ML19208A089

LER 79-028/03L-0:on 790807,during Routine Surveillance of Core Spray Sys 1,parallel Isolation Valve V-20-15 Became Inoperable in Open Position.Caused by High Motor Current Drawn When Close Signal Inadvertently Initiated

ML19208A089
Person / Time
Site:	Oyster Creek
Issue date:	09/06/1979
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19208A087	List: ML19208A086 ML19208A089
References
LER-79-028-03L, LER-79-28-3L, NUDOCS 7909120521
Download: ML19208A089 (3)

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HEPORT D AT E d S f,) C4 EP Et ENT C ATE EVENT DEsCRIDTtoN AND FFoBAsLE CONSECUENCEs h a 12'l l On August 7, 1979, during routine surveillance of Core spray system I, I o 3 L parallel isolation valve v-20-Is became inope-able in the open position. l i a3 4i i The circuit breaker for the motor operator tripped when the actuation j i oisi i pressure sensor was reset. A parallel valve V-20-40, which is actuated l

!:le by the same pressure sensor, operated normally. Valve stroking currents l lal : i i were read with the breaker reset and found to be normal. The valve was  !

, O i E I i_ stroked to determine operability and resurveilled without incident. l E y '

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5:_t l_ The apparent cause of the occurrence was the high motor current drawn  ;

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(201)455-8200 OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/79-28/3L-0

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Report Date September 6, 1979 Occurrence Date August 7, 1979 Identification of Occurrence Core Spray System parallel isolation va!ve V-20-15 became inoperable in the open position when the motor breaker tripped. This event is considered to be a reportable occurrence as defined in the Technical Specifications, pa rag ra ph 6. 9. 2. B. 2.

Conditions Prior to Occurrence The plant was operating at steady state power.

Power: Core, 1930 MWt Electric, 641 MWe Floa: Recirculating, 15.2 x 10 gpm 4 Feedwater, 7.143 x 106 lb/hr Stack Gas: 34,100 pci/sec Description of Occurrence On Tuesday, August 7, 1979, at approximately 2:00 p.m., during routine surveillance of Core Spray System I, parallel isolation valve V-20-15 motor circuit breaker tripped when the actuation pressure sensor was reset.

The parallel valve V-20-40, which is actuated by the same pressure sensor, operated normally. The circuit breaker for V-204 5 was meggered as were the motor and cables with no abnormal conditions found. Valve stroking currents were read with the breaker reset and the tripping elements were tested to determine their setpoints. All parameters were found to be normal. The valve was stroked to determine operability and resurveilled without incident.

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Reportable Occurrence No. 50-219/79-28/3L-0 Page 2 September 6, 1979 Apparent Cause of Occurrence The apparent cause of the occurrence was the inadvertent initiation of a valve close signal during the period when the valve was still stroking open.

This occurs when the valve open signal is removed in less time than is re-quired for the valve to assume the full open stop position. The i. .itaneous reversal in direction of the motor operator is not the intended mode of operation. Reversal cf motor inertia while driving requires greater torque causing greater than normal starting current to be seen by the motor circuit breaker. The added current is believed to have causea the circuit breaker to trip.

Analysis of Occurrence The safety significance of this event is ;onsidered to be minimal, since each of the parallel isolation valve: are designed fcr rated system flow and the alternate parallel valve, V-20 43, functioned as designed. Had the Core Spray System been required at the time the valve became inoperable, the system would have operated as intended.

Corrective Action initial corrective action consisted of the testing of the breaker and electrical valve components to assure proper functional capability and designed setpoints. In addition, the surveillance procedure was revised to include more specific guidance to avoid inadvertent operational modes.

Subsequently, a test was conducted by the electrical staff to demonstrate the changes in current magnitude during simulated identical conditions.

The starting current during an instantaneous reversal in motor direction was found to be approximately 20% higher than normal starting current which tends to confirm the susoected cause for breaker trip. The same current / time traces were made under similar conditions for parallel isolation valve V-20-40.

Since the results show the identical response found for V-20-15, we are assured that such response is not indicative of component failure or abnormal rea:tions of circuit elements.

Failure Data None O

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