (Newmark) response spectrum.
an Pacific Gas and Electric Company Diabjo Canyon Power Plan Long Term Seismic Pugra m
Int
 
Chapter 7                                                                                                                                                    Page 7-5 6                                    e    !          . l  .      .    .    .    .    .    .* i                                                              I 5% D~am ninn 5
E ..........                                                                                  .......... ...........
-    4
: 0)  3'                                        S...........................
U                      .. .. .. ... .. . ..  .  ..    .    ..    .    .  ..    .  ..  .  ..      ..  .  .. . ..  .  . ..    . ..    . ..  .  ..  .  ..  . ..  . .
U 4-In Scaled    free    field 0)
                                                                                                              -...        soil/structure interaction 84% site-specific 0                                                        I          I      I    I    I      II                                                                I  I  I 2
100                                                                                        11101                                                                      `0 Frequency (Hz)
Figure 7-3 Comparison of scaled soil/sutucture interaction input spectrum with 84 percent probability of nonexceedance site-specific spectrum.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                                                                        Long Tram Seismic Program
 
Chapter 7                                                                                                          Page 7-6 Coherent ground motion                                Incoherent ground motion Spectral Soit/structure    S5        S,            ~      rotio rateio Sa                              interaction analysis                                            1.0 IF                                                                  f Smoothed                                        In-structurc soilistructure                                    soil/structure Iteacention                                      interaction inputIspectrunt                                      spectrum Soil/structure interaction response Deterministic Plant response S,                At ft Smoothed site-specific spectrum In-structure                              In-stnructure coherent                                spectrum for spectrum                                  atle-specitte spectrum If Smoothed otllstructsure Interaction Input spectrum Figure 7-4 Overall process of developing plant responses.
Diablo Canyon Power Plant N      Pacific Gas and Electric Company                                                            Long Term Seismic Program
 
Chapter 7                                                                                        Page 7-7 Chapter 7                                                                                        Page 7-7 response spectral ordinates of the free-field          of soil/structure interaction. Figures 7-11 site-specific        ground-motion      spectrum      through 7-18 show comparisons of free-field (Figure 7-2) and the spectral ordinates of            and basemat spectra, including the effects of soil/structure interaction analysis smoothed          ground-motion incoherence.
* input spectrum (Figure 5-22). For the 84 percent      probability      of nonexceedance site-specific ground-motion spectrum, this        Comparisons of Plant Responses for factor ranges from about 0.86 to 1.0.            Site-Specific Ground Motions and Seismic Qualification Bases Motions The factors Fss              are applied to the soil/structure interaction in-structure response The Plant seismic qualification basis events spectra to obtain the Plant responses at various floor levels due to coherent              included two large earthquakes: the double design site-specific ground motions. Figures 7-5        earthquake and the Hosgri earthquake. The through 7-10 show plots of the site-specific      seismic design and qualification requirements free-field ground-motion spectrum (at the 50      associated with those two earthquakes were and 84 percent probability of nonexceedance      developed at different times during the levels) with the corresponding basemat            plant-licensing process. As a result, the response spectra (El 85 feet) of the major        corresponding analysis parameters, method, and criteria  (for example,    structural damping, structures.
modeling assumptions, treatment of soil/structure interaction, and so forth), differ not only from For frequencies above about 10 hertz, the        those used in the current                deterministic soil/structure interaction effect (coherent      evaluations, but also from one another. Because motion) results in a reduction of the input      of these differences, one-to-one comparison of motion to the basemat from the free-field        response spectra due to the site-specific ground motion. For the frequencies lower than            motions with the governing seismic qualification 10 hertz, that basemat motion is slightly        bases spectra is not always appropriate. However, amplified.                                        comparisons of response spectra are provided, in response to a request from Nuclear Regulatory
: 2) A spatial incoherence factor (Foe) that          Commission (NRC) Staff.
accounts for the spatial variations of ground motion. The development of this factor is discussed in Chapter 5. For a specific site, this FREE-FIELD AND BASEMAT RESPONSE factor, in general, results in a reduction of      SPECTRA building responses and is dependent on the plan area of the building foundation and the During the previous Hosgri evaluations, Plant frequency of vibration of the building, among response was evaluated for both a Hosgri other parameters. For the frequency range        spectrum recommended by Newmark and a above about 5 hertz, the reduction in Hosgri spectrum recommended by Blume. Seismic translational motion is about 6 percent for the evaluations were based on whichever of these containment, 15 percent for the auxiliary spectra proved to be more conservative for any building, and 20 percent for the turbine given structure or equipment item at any given building. When considered in conjunction frequency. Figure 7-19 shows comparisons of the with rocking and torsional motions, there is      enveloped Hosgri (Newmark and Blume) 0.75 g generally a decrease in the above effects.        free-field response spectrum with the site-specific ground-motion spectra, at the 50 percent and 84 The Fo,. factors are applied to the response      percent probabibility of nonexceedance levels.
spectra developed for coherent site-specific      This figure shows that the 50 percent probability ground motions to obtain the composite effect    of nonexceedance of site-specific ground-motion Diablo Canyon Power Plant Pacific Gas and Electtic Company                                              Long Term Seismic Program
 
Chanter 7                                                                                          Page 7-8 ChanteT  7 0.
33 go
'E .
0~
102 Frequency (Hz)
Figure 7-S Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, containment building, north/south response, using coherent ground motions.
Olablo Canyon Power Plant
: 1. Pacific Gas and Electric Company                                                Long Term Seismic Program
 
Chapter 7                                                                                                Page 7-9 Chapter 7                                                                                                Page 7-9 6
5% Damping 51-.......................................................................
4  -...........    ............ ....... .................  ........... ... ............ ................
2 3
Basemat (84%)
0.
2
                                                                                , Free field (84%)
1 Free field (50%)
I      I        I  I  I i 101                                                    102 Frequency (Hz)
Figure 7-6 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, containment building,. east/west response, using coherent ground motions.
Olablo Canyon Power Plant I    Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 7                                                                                                                                                                                              Page 7-10 6                                                                                        e    i        i    I        I o    l                              I                      I      I      i    l      I    iI 5% Damping 5
                                        . , *o .. &deg; , ,. . , o. , . J . , , .        &deg; .    * , oo      . . ,      *, &deg;
                                                                                                                              .o . . ..    ..      ..    . . . e~. ... o . ..  ~....
l..      . ... .
-    4.
U  3,            ...          .........................................                                              At            ..................................................
                                                                                                                          -, l+-    Basemat (84%)
U)  2 1
(50%mt5 Freefree                                                                      184)
Basemnat (50%)
0' fk 10O                                                                                                                      101                                                                                            102 Frequency (Hz)
Figure 7-7 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, auxiliary building, north/south response, using coherent ground motions.
Ian  Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Charter 7                                                                                                                                                          Page 7-11 Chanter 7                                                                                                                                                          Page 7-11 6                                                                                      I                                  l        I          g
* I  g  I I 5% Damping 5 ..................................................................................-
                          ..................... ,.....o..,...o.,.......,.,.......o................,                                        .....      &deg;,...o..&deg;..,,
4.
121 to
                                                                                                        /*'--// --  Basemat (84%)
CL W-2, ...............                                                                                *. . . . ..................................................
Free field (84%)
I Free field (50%)
Basemat (50%)
S                              S    *
* I            l    I      10ii                      I          I              I  l        102 100                                                                                                      lO1                                                                10'2 Frequency (Hz)
Figure 7-8 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, auxiliary building, east/west response, using coherent ground motions.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                                                                                        Long Term Seismic Program
 
    .Chanter 7                                                                                                                                                    Page 7-12 Chaoter 7                                                                                                                                                    Page 7-12 6                                                                                                      I                    I 5% Damping 5
-a      4 C
.2
'U 0)
U
~.1
'U                                                                                      Basemat (84%)
L.
U 0
Co                                                                          *                      * .. -..
I Free field (84%)
Free field (50%)                          "'-*-        ---
Basemat (50%)
I                              -
10                                                                      10*
Frequency (Hz)
Figure 7-9 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis', turbine building, north/south response, using coherent ground motions.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                                                                          Long Term Seismic Program
 
Chapter 7                                                                                              Page 7-13 Chapter 7                                                                                              Page 7-13 6
4 C
0
                                                                                                                        -4:-
102 Frequency (Hz)
Figure 7-10 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, turbine building, east/west response, using coherent ground motions.
Diablo Canyon Power Plant.
in    Pacific Gas and Electric Company                                                    Long Term Seismic Program.
 
Chapter    7                                                                                                                  Page ?-14 Chapter 7                                                                                                                      Page 7-14 6.
5% Damping 5    ..........................................................................
S 3 ...................................................................
C)                                                                                                                                        .......
.2 Basemat (84%)
Cd, 2                                                                                .      .* ~Free field'-\(84%)
Basemat t50%) ..........................
Free field (50%)
ft
                                - I                        -_-t I    !
* I  I
_i"O                                                                            101                                                        102 Frequency (Hz)
Figure 7-11 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, containment building, north/south response, using incoherent ground motions.
Diable Canyon Power Plant Pacific Gas and Electric Company                                                                            Long Term Seismic Program
 
Chapter 7                                                                                                                          Page 7-15 Chapter 7                                                                                                                          Page 7-15 fti 5% Damping 51*....
S
                  ...  ..  . ..- .- ...l  .., . ....... .
                                              .~              ....
Q      .
0 3    ....
CL Basemat (84%)"
                  ...&deg;  ........                                                        I..........      , ,    o ,
oo &deg; , , ...............            ..      .......... o,.,
2
                                        .... .... .. .... .-N 4w                  :  N_....    ..: ..  . ..... .                        .. ..
1
                                                                                              -        ":z- -- --                        "--- ......
Basemat (50%)                                        Free      field        (50%)
I    II  I                                                      ..........            ........ U 101                                                                            10 "
Frequency (Hz)
Figure 7-12 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, containment building, east/west response, using incoherent ground motions.
Dlablo Canyon Power Plant Pacific Gas and Electric Company                                                                        Long Term Seismic Program
 
Chapter 7                                                                                                  Page 7-16 Chanter 7                                                                                                  Page 7-16 6
5% Damping 5.
          .  . .  . .  . . .  . . . .  . .. . .  . . .  . .  ...  &deg; .  .o&deg;&deg;. ..
                                                                                &deg;....                                    .......
* a    41 Key plan 3
Basemat (84%)
t; CL
'      2
                      *~ ~ ~~~~~~:.....            ;,,;,; .. .,. ..................
Free field (50%)                  -
:    Basemnat (50%)
0 102 10W Frequency (Hz)
Figure 7-13 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, auxiliary building, north/south response, using incoherent ground motions.
Diablo Canyon Power Plant i~~Pacific Gas and Electric Company                                                        Long lerm Seismic Program
 
1-                                                                                                                                  . Page 7-17 Chanter 7Pae77 W                                *            ,      .        ,  S          S      Il                              S
* 5% Damping 51                                                                                                                                                    4
_. .. .l* *... . ..  .  ..
                                  ,oo.. ..    ,o    o  . o . , .. ,  . e.. o. ,...... %  . ..,~ .
* o.....o.
N  -
S 4
00 Key plan
'U 3-0 Basemat (84%)
        . ... ............                  .                    *...kv    . ....        L  .... ... . ... .. .. ... .. ... ...
ca 2.
1I                                                                                                              . ....'-:*........................
Frefil(-)\                                                      Basemat (50%)
* S      S      S        S  S      S    S      I                              .    , .
U I 100                                                                              101                                                              102 Frequency (Hz)
Figure 7-14 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, auxiliary building, east/west response, using incoherent ground motions.
El                                                                                              Diablo Canyon Power Plant u Pacific Gas and Electric Company                                                                                          Long Term Seismic Program
 
Chapter 7                                                                                                                                                          Page 7-18 5% Damping 5    ....................            '.  .  ......    ,....,
                                                                ...        .. ,.......,,      ... ,. ..  .  ..  . o **
                                                                                                                    ......... 1  . o  .  **.... .......          ..  ,.  ..... ,..
N 0
Key plan 3  ....          ,..      &deg;...
                                                                            .......................................    ,.        &deg;&deg;  *,    ,    .    ,.. ... ..  ,    *. &deg;.....
i                                                                      Basemat (84%)
        ,.cO.
2 ...........................                                                                                                                                              .......
Free field (50%)
0                                        I              i    l          l    i  I. I.,                        IB                  -    I      I      I    l    l 100                                                                                              10'                                                                              102 Frequency (Hz)
Figure 7-15 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, turbine building, wall A area, north/south response, using incoherent ground motions.
Diablo Canyon Power Plant
(    Pacitic Gas and Electric Company                                                                                                          Long term Seismic Program
 
Chapter 7                                                                                                                                          Page 7-19 Chapter 7                                                                                                                                          Page 7-19
                                              *      *    .        I      *  *
* i                                                    .1 5% Damping m,..
                          .. o .,..D. ,., ,,.  ,.o, .o. , o  ...      t..    ,o.      ..    ..... o . o........      .......  .....    ........    ..  ... .  .
5 N
4 ..................................                .. .        ......................                                    E                      1:"
4U-Key plan La Basemat (84%)
CL,    2 . ......................            .                        ..........
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: 0. 1Free                                              field (50%)
0                                                    i                                              I                                      L*    A          I 100                                                                          101 Frequency (Hz)
Figure 7-16 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, turbine building, wall A area, east/west response, using incoherent ground motions.
Dlablo Canyon Power Plant Ian Pacific Gas and Electric Company                                                                                                Long Term Seismic Program
 
Chapter 7                                                                                          Page 7-20 Chapter 7                                                                                          Page 7-20 6
5 U,  4 C
  .2 a,
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  .5 I..
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C',  2 1
0 102 Frequency (Hz)
Figure 7-17 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, turbine building, diesel generator area, north/south response, using incoherent ground motions.
Diablo Canyon Power Plant A  Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 7                                                                                                        Page 7-21 5% Damping N-4}
Key plan 3 .........................                                        I................................................
U                        Basemnat  (84%)
ca 2*...................
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0.
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                    ,.-*                        u~asemat (50%)                              "*    . ...................
                                                                                                **"          Free field (509, 0                          I.      I              ,  1 I I      J      I                        .a ..  . aI 100                                                            101 Frequency (Hz)
Figure 7-18 Comparison of spectra for free-field ground motions with basemat spectra determined by soil/structure interaction analysis, turbine building, diesel generator area, east/west response, using incoherent ground motions.
Diablo Canyon Power Plant Iin Pacific Gas and Electric Company                                                                Long Term Seismic Program
 
Chapter 7                                                                                                                                Page 7-22 ChaDter 7                                                                                                                                Page 7-22 6                        -- 5                U        U
* S          S    iI                            .        .
5 % Damping 5,                                                                                        ........... ..............  .....................
m 4.      ..      ............                                ..........................
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2 .................              ......
                                            /*  *                                -" -'*--84%
site-specific
                                        *'"    .....  ......                        _.        i    *',,%            50%site-specific 1
* 2* :* .* -. .............. . --.                                                    .............                ..-.
0 100                                                                                  101                                                        II 032I Frequency (Hz)
Figure 7-19 Comparison of free-field, site-specific spectra with 1977 Hosgri evaluation spectrum for horizontal ground motion.
Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                                                      Long Term Seismic Program
 
Chapter 7                                                                                              Page 7-23 Chanter '7 6
Page 7-23 spectrum is enveloped by the Hosgri evaluation          auxiliary building. These exceedances are not spectrum.        The      84 percent    probability  of significant as they can be accommodated by the nonexceedance site-specific ground spectrum              existing design margin, as discussed later.
exceeds the Hosgri evaluation spectrum. only at frequencies greater than about 15 hertz, and the exceedance is only about 10 percent.                    IN-STRUCTURE RESPONSE SPECTRA In-structure response spectra at selected locations Figures 7-20 through 7-29 show a comparison of          in the major structures are shown in Figures 7-30 the Hosgri (envelope of Newmark and Blume                through 7-39. These spectra include the effects of spectra) evaluation basemat (El 85 feet) response        soil/structure interaction, foundation embedment, spectra, which had been reduced from the                and spatial incoherence of ground motions, and free-field spectra to account for the tau-filtering    are compared with Plant seismic qualification effect (USNRC, 1976), with the basemat spectra          basis (Hosgri or double design earthquake) computed from the site-specific ground motions          in-structure response spectra. The locations for in this study including soil/structure interaction      which these comparisons are shown were based on incoherence effects.                                    their importance in terms of structural design, or locations of critical safety-related components.
These spectra are for:
It should be noted that the effects of tau-filtering in the Hosgri evaluation studies were generally
                                                          "  Containment interior structure at El 140 feet analogous to the combined effect of soil/structure (operating floor level) interaction,        foundation      embedment,    and incoherent ground-motion effects in the current soil/structure interaction analysis. However, these      "  Auxiliary building at El 100, 115, and 140 effects vary from point to point on the foundation          feet (various equipment of interest) basemats in the current study results. This is reflected in the difference in spectral amplitudes
* Turbine building      at  El  119    feet  (4-kV shown in Figures 7-20 through 7-29 for different            switchgear area) locations on a building structure. For the Hosgri evaluation, the dynamic models used for analysis were considered to be fixed at the base and,            The primary        purpose      of    these spectral therefore, the variations in the tau-filtering          comparisons is to assess the effect of the reduction for different locations on the basemat        sue-specific ground motion in-structure response could not be considered. Instead, an average            spectra on seismic qualification of equipment.
motion was assumed for all points on the                Comparison of the spectra shows the following:
foundation of a building. Becuase of this, a one-to-one comparison of basemat motions for                For the containment building operating floor the Hosgri evaluation spectra with those due to              at El 140 feet (Figures 7-30 and 7-31), the the site-specific ground motions in this study will          seismic qualification basis spectra are well show some differences.                                      above (by up to 100 percent) the site-specific ground motion in-structure spectra between 8 and 18 hertz. For other frequencies that are The comparison shows that the responses to the              significant for qualification of equipment (5 to 84th percentile site-specific spectra exceed the            8 hertz), the site-specific ground-motion responses to the Hosgri evaluation spectra at                in-structure spectra, in general, exceed the various structural frequencies. The average values            seismic    qualification    basis    spectra      by of these exceedances at key frequencies range                approximately 15 percent. This exceedance is from about 5 percent for the containment building            not significant and can be accommodated in interior structure to about 10 percent for the              design margin.
Dlablo Canyon Power Plant I      Pacific Gas and Electric Company                                                  Long Tem Seismic Program
 
Chapter 7                                                                                            Page 7-24 Charter 7                                                                                            Page 7-24 6                                a            j                        U          m        D    I    .    .  .  .
5% Damping 5 ...............................................................................
4  ...............................................................................
S                    Containment building exterior structure fundamental frequency= 4.1 Hz CU 3
cc                                                          Containment building 84% site-specific                          : interior structure CO)2
        ............    .......
* fundamental frequency = 8.9 Hz Hosgri evaluation 1                                                        ...........................
50% site-specific 0.4--                                                                                                          i  i  1 100                                                10t                                                              II022 Frequency (Hz)
Figure 7-Z0 Comparison of spectra for motion at top of basemat, containment building, north/south response.
Diablo Canyon Power Plant IN Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 7                                                                                                                              Page 7-25 Chapter 7                                                                                                                              Page 7-25 6                                                                                  4  9                              I        W      U    U    g W W 5% Damping
            ........ Coa inm.                      . ...      entbuilding..........................
Containment building exterior structuru fundamental frequenc y -4.1 Hz CL V) 3 84% site-specific
                                                                                      ..  .. ...  . Containment building interior structure fundamental frequency = 9.5 Hz
        ....  ...    &deg;....        ... ....                ...:;-,,......,
2 1
V 50% site-specific 0 4-100                                                                                          101                                                    102 Frequency (Hz),
Figure 7-21 Comparison of spectra for motion at top of basemat, containment building, east/west response.
Diablo Canyon Power Plant In  Pacific Gas and Electric Company                                                                                      Long Term Seismic Program
 
Chapter 7.                                                                                        Page 7-26 5% Damping Auxiliary building significant frequency 8.2 - 10.5 Hz
'a 4 .........................            .      .    .      ..........................
C 2                                                              Key plan 840/6 site-specific                                  "
100                                                      10,                                                  1o2 Frequency (Hz)
Figure 7-22 Comparison of spectra for motion at top of basemat, auxiliary building, north/south response.
Olablo Canyon Power Plant Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Charter 7                                                                                                      Page 7-27 Chanter 7Pae-7 I      I    I    I    I I  I  l                -            I        I    I          l  I 5%Damping 5
N-uI 4
Key plan CL 3              .84% site-specific                                    Auxiliary building 0a significant frequency          8.5- 9.7 Hz 2    ......................      .............            ....................................
Hosgri evaluation 1
A          site-sp-cific
  .0 10U                                                      101                                                              10z Frequency (Hz)
Figure 7-23 Comparison of spectra for motion at top of basemat, auxiliary building, east/west response.
Dlablo Canyon Power Plant 19 Pacific Gas and Electric Company                                                                Long Term Seismic Program
 
Chapter 7                                                                                                  Page 7-28 Chapter 7                                                                                                  Page 7-28 6
5                                                                                  N    --
C    4  ................................              ................                  L i Turbine building significant 0              elastic frequency = 5 to 10 hertz                                            Key plan 3 ...            ..............    ! ...      ....                .....      .........................
10                  84% site-specific 0    2 Hosgri evaluation 1                                                                        ..
Frequency (Hz)
Figure 7-24 Comparison of spectra for motion at top of basemat, turbine building, wall A area, north/south response.
Diablo Canyon Power Plant In  Pacific Gas and Electric Company                                                        Long Term Seisnrdc Program I
 
Chpe                                                                                          Page 7-29 Chapter 7                                                                                        Page 7-29 6.
5% Damping 5'    ........ ..... ........ ...............                      ..
4.
Turbine building significant elnatic freanuenv = 5 to 10 hertz elastic freauencv = 5 to 10 hertz                                Key plan 314.......................
ca 84% site-specific 2
1 0
102 Frequency (Hz)
Figure 7-25 Comparison of spectra for motion at top of basemat, turbine building, wall A area, east/west response.
Diablo Canyon Power Plant I    Pacific Gas and Electric Company                                              Long Term Seismic Program
 
Chapter 7                                                                                                                    Page 7-30 Chavter 7                                                                                                                    Page 7-30 6                                      I
* Ii    I I                                                          I          I  o 5% Damping
: 5.                                                                                          N -,it-f                ..................
4 S
.2-              Turbine building significant elastic frequency = 5 to 10 hertz                      o tl e.
e&deg;        .....
              ,  o....
o...    ... ..  .*.
plan Key 3                                                                                .~~.e.......................ell~
84% site-specific Hosgri evaluation I
101                                                                          10 Frequency (Hz)
Figure 7-26 Comparison of spectra for motion at top of basemat, turbine building, wall 19 area, north/south response.
Diablo Canyon Power Plaint In  Pacific Gas and Electric Company                                                                            Long Term Seismic Program
 
Chapter 7                                                                                              Page 7-31 6
5% Damping N 1HI Turbine building significant elastic frequency = 5 to 10 hertz                                          Key plan 6
84% site-specific 2 .........................                A                .. ..............................................
                  ,../            . NO                                            Hosgri evaluation 50% site-specific 0                                      uII                                            I            I    !    I    I I 100                                                      10'                                                            10o Frequency (Hz)
Figure 7-27 Comparison of spectra for motion at top of basemat, turbine building, wall 19 area, I      eastJwest response.
Diable Canyon Power Plant In  Pacific Gas and Electfic Company                                                      tonu 7emn Seismit Progtram
 
Chapter    7                                                                                            Page 7-32
            &deg; Chapter 7                                                                                                Page 7-32 6
5% Damping 5                                                                                      N-    -
4    ...........                I................... ...............                EI
    .2                  Turbine building significant 4-
    'U I.
elastic frequency = 5 to 10 hertz  ....                            ,. Key plan S
iz9 .. .. .."... .. .. .. ..........
          .3 U
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0 11                                                          101                                                    102 Frequency (Hz)
Figure 7-28 Comparison of spectra for motion at top of basemat, turbine building, diesel generator area, north/south response.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                      Long Term Seismic Program
 
Chapter 7                                                                                                                      Page 7-33 Chapter 7                                                                                                                      Page 7-33 6
5 4 .............................................                    ...... . ... .........
oTurbine                        building significant elastic frequency = 5 to 10 hertz                                                            Key plan S  3    .. o...
                    . ..  .  ..o...o...&deg;+.
                                                    ,..... .l                        ..o ..    +
                                                                                            ...... l.l*
                                                                                                    ..        i.    +.+....... ..... ...
84% site-specific CO0. 2  .......................            a .. . ... . ...
50% site-specific Hosgri evaluation 0
100                                                                  101 Frequency (Hz)
Figure 7-29 Comparison of spectra for motion at top of basemat, turbine building, diesel generator area, east/west response.
WDiablo                                                                                                                Canyon Power Plant Pacific Gas and Electric Company                                                                            Long Term Seismic Program
 
Chapter 7                                                                                                                                                                                    Page 7-34 12                                                                                                                  *                                    ....                                              .
10      ................................................                                                              .. . . . . . . .. . . . . . . . .. . . . . . . .
Main frequency range for equipment and piping Z      8        o..      o....  . .....      . ..          . o . o . . . , . , . , ... l  ,      ,,......    .  . ,... &deg;..    . o.  ,  ,  o,...,.........,                  ...        ...
                                                                                                                                                                                        &deg;.....,....
h.2 6  ..................                        , .. ,,......          .......      .  ......          .o .        .......    .. ... ...    .,      ,.  ,... ..    &deg;. &deg;.........    ....    .  .... .
QW                                                                                                                                                    ---. Seismic qualification basis CA--  4  .....................................                                            ....            .      .....    ..  ..                              .  .  .    . .  . .  . .    . .  .  .  . .
                                                                                                    //                                                                  84% site-specific 0                                                                                                                                                                  L 100                                                                                                                101 Frequency (Hz)
Figure 7-30 Comparison of floor response spectra for equipment qualification for the containment building, interior structure, El 140 feet, north/south response.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                                                                                                    Long Term Seismic Program
 
Chapter 7                                                                                                Page 7-35 Chapter 7                                                                                                Page 7-35 12            *    *.......I.              ,  I  I
* 3
* I              I 10 Main frequency range for equipment and piping 8
0 6
CL                                                                                      Seismic qualification basis 4
                                                            /                          84% site-specific 2 .................              ...-.            . .      . . . .\ . ...    ..................................
II                                                                      A  ..
100                                                    101                                                        102 Frequency (Hz)
Figure 7-31 Comparison of floor response spectra for equipment qualification for the containment building, interior structure, El 140 feet, east/west response.
mDlablo IN Pacific Gas and Electric Company Canyon Power Plant Long Term Seismic Program
 
Chapter 7                                                                                                      Page 7-36 Chatter 7                                                                                                      Page 7-36 12                                                    I                                        a 10    ................. .............          "............... . . ...
Equipment and components in this range of exceedance qualified based on the seismic fragility                                      Key plan evaluation.
a I..................            ......... Sismic qaifi
                                                                                  .......            cti      b............a I-4 4 .......................
                                                                                          / 84% site-specific 2          ..  . ..  .      ...
I a    a  . a    a  a  S U  9
      -100                                                            101                                                      102 Frequency (Hz)
Figure 7-32 Comparison of floor response spectra for equipment qualification for the auxiliary building, El 105 feet, north/south response.
m    Pacific Gas and Electric Company Diablo Canyon Power Plant Long Term Seismic Program
 
Chapter 7                                                                                                          Page 7-3 7 Chapter 7                                                                                                          Page 7-37 12                                I          I    i  I  i    I  I  l Equipment and components in" 10 -.......              .. .... this range of exceedance qualified .....
based on the seismic fragility evaluation.
Key plan 84-........ .... .........
C 6      .........          ...  . .....  ..............      .. . .....  . . . ..*Se. .m...
* ual.o*, c. ...tion.b.a.
.2 C4 i /      Seismic qualification basis 4      -................
                                                                                    /, 84% site-specific 2
                                                                                      -  ~-
0                          I          I -  - I. I  I    I  I  IS                S i
                                                                                                  ~
I I
i I
e I
I S
I I
i S
i 100                                                                10 1                                                      10 2 Frequency (Hz)
Figure 7-33 Comparison of floor response spectra for equipment qualification for the auxiliary building, El 105 feet, east/west response.
Dlablo Canyon Power Plant an Pacific Gas and Electric Company                                                                Long Term Seismic Program
 
Chapter 7                                                                                                                                                      Page 7-38 Chapter 7                                                                                                                                                      Page 7-38 121                    I                      I            I      I          I    I    I  I    I                            I        I        !I 10.
                    -              Equipment and components in:
this range of exceedance qualified based on the seismic fragility evaluation.                                                                                  N moo....
                                              ....      . o.&deg;.
                                                          .......    ,o  &deg;,....                  ....* ....  ,,....    ,    &deg; ..                    d...*
0 Key plan 6  m. &deg;.... . . .  ..  . .  .      .                      .....
Seismic qualification basis CL,    4 84% site-specific 2
n4 100                                                                                          101                                                                        102 Frequency (Hz)
Figure 7-34 Comparison of floor response spectra for equipment qualification for the auxiliary building, El 115 feet, north/south response.
WDiablo                                                                                                                                                  Canyon Power Plant I    Pacific Gas and Electric Company                                                                                                        Long Term Seismic Program
 
Chapter 7                                                                                                                              Page 7-39 Chapter 7                                                                                                                              Page 7-39 12                      I          I            I        I  I    I  I  I                        a l
I I
I I
I I
I I
I I
I I
I
                                      ........  . .&deg;&deg;.,......
            ,........................................                                    &deg;.,.o.o&deg;.,.,.
                                                                                    .&deg;.,o.o.&deg;  . .. o.    . . o &deg;. . . ..  &deg;...  . .o .................
Equipment and components in:
this range of exceedance qualified based on the seismic fragility                                          N-                      i evaluation.  ...........              .................
:j... ..
a"    8                                                                                                              1          ,
CL I-P Key plan 4
2,
                                                                                              /    Seismic qualification basis
: 0. 4 C'
S584% site-specific 2
                            !                      I          I I    I
* I  I u.
v 100                                                                    101                                                                        102 Frequency (Hz)
Figure 7-35 Comparison of floor response spectra for equipment qualification for the auxiliary building, El 115 feet, east/west response.
Diablo Canyon Power Plant an Pacific Gas and Electric Company                                                                                  Long Term Seismic Program
 
Chapter 7                                                                                                                                                                        Page 7-40 Chanter 7Pae-4 12                                      II                    I    -I        I        I    I  1    1                                  I                I          1          6      s    I    I  I
: 10.  ...........................                        * * ;"*........
Equipment and components in:
                                                                              ; n,*t;i zq*p              ,....................... i............""....... I.........
this range of exceedance qualified                                                                N4 N                                                        based on the seismic fragility evaluation.
: 8.                                                                              .......................
Key plan
.2
        .....        .... to.... ,  &deg;.....  . , . .&deg;    * .    &deg;.....  .  ..&deg;&deg;....................&deg;e
                                                                                    . .......                                                            &deg;&deg;      &deg;  &deg;&deg;    o    &deg;&deg;..    &deg;.........  .....
U  6 Seismic qualification basis Ca 4-  m....  .....    &deg;......  .......          [..    &deg;.............    ..    &deg;.e..        ..      ......          &deg;. ......    .    .... &deg;.    &deg;.. ........      ... o..&deg;......    ......
84%    site-specific 2
I    ,  ,    i 0
100                                                                                              101                                                                                                  102 Frequency (Hz)
Figure 7-36 Comparison of floor response spectra for equipment qualification for the auxiliary building. El 140 feet. north/south response.
Diablo Canyon Power Plant Pacific Gas and Electric Company                                                                                                                            Long Term Seismic Program
 
Chapter 7                                                                                                                                              Page 7-41 Chapter 7                                                                                                                                              Page 7-41 12
        ......          .......................        x..d.... fr.iityuaifid e.....................                        ................
                                                                                            ...............            N    --      *          '  ***l~'          ....  ..
10
              -.......                Equipment and components in........
this range of exceedance qualified                                              N -a!-
based on the seismic fragility evaluation.
8
                                                                                -        .Key                                                      plan CL  6                                        ....
                                                .  .  .          p.&deg;...                              .            &deg;..p....,                p.............o..........
.O 4
        .. .    .    ..  .  . .                              .  . . .. .      . .. ..          .&deg;...    ... . . .    . ..    .,...&deg; . &deg; 2
01                                        a      a    I    I      I 10 D                                                                            101                                                                                      102 Frequency (Hz)
Figure 7-37 Comparison of floor response spectra for equipment qualification for the auxiliary building, El 140 feet, east/west response.
Dlablo Canyon Power Plant IM  Pacific Gas and Electric Company                                                                                                  Long Term Seismic Program
 
Chapter 7                                                                                                                                                                Page 7-42 Chapter 7                                                                                                                                                                Page 7-42 12                                        I        -i        I          I        I      I    I  I                          I        I                            I    i  '      II    U 5% Damping 10      ................................................... ................ !..........                                                                    ...........
4 C
W2 Key plan cc 6'
CL                      * . e1 oe, , ,..,    *  .
* o  *  ,        . .* p. .,        . . . . .&deg; ., ...    . .  .o..
                                                                                                                                            .eo.. e *          . ....o...  * . o.  .e... ....  .
W.
4 j:                                *Seismic                                qualification basis
          .............                  ..      .*.*. .......      , ....................                      ....    = .....                  ...................                    ..  . .
84% site-specific a                I        I          I        I      I    I  I    I                    I            i*                            i U      U 0)I!,=
10 O                                                                                                101                                                                                      102 Frequency (Hz)
Figure 7-38 Comparison of floor response spectra for equipment qualification for the turbine building, El 119 feet, switchgear area, north/south response.
nlablo Canyon Power Plant tc Pacific Gas and Electric Company                                                                                                            Long Term Seismic Program
 
Chapter 7                                                                                                                    Page 7-43 12 5% Damping 10  .. ..  ..  .. ..  ..  ..  ..ell.. .. e..  ..  ............4e~..................................................                      4 N -4+--
8.
C Key plan
.2 l!  6                                                                f............ .,.........................................
4j CL I
                                                    ;          .                                        Seismic qualification basis 4
2, 84% site-specific I ,    I              I    I      I    I                        I            I        I    I    I    ' '
01 10)0                                                                10'                                                                  102 Frequency (Hz)
Figure 7-39 Comparison of floor response spectra for equipment qualification for the turbine building, El 119 feet, switchgear area, east/west response.
Olablo Canyon Power Plant a Pacific Gas and Electric Company                                                                              Long Term Seismic Program
 
Chanter  ...                                                                                                Page 7-44 Chanter 7                                                                                                      Page 7-44
"        For the auxiliary building (Figures 7-32 to            failure (HCLPF) seismic capacity estimates be 7-37), the seismic qualification basis spectra        used in seismic margin evaluations of nuclear exceed the site-specific ground-motion                power plants (Budnitz and others, 1985). Several in-structure spectra at all frequencies above          authors have suggested that these seismic about 8 hertz (by amounts up to 100 percent)          capacities can be back-calculated from full and at frequencies between 3 and 8 hertz,              fragility curves used in seismic probabilistic risk they      fail    below        the    site-specific  assessment studies (Campbell, 1987; Kennedy, ground-motion in-structure spectra by an                1984; Prassinos and others, 1986). This method average of about 5 percent. However,                  has been endorsed by the NRC Seismic-Design equipment in the latter range is qualified on          Margins Working Group.
the basis of the seismic fragility evaluations as discussed later.                                      The HCLPF capacities of structures, systems and components back-calculated from full fragility a      For the turbine building (El 119 feet) (Figures        curves are presented in this section. As part of the 7-38 and 7-39), the site-specific ground-              probabilistic risk assessment, fragility descriptions motion in-structure spectra, in general, are          were developed for structures and major enveloped by the seismic qualification basis          mechanical and electrical systems required for spectra. Any exceptions are insignificant and          safe shutdown. In all cases, the fragility analyses they can be accommodated in the design                were based on Plant-specific structures or margin.                                                equipment seismic qualification analyses directly related to elements in place at the Diablo Canyon
"        For the majority of items of equipment that            Plant. The structure, system, and component are essential to Plant seismic safety (therefore,      fragility descriptions were used as inputs to included in the Plant system model used for            systems analysis models and HCLPF capacities the probabilistic risk assessment studies), the        were developed for each.
existing seismic qualification is unaffected, because      the    in-structure    spectra    are All fragility estimates presented in Chapter 6 and enveloped by the corresponding seismic used in the seismic probabilistic risk assessment qualification basis spectra.
were defined in terms of a free-field ground-surface control motion response spectral
"        For those essential items of equipment whose shape anchored to an average 5 percent-damped seismic qualification basis spectra do not spectral    acceleration      (ga), averaged over envelop the site-specific ground-motion in-structure      spectra,      seismic    fragility the 3.0 to 8.5 hertz frequency range.
evaluations (C'iapter 6) and the seismic              Therefore, all HCLPF capacities are also defined margin assessment described later in this              in terms of average spectral acceleration and this chapter show that each of these items is              same spectral shape. Because the spectral shape qualified for the site-specific ground-motion          used for fragility estimates is nearly identical to spectra.                                              the site-specific ground-motion 84 percent probability of nonexceedance spectral shape when both are anchored to the same 5 percent damped DETERMINISTIC SEISMIC MARGIN                                  average, spectral acceleration (Figure '7-3), the ASSESSMENT                                                    appropriate HCLPF capacities in terms of average spectral acceleration can be compared directly to Capacities for Structures, Systems, and                        the average spectral acceleration for the Components                                                    site-specific ground-motion spectra:
The Expert Panel on Quantification of Seismic                    Site-Specific Ground-Motion Spectra:
Margins organized and funded by the Nuclear 50 percent probability of nonexceedance S,  = 1.30  g Regulatory          Commission has          recommended that          high-confidence-of-low-probability-of-            84 percent probability of nonexceedance &sect;, = 1.94 g Diablo Canyon Power Plant I        Pacific Gas and Electric Company                                                        Long Term Seismic Program
 
Chapter 8      7                                                                                        Page 7--45 Chapter 7                                                                                            Page 7-45 It should be noted that the HCLPF capacities                                      65 (p,' Pu)
HCLPF 9a = ise-1.
represent a conservative estimate of seismic capacity and that direct comparisons of                  where    S* = median spectral acceleration appropriate        HCLPF        capacities  with the                      capacity site-specific ground motion 9. provide a very                      Ol = logarithmic standard deviation conservative 'estimate of the seismic margin of the                        for randomness P3u = logarithmic standard deviation plant. In this regard the Expert Panel on                                  for uncertainty Quantification of Seismic Margins (Page 5-2 of Budnitz and others, 1985) has stated:
However, the fragility estimates provided in The measure of margin adopted by the Panel      Chapter 6 include consideration of both Is a high-confidence-of-low-probability-of-      peak-and-valley        variability    and directional failure (HCLPF) capacity. This Is a              variability of spectral response at any given conservative representationof capacity and in    frequency for any given response direction, and simple terms corresponds to the earthquake      assume a 50 percent probability that these sources level at which, with considerable confidence,    of variability will increase the response of any it is extremely unlikely that failure of the    component above its median response estimate.
component          will      occur. From  the Inclusion of both peak-and-valley and directional mathematical perspective of a probability        variabilities in the fragility analysis method results distribution on capacity developed in seismic    in a reduction in the estimated HCLPF capacity.
PRA calculations, the HCLPF capacity values      The fragility analysis method is primarily intended are approximately equal to a 95 percent          for use in seismic probabilistic risk assessment probability of not exceeding about a five        studies,    and      defining      the      site-specific percent probability.of failure.                  ground-motion spectrum at the 50 percent probability of nonexceedance level is consistent There Is a margin above the conservative        with this usage.
capacity values selected by the Panel. The median capacity, which corresponds to the        Such HCLPF capacity estimates may be directly 50 percent probability of exceedance, is        compared to the 50 percent probability of generally at least a factor of 2 greater than    nonexceedance        site-specific      ground-motion the HCLPF capacity. Thus, there Is no            average spectral acceleration. Both the HCLPF proverbial 'cliff" or sudden failure. which is    capacity      estimate      and      the      site-specific expected to occur immediately beyond the        ground-motion spectrum assume that at any HCLFF capacity. From another perspective,        frequency, the spectral acceleration is equally the conservative capacities are close to the    likely either to exceed or to fall below the lower-bound cutoff values below which there      smoothed spectrum shape.
is no significant likelihood of failure.
On the        other hand, direct              comparison These points should also be considered in            of HCLPF capacities from the fragility analysis evaluating the comparisons made in the following      method with an 84 percent probability of sections of this report.                              nonexceedance          site-specific ground-motion average      spectral      acceleration      results      in unintentional double-counting of the effects of DEVELOPMENT OF COMPONENT HIGH-                        peak-and-valley and directional variabilities,'
CONFIDENCE-OF;-LOW-PROBABILITY-OF-                    because these variabilities are considered both in FAILURE CAPACITIES                                    reducing the HCLPF capacity and in increasing-the 84 percent probability of nonexceedance High-confldence-of-low-probability-of-failure          site-specific ground-motion level. To avoid this capacity estimates may be directly computed from      double-counting of the effects of peak-and-valley the fragility estimates (Chapter 6) by (Budnitz and    and directional variabilities, the fragility median others, 1985; Kennedy, 1984):                          and resultant HCLPF capacities must be modified Diablo Canyon Power Plant IJ    Pacific Gas and Electric Company                                                  Long Term Seismic Program
 
Chapter 7                                                                                        Page 7-46 before (being compared to an 84 percent              upon a study of these sources of variability using probability of          nonexceedance site-specific 38 pairs of ground-motion records for two ground-motion average spectral acceleration. This  horizontal components considered appropriate for point has been recognized and the appropriate        the spectral accelerations at the Diablo Canyon modifications have been made in past seismic        site. All 38 pairs of two horizontal components margin reviews.                                    were first scaled linearly over all frequencies to produce the same average spectral acceleration The 84 percent probability of nonexceedance        over the frequency range of 4.8 to 14.7 hertz for the average of the two horizontal components.
site-specific spectrum defined in Chapter 4 is for The      ratio    (RP1 5 0),  to      account        for the average of the two horizontal components. As such, it does not include directional variability. peak-and-valley variabilities, was then obtained Therefore, for comparison with this spectrum,      at many different frequencies from these 38 pairs the HCLPF capacities from the fragility analysis    of two horizontal components. For frequencies of method only needs to be corrected for              3.5 hertz and greater, the ratio (11841m) associated peak-and-valley variability effects, and not for    with peak-and-valley variability is reasonably constant and averages 1.20. At frequencies below directional variability effects.
3.5 hertz, this ratio rapidly increases to about 1.55 near 3 hertz. Thus:
When median and HCLPF capacities from the fragility analysis method are to be directly compared with a desired 84 percent probability of      la4150 = 1.20                                  (7-2) nonexceedance site-specific ground-motion level, these median and HCLPF capacities must first be redefined so that they are appropriate for the control motion response spectrum being defined      The ratios defined by equation (7-2) were at the 84 percent level instead of the 50 percent  included in the current fragility evaluations, which level. Redefined HCLPF84 and MEDIANs4              are conditional on definition of the site-specific capacities appropriate for an 84 percent ground motions at the 50 percent probability of probability of nonexceedance site-specific          nonexceedance level.
ground-motion level are given by:
When the fragility evaluation HCLPF capacities
    .HCLPF84 = (P so)
* HCLPF are compared to a desired 84 percent probability MEDIAN6 = (Rs 4, 8 o)
* MEDIAN          (7-1)  of nonexceedance level, they should first be scaled by equation 7-2 to obtain HCLPF4 seismic capacities that are conditional on 84 percent probability of nonexceedance ground motions.
where (R94/60) represents the ratio of the 84 percent probability of nonexceedance response Tables 7-1 and 7-2 present HCLPF capacities for spectral acceleration for the average of the two each structure and equipment items included in horizontal response components at a given frequency to the 50 percent probability of          the seismic probabilistic risk assessment.
nonexceedance response spectral acceleration for    Capacities appropriate for comparison with both the 50 and 84 percent probability of the average of the two horizontal components considering only the peak-and-valley variabilities  nonexceedance ground motions are presented. In that have been included in the fragility            accordance with past practice, the comparison at the 84 percent probability of nonexceedance level evaluations.
will be emphasized. These HCLPF capacities are reported in terms of the 5 percent damped The peak-and-valley variabilities inclhded in the  average spectral acceleration in the 3 to 8.5 hertz fragility evaluations for Diablo Canyon were based  frequency range.
Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                              Long Term Seismic Program
 
f'hrnit~  7                                                                                  Page 7-47 rharner 7 Table 7-1 STRUCTURE HCLPF CAPACITIES HCLPF Spectral Acceleration Capacity (g)'
Structure                                      50%2                            84%3 Containment Building                                                3.34                            4.01 Concrete Internal Structure                                          2.98                            3.58 Intake Structure                                                    3.23                            3.88 Auxiliary Building                                                  2.66                            3.19 Turbine Building                                                    1.84                            2.21 Refueling Water Storage Tank                                        3.40                            4.08 Condensate Storage Tank                                                >5                              >5 Diesel Generator Fuel-Oil Storage Tank                                >5                              >5 Auxiliary Saltwater Piping                                          4.85                            5.82 NOTES:
1 Values quoted are referenced to average spectral acceleration between 3 and 8.5 hertz for free-field motions.
2 Values quoted from fragility evaluation in Table 6-23, Chapter 6.
3 Values determined from HCLPFso multiplied by 1.20 (see text for explanation). These values are to be compared with site-specific ground-motion demand [S.) 3-8.S benz = 1.94 g.
Diablo Canyon Power Plant In    Pacific Gas and Electric Company                                            Long Term Seismic Program
 
Chapter 7                                                                      Page 7-48 Chapter 7                                                                      Page 7-48 Table 7-2 EQUIPMENT HCLPF CAPACITIES HCLPF Spectral Acceleration Capacity (g)l System and Component                                    50'-42                84%3 Nuclear Steam Supply Reactor Pressure Vessel                                      3.34                  4.01 Reactor Internals                                            3.55                  4.26 Steam Generators                                              2.55                  3.06 Pressurizer                                                  3.33                  4.00 Pressurizer Safety Valves,                                    >3                    >3 Power Operated Relief Valves                                  2.32                  2.78 Reactor Coolant Pumps                                        2.83                  3.40 Control Rod Drives                                            3.40                  4.08 MSSS Piping                                                    >3                    >3 Residual Heat Removal RHR Pumps                                                    3.35                  4.02 RHR Heat Exchangers                                          3.48                  4.18 Safety Injection Sl Accumulators                                              4.53                  S.4 SI Pumps                                                      4.64                  5.57 Boron Injection Tank                                          3.96                  4.75 Component Cooling Water CCW Pumps                                                    3.74                  4.49 CCW Heat Exchangers                                          2.55                  3.06 CCW Surge Tank                                                2.91                  3.49 Chemical and Volume Control Charging Pumps (Centrifugal)                                  4.45                  5.34 Charging Pumps (Reciprocal)                                    >3                  >3 Auxiliary Saltwater Auxiliary Saltwater Pumps                                      >3                  >3 Containment Spray CS Pumps                                                      3.85                4.62 Spray Additive Tank                                          3.07                3.68 Main Steam MS Isolation Valves                                            >3                  >3 MS Safety Valves                                                >3                  >3 MS PORV's                                                      3.51                4.21 Auxiliary Feedwater AFW Pumps (Motor Driven)                                        >3                  >3 AFW Pumps (Turbine Driven)                                    3.38                4.06 Diablo Canyon Power Plant In  Pacific Gas and Electric Company                              Long Term Seismic Program
 
Chapter 7                                                                                  Page 7-49 Chapter 7                                                                                  Page 7-49 Table 7-2 (Continued)
EQUIPMENT HCLPF CAPACITIES HCLPF Spectral Acceleration Capacity (g)l System and Component                                                5O%2                  849613 Diesel Generator DO Fuel Oil Day Tank                                                        >3                    >3 DO Fuel Oil Pumps/Filters                                      )          3.65                  4.38 DO Fuel Oil Shutoff Valve                                      )          >3                    >3 DO Air Start Compressor                                                    >3                    >3 DO Air Start Receiver                                                      >3                    >3 Diesel Generators                                                          3.64                  4.37 DO Radiator/Water Pump                                                    3.66                  4.39 DO Inlet Silencer/Air Filter                                                >3                    >3 Y
DO Excitation Cubical                                                                            3.08 DO Control Panel                                              Chatter    4.08                  4.90 Structural  2.24                  2.69 DO Main Lead Terminal/Box Containment Building Ventilation Containment Fan Cooler                                                    2.82                  3.38 Control Room Ventilation Supply Fans                                                        )      3.82                  4.58 AC Unzts/Compressor                                                        >3                    >3 Control Cabinets                                                          >3                    >3 480V Swltchgear/Inverter/DC Switchgear/Spreading Room Ventilation Supply/Return Fans                                                        3.95                  4.74 Backdraft and Shutoff Dampers                                              >3                    >3 4160V (Vital) Electric Power Switchgear                                                    Chatter    1.31                  1.57 Structural  2.95                  3.54 Potential Transformers (Bus F)                                            3.47                  4.16 (Bus 0 & H)
                                                                                >3                    >3 Safeguard Relay Panel                                                    3.39                  4.07 125V DC Electric Power Batteries                                                                2.74                  3.29 Battery Racks                                                            5.40                  6.48 Battery Chargers                                                          2.93                  3.52 Switchgear/Breaker Panels                                                2.36                  2.83 120V AC Electric Power Instrument Breaker Panels                                                  >3                    >3 Inverters                                                                2.75                  3.30 480V (Vital) Electric Power 460V/480V Transformers                                                    2.42                  2.90 Breaker Cabinets (Load Centers                                            >3                    >3 Auxiliary Relay Panel                                                    3.57                  4.28 Diablo Canyon Power Plant IJ    Pacific Gas and Electric Company                                          Long Term Seismic Program
 
Chapter 7                                                                                    Page 7-50 ChaDter 7 Page 7-50 Table 7-2 (Continued)
EQUIPMENT HCLPF CAPACITIES HCLPF Spectral Acceleration Capacity (g)l System and Component                                                  50%2                  84%3 Control Room Main Control Boards                                                          >3                    >3 2.98                  3.58 Hot Shutdown Panel                                                          3.22                  3.86 3.52                4.22 Audliary Safeguards Cabinet                                                  >3                    >3 MSSS Control Process Control and Protection System                                        3.57                  4.28 Solid State Protection System                                                4.32                  5.18 Reactor Trip Switchgear                                                      3.14                  3.77
  - Resistance and Temperature Detectors                                          >3                    >3 Pressure and AP Transmitters                                                4.11                4.93 Miscellaneous Components Auxiliary Relay RLack                                                        >3                    >3 Local Starter Boards                                                          >3                    >3 Molded Case Circuit Breakers                                                  >3                    >3 Valve Limit Switches                                                          >3                    >3 Impulse Lines                                                                2.63                  3.16 Containment Purge Valves                                                      >3                    >3 Generic Components Penetrations/Penctraflon Boxes                                              2.83                  3.40 80P Piping and Supports                                                      3.00                  3.60 Hand, Relief, Solenoid, and Check Valves                                      >3                    >*3 Air and Motor Operated Valves                                                3.57                  4.28 Cable Trays and Supports                                                      >3                    >3 HVAC Ducting and Supports                                                    2.49                  2.99 NOTES:
'Values quoted are referenced to average spectral acceleration between 3 and 8.5 hertz for free-field motions.
2 Values quoted from fragility evaluation in Table 6-24, Chapter 6.
WValues determined from HCLPFso multiplied by 1.20 (see text for explanation). These values are to be compared with site-specific ground-motion demand (Sa] 3-8.5 hertz = 1.94 g.
Dlablo Canyon Power Plant In    Pacilfic Gas and Electric Company                                          Long term Seismic Program
 
Chapter 7                                                                                                Page 7-51 Chapter 7                                                                                                Page 7-51 Margin Assessment                                          reported HCLPF4 capacity is a factor of 1.14 times greater than the 84 percent probability When compared to the average 5 percent damped              of nonexceedance site-specific average spectral spectral acceleration in the 3 to 8.5 hertz                acceleration, so that a 14 percent margin exists frequency        range      for    the    site-specific before this HCLPF84 capacity is reached. Even if ground-motion spectra (Oa = 1.30 g and 1.94 g              the demand were to reach this level, failure is for the 50 percent and 84 percent probability of          unlikely, because the median capacity is estimated nonexceedance          site-specific    ground-motion    to be a factor of 2.65 greater than the HCLPF spectra, respectively), it may be seen from Tables        capacity. Furthermore, as will be discussed in the 7-1 and 7-2 that all structures and equipment              following section, there are several sources of items are found to have capacities greater than the        conservatism in the estimation of the turbine earthquake review level, except for the 4-kV              building HCLPF84 capacity, so the actual switchgear. As discussed above, this comparison            HCLPFe4 capacity margin over the 84 percent may be made for either the 50 percent or 84                probability    of nonexceedance            site-specific percent        probability        of      nonexceedance    ground-motion average spectral acceleration is level    capacities.      Figure      7-42 illustrates  likely to be more than 40 percent, rather than schematically the relationship of the structure and        14 percent.
equipment items HCLPF capacities in reference to the site-specific ground-motion spectrum for            The diesel generator control panel has the third the 84 percent probability of nonexceedance                lowest HCLPF84 capacity, 2.69 g, which is a level, and the procedure for evaluating seismic            factor of 1.39. greater than the 84 percent margins.                                                  probability of nonexceedance site-specific average spectral acceleration. The only other components having reported HCLPF84 capacities less than 3.0 g are the power-operated relief valves on the The 4-kV switchgear relay chatter mode has the            primary system (2.78 g), and the 125-volt DC lowest HCLPF4 capacity, 1.57 g, or 81 percent of          electric power switchgear/breaker panel (2.83 g),
the 84 percent probability of nonexceedance                both of which exceed              the    site-specific site-specific 5 percent damped average spectral            ground-motion average spectral acceleration by a acceleration of 1.94 g. However, the relay chatter        factor greater than 1.43.
function mode has a median capacity about 2.7 times its HCLPF capacity, 2.2 times as great at the        Thus, except for the turbine building, all 84 percent probability of nonexceedance                    components whose failure could lead to seismic site-specific average spectral acceleration. Thus,        risk to the Plant have at least a 40 percent margin at this earthquake level, relay chatter of the 4-kV        between the HCLPFe4 capacity and the switchgear is highly unlikely. Furthermore, the            84 percent      probability    of      nonexceedance consequences of 4-kV switchgear relay chatter              site-specific ground motion. Conservatisms in the are easily recoverable by operator action, as              turbine building capacity evaluation are discussed discussed in Chapter 6. Even though the 4-kV              below.
switchgear relay chatter fragility estimate was included in the seismic probabilistic risk assessment, it did not turn out to be a significant      CONSERVATISMS IN TURBINE BUILDING contributor to seismic risk because operators can          STRUCTURE CAPACITY EVALUATION reset any tripped circuits. Therefore, the 4-kV            (FRAGILITY ESTIMATES) switchgear relay chatter HCLPF8 capacity Is not an appropriate descriptor of the plant seismic            Because the Plant fragility is governed by that for margin.                                                    the turbine building, a further evaluation of the conservatism used in the turbine building analysis The second lowest HCLPF84 capacity, 2.21 g, is            has been made (Kennedy and others, 1988). The for the overall turbine building structure. The            results of this evaluation are summarized here.
                                              .1 Diablo Canyon Power Plant I      Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
Chapter 7                                                                                            Page 7-52 Chapter 7                                                                                            Page 7-52 I                      I I                      I I                      I  IN1 Range of component capacities determined by I
HCLPF8 4 values are shown in Tables 7-1 and 7-2
                                                                /
I                              (excluding switchgear relay chatter)
I            -        I C
I          .          I I                      I I                      I Average spectral              I                      I CL acceleration                  I
* 2.21g1  I from 3 to 8.5 Hz
_*_1              t194 g 84%'ite&#xfd;-specific II II II 3                    8.5 Frequency (Hz)
Figure 7-40 Schematic illustration for determining seismic margins.
Diablo Canyon Power Plant an Pacific Gas and Electric Company                                                    Long Term Seismic Program
 
(nh~,t~rn  '7 rh _r ter 7                                                                                        Page 7-53 A number of possible failure modes that could        It was found that considerable differences existed lead to overall severe distress of the turbine        in the computed shear wall drifts (measure of building were investigated using the standard        damage) for different ground-motion records fragility evaluation method for the seismic          when each was scaled to the same average spectral probabilistic risk assessment. It was concluded      acceleration level. In fact, the records such as that the most probable cause of overall severe        Tabas, Pacoima Dam, and Karakyr Point (Gazli) distress of the turbine building was substantial      which actually had the highest average spectral inelastic drift and strength degradation of the two  acceleration and thus had to be scaled and major east/west load-carrying          shear walls  modified the least to achieve a reference 9a such spanning from foundation level (El 85 feet) to the    as 3.0 g, consistently produced lesser drifts operating floor (El 140 feet). An extensive study    (damage) than did the records that had greater was then performed to define the fragility estimate  scaling and modification. The records such as for the major east/west load-carrying shear walls. Tremblor (Parlfield), Coyote Lake Dam (Morgan This study is summarized in Chapter 6. In this        Hill, 1984), Pleasant Valley Pump Station study, 200 nonlinear time-history analyses, using      (Coalinga), and Dayhook (Tabas) which had to 25 different ground-motion time history inputs,      be scaled upward and modified the most to were performed to define the fragility estimate.      produce a reference 9a = 3.0 g consistently produced the largest drifts (damage) after being scaled upward to that level. Results using each The turbine building fragility estimate specifically  ground-motion record were equally weighted; this applies to the onset of severe structural distress    decision produced a much lower HCLPF &sect;.
(significant strength degradation) to the major      capacity estimate than would have resulted if only east/west shear walls. Structural distress generally  the highest ground-motion records had been does not correspond to partial collapse, depending    used. Basically, average spectral acceleration is on the power of the ground-motion record that        one of the best single ground-motion parameters; remains after this state of distress is reached.      it does not serve as a highly accurate descriptor of Furthermore, partial collapse is likely to be well    the capability of ground motions to damage the short of total collapse, even if partial collapse    turbine building shear walls. Because of the large occurs. Even so, in the seismic probabilistic risk    scatter of computed drifts for the same average assessment study, and in this margin evaluation,      spectral acceleration, the fragility variability the onset of structural distress of these shear walls factors PR and pu were significantly increased.
has been conservatively used as a surrogate for a    This resulted in significant reduction of the structure-induced failure of all safety equipment    HCLPF S. capacity. When compared to a specific housed in the turbine building. This substitution    ground-response      spectrum,      such      as    the introduces an Indeterminate, but probably            84 percent      probability  of      nonexceedance substantial conservatism.                            site-specific ground-motion spectrum, the single-parameter fragility method HCLPF84 9, capacity is conservatively biased, because it must also cover Fragility statements on the onset of shear wall ground motions having differing spectral shapes.
distress were anchored to the average 5 percent damped spectral acceleration in the 3 to 8.5 hertz frequency range for use in the seismic probabilistic  The 75 deterministic time history analyses risk assessment. Therefore, all 25 ground-motion      performed for the 25 ground-motion records each records that were used in the nonlinear analyses      scaled to 9. = 3.0 g provide a more precise were scaled upward so that each had the same          multiple parameter description of the seismic average spectral accelerations &sect;,. A total of 75      margin of the turbine building shear walls than nonlinear analyses were performed at 9. = 3.0 g      could be incorporated into the single parameter and 6.0 g, and 50 nonlinear analyses were            average spectral acceleration used in the seismic performed        at &sect;.      = 4.0 g, with each      probabilistic risk assessment. It was found that ground-motion recording being used an equal          large shear wall drifts (and thus, damage) only number of times.                                      resulted when the ground motions produced high Dialito Canyon Powet Plant IQ    Pacific Gas and Electdc Company                                              Long Term Seismic Program
 
Chapter 7                                                                                            Page 7-54 Chai:,ter 7                                                                                          Page 7-54 spectral accelerations, both at high frequency (8.6      there is a 45 percent margin between the 84 to 9.5 hertz) associated with the elastic frequency      percent site-specific ground-motion response of the shear walls, and at low frequency (1.7 to        spectrum and the deterministically defined turbine 2.8 hertz). Substantial spectral accelerations were      building shear wall HCLPF capacity.
needed at high frequency to drive the shear walls into the inelastic regime. Substantial low-              Multiple nonlinear time-history analyses were not frequency spectral acceleration was then needed          performed for other failure modes of the turbine to produce damaging levels of shear wall drift as        building. These failure modes have HCLPF8 Sa the shear wall frequencies shifted due to inelastic      capacities back-calculated from fragility estimates behavior. In other words, very broad frequency          that are greater than the 2.21 g obtained for the content (1.7 to 9.5 hertz) was necessary within          turbine building east/west shear walls. It is our the ground-motion record to produce severe              judgment that these other failure modes would damage at $. = 3.0 g. The required breadth of            have multiple parameter deterministic HCLPF frequency content was not adequately captured by        capacities also greater than those for the turbine a single ground-motion parameter. An improved            building east/west shear walls.
deterministic seismic margin HCLPF capacity Defining seismic margin as the difference between statement is obtained by requiring both the following high frequency and either of the two low      the    appropriate  HCLPF      capacity      and    the frequency limits to be exceeded:                        84 percent      probability  of      nonexceedance site-specific ground-motion average spectral HCLPF Limits acceleration, the following conclusions can be reached:
High Frequency Limit
* The seismic margin for the turbine building is at least 14 percent, and most likely in excess Maximum S,5,,            : 1.6 g (within 8.6 to 9.5      of 40 percent.
hertz)
* The HCLPF capacity does not represent a and                                                            "cliff" beyond which failure immediately occurs. Instead, it is close to a lower-bound, Low Frequency Limit                                          below which there is no significant likelihood of failure. The median capacity for the Maximum Sa59.              2.8 g  (within 2.4 to turbine building is more than 2.5 times its 2.8 hertz)
HCLPF capacity, and the probability of or failure would only gradually increase if the Maximum Sa,,              *2.25 g (within 1.7.to        ground motion were to exceed the HCLPF 2.0 hertz)            capacity.
The 84 percent probability of nonexceedance
* Other than the turbine building, all structures site-specific ground motion 5 percent damped                  and equipment items whose failure could lead response spectrum gives spectral accelerations of            to seismic risk to the Plant have at least a 1.79 g, 1.83 g, and 1.55 g at 8.6 hertz, 2.8 hertz            40-percent margin between the HCLPF and 2.0 hertz, respectively. Thus, the high                  capacity and the 84 percent probability of frequency HCLPF limit of the turbine building                nonexceedance site-specific ground motion.
shear wall is exceeded and nonlinear drift is possible. However, the low-frequency HCLPF              Conclusions of Margin Assessment limits are well above the 84 percent probability of nonexceedance          site-specific      ground-motion The deterministic evaluation discussed in this response spectrum, so nonlinear drifts cannot            chapter demonstrates that the Diablo Canyon become large. The ratio at 2.8 hertz is 2.8/1.83 =      Plant has adequate margin 'to accommodate the 1.53, and at 2.0 hertz, is 2.25/1.55 = 1.45. Thus,      site-specific ground motions for the maximum Olablo Canyon Power Plant I    Pacilic Gas and Electric Company                                                  Long Term Seismic Program
 
Chanter 7                                                                                      Page 7-55 Chanter 7                                                                                      Page 7-55 earthquake on the Hosgri fault, as evidenced by      Prassinos, P. G., Ravindra, M. K., and Savy, the following:                                            J. B., 1986, Recommendations to the Nuclear Regulatory Commission on trial guidelines for
"  The containment building has a seismic                seismic margin reviews: NUREG/CR4482 margin of at least 100 percent and the                (draft).
auxiliary building has a seismic margin of at least 70 percent. The most critical structure    Prassinos, P. G., Murray, R. C., and Cummings, was identified as the turbine building, which        G. E., 1987, Seismic margin review of Maine.
has a seismic margin at least 14 percent, and        Yankee        Atomic      Power          Station:
most likely in excess of 40 percent.                  NUREG/CR4826.
U.S. Nuclear Regulatory Commission, 1976,
* Among the plant components, relay chatter of Supplement No. 5 to the safety evaluation the 4-kV switchgear may occur. However, the report of the Diablo Canyon Nuclear Power switchgear structure has ample margin to Station Units 1 and 2.
accommodate          demands    due  to the site-specific ground motions. Therefore, no structural failure will occur. Also, the ease of recovery and specific plant procedures essentially eliminate any concern due to relay chatter.
* For all components, except the 4-kV switchgear, the minimum seismic margin is shown to be in excess of 40 percent.
REFERENCES Budnitz, R. J., Annico, P. J., Cornell, C. A.,
Hall, W. J., Kennedy, R. P., Reed, J. W.,
and Shinozuka, M., 1985,- An approach to quantification of seismic margins in nuclear power plants: NUREG/CR4334.
Campbell, R.D., and Others, 1987, Evaluation of nuclear power plant seismic margin: NTS Engineering Report No. 1551.05, Electric Power Research Institute (draft).
Kennedy, R. P., 1984, Various types of reported seismic margins and their uses: Section 2, Proceedings of EPRI/NRC Workshop on Nuclear Power Plant Reevaluation for Earthquakes Larger than SSE, Palo Alto, California.
Kennedy, R. P., Wesley, D. A., and Tong, W. H., 1988, Probabilistic evaluation of the Diablo Canyon turbine building seismic capacity using nonlinear time history analyses:
NTS Engineering Report No. 1643.01.
Diabto Canyon Power Plant IN    Pacific Gas and Electric Company                                            Long Term Seismic Program}}

Latest revision as of 22:23, 12 January 2025

License Amendment Request 11-05, Evaluation Process for New Seismic Information and Clarifying the Diablo Canyon Power Plant Safe Shutdown Earthquake
ML11312A166
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 10/20/2011
From: Becker J
Pacific Gas & Electric Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
PG&E Letter DCL-11-097, DCL-11-097
Download: ML11312A166 (408)
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