ML043350244
| ML043350244 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/30/2004 |
| From: | Fields M NRC/NRR/DLPM/LPD4 |
| To: | Overbeck G Arizona Public Service Co |
| Fields M, NRR/DLPM, 415-3062 | |
| Shared Package | |
| ML043350261 | List: |
| References | |
| IR-04-012 | |
| Download: ML043350244 (6) | |
Text
November 30, 2004 Mr. Gregg R. Overbeck Senior Vice President, Nuclear Arizona Public Service Company P. O. Box 52034 Phoenix, AZ 85072-2034
SUBJECT:
PALO VERDE NUCLEAR GENERATING STATION, UNITS 1, 2, AND 3 -
REVIEW OF PRELIMINARY ACCIDENT SEQUENCE PRECURSOR ANALYSIS OF THE JUNE 14, 2004, LOSS OF OFFSITE POWER EVENT
Dear Mr. Overbeck:
Enclosed for your review and comment is a copy of the preliminary Accident Sequence Precursor (ASP) Program analysis of a loss of offsite power event which occurred at Palo Verde Nuclear Generating Station (Palo Verde), Units 1, 2, and 3, on June 14, 2004. This event was documented by Arizona Company in Licensee Event Report 50-528/2004-006, dated August 13, 2004, and by the U.S. Nuclear Regulatory Commission (NRC) staff in Inspection Report 05000528/2004012 dated July 16, 2004. The results of the preliminary ASP analysis indicate that this event is an accident precursor (i.e., conditional core damage probability > 1 x10-6).
In assessing operational events, the NRC staff strives to make the ASP models as realistic as possible regarding the specific features and response of a given plant to various accident sequence initiators. The NRC staff realizes that licensees may have additional systems and emergency procedures or other features at its plants that might affect the analysis. Therefore, the NRC staff is providing you an opportunity to review and comment on the technical adequacy of the preliminary ASP analysis, including the depiction of plant equipment and equipment capabilities. Upon receipt and evaluation of your comments, the NRC staff will revise the conditional core damage probability calculations where necessary to consider the specific information you provided. The object of the review process is to provide as realistic an analysis of the significance of the event as possible.
In order for the NRC staff to incorporate your comments, perform any required re-analysis, and prepare the final report of analysis in a timely manner, you are requested to complete your review and to provide any comments within 60 calendar days from the date of this letter. As soon as the final analysis of this event has been completed, the NRC staff will provide for your information the final precursor analysis and the resolution of your comments.
The NRC staff has also enclosed information to facilitate your review. Enclosure 2 contains specific guidance for performing the requested review, identifies the criteria which the NRC staff will apply to determine whether any credit should be given in the analysis for the use of licensee-identified additional equipment or specific actions in recovering from the event, and describes the specific information that you should provide to support such a claim.
G. Overbeck This request is covered by the existing OMB clearance number (3150-0104) for NRC staff follow-up reviews of events documented in licensee event reports. Your response to this request is voluntary and does not constitute a licensing requirement.
The NRC staff is continuing to review the appropriate classification of these documents within our records management program, considering changes in our practices following the events of September 11, 2001. Pending a final determination, the enclosed analyses have been marked as sensitive information. Therefore, the NRC staff has not made it publicly available. Please control the document accordingly. You will be informed if the classification of the document changes as a result of our ongoing assessments. If you believe that your response to this letter includes potentially sensitive information, please discuss the matter with me prior to submitting the information.
If you have any questions regarding the analysis, please contact me at (301) 415-3062.
Sincerely,
/RA/
Mel B. Fields, Senior Project Manager Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. STN 50-528, STN 50-529, and STN 50-530
Enclosures:
- 1. Preliminary ASP Analysis (Sensitive - Not For Public Disclosure)
- 2. ASP Review Guidance cc w/encl. 2 only: See next page
G. Overbeck November 30, 2004 This request is covered by the existing OMB clearance number (3150-0104) for NRC staff follow-up reviews of events documented in licensee event reports. Your response to this request is voluntary and does not constitute a licensing requirement.
The NRC staff is continuing to review the appropriate classification of these documents within our records management program, considering changes in our practices following the events of September 11, 2001. Pending a final determination, the enclosed analyses have been marked as sensitive information. Therefore, the NRC staff has not made it publicly available. Please control the document accordingly. You will be informed if the classification of the document changes as a result of our ongoing assessments. If you believe that your response to this letter includes potentially sensitive information, please discuss the matter with me prior to submitting the information.
If you have any questions regarding the analysis, please contact me at (301) 415-3062.
Sincerely,
/RA/
Mel B. Fields, Senior Project Manager Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. STN 50-528, STN 50-529, and STN 50-530
Enclosures:
- 1. Preliminary ASP Analysis (Sensitive - Not For Public Disclosure)
- 2. ASP Review Guidance cc w/encl. 2 only: See next page DISTRIBUTION w/o enclosure 1:
PUBLIC RidsNrrLpdivHBerkow RidsNrrPMMFields PDIV-2 r/f RidsAcrsAcnwMailCenter RidsRgn4MailCenter (TPruett)
GHill (6) RidsNrrLADBaxley RidsOgcRp JDixon-Herrity, EDO ENCLOSURE 1: ML04335271 PACKAGE NO.: ML043350261 ACCESSION NO: ML043350244 Nrr-106 OFFICE PDIV-2/PM PDIV-2/LA PDIV-2/SC NAME MFields:mp DBaxley RGramm DATE 11-29-04 11/29/04 11/30/04 OFFICIAL RECORD COPY
Enclosure 2 GUIDANCE FOR LICENSEE REVIEW OF PRELIMINARY ASP ANALYSIS
Background
- transients, The preliminary precursor analysis of an - small loss-of-coolant accidents (LOCAs),
event or condition that occurred at your - steam generator tube rupture (PWR plant has been provided for your review. only), and This analysis was performed as a part of the - loss of offsite power (LOSP).
NRC's Accident Sequence Precursor (ASP)
Program. The ASP Program uses The only support system modeled in Rev. 2 probabilistic risk assessment techniques to is the electric power system.
provide estimates of operating event significance in terms of the potential for core
- SPAR Rev. 3 models are currently being damage. developed to replace Rev. 2 models. The newer revision models have 11 types of The types of events evaluated include actual initiating events:
initiating events, such as a loss of off-site power or loss-of-coolant accident, - transients, degradation of plant conditions, and safety - small LOCAs, equipment failures or unavailabilities that - medium LOCA, could increase the probability of core - large LOCA, damage from postulated accident - interfacing system LOCA, sequences. - steam generator tube rupture (PWR only),
This preliminary analysis was conducted - LOSP, using the information contained in the plant- - loss of component cooling water (PWRs specific final safety analysis report (FSAR), only),
individual plant examination (IPE), and other - loss of service water, and pertinent reports, such as the licensee event - loss of DC power.
report (LER) and/or NRC inspection reports.
Both revisions have transfer events trees for Modeling Techniques station blackout and anticipated transient without scram.
The models used for the analysis of events were developed by the Idaho National The models may be modified to include Engineering and Environmental Laboratory. additional detail for the The models were developed using the systems/components of interest for a Systems Analysis Programs for Hands-on particular event. This may include additional Integrated Reliability Evaluations (SAPHIRE) equipment or mitigation strategies as software. The developed models are called outlined in the FSAR or IPE. Probabilities Standardized Plant Analysis Risk (SPAR) are modified to reflect the particular models. The SPAR models are based on circumstances of the event being analyzed.
linked fault trees. Fault trees were developed for each top event on the event Guidance for Peer Review trees to a super component level of detail.
Comments regarding the analysis should Two revisions of the SPAR models are address:
currently being used in the ASP analysis:
- Does the "Event Summary" section:
- SPAR Rev. 2 models have four types of - accurately describe the event as it initiating events: occurred; and 1
procedures,
- provide accurate additional information concerning the configuration of the plant
- piping and instrumentation diagrams and the operation of and procedures (P&IDs),
associated with relevant systems?
- electrical one-line diagrams,
- Does the "Modeling Assumptions" section:
- results of thermal-hydraulic analyses, and
- accurately describe the modeling done for the event;
- operator training (both procedures and simulation).
- accurately describe the modeling of the This documentation must be current at the event appropriate for the events that time of the event occurrence. Systems, occurred or that had the potential to equipment, or specific recovery actions that occur under the event conditions; and were not in place at the time of the event will not be considered. Also, the documentation
- include assumptions regarding the should address the impact (both positive likelihood of equipment recovery? and negative) of the use of the specific recovery measure on:
Appendix G of Reference 1 provides examples of comments and responses for
- the sequence of events, previous ASP analyses.
- the timing of events, Criteria for Evaluating Comments
- the probability of operator error in using Modifications to the event analysis may be the system or equipment, and made based on the comments that you provide. Specific documentation will be
- other systems/processes already modeled required to consider modifications to the in the analysis (including operator event analysis. References should be made actions).
to portions of the LER or other event documentation concerning the sequence of An Example of a Recovery Measure events. System and component capabilities Evaluation should be supported by references to the FSAR, IPE, plant procedures, or analyses. A pressurized-water reactor plant Comments related to operator response experiences a reactor trip. During the times and capabilities should reference plant subsequent recovery, it is discovered that procedures, the FSAR, the IPE, or applicable one train of the auxiliary feedwater (AFW) operator response models. Assumptions system is unavailable. Absent any further used in determining failure probabilities information regrading this event, the ASP should be clearly stated. Program would analyze it as a reactor trip with one train of AFW unavailable. The AFW Criteria for Evaluating Additional Recovery modeling would be patterned after Measures information gathered either from the plant FSAR or the IPE. However, if information is Additional systems, equipment, or specific received about the use of an additional recovery actions may be considered for system (such as a standby steam generator incorporation into the analysis. However, to feedwater system) in recovering from this assess the viability and effectiveness of the event, the transient would be modeled as a equipment and methods, the appropriate reactor trip with one train of AFW documentation must be included in your unavailable, but this unavailability would be response. This includes: mitigated by the use of the standby feedwater system.
- normal or emergency operating 2
The mitigation effect for the standby system on the operation and recovery of feedwater system would be credited in the systems or procedures that are already analysis provided that the following material included in the event modeling. In this was available: case, use of the standby feedwater system may reduce the likelihood of recovering
- standby feedwater system characteristics failed AFW equipment or initiating feed-are documented in the FSAR or accounted and-bleed due to time and personnel for in the IPE, constraints.
- procedures for using the system during Schedule recovery existed at the time of the event, Please refer to the transmittal letter for
- the plant operators had been trained in the schedules and procedures for submitting use of the system prior to the event, your comments.
- a clear diagram of the system is available Reference (either in the FSAR, IPE, or supplied by the licensee), 1. R. J. Belles, et al., Precursors to Potential Severe Core Damage
- previous analyses have indicated that Accidents: 1997, A Status Report, there would be sufficient time available to USNRC Report NUREG/CR-4674 implement the procedure successfully (ORNL/NOAC-232) Volume 26, Lockheed under the circumstances of the event Martin Energy Research Corp., Oak under analysis, and Ridge National Laboratory, and Science Applications International Corp., Oak
- the effects of using the standby feedwater Ridge, Tennessee, November 1998.
3
Palo Verde Generating Station, Units 1, 2, and 3 cc:
Mr. Steve Olea Mr. John Taylor Arizona Corporation Commission Public Service Company of New Mexico 1200 W. Washington Street 2401 Aztec NE, MS Z110 Phoenix, AZ 85007 Albuquerque, NM 87107-4224 Douglas Kent Porter Ms. Cheryl Adams Senior Counsel Southern California Edison Company Southern California Edison Company 5000 Pacific Coast Hwy Bldg DIN Law Department, Generation Resources San Clemente, CA 92672 P.O. Box 800 Rosemead, CA 91770 Mr. Robert Henry Salt River Project Senior Resident Inspector 6504 East Thomas Road U.S. Nuclear Regulatory Commission Scottsdale, AZ 85251 P. O. Box 40 Buckeye, AZ 85326 Mr. Jeffrey T. Weikert Assistant General Counsel Regional Administrator, Region IV El Paso Electric Company U.S. Nuclear Regulatory Commission Mail Location 167 Harris Tower & Pavillion 123 W. Mills 611 Ryan Plaza Drive, Suite 400 El Paso, TX 79901 Arlington, TX 76011-8064 Mr. John Schumann Chairman Los Angeles Department of Water & Power Maricopa County Board of Supervisors Southern California Public Power Authority 301 W. Jefferson, 10th Floor P.O. Box 51111, Room 1255-C Phoenix, AZ 85003 Los Angeles, CA 90051-0100 Mr. Aubrey V. Godwin, Director Brian Almon Arizona Radiation Regulatory Agency Public Utility Commission 4814 South 40 Street William B. Travis Building Phoenix, AZ 85040 P. O. Box 13326 1701 North Congress Avenue Mr. M. Dwayne Carnes, Director Austin, TX 78701-3326 Regulatory Affairs/Nuclear Assurance Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072-2034 Mr. Hector R. Puente Vice President, Power Generation El Paso Electric Company 310 E. Palm Lane, Suite 310 Phoenix, AZ 85004 November 2003