ML20086D749

AO 73-13:on 730523,RHR Svc Water Pump a Failed to Shut Down from Crp 9-3 During Surveillance Testing.Mechanical Trip Mechanism in Breaker Undependable Due to Misalignment of Mechanism & High Resistance Breaker Contact

ML20086D749
Person / Time
Site:	Vermont Yankee
Issue date:	05/31/1973
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
AO-73-13, VYV-2697, NUDOCS 8312050070
Download: ML20086D749 (1)

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Of *O V MRMONT Y ANImic NUCLMAR 1'OW MR COR PORATION Oh k n e vnerry neven onove ra orcT ,

l RUTLAND,Yi:lu10NT 03701 l VYV 2697 e. o. uox 157 i VtHNON, VCffMONT 05354 May 31, 1973 Director Directorate of Licensing hv U.S. Atomic Energy Commission bj/  ;

Washington, D.C. 20545 !l [

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REFERENCE- Operatina Li cense DPR-28 '

Docke t ik. .30-271 Abnormal Occurrence No. A0-73-13

Dear Sir:

As defined by Technical Specifications for the Vernont Yankee

v. i--.o,.,. e .w <.w c 7 v .i ,,, - , . , ,. e ., e , u ,. n,e r- 1 u. .u o nonorinal occurrence as nu-ia-13.

-Atq)315 on May 23, 1973, RlIR SW Pump "A" failed to shutdown from

[ CRP 9-3,during surveillance testing.

~

The pun p was tripped locally at

--the h~rTake r . 'lhir, equipment failure exceeds the limiting conditions for operation as defined by Section 3.S.C.1 of the Technical Specifications.

'lh i r. section requires the system to be operational whenever irradiated fuel is in the core and reactor coolant temperature is greater than 212 F. The reactor was at 78% power at the time of the incident.

The surveillance test requirements of Section 4.5.C.2 were completed.

A spare breaker was installed and tested, and the system was operational at 1013 May 23, 1973.

s Initial investigation revealed the mechanical trip mechanism in

} the breaker was undependable. The Plant Operations Review Committec reviewed the reported incident and recommended that the 4RV circuit breaker inspection program include verification of the trip mechanism setpoint and inspection of auxiliary contacts. Further investigation concluded that f ailure of the breaker to trip was caused by a misalign-ment of the mechanical trip mechanism along with high resistance breaker I auxiliary contacts in the trip circuit.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION 8312050070 730531 f *

{0 B.W. Riley

==- 03092 FJB/1k Plant Superintendent L __ a