ML20004F374

LER 81-011/01T-0:on 810508,pits Observed on Exterior Surface of Svc Water Pump Discharge Piping.Caused by External Corrosion,Resulting in Local Areas Below Min Wall Thickness. Areas Sand Blasted,Patch Welded & Repainted

ML20004F374
Person / Time
Site:	Indian Point
Issue date:	05/22/1981
From:	CONSOLIDATED EDISON CO. OF NEW YORK, INC.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML093620883	List: ML093620882 ML20004F374
References
LER-81-011-01T, LER-81-11-1T, NUDOCS 8106180251
Download: ML20004F374 (2)

Text

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[,i,i l thickness. The areas were sand .-13. ee, a patch was welded oter ca:n 1

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, ATTACllMENT 1 Docket No. 05000247 consolidated Edison company of New York, Inc.

LER 81-011/03L-0 Indian Point Unit No. 2 ,

While in cold shutdown the service water piping in the pump pit was sand blasted to remove surface corrosion. Visual inspection of the cleaned pipe showed a total of seven (7) pits had formed on three of six service water pump discharge lines. The depth of the pits and. surrounding wall thickness were measured using a pipe pit gage and an ultrasonic meter respectively. The remain-ing wall thickness under each pit was then calculated using the measured values.

Using an allowable wall thickness of 0.135 inches, which was based on seismic considerations, it was found that there were four pits which were below the value. These wall thicknesses were: Line No. 23, 0.060 inches; Line No. 24, 0.060, 0.105 and 0.125 inches.

The cause of the pitting is believed to have been e>:ternal corrosion resulting from the damp conditions fcund in the pump pit. A patch was welded over each pitted area and the entire

-surfaces of the pipes repainted to prevent further c rr:sion.

The si::e and small number of pits did not reduce the ability of the piping to withstand a design basis seismic event. Had one or more pits devolcped into through holes, the result would have been " pinhole" leaks which wculd not have significantly degraded the operability of the system.

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