ML20039B114

Updated LER 81-027/03X-1:on 811016,MSIV-80C Failed to Close on Receipt of Group 1 Isolation Signal During Reactor Scram. Caused by Actuator Failure.Actuator Completely Overhauled & Guide Rods,Spring Plate & Bushings Replaced

ML20039B114
Person / Time
Site:	Vermont Yankee
Issue date:	12/07/1981
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20039B109	List: ML20039B108 ML20039B114
References
LER-81-027-03X, LER-81-27-3X, NUDOCS 8112220304
Download: ML20039B114 (2)

Text

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U. S. NUCLEAfl REGULATO;tY COMMISSION

",",c,,Fom aos CORRECTIVE UPDATE - Previouu Report 11/14/81

, , LICENSEE EVENT REPORT LER 81-27/3x l (PLEASE PRINT OR TYPE ALL REQUIREO INFORMATION)

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? 8 60 61 74 76 REPORT D ATE 80 EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h 10121 l MSIV-80C failed to close upon receipt of a Group 1 isolation sicnal durine n l 10 6 31 l reactor scram. This failure is contrary to T. S. Section 3.7.D.1. Redundant valve l Io14IlMSIV-86C'successfully 4losed unon the isolation sienn1 nroviding containment isola- l j

i o i s 1 I tion. There were no (Onsequences to the public health and safety as a result of l lO16I Ithis event. No similar occurrences have been reported to the commission within the 1 loI7l llast five years. l f

10181 l- l 7 8 9 80 SYSTEM CAUSE CAUSE COMP. VALV E CODE COCE SUSCODE COMPONENT CODE SU8 CODE SU8 CODE R l Cl Dl@ y@ y@ l Vl Al Ll Vl Ol Pl@ y@ y @

9 10 20 1 8 11 12 13 18 19 i SEQUENTI AL OCCURRENCE REPORT REVISION  !

LER _ EVENT YE AR R EPORT NO. CODE TYPE N O.

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CORRECTIVE UPDATE - Previous Report 11/14/81 VTVYS1

• 05000271 LER 81-27/3X CAUSE DESCRIPTION AND CORRECTIVE ACTIONS The cause of the MSIV failure to close was due to the inoperability of the actuator to function upon receipt of a Group 1 isolation signal. After a complete investigation of the actuator, no one part of the acutator could be associated with the failure. The corrective action taken was to completely overhaul and inspect the actuator. The electric Soleniods were rebuilt; this included replacing scals, cleaning, inspecting and functional testing upon assembly. The actuator's limit switches were visually inspected and functional-ly tested. The air pilot valves were dismantled, seals replaced, internal parts cleaned, inspected and functionally tested upon assembly. The hydraulic snub-ber was dismantled, seals replaced, hydraulic oil changed, internal parts cleaned, inspected and functionally tested upon assembly. The actuator guide rods showed slight signs of gauling. They were replaced along with the spring plate and new brass bushings. Finally, the air filter elements in the supply line to the pilot valves and actuator were replaced. Subsequently, the complete actuator was installed and verified to be operable by stroking the MSIV. Replacement of the guide rods, spring plate and bushings is part of a continuing preventative mainten-ance program, i

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