ML19242A393

Forwards LER 79-016/03L-0

ML19242A393
Person / Time
Site:	Cooper
Issue date:	06/26/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19242A394	List: ML19242A393 ML19242A395
References
CNSS790290, NUDOCS 7908010555
Download: ML19242A393 (2)

Text

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x, ] COOPER NUCLEAR ST ATloN p.O. GO x 98, BROWNVILLE, NE BR ASKA 68321 e

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Nebraska Public Power Distr.ic t m.E~o~E m e sae n

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CNSS790290 June 26, 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 Sec tion 6.7.2.3.2 of the Technical Spe :ifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on May 31, 1979. A licensee event report form is also enclosed.

Report No.- 50-298-79-16 Report Date: June 26, 1979 Occurrence Date: >by 31, 1979 Facility: Cooper Nuclear Station Brownville. Nebraska 68321 Identification of Occurrence:

A condition which lead to operation in a degraded mode permitted Ly a limiting condition for operation established in paragraph 3.5.A.4 of the Technical Specifications.

Conditions Prior to Occurrence:

Steady state power operation at 650 L'e .

Description of Occurreace:

Ducing perfor.ance of surveillance procedure 6.3.5. , RHF Pump 1A tripped during start due to overcurrent in phase C.

Designation of Apparent Cause of Occurrence:

A small particle of debris was found lodged between the operating disc and the magnet inside the phase C overcurrent relay. This prevented the disc to return to its normal position and resulted in a shorter time delay for the relay to close its contact. The relay, having its time delay reduced, closed its contact due to the no m 1 high current required for pu=p start and initiated a pump trip.

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Mr. K. V. Seyfrit June 26, 1979 Page 2.

Analysis of Occurrence:

The subject overcurrent relay is one of two overcurrent relays con-itoring the A & C phase current to the 4160V AC breaker for RHR pump 1A. The two relays are physically located on the door of breaker cabinet RHR 1A. It is believed a particle of debris got into the subject relay while a hole was being cut in the cabinet door to install an additional undervoltage relay adjacent to the overcurrent relay. The undervoltage relay was 1 of 5 being in-stalled in accordance with an approved minor design change. The tripping of RHR pu=p 1A did not affect the operation of other safety systems and the 3 redundant RHR pu=ps were verified oper-able. This occurrence presented no adverse consequences to the public health and safety.

Corrective Action:

The overcurrent relay time delay asse=bly was cleaned and the relay tested satisfactorily. RHR pump 1A was started and verified operable.

The remaining 4 breaker cabinets which had undervoltage relays in-stalled were inspected for cleanliness and the respective over-current relays were verified operable. All personnel involved with the work on the subject breaker cabinets have been informed of this occurrence.

Sincerely, L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attoih.

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