ML20050B758

Updated LER 81-040/03X-1:on 811206,during Cooldown,Valve 2-RC-403 Could Not Be Opened & Was Declared Inoperable. Caused by Electrical Failure in Valve Motor Operator.Switch & Switch Assemblies Replaced

ML20050B758
Person / Time
Site:	Millstone
Issue date:	03/30/1982
From:	NORTHEAST UTILITIES
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20050B755	List: ML20050B754 ML20050B758
References
LER-81-040-03X, LER-81-40-3X, NUDOCS 8204070329
Download: ML20050B758 (2)

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[ O_] 2] l During the cooldown following a reactor shutdown, valve 2-RC-403. blockino valve for J g o ,y g PORV 2-RC-402, could not be opened. 2-RC-403 had been shut on September 28, 1981 I gjy ; (See LER 81-33). 2-RC-402 was declared inoperable, and the plant was operated in 1 j o g ,) , accordance with Technical Specification Action Statement 3.4.9.3.a for 95 hours0.0011 days <br />0.0264 hours <br />1.570767e-4 weeks <br />3.61475e-5 months <br />. I g g Similar events: None. j I

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44 47 CAUSE DESCRirilON AND CORRECTIVE ACTIONS i o l The valve operator motor was found to have failed electrically. The ornhable raima I g,,,jg was a failure of the torque switch assembly, resulting in excessive current beina I g, applied to the motor. The motor torque switch and geared limit switch assemblies 1

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ATTACHMENT TO LER 81-40/3X-1 FACILITY OPERATING LICENSE N0. DPR-65 DOCKET N0. 50-336 Event Description and Probable Consequences During the cooldown following a routine reactor shutdown for refueling, isolation valve 2-RC-403, blocking valve for the pressurizer power operated relief valve (PORV) 2-RC-402, could not be opened. 2-RC-403 had been previously shut to reduce reactor coolant system leakage on September 28, 1981. (See LER 81-33). 2-RC-402 was declared inoperable for the purpose of low temperature /

over pressure protection. The plant operated in accordance with Technical Specification Action Statement 3.4.9.3.a for 95 hours0.0011 days <br />0.0264 hours <br />1.570767e-4 weeks <br />3.61475e-5 months <br /> when an RCS vent greater than 1.3 square inches was opened. Similar events: none.

Cause Description and Corrective Actions 3 The valve operator motor for 2-RC-403 was found to have been burned out. While the l exact cause cannot be determined, the original LER reported that the motor burnup was probably due to steam environment. Subsequent investigation has revealed a problem with the torque switch and geared limit switch assemblies. If the torque switch stuck, causing a locked rotor current to be applied to the motor, the motor

.would fail due to excessive current since the motor overload protection has been bypassed. Therefore the torque switch is considered to be the cause of the failure.

Since the valve operated in the steam environment and isolated the leak without a problem, the steam may not have been the cause. The motor torque switch and geared limit switch gear box and panel assemblies were replaced and the operator functionally tested. The operator is a Limitorque Type SMB 000.

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