ML20151U535

Interim Deficiency Rept CP-86-41 Re Evaluation of Effects of Small Break LOCAs During Mode 4 Operation.Cause Under Investigation.Final Rept to Be Submitted for Review by 880831

ML20151U535
Person / Time
Site:	Comanche Peak
Issue date:	08/10/1988
From:	Counsil W, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
CP-86-41, TXX-88603, NUDOCS 8808190165
Download: ML20151U535 (2)

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Log # TXX-88603 File # 10110 915.6 7UELECTR/C Ref. # 10CFR50.55(e)

August 10, 1988-Williera G. Counsil Executhe Ykr President U. S. Nuclear Regulatory Commis., ion Attn: Document Control Desk Washington, D.C. 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NOS. 50-445 AND 50-446 SMALL BREAK LOCA MODE 4 OPERATION SDAR: CP-86-41 (INTERIM REPORT)

Gentlemen:

On May 28, 1986, TU Electric verbally informed your Mr. I. Barnes of a deficiency Mode involving evaluation of the effects of small break LOCAs during 4 operation. This is an interim report of a potentially reportable item under the provisions of 10CFR50.55(e). The most recent interim report was logged TXX-88258, dated February 29, 1988.

Following the NRC Regulatory Staff's decision to not accept the Westinghouse Owners Group (WOG) plan to apply Leak Before Break technology in resolving the issue of a small break LOCA during Mode 3 or 4 operation, the WOG developed a new two-ste approach, identified in the last interim report (see TXX-88258 noted above .

At the present time three major program analysis tasks have been completed in this two-step approach. These involve (1) detennination of the failure rate of large bore piping for Mode 3 conditions-using structural reliability and risk assessment technology, (2) establishing that the risk associated with a large break LOCA in Mode 3 or 4 is less than that associated with Mode 1 by comparing core damage frequencies and, (3) performance of a LOCA analysis for a rupture of a 6-inch pipe with the plant in Mode 3 or 4 to demonstrate that adequate time is available for the operator to assess tSe situation and to activate the ECCS. A final report to be submitted for WOG member review, and eventually to the NRC, is in preparation and is currently scheduled for completion by the end of August, 1988.

8808190165 880810 PDR S

ADOCK 05000445 PDC AN 400 North Olbt street LB81 Dallas, Texas 73 01 h0

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t TXX-88603 August 10, 1988 Page 2-of 2 The WOG plans to discuss the report at its'next meeting,. scheduled for August, 1988. . TV Electric anticipates submitting its next report on this matter by February 13, 1989.

Very truly yours, T)b $1 W. G. Counsil g,( h f hS  :

R. D. Walker Manager, Nuclear Licensing RLA/grr c-Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3) 4