ML20084N688

AO 50-249/75-42:on 750920,motor Operated LPCI Suction Valve 3-1501-5D Failed to Open Twice During Testing. Apparently Caused by Defective Valve Motor.Valve Motor Will Be Replaced

ML20084N688
Person / Time
Site:	Dresden
Issue date:	10/20/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084N685	List: ML20084N683 ML20084N688
References
714-75, NUDOCS 8306080426
Download: ML20084N688 (2)

Text

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m l% Com wealth Edison

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Address Reply to: Post difice Box 767 Chicago, Illinois 60690 EBS Ltr. #714-75 Dresden Nuclear Power Station R. R. f1 Morris, Illinois October 20, 1975

1. os Mr. Jemes G. K,eppler, Regional Director Directorate of ReSulator-/ Operation-Region III U. S. Nuclear Regulatory Coc=ission 799 Roosevelt Road Glen Ellyn, Illinois 60137

SUBJECT:

REPORT OF UNUSUAL EVD2 PEl SECTION 6.6.0 0F THE TECE!ICAL SPECIFICATIONS LPCI VALVE

'-1 %1-5D MOTOR TRIP

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Drawing Number M-360 Report Number: 50-249/75 42 Report Date: October 20, 1975 Occurrence Date: September 20, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois ID37PIPIC/, TION OF OCCURRD!CE M Mor-operated LPCI suction valve 3-1501-5D failed to open twice during testlng.

CONDITIONS PRIOR TO CCCURRD CE Unit-3 was operating at a power level of 700 Elt and 2CX) M4e. The LPCI valve operability tent was in progress.

DESCRIPTION OF OCCURRDICE At 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> on September 20, 1975, motor-operated valve 3-1501-59 was being cycled as specified by the LPCI system valve operability test procedure. Since LPCI pump suction valves are normally o, pen, valve 1501-5D was first cloced to begin the cycle. As the valve was being opened, thermal overload devices opened up in the power circuit.of the valve motor, tripping the valve before it had

' fully opened. The overload devices reset automatically, and the valve was opened the remainder of travel without further difficulty.

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PDR ADOCK 05000249 s

PDR COPY SENT llEGION 6

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Mr. Jame] G. K:pplcr October 20, 1975 i

3y During a second a'ttempt to open valve 1501-5D, the thermal overload devices opened once again. As before, the valve subsequently opened without incident once the overload devices had autonatically reset.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE (Component Failure)

The apparent cause of the occurrence was a defective valve motor. The motor's themal overload devices tripped because the motor was drawing a hiCh, unbalanced current.

The motor current rating is 2 95 amps, with a thermal overload trip setting of approximately 3.4 amps. The phase currents of the motor were found to vary between 4.0 and 4.6 amps during opening operation, and between 4.5 and 5 0 amps during valve closure. The valve manufacturer is presently inspecting

.another valve motor which demonstrated similar characteristics and was subsequently replaced.

ANALYSIS OF OCCURRENCE The LPCI pump suction valves (1501-5A-D) remain in the open position during reactor operation and do not closo in response to any group isolation signal.

Had valve 1501-5D failed in the closed position concurrently with a loss of coolant accident, the remaining three LPCI pumps would have been capable of providing adequate c=ergency core cooling. Since valve 1501-5D was capable of being manually opened as well, this occurrence did not threaten the safety of plant personnel or the public.

, CORRECTIVE ACTICN To prevent a recurrence of this nature, the valve motor will be replaced with a new, similar motor ifnich is now on order. Further corrective action will be contingent,upon the valve manufacturce's evaluation of the defective valve motor mentioned above.

FAILURE DATA A similar valve motor failure occurred on valve 3-1501-5A on July 28, 1975 (see report no. 50-249/75--33).

The "1501-5" and "1402-4" valves, which are operated by this type of motor, have experienced several thermal trips on both Units 2 and 3.

The motor is a 440 volt, 2.95 ampere, 15 foot-pound motor manufactured by Reliance Elcetric Co.

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'tephenson Superintendent BBS:ELS:smp F'le/NRC i

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