ML20039F613

Deficiency Rept Re Error in ECCS Analysis for Facilities. Issue Reviewed by Westinghouse & Util.Determined Not Reportable Per 10CFR50.55e

ML20039F613
Person / Time
Site:	Wolf Creek, Callaway
Issue date:	01/07/1982
From:	Petrick N STANDARDIZED NUCLEAR UNIT POWER PLANT SYSTEM
To:	Harold Denton Office of Nuclear Reactor Regulation
References
10CFR-050.55E, 10CFR-50.55E, SLNRC-82-01, SLNRC-82-1, NUDOCS 8201130148
Download: ML20039F613 (2)

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e SNUPPS Standardized Nuclear Unit Power Plant System 5 Choke Cherry Road Nicholas A. Petrick Rockville. Maryland 20850 Executive Director (301) 86s40to January 7,1982 SLNRC 82- 01 FILE: 0278 SUBJ: SNUPPS ECCS Analysis p i rs C

' c, Mr.HaroldR.Denton,DirectorI '

Office of Nuclear Reactor Regulation RE M h5.0 U.S. Nuclear Regulatory Commission - -9

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Washington, D. C. 20555 JAN1119825

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Docket Nos: STN 50-482 and STN 50-483 N ,P f H t

Dear Mr. Denton:

4 Westinghouse has informed the SNUPPS Utilities of an error discovered in the ECCS analysis for the SNUPPS plants. The error involved is that the single failure of the emergency safeguard equipment assumed in the large break ECCS analysis does not represent the most limiting assumption possible.' Westinghouse has met with the NRC to review this subject on an generic basis. The NRC and Westinghouse agreed that no reanalyses are required to correct the error and that each utility should submit to the NRC a summary of the impact of this issue on their plant.

The SNUPPS ECCS analysis currently assumes minimum safeguards for the safety injection flow, which minimizes the amount of flow to the RCS by assining maximum injection line resistances, degraded pump performance, and the loss of one RHR pinp as the most limiting single f ailure. This is the limiting single failure assumption when offsite power is unavallable for most Westinghouse plants.

However, for some Westinghouse four loop, non-UHI, non-burst node limited plants, the nature of the Appendix K ECCS evaluation models is such that it may be more limiting to assine the maximum possible ECCS flow delivery. The maximum safety injection flow results in competing effects which impact each plant differently. For the SNUPPS plants, the combination of these effects is a net increase in calculated peak cladding temperature.

There is an 18 F penalty associated with the assumption of maximum safety injection flow fgr the SNUPPS plants. The SNUPPS FSAR ECCS anal-ysis results show a 112 F margin to the 10 CFR 50.46 ECCS acceptance criteria. Other changes to ECCS modeling, including low head and

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8201130148 820107' PDR ADOCK 05000482 S

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SLNRC 82-01 o Page Two accumulator injection interaction, reduction in initial pellet temperature, and use of the 1981 ECCS evaluation model, would yield a net margin of 1970F to the 50.46 criteria for the SNUPPS pl ants. It should also be noted that best estimate calculations would be expected to indicate a substantial benefit from maximum injection flow, rather than the penalty resulting from the Appendix K calculation.

This issue has been reviewed by the Westinghouse Safety Review t Committee and by the SNUPPS Utilities to determine whether the 2

matter was reportable under 10 CFR 50.55(e). Since there are sufficient margins to the 50.46 limits and since there are unused benefits from approved modeling changes, it was judged that the issue was not reportable. However, this letter serves to document the impact of the issue on the SNUPPS plants as agreed in the NRC-Westinghouse generic meetings. ,

Very truly yours, '

fMRV Nicholas A. Petrick i

RLS/5tk4a25 4~

cc: G. L. Koester KGE D. T. McPhee KCPL D. F. Schnell UE T. E. Vandel NRC/WC Resident Inspector NRC/ CAL i

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