ML20084N901

RO 50-249/75-33:on 750728,suction Valve for LPCI Pump MO-3-1501-5A Tripped Twice on Thermal Overload.Caused by Defective Motor.Motor Replaced

ML20084N901
Person / Time
Site:	Dresden
Issue date:	08/27/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
556-75, NUDOCS 8306090106
Download: ML20084N901 (2)

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'j Address Repiy toTPost Olhce Box 767 Chicago. litinois 60690 BBS Ltr. #556-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 August 27, 1975 A

Y'>e Mr. James G. Keppler, Regional Director Directorate of Re6ulatory Operation-Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 SUBJET: REPORT OF UNUSUAL EVENT PER SETION 6.6.C OF THE TECHNICAL SPECIFICATIONS LPCI VALVE 3-1501-5A THZRMAL TRIP

References:

1) Regulatory Ouide 1.16 Rev 1 Appendix A

2) Drawing Number M-360 Report Number 50-249/75-33 Report Date August 27, 1975 Occurrence Date: July 28, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois 60450 IDENTIFICATIdN OF OCCURR."NCE The suction valve for the "A" LPCI pump, MO-3-1501-5A, tripped twice on themal overload.

CONDITIONS PRIOR TO OCCURRENCE Unit-3 was shutdown in a refueling outage. Surveillance testing of the LPCI system was in progress.

DESCRIPTION OF OCCURRBICE At 1930 hours0.0223 days <br />0.536 hours <br />0.00319 weeks <br />7.34365e-4 months <br /> on July 28, 1975, the motor operator on valve 1501-5A tripped on thermal overload as the valve was being opened. The valve had just been closed with the motor operator. After opening, the valve could not be operated for approximately 40 minutes. As the valve was being closed once more, the motor operator tripped again.

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Mr. Jame3 G. Khpler, 2-V Augu;t 27, 1975 DESIGNATION OF APPARENT CAUSE OF OCCURRENCE (Component Failure)

The valve motor tripped on therinal overload. The 15 rt.-lb. motor is a limited-duty type rated at 2 95 amperes, with a therinal overload trip setting of approximately 3.4 amps. During valve operation the motor was drawing between 3 2 and 3.5 amps. Without any load the motor was found to draw roughly 2.8 4

ampe, or nearly the full-load current rating. Therefore, a defective motor appears to be the primary cause of the valve trips.

4 ANALYSIS OF OCCURRENCE The LPCI pump suction valves (1502-5A, -5B, -5C, and -5D) are in the open position during neactor operation and do not close in response to any group isolation signal. Had valve 1501-5A failed in the closed position during reactor operation, the remaining three LPCI pumps would have been fully capable of providing emer6ency core cooling in the event of an accident.

Plant personnel and the public were in no way endangered by this occurrence.

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CORRECTIVE ACTION i

'Ibe valve's motor was replaced with a similar type motor which draws.approximately l

19 amps with no load and 2 3 - 2 5 amps while operating the valve. The replacement motor successfully cycled the valve several times.

4 FAILURE DATA f

Valve 1501-5A and other valves with similar motor operators have experienced several tripping problems in the past. These problems are still under review.

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f M. B. Stephenson Superintendent BBS:ELS:smp File /NRC I

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