ML20086D611

Updated AO 73-19:on 730625,during RCIC Surveillance Testing to Check Auto Closure of RCIC Steam Isolation Valves 15 & 16,valve 15 Failed to Close as Required.Caused by Misalignment or Binding in Declutch Mechanism

ML20086D611
Person / Time
Site:	Vermont Yankee
Issue date:	07/03/1973
From:	Riley B, Riley R VERMONT YANKEE NUCLEAR POWER CORP.
To:	US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086D614	List: ML20086D611 ML20086D620
References
AO-73-19, VYV-2755, NUDOCS 8312020422
Download: ML20086D611 (2)

Text

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O O v-J VERMONT YANKMM NUCLEAR POWER CORPORATION SCVCNTY SCVCN OROVC STRCET RUTI.AND, VERF10NT 03701 REPLY TO:

VYV-2755 p. o. sox is7 VCRNON, VERMONT 05354 July 3, 1973

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'Of&&b Director ,

Directorate of Licensing i .Qg U.S. Atomic Energy Commission JUL0 1973> 'E Washington, D.C. 20545 kW "3 "*C Pact C

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REFERENCE:

Operating License DPR-28 [' W 'r Docket No. 50-271 9 @

Abnormal Occurrence No. A0-73-19 4 v

Dear Sir:

As defined by Technical Specifications for the Vermont Yankee Nuclear Power Station, Section 6.7.B.1, we are reporting the following Abnormal occurrence as A0-73-19.

At approximately 1015 on June 25, during conduct of RCIC Surveillance testing to check auto closure of RCIC steam isolation valves 15 and 16, valve 15 failed to close as required. Several attempts were made to close this valve remotely from the Control Room panel with no success. . The inoperability of this valve exceeds the Limiting Condition for Operation as defined by Sections 3.7.D.1 and 3.7.D.2 of Technical Specifications.

Section 3.7.D.1 requires that, during reactor power operating conditions, all isolation valves listed in. Table 3.7.1 shall be operabic except as specified in 3.7.D.2. Section 3.7.D.2 requires that in the event any isolation valve specified in Tabic 3.7.1 becomes inoperable, reactor power operation may continue provided at least one valve in each line having an inoperable valve is in the mode corresponding to the isolated condition.

The reactor was at approximately 78% power at the time of the incident.

Since the repair would require an outage, the plant elected to commence shutting down at 1400, June 25, rather than electing to close a second isolation valve in this line which would have allowed plant operation to continue for seven succeeding days. Plant cold shutdown condition was achieved at 0653 on June 26.

The operator was disassembled, repaired, and reinstalled on the valve.

It was tested by stroking the valve several times.

8312O20422 730703 PDR ADOCK 05000271 J.g

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- VERMONT Y,-,dKEE NUCLEAR POWER CORPORATION r

Conversation with the vendor of the valve operator indicated that the mest probabic cause of the f ailure of the valve to close was due to misalignment or binding in the declutch mechanism, so that the dogs on the bronze worm gear did not have full contact with the mating parts on the clutch ring. To correct any possible inherent binding within the valve operator, internal replacement parts have been ordered and will be installed at the next opportunity during a plant shutdowa.

The Plant Operations Review Committee concluded that this failure was an isolated instance of component failure and since the valve operability was proved several times af ter repair, recommended that no further action be taken.

Very truly yours ,

VERMONT YANKEE NUCLEAR POWER CORPORATION

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Bradford W. RI. ley "%

Plant Superintendent JWT/kbd i