ML19352A089

LER 77-010/03L-0:on 770423,while Performing Leak Rate Test, Outer MSIV NS04B Would Not Hold Pressure to Pressurized Vol & Inner MSIV NS03B.Caused by Tight Cracks Around Seat of Valve Body & Minor Degradation of Pilot Valve Seat

ML19352A089
Person / Time
Site:	Oyster Creek
Issue date:	05/20/1977
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
LER-77-010-03L, LER-77-10-3L, NUDOCS 8103040315
Download: ML19352A089 (4)

Text

LICENSEE EVENT REPORT Pags I of 2

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@ l At 9:_00 p.m. on Saturday, April 23, 1977, while performing local leak rate tests on 7 HU -

@ l the main steam isolation _ valves, it was discovered that outer MSIV NS0l B i would not 7 n9

@ l hold pressure when attempts 'were made to pressurize the volume between it and inner 7 00 --

@ l MSIV HS03B. The failure of NSO4B to hold pressure was indicative of a loss of 7 09

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$ l MSIV NSO4B is presently being disassembled and ins'pected. The inspection to date has 7 09 .

d b.e.yealed tiaht cracks located around the _ entire seat of the main valve along wi th sor.c 7 09 '

@ l_ minor degradction of the pilot valve seat. The Inspection is being continued 7 89 (CDUTThuto atxi RAGE / ,

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Licensee Event Report Page 2 of 2 Reportable Occurrence No. 50-219/77-10-3L May 20, 1977 CAUSE DESCRIPTION - continued to determine if additional causes for the valve leakage can be found.

CORRECTIVE ACTION Preparations are being made to replace the seat in the body of the main valve and to refurbish the seat in the pilot valve. Additional maintenance will be performed on the valve as required. A retest will be performed prior to reactor startup.

FAILURE DATA MSIV (NSO4B) 24" Air Operated Globe Valve .

Manufactured by Atwood Morrill Company Drawing No. 20451-H Donald A. Ross, Manager-Generating Stations-Nuclear 201-539-6111

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0YSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/77-10-3L g-Report Date May 20, 1977 Occurrence Date April 23, 1977 Identification of Occurrence Violation of Technical Specification 4.5.F.1.D. Failure of a main steam isolation valve to maintain leakage from the containment system within specified limits. This event is considered to be a 30-day reportable occurrence as defined in the Technical Specifications, paragraph 6.9 2.b.4.

Conditions Prior to Occurrence Reactor subcritical in the Refuel mode.

Description of Occurrence On Saturday, April 23, 1977, at 2100, a local leak rate test was performed on the main steam isolation valves (MSIV) in accordance with plant procedures.

While preparing to leak test MSIV NS03B (inner valve) with the reactor pressurized to 35 psig, an attempt was made to drain the volume between the inner and outer valves by pressurizing the volume to 10 psig and then venting the volume to a hub drain. The first attempt to pressurize the volume to 10 psig was unsuccessful and it was postulated that the cause of the problem was the failure of the outer valve (NSO4B) to seat properly.

The outer valve was then cycled and repeated attempts were made to pressurize the volume, all unsuccessfully. Further testing of the inner and outer valves was halted pending further investigation of the problem.

Apparent cause of Occurrence MSIV NSO4B is presently being disassembled and insrected in an effort to identify the cause(s) of the excessive leakage. The preliminary results of this inspection has revealed that tight cracks were located around the entire seat of the valve body along with some minor degradation of the pilot valve seat. The inspection is being continued to determine if additional causes were responsible for the leakage.

Analysis of Occurrence The MSIV(s) provide a dual purpose: (1) Reactor coolant isolation in the case of a main steam line break outside the dryweII; and (2) Primary containment isolation should a pipe break occur inside the containment. The main steam isolation valves are redundant in that one valve in each steam line will provide the necessary isolation function.

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. 1 Reportable Occurrence No. 50-219/77-10-3L Page 2 May 20, 1977 The safety significance of this event is considered to be a loss of system redundancy since valve NS03B was functional. Although the leak tightness I of NS03B cannot be conclusively determined until repairs are effected to NSO4B, it is anticipated that NS03B is within allowable leakage limits.

Corrective Action Based on the results of the inspection performed to date, preparations are bcIng made to replace the valve's main body seat and to refurbish the pilot valve seat. Additional maintenance, as required, will be performed on the valve followed by a retest prior to reactor startup.

Failure Data MSIV (NSO4B) 24" Air Operated Globe Valve Manufactured by Atwood Morrill Company Drawing No. 20451-H I

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