ML18353A850

Licensee Event Report AO-75-26: Excessive Leakage During Local Leak Test of Containment Penetrations

ML18353A850
Person / Time
Site:	Palisades
Issue date:	11/21/1975
From:	Bixel D Consumers Power Co
To:	Purple R Office of Nuclear Reactor Regulation
References
LER AO-1975-026-00
Download: ML18353A850 (3)

Text

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consumers

• Power company General Offices: 212 West Michigan Avenue, .Jackson, Michigan 49201

• Area Code 517 788-0550 November 21, 1975 Director of Nuclear Reactor Regulation Att : Mr Robert A. Purple, Chief Operating Reactor Branch No 1 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255, LICENSE DPR-20 PALISADES PLANT, A0-75-26 Attached is Abnormal Occurrence Report A0-75-26 which covers the discovery of excessive leakage during a local leak test of containment penetrations. One of the two valves used to isolate the penetration in question has been shown to work satisfactorily and has been tagged closed until appropriate repairs can be made. This action assures containment integrity.

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David A. Bixel Assistant Nuclear Licensing Administrator CC: JGKeppler, USNRC File

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• 1. Report No: A0-75-26 ABNORMAL OCCURRENCE REPORT Palisades Plant 255 2a. Report Date: November 21, 1975 2b. Occurrence Date: November 13, 1975

3. Facility: Palisades Nuclear Plant, Covert, Michigan

4. Identification of Occurrence: Excessive leakage was discovered during local leak test of Containment Penetration No 4 (containment purge air exhaust valve).

5. Conditions Prior to Occurrence: Plant was operating at 79% power.

6. Description of*Occurrence: During routine maintenance and testing of the purge air exhaust valves, it was determined that the minimum test pressure (55 psig) could not be maintained using the normal method. A larger air supply was utilized to raise the pressure above 55 psig. When the supply was removed, the pressure dropped rapidly to about 46 psig where it stabi-lized and indicated very little additional leakage. The leakage rate at test pressure was estimated to be in excess of 100,000 cc/min (the maximum

.allowable is 60,700 cc/min). With the test volume between the valves pres-surized, the downstream plenums were entered and both downstream valves were checked for seat leakage using "snoopy" to detect any minor leakage. No leakage was identified on either downstream valve. The upstream valve is not accessible under test conditions, but during subsequent operation of the valve it was noted that the valve operator was rotating slightly on the valve body.

7. Designation of Apparent Cause of Occurrence: The valves involved are butter-fly valves with inflatable seats. The seat is narrow and the valve is 48 inches in diameter. Apparently, the upstream valve is not getting aligned properly on the seat and when the pressure exceeds 46 psig, the seat becomes deformed sufficiently to permit air to "blow by."

8. Analysis of Occurrence: Close visual examination of the downstream valves demonstrated that containment integrity was established. Both downstream valves were "tagged" closed to prevent inadvertent opening during plant op-eration. Containment integrity has been established and as long as th~

valves are not moved, the redundancy supplied by.the upstream valve is not required and the health and safety of the public is not compromised.

9. Corrective Action:

a. All three valves involved have been "tagged" closed.

b. Repairs will be made to the leaking valve at the next scheduled shutdown .

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• 10. Failure Data:

a.

b.

Leakage past purge valve packing due to lack of greasing. A greasing schedule is now in effect.

Equipment identification: Continental Equipment Company, 48-inch butterfly valve *

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