ML19261D631

LER 79-017/03L-0 on 790517:during Routine Surveillance of Core Spray Sys Ii,Parallel Isolation Valve V-20-21 Failed to Operate.Caused by Circuit Breaker Contacts Making Poor Contact in B Phase,Creating Overcurrent.Part Replaced

ML19261D631
Person / Time
Site:	Oyster Creek
Issue date:	06/15/1979
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19261D629	List: ML19261D628 ML19261D631
References
LER-79-017-03L, LER-79-17-3L, NUDOCS 7906200419
Download: ML19261D631 (3)

Text

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74 75 REPORT CATE BC I 61 DOCKET NUVBER EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o I On May 17, 1979. durina routine surveillance of Core SDrav system II . I o 3 L parallei isolation valve V-20-21 failed to operate as required. The I o .: l l valve failed to close after testing pressure switch RE17C. Investiga- J n15 1 tion revealed that the motor opersor circuit breaker had tripped. Sub- l e e  ! sequent tests indicated that the "B" phase internal contacts in the cir- l IC171 i cuit breaker were not making proper contact. The safety significance of ois i this event is considered minimal since the redundant valve was operable. l du y 3 S v ".d i'. CAv3i CALSE C C'/ P. VALV E CCCE CCCE SLSCODE COf/POf.E'.T COOE SJBOOCE SUBCODF io;ml E

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.2 - A 3? 40 43 CALM DECCWTICN M.D CCPRECTIVE ACTIONS h 1 o l The cause of this event is attributed to the circuit breaker contacts  !

i i i making poor contact in the "B" phase, thus creating an overcurrent con- I dition. The circuit breaker was replaced with a new one of the same gl i 3 l make and model. Breakers of this type are tested through the preventive [

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• ----ff Madison Avenue at Punch Bo*t Road Mornstown, New Jersey 07960 (201)455-8203 OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/79-17/3L-0 Report Date June 15, 1979 Occurrer.ce Date May 17, 1979 Identification of Occurrence Corc Spray System 11 parallel isolation valve V-20-21 became Inoperable in the open position when the motor operator breaker tripped. This event is con-sidered to be a reportable occurrence as defined in the Technical Specifi-cat ions , paragraph 6.9 2.B.2.

Conditions Prior to Occurrence The plant vsas in a cold shutdown condition.

Plant parameters at the time of the occurrence were:

Reactor coolant temperature - 150.4*F Reactor level - 81.5" Yarway

• All control rods fully inserted Description of Occurrence On Thursday, May 17, 1979, at approximately 0258 hours0.00299 days <br />0.0717 hours <br />4.265873e-4 weeks <br />9.8169e-5 months <br />, during routine survell-lance of Core Spray System 11, parallel isolation valve V-20-21 failed to operate as required. Parallel isolation valve V-20-21 failed to close af ter testing pressure switch RE17C. Investigation revealed that the motor operator circuit breaker had tripped.

Subsequently, the valve motor operator and the breaker were checked and tested.

Results of the tests indicated that the valve motor operator was functioning properly, but the circuit breaker internal contacts in the "B" phase were not making proper contact.

Apparent Cause of Occurrence The apparent cause of this occurrence is attributed to the circuit breaker internal contacts making poor contact in the B phase, thus creating an over-current condition that caused the breaker to trip.

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. Reportable Occurrence No. 50-219/79-17/3L-0 Page 2 June 15, 1979 Analysis of Occurrence The safety significance of this event is considered to be minimal since each of the parallel isolation valves are designed for rated system flow and the alternate parallel valve, V-20-41, was demonstrated to be operable. Had the core spray system been required at the time the valve was inoperable, the system would have operated as intended.

Corrective Action The corrective action was to replace the circuit breaker with a new one of the same type and model. Due to the large number of breakers of this type on site and their operational history, this appears to be an isolated event. The failed breaker was inadvertently discarded; therefore, as a result, it was not possible to analyze it for the exact cause of failure. Breakers of this type are tested through the preventative maintenance program (current tested) and normal surveillance testing. This provides additional insurance of detecting a r e t c r. t i a , problem developing with these types of breakers.

Failure Data General Electric E100 Line Circuit Breaker Type TEF with Adjustable Magnetic Trip Only Model TEF136M1010 Magnetic Range Amps Mi,.. 2e Mex., 68 Poles -3 volts 600 AC 2286 221 Continuous Amperes 10

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