ML20003C392

AO 50-219/74/20:on 740310,MSIVs NS04A & NS04B Failed to Meet Allowable Leakage Requirements.Caused by Faulty Lower Packing Rings Around Valve Shaft.Valves Closed Until 1974 Refueling Outage

ML20003C392
Person / Time
Site:	Oyster Creek
Issue date:	03/18/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
References
AO-50-219-74-20, NUDOCS 8103030349
Download: ML20003C392 (2)

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. 1 OYSTER CREEK NUCLEAR CENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/20 i

Report Date March 18, 1974 Occurrence Date (}

March 10,1974 y

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Identification of Occurrence Violation of the Technical Specifications, paragraph 4.5.F.1.d, failure of main steam isolation valves NSO4A and NSO4B to meet the allowable leakage re-quirements. His event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15D and E.

Conditions Prior to Occurrence ne plant was shut dowr. with reactor coolant at <212*F.

Description of Occurrence The main steam isolation valves were leak rate tested in the "as found" condition.

Leakage rates of main steam isolation valves NSO4A and NSO4B were 64.7 SCFH and 12.2 SCFH, corrected to 20 psi. The maximt;m allowable leakage rate is 9.945 SCFH, as required by the Technical Specifications, paragraph 4.5.F.1.d.

Apparent Cause of Occurrence The cause of this occurrence is attributed to component failure. After checking the test assembly and the components of the main steam isolation valves, it was determined that the lower packing rings around the valve shaft was the cause of i the excessive leak rate. He leakage was out of the leakoff line between the upper and lower sets of packing.

Analysis of Occurrence The safety significance of the failure of NSO4A and NS04B to pass the leakage rate test was a loss of redundancy in an engineered safety feature designed to minimize the release of fission products under design bases accident conditions.

It should be noted that any leakage through the lower set of packing would be into the reactor building equipment drain tank end would be released through the plant stack via the standby gas treatment system. It should also be noted that

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Abnormal Occurrence No. 50-219/74/20 Page 2 the inside main steam isolation valves had no detectable leakage and, therefore, there would have been no leakage out of the primary containment during an accident condition.

Corrective Action The main steam isolation valve shaft packing leakoff valve (between upper and lower sets of packing) were closed and the main steam isolation valves were retested successfully. These valves will remain in the closed position until the 1974 refueling outage. At this time, main steam isolation valve NSO4A will receive complete preventive maintenance and NSO4B will be inspected and completely repacked.

The leak rate tests for NS03A and NS03B assume that NSO4A and NSO4B have

. negligible leakage. Therefore, NS03A and NS03B were retested after the packing leakoff valves of NSO4A and NSO4B had been closed. Valves NS03A rnd NS03B were found to have acceptable leakage rates.

Failure Data The valve stem packing on NSO4A failed on September 27, 1973 and again on January 16, 1974. Each time, the valve was repacked and subsequently passed its leak rate test. The valve stem packing on NSO4B failed on September 27, 1973 and was subsequently repacked and retested successfully. The above occurrences were reported by letter, Mr. A. Giambusso from D. A. Ross dated October 12, 1973 and by Abnormal Occurrence Report No. 50-219/74/S.

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