ML19317F863

Forwards AO-75-12.Provides Details

ML19317F863
Person / Time
Site:	Rancho Seco
Issue date:	09/26/1975
From:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML19317F864	List: ML19317F863 ML19317G008
References
NUDOCS 8002210600
Download: ML19317F863 (2)

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SACRAMtNTO MUNICIPA1. UTitiTY DISTRICT C 1708 59th Street, Box 15830 Sacramento California 95813:(916)452-3211-September 26, 1975 Mr. R. H. Engelken Director of Regulatory Operations,_ Region V

.NRC Operations Office.

.1990 N. California Boulevard I

' Walnut Creek-Plaza, Suite 202

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Walnut Creek, CA 94596 Re: Operating I.icense DPR-54 Docket'No. 50-312 Abnormal Occurrence 75-12

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Dear Mr. Engelken:

IE FILE COPY.l As defined by Proposed Amendment No. 30 to Technical Specifications d' f or the Rancho Seco Nuclear Generating Station, Section 6.9.1, an( Regulatory

• Cuide 1.16, Revision 3, Section C.2.B.2, we are reporting the following Abhor-mal Occurrence as A0-75-12.

Excessive air leakage of the Reactor Building Purge Outlet Penetra-

's tion was detected August 27, 1975, while the, Surveillance Procedure for local

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leak rate testing was being performed. The plant was in a cold shutdown con-i

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dition for maintenance during this period.

Initial attempts to pressurize the penetration for measuring the leak rate failed, and leakage was detected through the 66 inch inner butterfly valve.

t' The valve seats on the inner valve were adjusted, and subsequent testing revealed leakage from the penetration of greater than 300,000 standard' cc per minute, with a penetration pressure of 10 psig. Total-leakage allowable from all penetrations inspected during a local leak rate test, as stated in Technical Specifications Section 4.4.1.2.3, is.06 percent of the Reactor Building atmosphere every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. 1This limit converted to a leakage rate is 106,000 standard ce per minute at the minimum allowable test pressure (52 psig).

- Further adjustments were made to the inner valve seats which reduced leakage through that valve essentially to zero, as verified by local bubble 1_.

testing. The penetration leakage was measured at 33,550 standard ce per minute, which was through the outer penetration valve. Attempts to reduce 2^

leakage'by adjustment of the valve' seats were not successful, so the seats will.be replaced 'and adjusted to give a proper seal.

To ansure that the leaka_ge through the penetration remains within acceptable limits, the surveil-lance procedure will be repeated prior-to reactor startup which is scheduled for November 7,-1975.

A thin film of silicon grease will periodically be applied to the seats to improve the seal.

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rMr.'R. H.;Engelken. '

September 26, 1975 i

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.The' purge valves are 66 inch butterfly. valves, Model'60 WR manu-r _-

'factured-by Allis -Chalmers Company.

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There was no plant transient associated with tais event, i

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Respectfully, k'

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4[ g Mattimoe-Assistant General Manager 3

and Chief Engineer f'

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Enclosure-

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