ML20128B355
| ML20128B355 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 01/28/1993 |
| From: | Burski R ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| W3F193-0006, W3F193-6, NUDOCS 9302030021 | |
| Download: ML20128B355 (2) | |
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QA January 28, 1993 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.
20555
Subject:
Waterford 3 SES Docket No. 50-382 License No. NPF-38 Individual Plant Examination (IPE) Report
Dear Gentlemen:
Entergy Operations, Inc., Waterford 3, on August 28, 1992 submitted to the NRC via letter W3F192-0311 the IPE report.
In this letter, it was noted that a more detailed review of the final level 2 results would be completed by December 31, 1992.
The detailed review was completed prior to December 31, 1992. The review has established that the results reported to the NRC in the IPE report conservatively describe the probability and consequence of a severe accident on containment performance.
Waterford 3 identified two areas, based on the internal review of the Level 2 analysis, wherein statements in the IPE report were affected, first, the probability for containment failure decreased because of a correction in translating data from the Modular Accident Analysis Program (MAAP) results into containment failure probabilities.
Secondly, the consequences of containment failures decreased after including the effects of water over ex-vessel debris.
As a result of the first correction, the probability of no containment failure increased from 46% to 61%, and the probability of early containment failure decreased from 26% to 8%.
PDS IH (SBLOCA with no containment cooling) decreased in relative importance because the peak pressure caused by High Pressure Melt Ejection (HPME) following a SBLOCA has a relatively smaller probability of causing early containment failure. HPME is when high pressure suddenly ejects in-vessel debris into containment upon reactor vessel failure.
The decreased importance of HPME changes a Level 2 statement given in the IPE report, section 4.8.5.
That is, the sudden addition of HPME loads to containment is no longer considered a likely containment failure mode at Waterford 3.
Thus, the IPE report conservatively describes the importance of containment failure upon HPME.
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h US!tRC Individual Plant Examination (IPE) Report W3F193-0006 Page 2 January 28, 1993 Also, ISLOCA is now the most significant contributor to the large containment release group.
ISLOCA is as likely as before, but it becomes more important because other accidents are less likely to cause large fission product releases.
The inclusion of scrubbing because of water over ex-vessel debris decreased the estimated amount of fission products which escape containment given reactor vessel failure.
As noted in page 1.1-2 of the IPE report, periodic changes and revisions to the model are expected to be performed in the future because of changes in plant design and evolution of PRA methods.
Waterford 3 does not anticipate that the IPE report will be updated and sent to the NRC for review as the foregoing changes are made.
Please contact me or Robert J. Murillo should there be any questions regarding this letter.
Very truly yours.
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R.F. Burski Director, Nuclear Safety RFB/RJH/dc cc:
J.L. M11hoan, HRC Region IV D.L. Wigginton, HRC-liRR R.B. McGehee N.S. Reynolds NRC Resident inspectors Office