ML20112B040
| ML20112B040 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/11/1985 |
| From: | Linderman R BECHTEL GROUP, INC. |
| To: | |
| Shared Package | |
| ML20112B019 | List: |
| References | |
| OL, NUDOCS 8503180576 | |
| Download: ML20112B040 (44) | |
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' 5 f.Ul 18 All :15 EXHIBIT 2
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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HOUSTON LIGHTING & POWER
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Docket Nos. 50-498 OL COMPANY, ET AL.
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50-499 OL
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(South Texas Project,
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Units 1 and 2)
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AFFIDAVIT OF R.
BRUCE LINDERMAN 1.
My name is R. Bruce Linderman.
My business address is 12440 E.
Imperial Highway, Norwalk, California.
I am an Engineering Specialist for the Western Power Division of the Bechtel Power Corporation.
A statement of my background and qualifications is provided as Attachment I to this Affidavit.
2.
The purpose of this Affidavit is to describe how i
Category I structures and equipment for the South Texas Project
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(STP) are designed to' withstand hurricane wind loads, and how such structures and equipment are protected against hurricane-induced collapse of non-Category I structures and hurricane-generated missiles.
In preparing this Affidavit, I have reviewed pertinent portions of the STP FSAR, as well as various design calculations and other information relating to STP wind design.
8503180576 850312 PDR ADOCK 05000498 G
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3.
Before addressing the STP design itself, I would like to describe, in general terms, how forces resulting from winds are factored into nuclear power plant design.
4.
The design of a nuclear power plant takes into account various load " combinations" under which Category I structures must be capable of performing their safety functions.
Some of these combinations include " severe" conditions (such as an operating basis wind (OBW) or operating basis earthquake) which, although unlikely, are utilized as operating basis conditions.
Structures, systems and components necessary for continued operation must be designed to remain functional under such conditions without posing an undue risk to the public health and safety.
5.
Other load combinations include " extreme" conditions (such as a design basis tornado (DBT) or safe shutdown earthquake), which are even less likely to occur and are utilized as design basis conditions.
Under such conditions, safety-related structures, cystemsandcomponenthmustbedesignedto perform their safety functions and thereby ensure that there is no undue risk to the public health and safety, though subsequent operation would not be assumed.
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6.
Since severe conditions are more likely to occur than extreme conditions, an additional margin of safety is provided through the application of " load factors," or through other means, in order to account for uncertainties in data and the quality of construction.
Application of the load factor increases the load assumed to result from the specific severe condition.
7.
Section 2.3.1 of the NRC Standard Review Plan (Rev. 2, July 1981) (SRP) provides for the calculation of an OBW on the basis of a 100-year recurrence fastest-mile wind speed.
Thus, nuclear power plants are designed to continue operation without creating an undue risk to the public health and safety under wind conditions anticipated to occur only once in 100 years.
Even if an OBW is exceeded, however, nuclear power plants are still designed to perform all necessary safety functions under design basis conditions (such as a DBT).
Accordingly, while operation may be prohibited should the 100-year recurrence operating basis event be exceeded, there would be no adverse effect on the public health and safety. *
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As a result, use of a less frequent recurrence interval value for calculating an OBW would necessitate costly recalculations or analyses without resulting in additional protection to the public health and safety.
8.
Once the OBW is determined, the resulting load on Category I structures is calculated in accordance with section 3.3.1 of the SRP and Reference 1 and utilized in the appropriate load combinations in accordance with SRP sections 3.8.1 and 3.8.4.
9.
The design of a nuclear power plant should also take into account a DBT as defined in NRC Regulatory Guide 1.76 (Reg. Guide 1.76), in combination with other appropriate loads.
Reg. Guide 1.76 provides that within the geographic region where l
the STP is located, the design o'f a nuclear power plant should consider a DBT having a maximum wind speed of 360 mph (comprised of a rotational elementlof 290 mph and a translational element of 70 mph), a pressure drop of 3.0 psi and a pressure drop rate of 2.0 psi per second.
Adequate protection against extreme-wind generated missiles should also be provided in accordance with SRP section 3.5.1.4.
10.
In accordance with sections 3.3.1 and 3.3.2 of the SRP, the design of Category I structures at the STP takes into consideration both an OBW and a DBT.
The STP Category I structures have also been designed to withstand the combined effects of the DBT loads including those resulting from wind, pressurs differential and postulated tornado missiles (discussed further below).
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The OBW for STP is 125 mph at a standard reference height;of 30 feet.
See FSAR at 3.3-1.
The OBW was converted into an equivalent effective pressure in accordance with section 3.3.1 of the SRP and Reference 1.
This effective pressure was utilized in the design of STP Category I structures.- Conversion of the OBW into an equivalent effective pressure was performed in accordance with a methodology generally accepted in the industry and approved by the NRC Staff, which accounts for gusts, as well as sustained winds, and recognizes that wind speeds increase with elevation.
12.
In order to account for the increased loado due to gusts and instantaneous wind speeds, gust factors were applied in calculating loads on STP Category I structures, in accordance with SRP SS 2.3.1, 3.3.1, and Reference 1.
Once the STP 100-year recurrence fastest-mile wind speed at 30 feet was determined, a vertical velocity distribution coefficient was applied to that value to account for increases in wind velocity with elevation above the 30 foot standard reference height in accordance with SRP section 2.3.1 and Reference 1.
See F5'AR at 3.3-1 to 3.3-2.
13.
In designing STP Category I structures, the effects of OBW-generated loads were considered in various combinations with other loads.
An additional margin of safety l
was provided in accordance with SRP sections 3.8.1 and 3.8.4 and the applicable industry codes (References 2,3,4 an'd 5).
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14.
For example, one load combination utilized in the design:of concrete Category I structures other than the contain-ment, considers dead loads (increased by a factor of 1.4), plus live loads (increased by a factor of 1.7), plus OBW loads (increased by a factor of 1.7), plus operating thermal loads (increased by a factor of 1.7), plu,s operating piping loads (increased by a factor of 1.7).
See FSAR Table 3.8.4.-1.
15.
Thus, by virtue of the safety margins provided,-
and the other loads in the applicable load combinations, structures designed on the basis of the 125 mph OBW will be capable of continuing to operate safely under considerably faster wind speeds.
16.
STP Category I structures are also designed to withstand loads generated by a DBT, as defined in Reg. Guide 1.76, in combination with other design basis conditions.
For example, one such load combination utilized in the design of STP concrete Category I structures other than the containment, considers the sum of the dead loads, livei loads, operating thermal loads, operating piping loads and DBT loads (including wind, pressure differential and missiles).
See FSAR Table 3.8.4-1. */ Under the DBT induced load, as well as the loads generate 3 by the other design basis conditions in the applicable
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Other load combinaticns are shown in FSAR Tables 3.8.4-2 and
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3.8.1-1.
load combinations, STP safety-related structures, systems and components are designed to perform their safety functions, ensuring that no undue risk to the public health and safety is created.
17.
The load combinations which include the DBT result in loads on STP Category I structures that are far greater than those resulting from the load combinations which include the OBW.
The wind load resulting from the DBT alone is 332 pounds per square foot, while the OBW-induced load (with applicable gust factor applied) is only 52 pounds per square foot at the 30 foot standard reference height.
Even a 200 mph fastest-mile wind, which is higher than any wind speeds cited by the intervenors (Affidavit of Dale E. Wolfe (Wolfe) at TT 16-18), with gust factor applied, would exert a force of only 133 pounds per square foot at 30 feet and approximately 205 pounds per square foot at the top of the containments.
18.
Thus, although the OBW loads were calculated and factored into the STP design, the loads 15 parted by the DBT are considerably greater in view of the higher wind velocities and the consideration of the combined effects of extensive pressure differentials and missiles. */
When DBT loads are considered in
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Although a hurricane-induced load may be of longer duration than that generated by a tornado, neither exceeds the l
" elastic" range of STP Category I structures under which such structures will withstand loads.without degradation regardless of the length of the load application.
Thus, the
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combination with other design basis conditions, additional assurance is provided that STP Category I structures are designed to withstand loads far in' excess of those generated by even the fastest hurricane wind speeds.
19.
The STP has also been designed to ensure that Category I structures and equipment will not be adversely affected by failure of non-Category I structuree under OBW loads.
Safety-related equipment is housed in Category I structures. **/
With the exception of the STP Turbine Generator Building, non-Category I structures are separated from Category I structures such that the failure of the former.will not impair the ability i
of the latter to perform their intended safety functions.
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20.
In the case of the Turbine Generator Building, where such physical separation cannot be provided, an analysis has been performed which demonstrates that it will withstand the possibility that a hurricane-induced load may be applied to STP Category I structures for a longer period than tornado-induced loads is irrelevant to the analysis' described above.
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Certain Class IE instrumentation circuits are located in a
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non-Category I structure (Turbine Generator Building). Since these circuits are not required for safe shutdown, even their com,lete failure.would not jeopardize the public health and safety.
_ Certain piping containing radioactive fluid, associated with the steam generator blowdown system, is also housed in l-the Turbine Generator Building.. Even in the event of the complete failure of this piping, the system has been designed to maintain radioactive releases within a small fraction of 10 C.F.R. Part.100' guidelines and will not, j
therefore, jeopardize the public health and safety.
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i DBT loads governing the design of Category I structures, though some l'oss of siding may occur.
The potential loss of siding will have no effect on Category I structures at the site.
Since the DBT criteria envelope potential hurricane-induced failures of non-Category I structures, adequate assurance has been provided that Category I structures (and saf'ety-related equipment contained therein) will not be adversely affected by collapse of non-Category I structures under hurricane wind loads.
21.
Thus, STP Category I structures and equipment are designed to be adequately protected against the consequences of failure of non-Category I structures as a result of hurricane wind loads.
22.
Category I structures at STP (with the exception of the Isolation Valve cubicle (IVC) roof) are also designed to withstand a spectrum of missiles which might be generated by a-DBT in accordance with section 3.5.1.4 of the SRP.
See FSAR at 3.5-15.
As defined in that section of the SRP, the missile spectrum utilized includes steel reinforcing bar, several varieties of steel pipe, utility poles, wooden planks and automobiles.
This spectrum envelopes missiles which could be generated from non-Category I structures.
4 1.
23.
Furthermore, the spectrum also encompasses those missiles which could credibly be generated by hurricanes.
Missile velocities, calculated on the basis of a DBT velocity of 360 mph, exceed the velocities of missiles potentially generated by hurricanes.
In addition, tornadoes create suction which results in a significantly greater potential for missile genera-tion than hurricanes.
Thus, consideration of DBT-generated missiles in the design of Category I structures (other than the IVC roof) provides further assurance that such structures are capable of withstanding hurricane-generated missiles.
24.
Rather than designing the IVC roof to withstand DBT-generated missiles, HL&P has demonstrated, in accordance with SRP section 3.5.1.4 and Regulatory Guide 1.117, that the probability of a tornado-generated missile striking the IVC roof is sufficiently low (a median value of 2x10-10 per year) that the design need not take into account the possibility of such an event.
See Letter, J. H. Goldberg to Thomas M. Novak (September 13, 1983), Attachment 3 at 4 (provided as Attachment II to this Affidavit).
Thepossibilityofahurricabe-inducedmissile striking the IVC roof (a median value of 1.2x10-10 per year) has also been evaluated and determined to be an insignificant threat to the IVC.
See Letter, J. H. Goldberg to Thomas M. Novak (Novembei 14, 1983), Attachment 2 at 1-2, 4 (provided as 1
Attachment III to this Affidavit).
The NRC Staff, after review
- of the STP analyses, and the evaluation by its consultant
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commissioned to review those analyses, concluded that HLEP had demonstrated compliance with applicable requirements governing the design of the IVC for. tornado and hurricane-generated missiles.
See Letter, Thomas M. Novak to J. H. Goldberg (January 6, 1984), Enclosure 1 at 6 (provided as Attachment IV to this Affidavit).
25.
Finally, the potential of hurricane-induced storm surge or heavy rains jeopardizing STP Category I structures and equipment has been addressed in FSAR sections 2.4.5 and'2.4.14.
The probable maximum hurricane storm surge, combined with the 100-year flood level in the Colorado River,' produces a water surface elevation of 26.74 feet.
This is below the grade level in the power block area of the Plant of 28.0 feet, where Category I structures are located, and below the elevation of roads bounding the power block (30.0 feet) and will, therefore, not jeopardize such structures.
CONCLUSION
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26.
STP Category I structures and equipment have'been adequately designed to withstand hurricane w'ind loads.
Category I structures have'been designed to withstand loads generated by a DBT in combination with other extreme conditions, which envelope loads gederated by the OBW and other severe conditions.
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27.
Furthermore, through physical separation or other design' characteristics of non-Category I structures, adequate assurance has been provided that Category I structures (and the safety-related equipment contained therein) will not be adversely affected by collapse of non-Category I structures under hurricane and DBT wind loads.
28.
Finally, use of the DBT in defining the spectrum and velocities of missiles which might impact upon Category I structures provides assurance that such structures will not be.-
adversely affected by hurricane-generated missiles.
Similar assurance regarding safety-related equipment in the IVC has been demonstrated through probabilistic analyses consistent with applicable Staff guidance.
As a result, STP Category I structures have been adequately designed to withstand the effects of hurricane winds.
REFERENCES 1.
ANSI A58.1, Building Code Requirements for Minimum Design Loads in Buildings and Other Structures (1972).
2.
Building Code Requirements for Reinforced Concrete, American Concrete Institute 318 (1977).
3.
Manual of Steel Construction, American Institute i
of Steel Construction (1973).
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4.
Proposed Standard Code for Concrete Reactor i
Vessels and Containments, American Concrete Institute 359.
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5.
American Society of Mechanical Engineers Code,Section III, Division 2 (including addenda 1-6).
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State of California
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ss County of Los Angeles
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I, R.
Bruce Linderman, Engineering Specialist, Western Power Division. Bechtel Power Corporation, of lawful age, being first duly sworn, upon my oath certify that I have reviewed and am thoroughly familiar with the statements contained in this Affidavit and that all statements contained herein are true and correct to the best of my knowledge and belief.
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Subscribed and sworn to before me this //
day of OC A-1985-gg.c k..
r OFFICIAL SEAL NANCY A GETMAN NOTARY PUBLIC - CAUFORNIA LOS ANGELES COUNTY W gmus echs CCT 1.1986
LINDERMAN AFFIDAVIT ATTACHMENT I R. BRUCE LINDERMAN EDUCATION BS, Civil Engineering, Utah State University (1949)
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MS, Civil Engineering, California Institute of Technology (1950)
Engineer's Degree, Civil Engineering, California Institute of Technology (1952)
MBA, Golden Gate University (1974)
EXPERIENCE In a Bechtel career of more than 30 years, Mr. Linderman has specialized in seismic and dynamic force considerations in the design of nuclear and fossil power plants, dams, hardened missile sites, and industrial complexes.
He is p'resently an Engineering Specialist on special problems with nuclear power plants, includ-ing seismic equipment qualification, missile-impact problems, seismic design, and other topics.
Mr. Linderman supervises, prepares, and reviews guidelines and topicals for the Bechtel thermo nuclear power group. Subjects Design Guide for Design of Structures for Missile Impact; are:
Tornado and Extreme Wind Design Criteria for Nuclear Power Plants; Design Guide for Design of Structures for Tornado Missile Impact; Proof of Operability of Active Valves; and Standard Specification for Seismic Qualification of Category I Equipment.
Mr. Linderman also provides consulting services to nuclear projects on preparing PSARs, FSARs and specifications, and gives technical assistance on special topics such as dynamic problems including seismic, impacting projectiles, and shock loadings.
He consults for projects on designing facilities to resist ground shock and overpressures resulting from nuclear weapons or other explosives.
MEMBERSHIP 3 AND PROFESSIONAL AFFILIATIONS i
Registered Professional Engineer, Civil and Structural, I
California Member, Structural Engineers Association of Southern California Member, American Society of Civil Engineers
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Member, Seismological Society of America Member," Earthquake Engineering Research Institute Member, Recommended Practices for Seismic Qualification of Class lE Equipment for Nuclear Power Generation Systems l
Member, ANS 56.9 Environmental Envelopes for Light Water Reactor Nuclear Power Plants Director, Applied Technology Council
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LINDERMAN AFFIDAVIT ATTACHMENT II 1"
The Light OIIIhEf Houston Lighting & Power P.O. Box 1700 Houston, Texas 77001 (713)228-9211
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September 13, 1983 ST-HL-AE-1003 File Number: C22/G2/G25 Mr. Thomas M. Novak Assistant Director of Licensing U. S. Nuclear Regulatory Comission Washington, D.C.
20555
Dear Mr. Novak:
South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Isolation Valve Cubicle Roof Design On July 14, 1983 representatives of Houston Lighting & Power Company (HL&P) and Bechtel met with members of your staff to discuss the South Texas Project (STP) proposed design for the roof of the Isolation Valve Cubicle (IVC). As a result of that meeting, the NRC requested that supplemental information be provided. HL&P committed to provide a description of the various design / analysis alternatives which were evaluated as part of the IVC design and a detailed report regarding the probabilistic evaluations for hurricane and tornado-generated missiles. The attachments to this letter provide the requested infonnation. A sumary of the attachments is discussed below.
Attachment #1 provides a comparison of the various design alternatives which were considered, including estimates of the cost and schedule implications for each.
In addition, the advantages and disadvantages of each alternative are provided. Based upon this comparison, we believe the IVC roof design without tornado missile protection to be justified.
Attachment #2 provides a report regarding the probabilistic evaluation of hurricane-generated missiles and their potential impact to the IVC roof.
The results indicate that hurricane-generated missiles are not a significant hazard to the IVC and that no physical barriers are required for the roof.
Hurricane Alicia is not addressed in this analysis. However, preliminary information obtained from the National Weather Service indicates that this hurricane would not affect the outcome of the analysis. A straight-line wind of at least 180 m.p.h. is required to generate a missile of the type that was identified and evaluated in the study perfonned by the Electric Power Research Institute (EPRI). Therefore, only tornadic winds pose a potential for missile generation that needs to be considered in the probabilistic evaluation.
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1 September 13 1983 ST-HL-AE-1005 File Number: C22/G2/G25 Page 2 Lastly, Attachment #3 provides a report regarding the probabilistic evaluation of tornado-generated missiles and their potential. impact on the IVC roof..The results indicate that tornado-generated missiles are not a significant hazard to the IVC and that no physical barriers are required at the top of the IVC to protect equipment located in the IVC from potential tornado-generated missiles. The median valu for the probability for tornado missiledamagetotheIVCequipmentof2x10f0 per year is well within the NRC acceptance criteria of 10 to 10-6 per year (as identified in the 4
Standard Review Plan (SRP), Section 2.2.3).
j It should be noted that significant conservative assumptions are used in l
the probability analysis. As sumarized on pages 3 and 4 of Attachment #3 these conservatisms provide significant added justification for the proposed IVC roof design.
In particular, the design of in6ividual compartment walls.
i up to the IVC roof level substantially decreases the probability that a l
single missile would be capable of damaging more than one train. Further-more, the assumption of severe damage associated with any missile strike is itself an additional highly conservative effect. Thus a requirement to provide missile protection for the IVC roof is associated with an event that has a vanishingly small probability of occurrence.
Indeed, the probability of IVC missile damage is significantly less than the normal acceptance criteria associated with aircraft hazard analyses. To our knowledge, protection for these types of events with extremely low probability of occurrence has not been required. The resources that would be required to provide missile protection can better be used on other features of plant design with a more direct bearing on the safety of operation of the plant.
i The attached reports should provide sufficient infonnation for the NRC i
staff to complete their review of our proposed design.
In light of construction milestones which impact the IVC, your immediate review and concurrence is requested. Resolution of this matter is required by September 30, 1983 so as not to impact the design and construction schedule.
Mr. Michael E. Powell at (y questions concerning this item, please contact If you should have an 713)877-3281.
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.it Very truly yours, l
J. H. Goldberg Vice President l
Nuclear Engineering & Construction MEP/mg Attachments (3)
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Houston Ughdngic Power Company cc:
G. W. Oprea, Jr.
l INN 1b J. H. Goldberg File Number: C22/G2 J. G. Dewease G25 J. D. Parsons Page 3 D..G. Barker M. R. Wisenburg R. A. Frazar J. W. Williams R. J. Maroni J. E. Geiger H. A. Walker
- 5. M. Dew J. T. Collins A. Vietti W. M. Hill, Jr.
M. D. Schwarz Baker & Botts)
R. Gordon Gooch Baker & Botts)
J. R. Newman Lowenstein Newman, Reis, 8 Axelrad)
Director, Office of Inspection & Enforcement Nuclear Regulatory Comission Washington, D. C. 20555 G. W. Muench/R. L. Range Charles Bechhoefer Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board i
P. O. Box 2121 U. S. Nuclear Regulatory Comission Corpus Christi, Texas 78403 Washington, D. C.
20555 4
H. L. Peterson/G. Pokorny Dr. James C. Lamb III City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514
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J. B. Poston/A. vonRosenberg Mr. Ernest E. Hill City Public Service Board Lawrence Livermore Laboratory P. O. Box 1771 University of California l
San Antonio, Texas 78296 -
P. D. Box 808 L-46 l
Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan, III Assistant Attorney General Harmon & Weiss for the State of Texas 1725 I Street, N. W.
P. O. Box 12548 Suite 506 Capitol Station Washington, D. C.
.Lenny Sinkin Citizens for Equitable Utilities Inc.
Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn 5106 Casa Oro Route 1. Box 1684 San Antonio, Texas 78233 Brazoria Texas 77422 i
l Robert G. Perlis, Esquire Hearing Attorney-Office of the Executive Legal Director U. S. Nuclear Regulatory Comission Washington, D. C.
20555 Revision Date 07-05-83 Note: Due to the bulk of the attachments, they were sent only to the addressee, J. T. Collins, A. Vietti, Office of ISE and members of the ASLB. Others on the cc list received the transmittal letter only.
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e ATTACHMENT 3 ST-HL-AE-1003 1
1 hi South Texas Project Probabilistic Evaluation of Tornado Missile Hazard to the Containment Isolation Valve Compartment Equipment 14926-001 I
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Risk / Reliability Group 3
Los Angeles Power Division Bechtel Power Corporation I
August 1983 1
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SOUTH TEXAS PROJECT TORNADO MISSILE EVALUATION REPORT I.
I t'roduction 3
This study uses the Probabilistic Risk Assessment (FRA) methodology to evaluate the probability of damage to equipment located in the containment isolation valve cubicle (IVC) from tornado generated missiles. Tornado-generated missiles include objects, on or near the plant site, that could become airborne during a tornado and be transported to the top of the IVC.
The study includes an evaluation of the likelihood of a tornado occur-rence, as well as the probability of tornado generated missiles entering through the top of the IVC. The extent of damage is not evaluated, but is conservatively assumed to be certain and total for all missile strikes.
II.
Acceptance Criteria l
The NRC's acceptance criteria are contained in the " General Design Criteria (GDC) for Nuclear Plants" [1]. Specifically, GDC 2 and 4 apply to this evaluation and are summarized below:
I GDC 2 requires that " Structures, systems, and components important a.
I to safety shall be designed to withstand the effects of natural i(
phenomena such as - tornadoes - without loss of capability to per-form their safety functions..."
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GDC 4 requires that "... structures, systems, and components shall be appropriately protected against dynamic effects, includ-ing the effects of missiles,... from events and conditions out-side the nuclear power unit."
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The Standard Review Plan (SRP) [2] Section 3.5.1.4 and NRC Regulatory Guide 1.76 [3] provide further guidance in meeting GDC 2 and 4 require-Specifically, SRP Section 3.5.1.4 refers to the acceptance ments.
J criteria of SRP 2.2.3 which states "... design basis events include each postulated type of accident for which the expected rate of occur-rence of potential exposures in excess of the 10 CFR Part 100 guide is estimated to exceed the NRC st'aff objective of approximately 10 }ines
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per year... expected rate of occurrence of potentgl exposures in excess of the 10 CFR 100 guidelines of approximately 10 per year is acceptable if, when combined with reasonable qualitative arguments, the realistic probability can be shown to be lower..."
III.
Summary The probability of failure of the equipment located in the IVC to perform its safety function in the event of a tornado is evaluated using the PRA metho'dology. The study quantifies the probability of tornado generated
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I missiles entering through the top of the IVC. Since there is consider-able uncertainty in all factors, probability distributions are propagated throughout the analysis. The results are compared to the NRC acceptance criteria. The results indicate that tornado-generated missiles are not a significant threat to the IVC equipment. The results further indicate that no physical barriers are required at the top of the IVC.
IV. Analysis Approach The probability of damage to equipment located in the IVC depends on three factors:
A.
The tornado occurrence rate at the plant site, B.
The conditional probability of one or more tornado generated missiles striking the top of any one of four
's, given the tornado occurrence, and C.
The conditional probability of IVC equipment being damaged, given that the tornado-generated missile or missiles have entered the IVC.
l The tornado occurrence rate is based 'on the National Weather Service record of tornado strikes for the site region between 1953 and 1982 I.
[4]. The probability of tornado occurrence at the plant site and its contributors are shown in Table I.
The distributions of annual frequency,
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v, of tornado occurrences in area, S = 10000 mi, and tornado path area, 2
a, are based on plant specific historical data. These data are in good agreement with nationwide and regional assessments.
The conditional probability of the missile strike, given the tornado occurrence, depends on the following subfactors:
A.
The number of potential missiles, B.
The conditional probability of the potential missile becoming airborne (or injected), given the occurrence of a tornado, a
C.
The conditional probability of missiles being transported from their origin to the target, given that they become airborne, and D.
The target area.
The number of potential missiles is based on data from Electric Power Research Institute (EPRI) surveys at seven nuclear power plant sites [5].
The probability of the potential missiles becoming airborne is calculated using a missile model developed at Jet Propulsion I,aboratory (JPL) [6].
The conditional probability of missiles being transported from their origin to the target is based on a statistical mechanics model [7], [8].
This approach develops a modified Green's function to quantify the probdbility of the airborne missile striking a unit target area at some distance and elevation from its origin. This probability is then
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multiplied by the area of the target to get the total probability of strike. The area of the top of each of the four IVCs is 745 square feet (total target area is 2980 square feet). The IVC height is 55 feet above the grade and the grade elevation does not vary significantly within 300 feet of the IVC. The number of potential missiles and the missile density incorporated into this study are shown in Table II.
The conditional probability of IVC equipment being damaged, given that the tornado generated missile or missiles have entered the IVC, is con-l servatively taken to be certain and total. That is, the conditional I
probability is taken as unity.
Each of the above factors has a considerable amount of uncertainty associated with it. For some factors, the uncertainty is associated with the statistical nature of the data, and in others, it is associated with the modeling techniques. For this reason, a probability distribu-tion is used for each factor. These uncertainties are propagated L
throughout the analysis. Therefore, the final results are not a single value for probability of damage, but a distribution of values. The f
median (50th) and 95th percentile values are reported in Table III.
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The median is then compared to the NRC acceptance criteria.
The NRC acceptance criteria values require,yareful egnsideration because they_are given as point values (10 and 10 peryear).
However, as mentioned above, there are significant uncertainties
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associated with the probability of damage, ranging over orders of l
magnitude. The median is often compared to the acceptance criteria value because the median is interpreted as the "best estimate" or
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" recommended" value [9].
V.
Assumptions and Conservatisms The following assurptions are used in this study:
A.
The IVC roof area is assumed to be transparent to tornado missiles.
That is, the top of the IVC is assumed to be open and without l
missile protection of any kind.
B.
A tornado missile strike in the open top of any one IVC compart-ment represents failure (see conservatisms A and D, below).
C.
The distribution of potential tornado missiles by number and length are based on an EPRI survey of seven nuclear plants [5].
Conservatisms incorporated in this study are:
A. _ The comparison of the strike probability to the activity release
- frequency acceptance criteria, assumes; i 1.
Missile inflicted damage is certain and total and
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2.
Damage leads directly to activity releases in excess of 10CFR100.
3
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B.
The potential missile model assumes j 1.
A missile distribution based on EPRI survey maximum, 2.
A missile density increased by factor of 2.5 over EPRI t
- survey, 3.
One half of missiles are distributed up to 20 feet above grade, remainder at grade, and i
l 4.
The number of unrestrained missiles postulated for this study is equal to the total number of missiles (restrained and unrestrained) in the EPRI survey.
C.
The tornado frequency is based on a 30-year historical record fitted with a more conservative lognormal distribution having a larger mean and spread than the empirical distribution.
~
D.
Geometric factors that result in further conservatisms are:
1.
Sheltering by other structures is neglected, 2.
A missile strike in any IVC opening results in failure (i.e, no credit is taken for the existence of redundant components or for separation between safety-related trains), and
(.
3.
Safety related target areas are less than IVC open area.
VI.
Results and Conclusions The results of the analysis is a probability distribution for tornado missile damage to the IVC equipment. The median (50th percentile) and upperbound(95thpercegile)valuesarereportedinTabgeIII. The
[
median value is 2 x 10 and the upper bound g 6 x 10 per year.
L The median or "best estimate" value of 2 x 10 per year is6very small 7
compared to the NRC acceptance criteria value of 10 to 10 per year.
r The above results indicate that tornado-generated missiles are not a significant threat to the IVC equipment. These results further indicate that no physical barriers are required at tlie IVC top opening to protect IVC equipment from potential tornado generated missiles.
i 4
(
i LINDERMAN AFFIDAVIT ATTACHMENT III
)
The Light t
mmPuy "eestee tis ties & re er e.o.nex ivoo nees ee.T
> 77ooi (vis> 22s.,2ii a
November 14, 1983 ST-HL-AE-1028 File No.: C22/G2/G25 Mr. Thomas M. Novak Assistant Director for Licensing Division of Licensing 7920 Norfolk Avenue Bethesda, Maryland 70016
Dear Mr. Novak:
South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Additional Information Concerning the Isolation Valve Cubicle Roof Design
(
By the letter dated September 13,1983(ReferenceST-HL-AE-1003),
Houston Lighting & Power Company (HL&P) submitted a description of the various design / analysis alternatives which were evaluated as part of the Isolation Valve Cubicle (IVC) design and a detailed report regarding the probabilistic evaluations for hurricane and tornado-generated missiles.
During discussions of our submittal with the NRC's consultant, he requested that we document the verbal responses to certain questions which arose concerning our September 13, 1983 submittal.
Attachments 1 and 2 to 1
this letter provide that documentation and should resolve any remaining i
questions that the NRC or its consultant may have.
D you should any questions concerning this letter, please contact Mr.
Michael E. Powell at (713) 993-1328.
I 1
Very truly yours, 4
J. H. Goldberg Vice President Nuclear Engineering and Construction MEP/ mpg
(
Attachments (2)
- 1) Probabilistic Evaluation of Tornado Missile Hazard to the Containment Isolation Valve Compartment Equipment - ERRATA (November 14,1983)
- 2) Probabilistic Evaluation of Hurricane Generated Missile Hazard to the Containment Isolation Valve Compcrtment Equipment, Rev. 1, November 1983 1
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~ - - - -
Houston Lighting & Power Company cc:
G. W. Oprea, Jr.
ST-HL-AE-1028
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J. H. Goldberg File Number:
J. G. Dewease Page 2 J. D. Parsons D. G. Barker M. R. Wisenburg R. A. Frazar J. W. Williams R. J. Maroni J. E. Geiger S. M. Dew J. T. Collins NRC A. Vietti NRC D. P. Tomlinson NRC M. D. Schwarz Baker &Botts)
R. Gordon Gooch Baker & Botts)
J. R. Newman Lowenstein,Newman,Reis,&Axelrad)
STP RMS Director Office of Inspection & Enforcement Nuclear Regulatory Comission Washington, D. C. 20555 E. R. Brooks /R. L. Range Charles Bechhoefer, Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board P. O. Box 2121 U. S. Nuclear Regulatory Commission Corpus Christi, Texas 78403 Washington, D. C.
20555 4
(
H. L. Peterson/G. Pokorny Dr. James C. Lamb, III i
City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514 Austin, Texas 78767 J. B. Poston/A. vonRosenberg Mr. Ernest E. Hill City Public Service Board Lawrence Livermore Laboratory P. O. Box 1771 University of California San Antonio, Texas 78296 P. O. Box 808 L-46 Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan. III Assistant Attorney General Harmon & Weiss for the State of Texas 1725 I S.treet, N. W.
i P. O. Box 12548 Suite 506 Capitol Station Washington, D. C.
20006 Austin, Texas 78711 Lanny Sinkin Citizens for Equitable Utilities, Inc.
Citizens Concerned Abcut Nuclear Power c/o Ms. Peggy Buchorn 114 W. 7th.. Suite 220 Route 1. Box 1684 j
Austin, T_exas.78701 Brazoria, Texas 77422 i
~
Robert G. Perlis, Esquire i
j Hearing Attorney i
/
Office of the Executive Legal Director
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U. S. Nuclear Regulatory Comission Washington, D. C.
20555 Revision Date 10-10-83 i
i f
3 ST-HL-AE-1028 11/14/83 6
i ERRATA
~
Probabilistic Evaluation of Tornado Missile Bazard.to the Containment Isolation Valve Compartment Equipment Pg. 4. Paragraph 3: Replace with the following 3.
The potential missile model assumes 1.
A missile distribution based on EPRI survey without censoring as was done for the' EPRI studies.
2.
A missile density upper limit increased by a factor of 2.5 over the EPRI survey to account for local variations in missile density.
3.
One half of the potential missiles are distributed up to 20 f t above grade.with the remainder at grade.
1 4
The number of unrestrained potential missiles is con ;
servatively chosen to be 10% of all potential missiles.
Pg. D-16. Section D.10, 2nd Paragraph:
Replace the word " Twenty" in the second line with the word "Ninety".
Delete the word " elevated" in this sentence and the next.
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ST-HL-AE-1028 11/14/83 6
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South Texas Project
- 'Probabilistic Evaluation of Hurricane-Generated Missile Ha'zard to the Containment Isolation Valve Compartment Equipment 14926-001 Risk / Reliability Group I,os Angeles Power Division Bechtel Power Corporation movision 1 November 1983
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1.
i SOUTH TEXAS PROJECT EURRICANE MISSILE EVALUATION REPORT
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I.
Introduction This study uses Probabilistic Risk Assessment (PRA) methodology to evaluate the probability that equipment located in the containment isolation valve cubicle (IVC) might be damaged by hurricane-generated missiles. Murricane generated missiles include objects on or near the plant site that could become airborne during a hurricane and be transported to the top of the IVC.
The study includes an evaluation of the likelihood of a hurricane occurrence, as well as the probability of potential missiles becoming airborne and being transported to the top of the IVC. The extent of damage is not evaluated, but is conservatively assumed to be certain J
and total for all missile strikes.
l II.
Acceptance Criteria The NRC's acceptance criteria are contained in the " General Design -
Criteria (GDC) for Nuclear Plants" [1]. Specifically, GDC 2 and 4 apply to this evaluation and are summarized below:
GDC 2 requires that " Structures, systems, and components important a.
to safety shall be designed to withstand the effects of natural phenomena such as - hurricanes - without loss of capability to
(
perform their safety functions..."
(
b.
GDC 4 requires that "... structures, systems, and components shall be appropriately protected against dynamic effects, includ-l ing the effects of missiles,... from events and conditions outside the nuclear power unit."
i The Standard Review Plan (SRP) [2] Section 3.5.1.4 provides further guidance in meeting GDC 2 and 4 requirements. Specifically, SRP Section 3.5.1.4 refers to the acceptance criteria of SRP 2.2.3, which states "... design basis events include each postulated type of accident for which the expected rate of occurrence of potential exposures inexcessofthe10CFRPart100guidelgesisestimatedtoexceedthe NRC staff objective of approximately 10 per year.-.. expected rate
~
of occurrence of potential expogures in excess of the 10 CFR 100 guidelines of approximately 10 per year fs acceptable if, when l
combined with reasonable qualitative arguments, the realistic probability can be shown to be lover..."
h III.
Summary I
The probability of failure of the equipment in the IVC to perform its safety fune*4on in the event of a hurricane is evaluated using PRA methodology.
the study quantifies the probability of hurricane-generated missiles hitting the top of the IVC. The results are compared to the NRC
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acceptance criteria. The results indicate that hurricane-generated
' (r missile: are not a significant threat to the IVC equipment. The t.
results'further indicate that no physical barriers are required at the top of the IVC,.
IV. Analysis Approach The probability of damage to equipment located in the IVC depends on three factors:
A.
The probability distribution function for hurricane occurrence l
at the plant site f(w).
E B.
The conditional probability of one or more hurricane-generated missiles striking the top of any one of four IVC compartments, given the l hurricane occurrence, P I")*
H C.
The conditional probability of IVC equipment being damaged, given that the hurricane generated wissile or missiles have entered the IVC, P
- D So:
s PT=
f(w)P (w)P (w)dw (1) g D
t The hurricane occurrence rate is developed in Appendix B.
The l
l cumulative probability of exceeding a given hurricane wind speed at the plant site is shown in Table 1.
The conditional probability of the missile strike, given the hurricane occurrence, depends on the following subfactors:
A.
The number of potential missiles.
)
i B.
The conditional probability of the potential missiles becoming airborne (or injected), given the occurrence of a hurricane.
C.
The conditional probability of missiles being transported from their origin to the target, given that' they become airborne.
i D.
The target area.
The number of potential missiles is based on data from Electric Power Research Institute (EPRI) surveys at seven nuclear power plant sites [5].
The probability' of the potential missiles becoming airborne is calculated usi_n3 a missile model developed at Jet Propulsion I.aboratory (JPL) [6).
The. conditional probability of missiles being transported from their eigin te the target is based on a statistical mechanics model [7], [8].
(..
TLe araa 3f-the top of each of the four IVC compartments is 745 square feet l i
(total target area is 2980 square feet). The IVC height is 55 feet
,(
above grade sad the grade elevation does not very significantly l
t l
2 2
within 300 feet of the IVC. The number of potential missiles and the missile density incorporated into this study are shown in Table II.
a The conditional probability of IVC equipment being damaged, given that the hurricane-generated missile or missiles have entered the IVC, is conservatively taken to be certain and total. That is, the conditional probability is.taken as unity.
The result of this very co9servativg estimate is compared with the MRC acceptance criteria of 10 and 10 per year. Because of the uncertainty of some factors, we use the median as the "best estimate" or "reconnended" value [9].
V.
Assumptions and Conservatisms The following assumptions are used in this study:
A.
A hurricane missile strike on the top of any one IVC represents failure (see conservatisms A and C, below).
l B.
The distribution of potential missiles by number and length is based on an EPRI survey of seven nuclear plants [5].
C.
The conditional probability of a missile striking the target, given the hurricane occurrence, is adopted from the tornado missile model [7, 8, 11].
D.
The frequency of hurricane wind speed is fitted with a Weibull distribution.
Conservatises incorporated in this study are:
A.
The strike probabiMty, in comparison to the NRC's activity release l
frequency acceptance criteria, assumes:
1.
Missile-inflicted damage is certain and total.
i 2.
For purposes of this study damage was not evaluated. It is assumed that damage could lead directly to " potential exposures in excess of the 10CFR100 guidelines..." (SRP 2.2.3 acceptance criteria).
B.
The potential missile model assumes:
1.
A missile distribution based on EPRI survey without censoring as was done for the EPRI studies.
2.
A missile density upper limit increased by a factor of 2.5 over the EPRI survey to account for local variations in missile density.
- 73. 'Alfthemissilesaredistributedupto20feetabove grade.
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The number of unrestrained missiles was conservatively chosen to be 10% of all missiles.
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Geometric factors that result in further conservetisms'are:
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Sheltering by other structures is neglected.
2.
A missil'e strike in any IVC opening results in failure.
3.
The' area of safety-related equipment inside the IVC is less than the IVC top area.
VI.
Results and Conclusions The result of the analysis is the probability of hurricane missile damage to the IVC equipment. The median (50th percentile) value is reported in Table III. The median or,' gest estimate" value of strike probability is approximately 1.2 x 10 per year. This is very smal l
compargdtotheNRCactivityreleaseacceptancecriteriavalueof10}
to 10 per year.
The above results indicate that hurricane-generated missiles are not.a significant threat to the IVC equipment. These results further indicate that no physical barriers are required at the top of the IVC to protect IVC equipment from potential hurricane-generated missiles.
VII.
REFERENCES
[1] 10 CFR Part 50, Appendix A, " Design Basis for Protection Against Natural Phenomena."
[2] Standard Review Plan, U.S. Nuclear Regulatory Commission, NUREG-75087.
[3] Nuclear Regulatory Commission, " Design Basis Tornado for Nuclear Power Plants," Regulatory Guide 1.76, April 1974.
i
[4] Batts, M. E., "Probabilistic Description of Burricane Wind Speeds," Journal of the Structural Division, Proceedings of the American Society of Civil Engineers, Vol 108, No. ST7, July 1982.
[5] Twisdale, I,. A., et al., " Tornado Missile Risk Analysis," EPRI l
NP-768, May 1978, EPRI NP-769, May 1978.
l
[6] Redmann, G. M., et al., " Wind Field and Trajectory Models for l
Tornado-Propelled Objects," EPRI 308, Technical Report 1, February 1976.
[7] Goodman, J. and Koch., J. E., " Conditional Probability of the
, Tornado Missile Impact Given a Tornado Occurrence," Proceedings of the International ANS/ ENS Topical Meeting on Probabilistic Risk
. Assessment, Port Chester, New York, September 20-24, 1981, pp. 419-424.
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c57~ M M - [8 LINDERMAN AFFIDAVIT" ATTACHMENT IV N N 83./3
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1 UNITED STATES d* kM
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NUCLEAR REGULATORY COMMISSION n
wasenwaTow o.c.aossa
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s Docket Nos.: 50-498 and 50-499 JAN 0 81964 p.h y v,
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nr. a. H. soldberg W
Vice President - Nuclear Engineering 7' gr edI
-a and Construction Houston Lighting and Power Company M-FEB 151985 Ny
, L615Lbd U lb u to T
77001 Newman & Holtzinger
Dear Mr. Goldberg:
Subject:
South Texas Project Units 1 and 2 - Safety Evaluation Report Input on Tornado Missile Protection for the Isolation Valve Cubicles This is to infonn you that the staff has reviewed.the infomation provided by Houston Lighting and Power (HL&P) Company in submittals dated September 13 November.14, and December 20, 1983. In these submittals HL&P, in the design of the Isolation Valve Cubicles (IVCs) for missile protection, elected to demon-strate compliance with the tornado missile protection criteria in Standard Re-viewPlant(SRP) Sections 3.5.1.4and3.5.2bytheuseofaprobabilisticrisk assessment rather than providing a missile proof roof.
Enclosed is our safety evaluation report (SER) input regarding the tornado missile protection for the IVCs and our consultant's, the National Bureau of Standards (NBS), technical evaluation report (TER) as supplemented by a letter dated December 23, 1983.
As indicated in the SER, we conclude that the probability of tornado missile da:nage to the IVCs and associated essbntial equipment has been adequately dem-onstrated to be approximately 3 x 10- per year. Further, the thick concrete walls which constitute the sides of the IVCs provide protection for the equip-i ment contained therein from all tornado missiles except those entering the cubicles J
through the open roof area which we consider to be a low probability event. Thus, the applicant has satisfactorily demonstrated compliance with the requirements of GDC 2 and 4 with respect to tornado missile protection for the IVC, and the
}
Safety Related Equipment within them.
If you should have any questions concerning this letter, please contact the NRC ProjectManager,Ms.AnnetteVietti,at(301)492-4449.
Sincerely,
-g s M. Novak, ssistant Director j
for Licensing C; vision of Licensing
.)
Enclosures:
..]
As stated cc: See next page
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South Texas Mr. G. W. Oprea, Jr.
Executive Vice President Houston Lighting and Power Company P. O. Box'1700 Houston, Texas 77001,
Mr. J. H. Goldberg William S. Jordan, III, Esq.
Vice President - Nuclear Engineering Harmon & Weiss and Construction 1725 I Street, N.W.
Houston Lighting and Power Company Suite 506 P. O. Box 1700 Washington, DC 20006 Houston, Texas 77001 Brian Berwick, Esq.
Mr. D. G. Barker Assistant Attorney General Manager, South Texas Project Environmental Protection Division Houston Lighting and Power Company P. O. Box 12548 P. O. Box 1700 Capitol Station l
Houston, Texas 77001 Austin, Texas 78711 Mr. E. R. Brooks
. Mr. D. P. Tomlinson, Resident Mr. R. L. Range Inspector / South Texas Project Central Power and Light Company c/o U. S. NRC P. O. Box 2121 P. O. Box 910 Corpus Christi, Texas 78403 Bay City, Texas 77414 4
Mr. H. L. Peterson Mr. Jonathan Davis Mr. G. Pokorny Assistant City Attomey City of Austin City of Austin P. O. Box 1088 P. O. Box 1088 Austin, Texas 78767 Austin, Texas 78767 4
Mr. J. B. Poston Mr. A. Von Rosenberg Ms. Pat Coy City Public Service Board Citizens Concerned About Nuclear P. O. Box 1771 Power San Antonio, Texas 78296 5106 Casa Oro San Antonio, Texas 78233' Jack R. Newman, Esq.
Lowenstein, Newrian, Reis & Axelrad Mr. Mark R. Wisenburg 1025 Connecticut Avenue, NW Manager, Nuclear Licensing Washington, DC 20036 Houston Lighting and Power Company P. O. Box 1700 Melbert Schwartz,Jr., Esq.
Houston, Texas 77001 Baker & Botts One Shell Plaza Mr. Charles Halligan Houston, Texas 77002 Mr. Burton L. Lex l
Bechtel Corporation Mrs. Peggy Buchorn P. O. Box 2166 Executive Director Houston, Te,xas 77001 Citizens for Equitable Utilities, Inc.
Route 1. Box 1684 Brazoria, Texas 77422 4
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s Regional Administrator - Region IV U. S. Nuclear Regulatory Cor.nission 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 7601?
Mr. Lanny Sinkin 114 West 7th, Suite 220 Austin, Texas 70701 G
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SAFETY EVALUATION REPORT SOUTH TEXAS PROJECT UNITS 1 AND 2 TORNADO MISSILE PROTECTION FOR
. ISOLATION VALVE CUBICLE-AUXILIARY SYSTEMS BRANCH I.
INTR ODU C,T EQ3 Nuclear power plants must be designed to withstand the effects of tornado and high wind generated missiles so as not to impact the health and safety of the public in accordance with -
the requirements of General Design Criteria 2 and 4.
The i
s current Licensing criteria governing tornado missile pro-tection are contained in Standard Review Plan (SRP Section 3.5.1.4 and 3.5.2.
These criteria generally specify that safety-related systems be provided positive tornado missile protection (barriers) from the maximum credible tornado threat.
However, SRP Section 3.5.1.4 includes guidance on use of probabilistic risk assessment (PRA) methodology in Lieu of the deterministic approach for assessing tornado missile protection.
The acceptance criterion in this regard is similar to that identified in-SRP section 2.2.3 which deals with identification of design basis events using probabilistic methods.
The tornado missile acceptance criterion is as follows:
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"The probability of significant damage to structures, systems
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and components re' quired to prevent a rele'ase of radioactivity in excess of 10 CFR Part 100 following a miss1Le strike, assuming, loss of offsite power, shaLL be Less than or equal
~7
~0 to a median value of 10 per year or a mean value of 10 per year."
1 The fotLowing discussion of tornado missile protection is
~
concerned with the isolatiun valve cubicles and the safety-related equipment within them.
The South Texas plant has four separate isolation valve cubicles (IVCs) each of which contains a portion of a main steam and a feedwater Line.
The main steam and feedwater isolation valves and main steam safety and relief valves associated with the steam and feedwater Lines are also Located within the cubicles.
Each IVC is missile protected from atL sides by heavy concrete walls.
The tops of the cubicles however are open.
A tornado missit'e(s) could enter one or aLL of the cubicles through the open' top and damage the components therein.
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The applicants elected to demonstrate compliance with the tornado missile protection criterion for the IVCs by PRA methodology rather than provide positive protection for the roof opening.
The applicants provided a detailed PRA in a submittat dated September 13, 1983.
Additional information to support the PRA was provided in submittals dated November 14 and December 20, 1983.
i, Due to the specialized nature of the study, we have contracted with the National Bureau of Standards (NBS) to assist in the review of the applicants' analysis.
NBS provided a technical evaluation report (TER) regarding the probability of a tornado missile strike upon the IVCs.
Concerns which were identified during our review were satisfactorily resolved by the applicants' response dated December 20,1983 as i
indicated in our consultants TER supplement dated December 23, 1983.
In this supplement the consultant also addressed concerns associated with missiles generat,ed by non-tornadic and non-hurricane winds.. The consultant's TER as supplemented forms a part of our SER.
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As previously stated, the South Texas Plant is designed with four separate IVCs, each of which is missile protected from aLL sides by heavy concrete walls.
Each cubicle is com-The pletely protected except for the roof which is open.
height of the IVC wall is 55 feet above plant grade.
The appliicants' PRA considered atL of the SRP Section l
3.5.1.4, November 24, 1975 Missile Spectrum A as potential missiles including the utility pole and the automobile.
Revision 2 of the SRP however, allows the exclusion of the utility pole and the car at elevations up to 30 feet above aLL grade Levels within 1/2 mile of the facility structures under review.
As the insight of the IVC watL is 55 f eet above plant grade the missiles which we consider to apply from Missile Spectrum A are the wood plank, the steel rod and the steel pipes.
Our examination of elevated areas within 1/2 mile of the f acility structures disclosed only the dike area around the ultimate heat sink,which could be considered as a possible Launch point for the automobile or the utility pole.
The applicants have assured us that there witL be no utility pole storage along the dike area.
Additionally, the only vehicular traffic along the dike l
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.. t would be transient in nature in order to conduct inspection, and this traffic wilL be controlled.
In order for a missile to strike any of the components in a given IVC, it must approach the roof opening at a steep angle, within a given solid angle.
The roof opening of each 2VC is approximately 745 square feet thus presenting a relatively.
smaLL target.
Additionally, the safety-r. elated target areas within the IVCs are much smaller than the IVC open roof The fact that there are four separate cubicles areas.
1 substantialLy decreases the probability of single missile being capable of damaging more than the components in one I
cubicle.
Multiple missiles however, could enter separate cubicles.
We consider this a low probability event, as discussed further below.
Rather than utilize a deterministic argument, as discussed 1
above, the applicants chose to provide ajPRA evaluation.
The applicants' PRA was provided in their submittal of September 13, 1983.
We and our consultant have reviewed f
this submittal.
The review resulted in additional concerns i
which were identified to the applicants.
The applicants provided responses to.those concerns in a submittat dated December 20, 1983.
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,,.. 4 Our consultant's evaluation of the applicants' PRA considered the validity and.nonservatism of the approach, assumptions, and data used in the applicants' analysis to establish the probability of tornado and hurricane-borne missile damage to the IVC equipment.
Also included in the evaluation is an assessment of the correctness of the results'obtained in the study.
We have reviewed our consultant's TER and his supplement l
thereto contained in Letter dated December 23, 1983 which resolved the open items identified in the TER.
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i We concur with the findings and resulting estimate of the l
probability of damage to essential equipment in IVC of 3 x 10.
We further agree that this value is correct to within at least one order of magnitude uncertainty.
There-l fore additional positive tornade missile protection need not be provided for the IVCs since the probability of exceeding 10 CFR 100 doce criteria due to' tornado missiles
~I is Less than the 10 per year acceptance criterion.
Based on the above, we conclude that the applicants have 1
i satisf5ctority demonstrated compliance with General Design
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i criteria 2 and 4 with respect to tornado missile protection for the IVCs.
The design of the IVCs is therefore acceptable without the addition of further protection for the roof area.
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'ES Ul i8 All :16 EXHIBIT 3
-l C.rRM N E Cit _i?
C004Eiriiat" Crl aan;u UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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)
HOUSTON LIGHTING & POWER
)
Docket Nos. 50-498 OL COMPANY, _ET _AL.
)
50-499 OL (South Texas Project, Units 1
)
and 2)
)
MATERIAL FACTS AS TO WHICH THERE IS NO GENUINE ISSUE TO BE HEARD Pursuant to 10 C.F.R.
S 2.749(a). Applicants hereby submit a statement of material facts as to which there is no genuine issue to be heard in conjunction with their motion for summary disposition of CCANP Contention 4.
(1)
The design of Category I structures at the South Texas Project (STP) takes into consideration both an operating basis wind (OB ) of 125 mph at a j
standard reference height of 30 feet, under which the plant is designed to remain functional without l
posing an undue risk to the public health and i
safety, and a design basis tornado (DBT) with a maximum wind speed of 360 mph under which safety-l l
l
f 2-i, related structures, systems and components must perform their safety functions.
Affidavit of R.
- f Bruce Linderman (Linderman) at 11 10-11, 16.
(2)
Applicable NRC guidance provides that an OBW is i
i the 100-year recurrence interval fastest-mile wind speed calculated on the basis of reliable.
fastest-mile wind speed data from standard measurement stations with sufficient periods of record to develop reliable recurrence values.
Affidavit of Dale E. Wolfe (Wolfe) at 1 7.
4 (3)
The STP OBW of 125 mph is supported by reliable, l
recorded fastest-mile wind speed data which is 4
appropriate for calculating a reliable 100 year recurrence value, and has been verified on the basis of appropriate and conservative statistical methodologies.
Wolfe at 11 9-13, i
(4)
The OBW was considered in the design of STP 1
Category I structures in combination with other 1
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" severe" conditions, and an additional margin of safety was provided through the application of l
load factors and through other means.
Linderman at 11 13-15.
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(5)
STP Category I structures are also designed to l
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I withstand combinations of " extreme" conditions, including the DBT, which result in greater loads on such structures than those from the severe load combinations which include the OPW.
This aspect of the design of STP Category I structures provides additional assurance that such structures l
will withstand hurricane wind loads. Linderman at j
11 16-18.
i (6)
The STP has also been designed to ensure that Category I structures and equipment will not be i
adversely affected by failure of non-Category I l
structures under hurricane wind loads.
Through physical separation, or design of non-Category I l
structures capable of withstanding DBT-generated loads, non-Category I structures will not collapse on Category I structures under hurricane loads.
J Linderman at 11 19-21.
i (7)
STP Category I structures (with the exception of 3
the Isolation Valve cubicle (IVC) roof) have also been designed, in accordance with applicable NRC l
guidance, to withstand the' spectrum of missiles which might be generated by the DBT, indluding those which could be generated by non-Category I I
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i structures.
The characteristics of DBT-generated missiles envelope the potential spectrum of hurricane-generated missiles, providing assurance that Category I structures will not be adversely affected by hurricane-generated missiles.
The probability of a tornado or hurricane-generated missile striking the IVC roof has been demon-strated, in accordance with applicable NRC guidance, to be sufficiently low that the design need not take into account the possibility of such an event.
Linderman at 11 22-24.
(8)
STP Category I structures and equipment have been designed to withstand hurricane-generated wind loads in accordance with applicable requirements, NRC guidance and industry standards.
Such structures and equipment have been designed to withstand loads in excess of those resulting from any. credible hurricane wind and will not be jeopardized by collapse of non-Category I structures or hurricane-generated missiles.
i Linderman at 11 26-28.
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