ML25196A162
| ML25196A162 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/14/1977 |
| From: | Bender M Advisory Committee on Reactor Safeguards |
| To: | Rowden M NRC/Chairman |
| References | |
| Download: ML25196A162 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, D. C. 20555 January 14, 1977 Honorable Marcus A. Rowden Chairman U.S. Nuclear Regulatory Conmission Washinqton, DC 20555
Subject:
REPORl' 00 DAVIS-BESSE NUCLEAR PCMER STAT!~, UNIT 1
Dear Mr. Rowden:
At its 201st meeting, January 6-8, 1977, the Advisory Conmittee on Reactor Safeguards OOIDPleted its review of the application by the Toledo Edison Company and the Cleveland Electric Illuminating Conpany for a license to operate the Davis-Besse Nuclear Power Station, Unit 1. Members of the Conmittee visited the plant on May 18, 1976, and a subconmittee meeting was held in Washington, D.C. on December 21, 1976. During its review, the Conmittee had the benefit of discussions with representatives and consultants of the Applicant, the Babcock and Wilcox Coopany, the Bechtel Corporation, and the NRC Staff. The Ccmnittee also had the benefit of the docmnents listed. The Conmittee reported on the application for a construction permit for this unit on August 20, 1970.
The Davis-Besse Nuclear Power Station, Unit 1, is located on the south-western shore of Lake Erie about midway between the cities of Toledo and Sandusky, Ohio. The minimum exclusion distance is 2400 ft. The low population zone, with a radius of two miles, included about 870 people in the 197.0 census. The nearest population centers are Toledo (1970 popula-tion 383,818) and San:lusky (1970 population 32,674), both about 20 miles from the plant.
The nuclear steam supply system employs a Babcock and Wilcox pressurized water reactor similar in 100st respects to those first used in the Oconee Nuclear Station. This system differs from the Oconee units and several other similar units in that the steam generator loops are raised about 30 ft above the level in the original plant arrangement. Although this change was made t,o eliminate the need for internal vent valves, four such valves are provided because of their beneficial effect in reducing steam binding following a postulated loss-of-coolant accident.
327
Honorable Marcus January 14, 1977 The proposed power level for the unit is 2772 MWt, as compared to 2633 MWt proposed at the construction permit stage. This higher power level is the same as that proposed for the Rancho Seco and Three Mile Island,.
Unit 2 reactors, both of which have been reviewed by the NRC Staff and the Comittee and found acceptable.
The structures and conponents of Davis-Besse, Unit 1, were designed for a Safe Shutdown Earthquake (SSE) acceleration of 0.15g at the foundation level. Because of changes in the regulatory approacn to selection of seis-mic design bases, the Conmittee believes that an acceleration of 0.20g would be more appropriate for the SSE acceleration at a site such as this in the Central Stable Region. The Applicant presented the results of preliminary calculations concerning the safety margins of the plant for an SSE acceleration of O. 20g. The Conmittee reoomnends that the NRC Staff review this aspect of the design in detai1 and assure itself that signifi-cant margins exist in all systens required to accomplish safe shutdown of the reactor and continued shutdown heat reooval, in the event of an SSE at this higher level. The Comnittee believes that such an evaluation need not delay the start of operation of Davis-Besse, Unit 1. The Conmittee wishes to be kept informed.
The performance of the Emergency Core Cooling System (ECCS) has been evaluated using a Babcock and Wilcox evaluation nooel applicable to the raised-loop configuration. The NRC Staff has reviewed these evaluations and has determined that certain assumptions regarding return to nucleate boiling do not comply strictly with the provisions of Appendix K to 10 CFR Part 50. The NRC Staff is also reviewing several other areas relating to ECCS performance. These matters should be resolved in a manner satisfactory to the NRC Staff.
In conjunction with the evaluation and assessment of the inpact of routine waste releases from this plant, the Conmittee reconmends that the NRC Staff provide leadership in encouraging the developnent of inproved environmental radiation surveillance capabilities on the part of the State of Ohio and appropriate local regulatory agencies.
The Comnittee notes that post-accident operation of the plant to maintain safe shutdown conditions may be dependent on instrumentation and electrical equipnent within contairnnent which is susceptible to ingress of steam or water if the hermetic seals are either initially 328
Honorable Marcus January 14, 1977 defective or should become defective as a result of damage or aging.
The Committee believes that appropriate test and maintenance procedures should be developed to assure continuous long-term seal capability.
The Committee recommends that, prior to comnercial power operation of Davis-Besse, Unit 1, additional means for evaluating the cause and likely course of various accidents, including those of very low probability, should be in hand in order to provide improved bases for timely decisions concerning possible off-site emergency measures. 'lhe Canunittee wishes to be kept informed.
The question of whether the design of this plant must be m::>dified in order to comply with the requirements of WASH-1270, "Technical Report on Anticipated Transients Without Scram (ATWS) for Water-Cooled Reactors,"
remains an outstanding issue pending the NRC Staff conpletion of its review of the Babcock and Wilcox generic analyses of ATWS.
The Conmittee recorrnrends that the NRC Staff, the Applicant, and the Babcock and Wilcox Company continue to strive for an early resolution of this matter in a manner acceptable to the NRC Staff. The Committee wishes to be kept informed.
Davis-Besse, Unit 1, has installed a bypass loop containing two manually operated valves around the decay heat removal system suction line iso-lation valves. The normally closed bypass valves would be opened in the ~vent of a spurious closure of one of the decay heat removal system suction line isolation valves during system operation. The Committee recommends that further attention be given to the means errployed for iso-lation of the low pressure residual heat removal system from the primary system while the latter is pressurized, and that reliable means be developed to assure such isolation. This matter should be resolved in a manner sat-isfactory to the NRC Staff. The Committee wishes to be kept informed.
The Committee supports the NRC Staff program for evaluation of fire pro-tection in accordance with Appendix A to Auxiliary and Power Conversion Systems Branch Technical Position 9.5-1, "Guidelines for Fire Protection for Nuclear Power Plants." The Committee recorrnnends that the NRC Staff give high priority to the completion of both owner and staff evaluations and to recorrnnendations for Davis-Besse, Unit 1, and for other plants nearing com-pletion of construction in order to maximize the opportunity for :irrproving fire protection while areas are still accessible and changes are more feasible.
329
[*]
Honorable Marcus January 14, 1977 The Comnittee believes that the Applicants and the NRC Staff should fur-ther review security provisions for Davis-Besse, Unit 1, for measures that could significantly reduce the possibility and consequences of sabo-tage, and that such measures should be implemented where practical.
Other generic problems are discussed in the Conmittee's report, *status of Generic Items Relating to Light Water Reactors: Report No. 4," dated April 16, 1976 (Attached}. Those problems relevant to the Davis-Besse, Unit 1, should be dealt with by the NRC Staff and the Applicant as solu-tions are found.
The relevant items are: II-1, 2, 3, 4, 6, 7, 9, 11; II.A-1, 4, 5, 7, 8; II.C-1, 2, 3, 4, 5, 6.
The Advisory Comnittee on Reactor Safeguards believes that, if due re-gard is given to the items mentioned above, and subject to satisfactory conpletion of construction and pre-operational testing, there is reason-able assurance that the Davis-Besse Nuclear Power Station, Unit 1, can be operated at power levels up to 2772 MWt without undue risk to the health and safety of the public.
Attachment:
Status of Generic Items Relating to Light Water Reactors: Report No. 4 dated April 16, 1976
References:
Sincerely 9H M. Bender Chairman
- 1. Davis~Besse Nuclenr Power Station, Unit 1, Final Safety Analysis Report {Harch 1973) with Revisions 1 through 24.
- 2. Safety Evaluation Report (NUREG-0136) in the matter of the Davis-Besse Nuclear Power Station, Unit 1 (December 1976).
[*)Seepages 2240-2286, Volume IV 330