ML20136G147
| ML20136G147 | |
| Person / Time | |
|---|---|
| Issue date: | 06/27/1985 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20136G151 | List: |
| References | |
| FOIA-85-693, REF-GTECI-A-44, REF-GTECI-EL, TASK-A-44, TASK-OR NUDOCS 8507090500 | |
| Download: ML20136G147 (2) | |
Text
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( , k June 27, 1985 MEMORANDUM FOR: William J. Dircks Executive Director for Operations FROM: Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
COMMISSION PAPER ON STATION BLACK 0UT f f/G3A In SECYps-163, " Proposed Station Blackout Rule", we noted that the Nuclear Utility Group on Station Blackout (NUGSB0) was preparing an alternative proposal for resolution of USI A-44. We requested that the Commission not schedule meetings on the proposed rule until we had reviewed the industry submittal and forwarded our evaluation to the Commission.
We have prepared the enclosed Commission Paper for your review and signature. The paper notes that NUGSB0's conclusion that a rule is not warranted is based on: (i) optimistic projections of recent loss-of-offsite power data, (ii) assumed maintenance of high diesel generator reliabilities, and (iii) the assumption that all plants can withstand a two-hour loss of all ac power. Our proposed rule would require licensees to determine that their plants can withstand blackout events of an acceptable duration (not specified in the rule.). The associated proposed Regulatory Guide does; present a methodology that would lead to selection of a 4- or 8-hour duration, but allows plant-specific justification of shorter durations. We note in the paper that a blackout capability of only two hours, based on NUGSB0's assumptions, would leave very little margin for potential degradations in grid reliability or diesel generator reliability tha,t may occur, in spite of good-intentioned voluntary industry initiators td maintain and improve them.
I believe that the recent Davis-Besse event illustrates that, in the real world, system and component reliabilities can degrade below those we and the industry routinely assume in estimating core me.it frequencies. Our regulatory process should require margins against such degradation and also to reflect the uncertainties in our PRA estimates. 7-I.strongly support the recommendation in the enclosed paper that the (['
Cnmmission proceed with the proposed rulemaking. . 1<
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- June 27, 1985
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The paper also recommends an addition to the Notice of Rulemaking that would reference the NUGSB0 proposal, encourage development of more specific information regarding voluntary industry programs to assure reliability of
- onsite power' systems and procedures and training for blackout events, and invite comments on the effects of such programs on the proposed rule and f regulatory guide.
'! We have also enclosed a proposed letter for your signature to NUGSB0
){ consistent with the commission paper.
-i I recommend your approval of the commission paper.
.i Original Signed by M. R. Dentos ,
Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosures:
As stated
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