ML19256F642

Submits Part 21 Rept Re Potential Nonconservative Feature of Westinghouse Large Break LOCA-ECCS Evaluation Model. Defect Could Affect Peak Clad Temp Calculated for LOCA Transient.Analysis Will Be Completed by Early Dec 1979

ML19256F642
Person / Time
Site:	North Anna
Issue date:	11/28/1979
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
REF-PT21-79-174-000 948, NUDOCS 7912190668
Download: ML19256F642 (2)

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VxnotazA Ex.ncraxc Ann Powen COMPANY q Ricuwonn.Vxnorm 20261 November 28, 1979 N Sbl l4 Mr. James P. O'Reilly, Director Serial No. 948 Office of Inspection and Enforcement P0/PJ4T:baw U. S. Nuclear Regulatory Commission Docket No. 50-338 Region II License No. NPF-4 101 Marietta Street, Suite 3100 Atlanta, Ceorgia 30303

Dear Mr. O'Reilly:

Under the provisions of 10CFR21, NRC Region II was notified on November 14, 1979, that a potential significant deficiency or rubstantial safety hazard existed at North Anna Power Station, Unit 1.

In accordance with the reporting requirements of the above regulations,

' the following information is submitced:

A. Name and address of reporting individual:

C. M. Stallings Virginia Electric and Power Company P. O. Box 26666 Richmond, Virginia 23261 B. Facility, activity and/or component affected: North Anna, Unit 1 C. Name of firm supplying the component, activity or service:

Westinghouse Electric Corporation D. Description of defect, deficiency, or failure to comply:

Vepco was notified of an unreviewed safety question by Westinghouse Electric Corporation which concerned a potential non-conservative feature of the Westinghouse large break LOCA-ECCS evaluation model which could affect the peak clad temperature (PCT) calculated for the LOCA transient.

The unreviewed safety question involved the portion of the Westinghouse LOCA-ECCS evaluation model related to the fuel rod burst calculation.

Upon review of the current LOCA-ECCS analyses for operating plants, Westinghouse determined that calculated heat-up rates could be less than 25*F/second which was the basis for the fuel rod burst curve currently in the Westinghouse LOCA-ECCS evaluation model. Further investigation indicated that the use of fuel rod burst curves based on lower heat-up rates resulted in earlier predicted clad burst times.

A shift in clad burst time can potentially affect the peak clad tem-perature (PCT) calculated for the LOCA t-ansient. The current North Anna LOCA-ECCS analysis may not have sufficient PCT margin to the Appendix K limit of 2200*F to offset the potential impact resulting from the use of a more appropriate fuel rod burst curve. /k/9 SC 1626 528..

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a e Vinoasta Etretnic ano Powra Cownwy i Mr. James P. O'Reilly 2 E. Date of determination of reportability: November 14, 1979 F. Similar components, activities or services: North Anna, Unit 2 Correctiva actions which has been, is being, or will be taken, the individual responsible and the length of time to complete the action.

An analysis is currently underway using the Westinghouse February 1978 LOCA-ECCS evaluation model in conjunction with an appropriate fuel rod burst curve calculation procedure. This analysis will be completed in early Dece=ber 1979 and should indicate sufficient margin to the Appendix K PCT limit.

H. Other information:

Any additional information regarding the above topic will be submitted as a follow-up report.

Should you require further information, please contact this of fice.

Very truly yours,

b. a) b ddd<<) '

. C. M. Stallings Vice President-Power Supply and Production Operations cc: Director, Office of Inspection and Enforcement b? L