ML25196A507
| ML25196A507 | |
| Person / Time | |
|---|---|
| Issue date: | 04/16/1975 |
| From: | Moeller D Advisory Committee on Reactor Safeguards |
| To: | Rowden M NRC/Chairman |
| References | |
| Download: ML25196A507 (1) | |
Text
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 April 16, 1976 Honorable Marcus A. RJwden Acting Cllainnan
- u. s. Nuclear Regulatory Conmission washington, OC 20555 SOBJFX:T:
REl?ORT CN WAS~ POBLIC 1?0'mR SUPPLY SYSTEM NOCLFAR PRO.JECTS R>. 3 AND R>. 5
Dear Mr. R>'t.1den:
During its 192nd meeting, April 8-10, 1976, the A<<Visory Conmittee on Reactor safeguards canpleted a review of the application of the washington Public R>wer Supply Systen {WPPSS) for permission to construct the WPPSS Nuclear Project No. 3 and WPPSS Nuclear Project No. 5 (WNP-3 and WNP-5).
'!he site was visited on August 4, 1975, and SUbcamlittee meetings were held that same day in Elma, Washington, and on February 24, 1976, in Richland, wash-ington. 'Ihe project was also considered during the 191st meeting of the Conmittee in Washington, D. C., M:lrch 4-6, 1976. During its review, the Comnittee had the benefit of discussions with representatives of WPPSS and its consultants, Combustion Engineering, Inc., Ebasco Services, Inc., and the Nuclear Regulatory Corrmi.ssion (NR:) Staff. '!he Conmittee also had the benefit of the documents listed.
1he WNP-3 and WNP-5 site is located in Grays Barbor County, W:ishington, awroximately thirteen miles east of.Aberdeen-Hoquiam-Cosmopolis, W:lsh-ington, the nearest population center (1970 population 28,549). 'Ihe minimum exclusion distance is 1310 meters and the low population zone (LPZ) radius is three miles. 'Ihe total.1970 resident population within the LPZ was 260.
1be WNP-3 and WNP-5 application is sul::mitted in accordance with the Com-mission's standardization policy as described in Appendix Oto Part SO, "Licensing of Production and Utilization Facilities," and Section 2.110 of Part 2, "Rules of Practice," of Title 10 of the Code of Federal Regula-tions. For this application the reference system is the Combustion Engineer-ing Standardized Nuclear Steam SUpply System known as its Standard Reference System-80. '!his design has been reviewed by the ACRS and discussed in its report of September 17, 1975, "Combustion Engineering Standard Safety Analysis Report - CFSSAR-80."
1789
Honorable Marcus A. R:>t.,,,den April 16, 1976
'!he ultimate heat sink for each reactor will consist of a system of dry cooling towers and canponents that reject excess heat to the abnosphere.
Because of its design the ultimate heat sink does not require a makeup water supply.
'!he Applicant described his investigations of the geologic and seismic characteristics of the site and the surrounding region. Nlilc the geology of the surrounding area is canplex, and there is definite tectonic activity, there are no known geologic or seismic problems that cannot be solved by design. '!he proposed safe shutdown earthquake is 0.32:J horirontal accel-eration at the foundations. '!he operating basis earthquake is 0.16g.
Fach WNP reactor will employ a containment system including a free standing steel vessel surrounded by a reinforced concrete shield building. '!he*
inner steel vessel is designed for an internal pressure of 44 psig. '!he annulus, between the two structures, is maintained at subabnospheric pres-sure to penni t the C<'llection of leakage fran the steel vessel, in the unlikely event of a ux::A, and pennit its processing before release to the environment.
'!he Corrmittee recommended in its report of Septenber 10, 1973, on accept-ance criteria for ECCS, that significantly improved ECCS capability should be provided for reactors for which construction pennit requests were filed after January 7, 1972. '!he WNP-3 and WNP-5 design is in this category.
'lhese projects will use the 16 X 16 fuel assemblies similar to those to be used in Arkansas Nuclear Ole 'Olit 2 and St. Lucie Plant 'Olit 2. Although calculated peak clad temperatures, in the event of a postulated ux::A, may be less for 16 X 16 than for the 14 X 14 array, the Colllnittee believes that the Applicant should continue stooies that are responsive to the Com-mittee's Septenber 10, 1973, report. If stooies, conducted with the best available techniques, establish that significant* further ECCS improvements can be achieved, consideration should be given to incorporating them into WNP-3 and WNP-5.
A generic question has arisen concerning loads on the vessel support structure for certain postulated loss-of-coolant accidents in pressurized water reactors. '!his matter should be resolved for WNP-3 and WNP-5 in a manner satisfactory to the NOC Staff.
'!he Committee believes that the Applicant and the NOC Staff should continue to review the WNP-3 and WNP-5 design for features that could reduce the p:>ssi-bility and consequences of sabotage.
1790
Honorable Marcus A. lbwden 3 -
April 16, 1976 Following the Browns Ferry fire the NRC Executive Director for ~rations set up a special review group to determine what could be learned fran this incident. 'Ibis group has made recorrmendations that apply to future reactors, to reactors that are already operating, and to the NRC regulatory process.
'lhe review group p:>ints out that its recorrmendations are not specific to any single plant and that its reconmendations are based on knowledge at the ti~ of this investigation. 'lhe ACRS wishes to be kept informed of the specific application of the review group's recorrmendations, as they awly to WNP-3 and WNP-5, for the developnent of additional information on fire prevention, fire fighting, quality assurance, and the improve-ment of NRC policies, procedures, and criteria.
other generic problems relating to large water reactors are discussed in the Conmittee's rep:>rt dated April 16, 1976. 'lhese problems should be dealt with appropriately by the NRC Staff and the Applicant.
'lhe Mvisory Conmittee on Reactor Safeguards believes that the items men-tioned above can be resolved during construction and that, if due consider-ation is given to the foregoing and to items mentioned in its CESSAR-80 report of September 17, 1975, the Washington Public R:>wer Supply System Nuclear Projects It>. 3 and It>. 5 can be constructed with reasonable assur-ance that they can be operated without midue risk to the health and safety of the public.
Mditional comments by M:mlbers Max w. Carbon, David Okrent, Milton s. Plesset, Stephen Iawroski, and Myer Bender are presented below.
Sincerely yours, Dade w. M:>eller Chairman Mditional Comments by Members Max W. carbon, David Okrent, Milton s. Plesset, and Stephen Iawrosk1
'lhe site for WPPSS Nuclear Projects It>. 3 and It>. 5 lies in a seismically active region that has been subject to large earthquakes in historic time and includes active major faults. rllile we do not disagree with the proposed seismic design basis, we believe it ~uld be desirable to have the geologic and siesmic aspects of such sites, and perhaps most sites, also reviewed by the u. s. Geological survey to provide the benefit of an additional independent evaluation.
1791
Honorable Marcus A. R>wden April 16, 1976 Additional Corrrnents by Members David Okrent and Milton s. Plesset
'!he recurrence interval of an earthquake of the order of the safe shut-down earthquake may be about 1,000 years for this site. For such a recurrence interval the probability of not achieving safe shutdown, given the SSE, must be very small if the NRC Staff goal of less than 10-7 per year, of a serious accident fran any single cause, is to be achieved. Since seismic design adequacy is not subject to direct experimental confirmation, we believe that other measures, including independent design review, low-amplitooe shaking measurements of the
_canpleted structure, as-built construction validation, and detection of p>ssible inservice degradation, should be evaluated and the neces-sary steps taken to provide the high degree of detailed specific assurance required with regard to seismic capability of all safety-related features.
Additional Comnents ~y Member Myer Bender With increasing frequency, questions have arisen concerning the appro-priate degree of conservatism to be included in the seismic design criteria for nuclear power plants. '!he needs of public safety would be best served if the design practices currently in vogue were altered to permit inelastic response so as to enhance the energy absorption characteristics of nuclear structures tmder severe seismic loadings.
For the more severe seismic conditions inelastic design principles should be applied to foundations, concrete containments, floors, and SUR;X>rt structures in order to assure a high degree of damping and thus minimize the forces transmitted to critical safety features and to the primary coolant circuitry. '!his would eliminate the.need for many of the complex supplemental structural feaf!ures of questionable reliability which are now used to meet extreme seismic design con-ditions. 'Ibis design approach would allow nuclear structures to satisfy even the most pessimistic loading requirements of the most extreme seismic prophet. If it is not used there is doubtful value, and possibly some loss in public safety margin, fran the use of ultraconservative seismic design requirements because the relia-bility of the structural restraints cannot be assessed fran relevant structural.experience or post-construction vibrational testing.
~ferences:
- 1. N:lshington Public R>wer Supply Systems (WPPSS) Nuclear Projects No. 3 and No. 5 Preliminary Safety Analysis Report (PSAR) volumes 1-18
- 2. Amendments 1-30 to the PSAR 1792
Honorable Marcus A. R>wden April 16, 1976 References continued
- 3. Division of Reactor Licensing {DRL) Safety Evaluation Rep:>rt, dated February 1976
- 4. letter, dated December 31, 1976, WPPSS to DRL, concerning reactor pressure vessel support design, shutdown cooling system, and containment purging
- 5. letter, dated January 12, 1976, WPPSS to DRL, concerning abnospheric dump valve sizing 1793