ML20086E400

AO 74-16:on 741214,containment Air Sampling Sys Found Inoperable.Caused by Nonfunctioning Heat Tracing Circuit.Sys Repaired

ML20086E400
Person / Time
Site:	Vermont Yankee
Issue date:	12/16/1974
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20086E391	List: ML20086E393 ML20086E400
References
A-74-16, A0-74-16, VYV-3483, NUDOCS 8312070089
Download: ML20086E400 (2)

Text

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O VERMONT YANKEE NUCLEAR Pow En CORPORNI'10N sevenTv sevcw onovc sTnccT ltUTLAND, VERMONT 03701 VYV-34S3 P.O.DOX 157 VERNON. VERT 40NT C5354 December 16, 1974 0 $

Director p r Directorate of Regulatory Operations, Region I '

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United States Atomic Energy Commission .

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REFERENCE:

Operating License DPK-28 ritieI, ,

Docket No. 50-271 6['

Abnormal Occurrence No. A0-74-16 (24 Hour Report) -

Dear Sir:

As defined by Technical Specificaticns for the Vermont Yankee Nuclear Power Station, Section 6.7, we are reporting the. folleuing Abnormal Occurrence as A0-74-16 and confirming our telephone conversation with your office.

At 0457 on December 14, 1974, as a result of responding to an alarm in the control room, the Control Room Operator observed that the Containment Air Sampling System was inoperable. The Limiting Condition of Operation of Section 3.6.C.2 of the Technical Specifications requires that this system be operabic during power operation. The plant was operating at approximately 20% power at the time of this incident.

The system was repaired and declared operabic at 1415 on December 14, 1974.

Very truly yours,

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Bradford W. Riley Plant Superintendent k

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ldentification of Occurrence Q, t /

Failure of t he Contaitc at Air Sarpling System i

Conditiom P r i o r t o O_c_c_u_r.ce n c e Steady state power operation at 20%

Description of occurruce A t. 0457 en Dacer6er 24, 1974, as a result of responding to an alarm in the Control Ecom, the Control Room Operator observed that the Containment Air Sc apling Syste: was inoperable. The Lir:it in", Condition for Operation of Section 3.6.C.2 of the Technical Specificatione requires that this system be operable during power operation. t Designatica of Anparent Cause of Occurrence The failurc of the Containment Air Sn ,pling System was caused by not having the heat tracing circuit functioning while the Containr.icnt Air Sampling Systea was operating.

Analysis of Occurrence Investigation by raintenance personnel found n failed fuse for the vacuun pump subsyst ra's control contactor and a f ailed diode bridge assenbly in the tape drive subsysten. There f ai'ures were apparently caused by toisture accumulation, which was obrerved at the bottom of the  !

tape drive unit, and further resulted in the discovery that the heat tracing  !

circuit for this system was not operating. The feeder breaker for the  !

heat tracing circuit .cas found in an "O N" condition, and was inadvertently left in that condition af ter required mintenance work was completed during the recent refueling outage. This condition alloued noisture to accuculate, which caused the equipnent nalfunctions described above, and the resultant failure of the Containment Air Sampling Systou to be operational.

Corrective Action j

The Containnent Air Sampling System failure was repaired and the heat t racing circuit for this systen made operational. To prevent repetitien of this occurrence, the applicable plant operating procedure will be revised to include a check that heat tracing ic functioning when the system is nade operable. Additionally, the components subject to the affect of moisture l l

accumulation were repositioned to prevcnt repetition of the occurrence. l 1

Failure Data '

13025 Not applicable

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UE/kbd Plant Superintct6 mt 2 COPY SElThREGION 'm