ML19209B720

Interim Deficiency Rept Re Overpressurization of Containment from Main Steam Line Break Inside Containment. Util Evaluating Mods to Limit Auxiliary Feedwater Flow to Affected Steam Generator

ML19209B720
Person / Time
Site:	North Anna
Issue date:	10/04/1979
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
NUDOCS 7910100355
Download: ML19209B720 (1)

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Vepco October 4,1979 Mr. James P. O'Reilly, Director Serial No. 7241, Office of Inspection & Enfore ment PSE&C/WBR:mac: wang U. S. Nuclear Regulatory Comission Region II Docket Nos. 50-404 101 Marietta Street, Suite 3100 50-405 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

On Seotember 4, 1979, a report was made under the provisions of 10CFR50.55(e) concerning the overpressurization of the containment fran a Main Steam Line Break (MSLB) inside the containment.

The original PSAR containment pressure analyses did not consider the long term blowdown effects from a MSLB. Preliminary calculations taking the long term blowdown into account, show that the containment design pressure will be exceeded in approxima aly 9 minutes due to the unabated auxiliary feedwater (AFW) flow feeding a MSLB inside the containment. The long term addition of AFW results in the equivalent of a 174 sustained return to power which orovides the energy necessary to support the " boil off" of the AFW.

At this time, Vepco is still evaluating modifications to limit AFW flow to the affected steam generator in the event of a MSLB. We will inform the Commission of any modifications that we olan to implement in order to eliminate this containment overoressurization problem.

This report is forwarded as required by 10CFR50.55(e) and is an interim report on this subject.

Te ulypurs/

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Senior Victi President - Power Stetton Engineering and Constructio6 cc: Mr. Victor Stello, Director Office of Inspection & Enforcement v Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation 1135 349 A b is 791 01 00 3 6 S