ML19254F598

Responds to IE Bulletin 79-23, Potential Failure of Emergency Diesel Generator Field Exciter Transformer. No Connection Exists Between low- & high-rated Control Transformers

ML19254F598
Person / Time
Site:	Oyster Creek
Issue date:	10/12/1979
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 7911120487
Download: ML19254F598 (2)

Text

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Jersey Central Power & Ught Company k*.d[(f (

J Madison Avenue at Punch Bowl Road Morristown, New Jersey 07960 (201)455-8200 October 12, 1979 Mr. Boyce H. Grier, Di rector Office of Inspction and Enforcement United States Nuclear Regulatory Commission Region 1 631 Park Avenue King of Prussia, Pennsylvania 19406

Subject:

Oyster Creek Nuclear Generating Station Docket No. 50-219 IE Builetin No. 79-23 The purpose of this letter is to respond to the directives set forth in IE Bulletin No. 79-23 which has as its concern the potential failure of emsrgency diesel generator field exciter transformers. Our responses to the specific actions required by the subject bulletin are given below.

Item 1:

Determine whether or not connections have been made between low KVA rated transformers and high KVA rated EDGs witaout adequate limitations on the Flow of circulating currents. if applicable, provide a description of the corrective action being taken to address this problem.

Response

An inspection was performed on the emergency diesel generators (EDGs) at the Oyster Creek Station to determine whether or not a connection exists between the low KVA rated control transformers (CPTs) and the high KVA rated EDGs without adequate limitations on the flow of circulating currents. This inspection and a review of the history of the subject system revealed that such connections did at one time exist via cormion grounds. The connections were removed, however, subsequent to an incident which occurred on June 21, 1973, when a voltage surge caused by a nearby lightning storm resulted in the failure of the three (3) primary fuses of the 45 KVA CPT for EDG #2. As a result of the investigation of this incident, the grounds at the neutrais of the primary windings of the CPTs were IIfted. ,c

) ,') l 3! ..') ) b Item 2:

Provide a schedule for the completion of a sustained full-load operation test of the EDGs for a duration of not less that 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, or provide 7 91112 0 'g [

Jersey Central Power & Light Company is a Member cf me General Pubhc Ut.htes System

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IE Bulletin No. 79-23 October 12, 1979 the results of the similar long duration, full-load test which has already been completed on the EDGs installed at your facility. The test should demonstrate full-load carrying capability for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> should be at a load equivalent to the continuous rating of the diesel generator and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at a load equivalent to the 2-hour rating of the diesel generator. The test should also verify that voltage and frequency requirements are maintained and that the cooling system functions within design limits.

Response

A sustained full-load operation test of the EDGs will be completed no later than the end of the next refueling outage, which is now scheduled to begin on January 4, 1980. The test will demonstrate full-load carrying capability for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> will be at a load equivalent to the continuous rating of the diesel generator, and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at a load equivalent to the 2-hour rating of the diesel generator.

In addition, the test will verify that the requirements for voltage and frequency are maintained, and that the cooling system performs within the designed limits.

truly yours,

/ ., w -

Donald A. Ross, Manager Generating Stations-Nuclear cs cc: United States Nuclear Regulatory Commission Office of inspection and Enforcement Division or Reactor Operations inspection Washington, DC 20555

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