ML20086H321

AO 50-271/72-07:on 721010,alarm Annunicated in Main Control Room Indicating Leak in Bellows Assembly of Main Steam Relief Valve D.Caused by Residual Moisture Trapped in Tubing.Tubing Drained & Vented

ML20086H321
Person / Time
Site:	Vermont Yankee
Issue date:	10/19/1972
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086H319	List: ML20086H317 ML20086H321 ML20086H324 ML20086H336 ML20086H343 ML20086H345 ML20086H355
References
AO-50-271-72-07, AO-50-271-72-7, VYV-2295, NUDOCS 8401160374
Download: ML20086H321 (2)

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V VERMONT YANKEE NUCLEAR POWER CORPORATION SCVENTY SEVEN OROVC STREET RuTLAxo, Vensour osvon REPLY TO:

VYV-2295 p. o. sox is7 VERNON. VERMONT 05354 October 19, 1972

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• U.S. Atomic Energy Commission Washington, D.C.- 20545 [f f .

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Reference:

Operating License DPR-28 .h-f,l;f h Docket No. 50-271 '{/

e r,y e eN Abnormal Occurrence No. A0-72-07

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Dear Sir:

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As defined by Technical Specifications for the Vermont Yankee Nuclear Power Station, Section 6.7.B.d we are reporting the following abnormal occurrence as A0-72-07.

At 1831 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.966955e-4 months <br /> on October 10, 1972 an alarm annunciated in the main control room indicating a leak in the bollows assembly of main steam relief valve "D". The failure of the bhllows could render the one relief valve itMapable of automatically relieving reactor steam pressure at its set point of 1080 psig (1080 psig l%, Technical Specifications Section a 2.2.B).

This particular valve had experienced a similar failure on September 19, 1972 and was subsequently repaired during a scheduled plant outage.

The relief valve was restored to service on October 1, 1972. This relief valve unlike those on steam lines A, B, and C, has a silver plated 0-ring installed between the bellows and the preload spacer. An identical 0-ring l

l was determined to be the cause of the previous failure.

The vendor representative was on site for consultation immediately - '

following the incident, and his recommendations 'were considered in evaluatingp the situation. In addition, he confirmed that the operational dependability of the silver plated o-rings, in this application at other 6perating BWRs, '

has been excellent.

• A1401160374 721101 PDR ADOCK 05000271 S PDR 6g M i pp g g* I

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VERMONT YA KEE NUCLEAR POWER CORPORATIS 1

Directorate of Licensing October 19, 1972 ,

Page 2 On October 12, 1972 the tubing connecting the relief valve bellows to the pressure switch was drained, vented, and restored to service.

During the subsequent six days the bellows failure alarn did not annunciate.

However, on October 18, 1972 the alarn again annunciated and was drained,

vented, and returned to service as before. On the basis of this information it is concluded that both of these bellows failure alarms were caused by j, residual moisture from the first failure which had become trapped in the

[ instrunent tubing and flashed to steam during the ensuing plant heat up and operation. The Plant \0perations. Review Committee concluded that these additional alarms were not due.to bellows failure, posed no unresolved safety questions, and that no further action need be taken with regards to this abnormal occurrence. .

Yours very truly, VERMONT YANKEE NUCLEAR POWER CORPORATION B.W. Riley s

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Assistant Plant Superintendent PET /rph N. ' ,

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