ML19274F040

Forwards LER 79-008/03L-0

ML19274F040
Person / Time
Site:	Cooper
Issue date:	05/18/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19274F041	List: ML19274F040 ML19274F042
References
CNSS790214, NUDOCS 7906080251
Download: ML19274F040 (2)

Text

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~'] COOPER NUCLEAR STATICN P.o. Box 98. BHoWNVILLE NEBRASKA 68321

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CNSS790214 May 18, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on April 20, 1979. A licensee event report form is also enclosed.

Report No.- 50-298-79-8 Report Date: >by 18, 1979 Occurrence Date: April 20, 1979 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition which led to operation in a degraded mode permitted by a limiting condition for operation established in paragraph 3.9.A.1 of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was in cold shutdown for refueling.

Description of Occurrence:

4160 V breaker IFA, scheduled for a periodic inspection, failed to trip automatically when breaker 1FS was closed. Control circuits are so arranged that only one feeder breaker can be closed at one time.  ;

Furthermore, breaker 1FA failed to trip when its control switch, located on BD-C in the control room, was manually operated.

Designation of Apparent Cause of Occurrence:

The breaker auxiliary switch, designated 52H/lN, did not take proper electrical connection.

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l Mr. K. V. Seyfrit May 18, 1979 Page 2.

Analysis of Occurrence:

When breaker 1FA is racked in, the 52H/lN auxiliary switch is operated. Its contact closes electrical interlocks and permits remote tripping of the breaker. Breaker 1FA and breaker LAF, connected in series, tie the emergency bus IF to bus lA (offsite power). On loss of offsite power both breakers trip. Therefore, failure of breaker 1FA to trip would not affect operation of the emergency bus IF. This occurrence presented no adverse conse-quences from the standpoint of public health and safety.

Corrective Action:

The breaker 1FA was removed for annual inspection. Breaker aux-iliary switch 52H/lN was cleaned. Electrical continuity of its contact was verified. After the breaker 1FA was racked in, it was trip tested and correct operation of breaker was verified. Breakers 1FA and 1GB are to be trip tested when racked in to assure that their auxiliary switch 52H/IN is closed. Itis instruction has been added to standard operating procedure 2.2.18.

Sincerely, h

L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attach.

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