ML20045B209
| ML20045B209 | |
| Person / Time | |
|---|---|
| Issue date: | 03/18/1991 |
| From: | Lewis H Advisory Committee on Reactor Safeguards |
| To: | Beckjord E NRC |
| Shared Package | |
| ML20042D089 | List:
|
| References | |
| FRN-57FR14514, REF-GTECI-B-56, REF-GTECI-EL, RULE-PR-50, TASK-B-56, TASK-OR AE06-1-056, AE6-1-56, NUDOCS 9306160415 | |
| Download: ML20045B209 (1) | |
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ADVISORY COMMITTEE ON REACTOR SAFEGUARDS t
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C Washint, ton, D.C.
20555 ll.W. I.ewis: March 18,1991
Dear Eric:
I was surprised to receive your letter of March 7, misunderstanding my note to Jim Johnson as having said that the problem was one of personal choice, "rather than something more fundamental." What I said was that the choice of the limits for the sum was arbitrary, since confidence limits are not even defined for the case in hand (there is lots of sophisticated statistical literature making this point), but that it did,'t matter anyway, because the limits, however calculated, " don't have any regulatory value " I don't see how anything could be more fundamental than that, to the Nuclear Regulatory Commission.
While I can easily understand your desire to simply sweep this under the rug, the main point, and it is fundamental, is for the Commission itself to decide: do they want to base the diesel reliabilities embodied in the blackout rule on indefensible statistical practice embodied in a diesel rule? My recommendation to them, from the beginning, has been to achieve coherence by separating the two issues. Station blackout calculr_ tion un be carried out with assumed reliabilities of the diesels, without asking how these can be assured. Attention to diesels, on' the other hand, can be triggered by arbilmry failure rates, without asking what these imply for the underlying individual diesel reliability. To the extent that these have to be brought together, only to justify the practice, diesel reliability can be estimated for the whole population, for which the numbers are large enough to draw meaningful conclusions. It is a simple and intellectually honest way out, but it is in the Commission's hands, not yours or mine.
' You said in your note that you do not now think it necessary to make your views on this subject known to the Commission..While that judgment call is of course none of my business, I think it is necessary. The Commission needs help, and that is what both its staff and its advisory committee are for.
Si e 21y,
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- 11. W. Lewis
.9306160415 930422 PDR PR 50 57FR14514
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