ML20032D684
| ML20032D684 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 11/13/1981 |
| From: | Withers B PORTLAND GENERAL ELECTRIC CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-1.C.1, TASK-TM GL-81-21, TAC-44274, TAC-47179, NUDOCS 8111170387 | |
| Download: ML20032D684 (3) | |
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- Ell PodandGeremiBechicCompany RaDwms vte P eset November 13, 1981 Trojan Nuclear Plant Docket 50-344 4
License NPF-1
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'V Mr. Darrell G. Eisenhut, Director
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kl,'{ g Office of Nuclear Reactor Regulation
/\\y U. S. Nuclear Regulatory Commission Washington, DC 20555 A NOVI O 1981-
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N U.L u m n wunen
Dear Mr. Eisenhut:
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Response to Generic Letter 81-21, f 7.-
Natural Circulation Cooldown
-9Q'u-Generic Letter 81-21 identified NRC concerns stemming from the June 11, 1980 natural circulation cooldown event at the St. Lucie Plant, Unit No. 1.
of principal interest was the occurrence of reactor vessel voiding during the couldown, resulting in an undesirable challenge for the operators to maintain coni.rol and continue the cooldown process.
This letter requested that Portland General Electric (PGE) review cur-rent operations at the Trojan Nuclear Plant in light of these concerns and implement, as necescary, procedures and training that will enable operators to avoid (if possible), recognize and properly respond to reactor vessel voiding during natural circulation cooldown.
The occurrence of reactor vessel voiding during a untural circulation cooldown does not prerent a significant safety hazard, as long as the voided condition is not allowed to persist or increase to a point where core cooling r.ay be impaired. However, it does present potential concerns with regard to maintainire a stable plant configuration. Thus, PGE has supported the Westinghouse Owners Group's analysis and procedure develop-ment efforts related to this issue.
The Westinghouse Owners ';roup has an established program for the develop-ment of emergency procedure guidelines in accordance with NUREG-0737, Item I.C.1 requirements. The contents of this program, as outlined in Owners Group letter 0G-61, dated July 7,1981, include provisions for the development of guidelines for a natural circulation cooldown proce-O/
dure. A subsequent Owners Group letter OG-62, dated July 24, 1981, y
specifically addressed the program's outline concerning this topic. As noted in OG-62, the analytical basis for preventing reactor vessel
!h voiding during a natural circulation cooldown was submitted to the NRC 8111170337 811113 PDR ADOCh 05000344 P
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Portmid General BectricCoigwiy Mr. Darrell G. Eisanhat November 13, 1981 Page two in Owners Group letter 0G-57, dated April 20, 1981. The final guidelines based on these analyses were presented and distributed at the recent Westinghouse Emergency Response Guideline Seminar.
i A plant-specific natural circulation cooldown procedure, based on the Wectinghouse guidelines, is currently being developed for the Trojan Nuclear Plant. Adherance to the guidelines will ensure that reactor vessel voiding during a natural circulation cooldown should not occur.
Currently, a temporary procedure specifying a 15'F/hr cooldown rate is under development and will be instituted as soon as possible. This is consistent with the Westinghouse recommendations for the T-hot classification of plants (maximum recommended cooldown rate of 25*F/hr) as described in the attachment to OG-57.
A permanent procedure is expected to be in place no later.than startup of Cycle 5 (Spring 1982 refueling), following a more complete appraisal of the Westinghouse guidelines. This schedule cor. responds with the adoption of the new Emergency Procedure guidelines that have been developed in response to NUREG-0737, Item I.C.1 requirements.
A natural circulation cooldown to a point when the residual heat removal system can be used to remove decay heat will require continuous auxiliary feedwater flow over an extended period of time.
Based on a conservative analysis, but assuming normal operating coocitions, Trojan's condensate-grade auxiliary feedwater supply is sufficient to supplement an overall cooldown period of up to 18.5 hr following a reactor trip. However, if for any reason an adequate condensate grade supply is unavailable, auxiliary feedwater will be supplied by the safety grade Service Water System, taking suction from the Co?umbia River, or if necessary, from the Cooling Tower Basin. A descriptica. of the Serva :e Water System and Cooling Tower Basin is contained in the Trojan Final Safety Analysis keport, Section 9.2.1.
FCE has scheduled operator retraining prior te the 1982 refueling.
This corresponds with current schedules for implementation of the new Emergency Procedures. The retraining prograa will include an in-depth explanation and discussion of the new natural circulation cooldown procedure for all licensed operators, with emohasis placed on recognition I
of a voided condition and the response provisions as outlined in the Westinghouse guidelices.
In summary, PGE recognizes the need to carefully develop a natural circulation cooldown procedure and has taken steps towards meeting this need, with a scheduled full implementation, including operator training, by startup of Cycle S.
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f PDrtismd Gerierd BedricCor1@smy i
Mr. Darrell' G. Eisenhut J
November 13, 1981 i
Page three 4
i If you have any questions concerning this response, please contact me.
' Sincerely, W
i Bart D. Withers Vice President
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Nuclear l
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Mr. Lynn Frack,-Director State of Oregon Department of Energy i
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