ML20101Q443
| ML20101Q443 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 07/07/1992 |
| From: | Cottle W ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-143, REF-GTECI-NI, TASK-143, TASK-OR GNRO-92-00082, GNRO-92-82, NUDOCS 9207140285 | |
| Download: ML20101Q443 (2) | |
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Ib1 G tsm MS 39150 TW61437 6408 W. T. Cotue vcc N n n owu*tr July 7, 1992 aw on#9 sw U.S. Nuclear Regulatory Commission Mail Station F1-137 Washington, D.C.
20555 Attention:
Document Control Desk
Subject:
Grand Culf Nuclear Stat. ton Unit 1 Docket No. 50-416 License No. NPF-29 i
Generic Issue No. 143, " Availability of Chilled Water Systems and Room Cooling" GNRO-92/00082 Gentlemen:
On June 30, 1991, a-revision to NUREG 0933 was issued containing Generic Issue (GI) No. 143, " Availability of Chilled Water Systexs and Room Cooling". The issue was-promulgated on the belief _ that failure of air cooling systems for areas housing key components, e.g., RilR pumps, switchgear, and diesel t enerators, could significantly contrtbute to core-melt probability in some plants. Apparently,- the Grand Gulf Nuclear Station's probabilistic risk assessment (PRA) was one of two plant PRAs used to develop Generic Issue #143. The Advisory Committee on Reactor Safeguards (ACRS) is concerned-that the impact of the.se failures on the proper functioning of air cooling = systems have not been generically reflected in final PRAs.
Generic Issue #143,.as pt; posed, estimates a reduction in thf c re damage 6
4.
f requency ct the Grand Gulf Nuclear. Station (GGNS) of 8 x 10 events /kY, should the complete dependency _on certain air cooling systems be-i eliminated.
It further assumes some reduction in rP ' -of core damage for
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every nuclear. plant cognizant rf these dependencies. As discussed during our June 4, 1992 _ telephone conversation with members of the-Research/Reacter & Plant Safety _ Issues Branch, it appears that the prajected reduction in-core damage frequency at the Grand Gulf Nuclear Station, as a result of elimination of all dependence on' air cooling systems, alone is greater than-the total core damage frequency calculated in the final version of NUREG/CR 4550, w
_a We realize that the information contained in GI #143 is prelliinary in o
nature, and does not form the technical basis to resolve this issue.
M llowever, the risk reduction conclusions are used as key luputs to the value/ impact evaluation.
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s Ju1y 7, 1992 GNRO-92/00082 Page 2 of 3
= y This Generic Issue reinforces the nond to review the ef fects of support systems on core damage frequency.
It does not, however, conr.ider plants that may have more current PRA data availsble as a result of implementation of Generic Letter 68-20.
We would like to offer, for information purposes, that GGNS has included as part of its plant-specific Individual Plant Fxamination (IPET for severe accident vulnerabilities (Generic Letter No.
88-20), dependency on air coolir.g systems.
Entergy Operations, Inc. appreciates this opportunity to convey a current perspective on PRAs and efforts current.ly being made to identify areas in whics reductions in the core damage frequency are being pursued. We look forward to your July site visit concerning thir. Issue.
If you require any information prior to vout visit, please contact this office.
Yours truly, r
t
. Ce.O V *W WTC/JS/ams cc:
Mr. D. C. Ilintz Mr. J. L. Mathis Mr. R. B. hcGehee Mr. N. S. Reynolds Mr.11. L. Thomas Mr. Stewart D. Ebneter Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta St., N.'W., Suite 2900 Atineta, Georgia 30323 Mr. P. W. O'Connor, Project Manager Of fice of Nuclear Reactor Regulation-U.S. Nuclear Regulatory Commission Mail Stop 13113 Washington, D.C.
-20555
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