ML20095L119

Forwards Nonproprietary WCAP-13327 & Proprietary WCAP-13326, North Anna Unit 1 1992 SG Operating Cycle Evaluation, Per 920302 Meeting Re Unit 1 mid-cycle SG Insps.Proprietary WCAP-13326 Withheld (Ref 10CFR2.790)

ML20095L119
Person / Time
Site:	North Anna
Issue date:	05/01/1992
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19354F333	List: ML20095L119 ML20095L132 ML20095L134
References
92-141A, NUDOCS 9205060232
Download: ML20095L119 (2)

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YlltOINIA ELECTHIC AND I'OWUH COMPANY lticu>toxn Vinuina caeni May 1, 1992 U.S. Nuclear Regulatory Commission Serial No.92-141 A Attention: Document Control Desk NL&P/JBL: R2 Washington, D.C. 20555 Docket No. 50 338 License No. NPF-4 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 1 MID-CYCLE STEAM GENERATOR INSPECTION RESULTS AND STEAM GENERATOR OPERATING CYCLE EVALUATION On March 2,1992, Virginia Electric and Power Company and Westinghouse Electric Corporation met with the NRC to discuss the results of the North Anna Unit 1 mid-cycle steam generator inspections and to present a technical evaluation of those results.

The purpose of this letter is to transmit the Westinghouse report which provides the detailed written version of the information presented at the March 2,1992 meeting.

Enclosed are ten copies each of WCAP-13326," North Anna Unit 1 Steam Generator Operating Cycle Evaluation" (Proprietary) (Attachment 1) and WCAP-13327, ' North Anna Unit 1 Steam Generator Operating Cycle Evaluation" (Non-Proprietary)

(Attachment 2). Also enclosed is a Westinghouse application letter for withholding proprietary information, CAW-92-300, with accompanying affidavit, Proprietary Information Notice. and Copyright Notice (Attachment 3) .

The proprietary aspects of this information are supported by the affid'vit signed by Westinghouse, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR Section 2.790 of the Commission's regulations. Accordingly, it is respectfully requested that the information which is proprietary to Westinghouse be withheld from public disclosure in accordance with 10 CFR Section 2.790 of the Commission's regulations.

Correspondence with respect to the proprietary aspects of the items listed above or the supporting Westinghouse Affidavit should reference CAW-92-300 and should be addressed to Nicholas J. Liparuto, Manager of Nuclear Safety & Regulatory Affairs, Westinghouse Electric Corporation, P.O. Box 355, Pittsburgh, Pennsylvania 15230-0355.

One aspect of the information presented on March 2,1992 was in error and 'nas been corrected in the enclosed report. The primary-to-secondary leak rate as a result of a

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special main steam !ine break accident analysis was calculated to be 24.2 gpm. This value was represented as being based on the actual mid-cycle inspection results.

However, during preparation of the attached reports, an error was found in that a preliminary tube plugging list had been used in calculating the requested leak rate.

The calculated leak rate value for this special accident scenario should be 30.5 gpm based on the corrected crack distribution. An evaluation of the theoretical dose consequences at the s'ite boundary based on the 30.5 gpm primary to-secondary leak rate determined that the thyroid dose would be less than 24 Rem (versus the previously reported 19 Rem based on 24.2 gpm leak rate). Thi's dose remains within a small fraction of the 10 CFR Part 1M limits. Further, as described in the WCAP report, this improbable end-of-cycle leak rate would be reduced due to the mid cycle

" inspection transient" ano the reduced level of power for the remainder of the cycle. By letter dated March 26,1992, we provided to the NRC our evaluation of primary to-secondary leak rates for a postulated main steam line break accident which concluded that these conservative crack leak scenarios do not involve a significant hazards

- consideration as defined in 10 CFR 50.92. This correction of the calculated leak rate value does not change the no significant hazards consideration determination provided in that submittal.

Should you have any questior.s or require additional information, please contact us.

Very truly yours,

\

I n'A W. L. Stewart Senior Vice President - Nuclear Attachments

1. Westinghouse Electric Corporation Report, WCAP-13326," North Anna Unit 1 Steam Generator Operating Cycle Evaluation" (Proprietary) (10 Copies).

2. Westinghouse Electric Corporation Report, WCAP-13327," North Anna Unit 1 Steam Generator Operating Cycle Evaluation" (Non-Proprietary) (10 Copies).

3. Westinghouse letter, Application for Withholding Proprietary Information cc: U.S. Nuclear Regulatory Commission Region 11 101 Marietta Street, N.W.

Suite 2900 Atlanta. Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station l

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