ML20085K113

Ao:On 731214,diesel Generator Cooling Water Pump Breaker Tripped,Following Semiannual Maint Insp.Caused by Defective Breaker.Breaker Replaced

ML20085K113
Person / Time
Site:	Dresden
Issue date:	12/21/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085K115	List: ML20085K113 ML20085K117 ML20085K119
References
930-73, NUDOCS 8310200078
Download: ML20085K113 (2)

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One Fast.Jabonal P aza. Chicago, libnois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 WFW Ltr #930-73 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60h50 December 21, 1973 c;

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G 7/8 3 Directorate of Licensing ff. ug 4 3C'l Mr. J. F. O' Leary, Director f

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Washington, D. C.

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SUBJECT:

LICE'ISE DPR-25. DRESD.?I NUCLEAR POER STATION, UNIT #3, REF0rty O/ AMOMML CCC'JWi.;Cs Fia SsOflCG o.o.b.l.a OF THE T:EEilCAL SFsC1/ICATIO]S UNIT 3 DIESEL GHIERATCR CCOLING WATER RIMP TRIP

References:

1) Notification of Region III of AEC Regulatory Operations Telephone: Mr. Fiorelli, lh00 hours on December lh, 1973 Tele 8 ram:

Mr. J. Keppler, 12h0 hours on December lh, 1973

2) Dwgs: P & ID M-355

Dear Mr. O' Leary:

This letter is to report a condition relating to the operatien of the unit at about 0005 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> on December lk, 1973 At this time, the Unit 3 diesel generator cooling water punp breaker tripped, causing the Unit 3 diesel generator to trip on high temperature. This malfunction is contrary to section 3.5.F.1 of the Technical Specifications which requires that the reactor be in the cold shutdown condition within 2h hours when the diesel generator is inoperable and it cannot be verified that all of the low pressure core cooling and containment cooling subsystems are operable.

PROBLEM At the time of the occurrence, the reactor power was 690 MWe (2229 MWt). The deviation occurred when the operator attempted to verify the operability of the diesel ;;enerator following the semi-annual J$

maintenance inspection.

N NO.

".f The Unit 3 diesel generator was started at 2310 hours0.0267 days <br />0.642 hours <br />0.00382 weeks <br />8.78955e-4 months <br /> on 1

$n Decenber 13, 1973, to verify operability following the semi-annual maintenance inspection. It tripped at 23h0 hours -the same day on high mr :s temperature. Shift personnel conducted an immediate investigation, which revealed that the diesel Eenerator cooling water pump breaker had tripped.

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Q Inspection of the breaker and the cooling water punp revealed nothing y,g [,

o abnormal. Therefore, the breaker was reset and the operator re-started

$$m the Unit 3 diesel generator at 0029 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> on December lh, 1973. Two minutes [5 m a.

later, at 0031 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br />, the cooling water pump breaker tripped and the

} Q[]g operator shutdown the diesel generator. Work request #7623 was issued to C-OPY SENT REGION

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Mr. J. F. O' Leary December 21; 1973 the Electrical Maintenance Department to investigate and repair the problem.

INVESTIGATION The Electrical Maintenance Department inspected the diesel generator cooling water pump breaker and the related electrical systems, but could find nothing that would have caused the problem. At about 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, the Unit 3 diesel generator was again started, but tripped on high temperature approximately 20 minutes later. Following the unsuccessful trial run, the diesel generator cooling water pump and lines were meggered and tested satisfactorily. It was decided at this time that the breaker was defective and the decision was made to replace the breaker.

CORRECTIVE ACTION The cooling water pump breaker was replaced with an identical h80 volt,150 ampere breaker GE model TFJ236150 on December 15, 1973.

Following replacement of the breaker, the Unit 3 diesel generator was started and a one hour trial run was successfully completed at about 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br /> on December 15, 1973.

The defective breaker was tested, disassembled and inspected on site by General Electric Company personnel. The inspection revealed no physical damage to the breaker or missing parts. The test revealed that the breaker would hold 100 anps for only a few minutes before tripping and tripped out when a surge of between 100 and 110 anps was applied.

It was concluded that the breaker was defective. In order to determine the cause of the breaker failure it will be returned to the factory for analysis.

EVALUATION The safety of the public and the plant were not jeopardized by this incident because all of the systems required to be operable when the Unit 3 diesel generator is inoperable were tested and verified operable, in accordance with Technical Specification 3.5.F.1.

Since the cooling water pump and the associated breaker were recently installed in October as a station modification, no problems have been experienced with this breaker or like breakers on similar systems during preoperation or monthly testing.

Analysis of the breaker at the factory should identify the specific defect and help to preclude recurrence of similar defects in breakers manufactured in the future.

The incident posed no problem that justify limiting continued' operation of Unit 3.

, Sin,cerely, N bbb-WFWals W.~ P. Worden S4perintendent