ML20086D945

AO 73-27:on 730909,apparent Detonation in Offgas Sys Caused Sufficient Back Pressure to Fracture Air Ejector Rupture Disc,Thereby Degrading Boundary Designed to Contain Radioactive Matl

ML20086D945
Person / Time
Site:	Vermont Yankee
Issue date:	09/10/1973
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20086D943	List: ML20086D939 ML20086D945
References
AO-73-27, VYV-3019, NUDOCS 8312050692
Download: ML20086D945 (2)

Text

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.q VERMONT YANKME NUCLEAR POWER CORPORATION SCVCNTY GCVEN OROVC STRCCT Ruri.Axo, VEltF10NT OG701

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VYV-3019 P.O. BOX 157 VERNON, VERMONT 03354 September 10, 1973

/..--. 's United States Atomic Energy Commi'ision '

Directorate of Regulatory Operations, Region I 631 Park Avenuc 3

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REFERENCE:

Operating License DPR-28 6-

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.6hD b Docket No. 50-271 {,

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• g Abnormal Occurrence No. A0-73-27 Q Centlemen: @% fIs} l Ae dafin a bu h ehnical %aci fi cc i on s fnr the Verrnont Yankea Nuclear Powcr Station, Section 4.7.8.1, w are. regcrLiag the follo las Abnormal Occurrence as A0-73-27 and confirming our" telephone conversation with your office.

At 0210 on September 9,1973, while operating at approximately 65% power, an apparent detonation in the Off-gas System caused sufficient back pressure to fracture the air ejector rupture disc, thereby degrading a boundary decigned to contain radioactive materials as defined by

',. Technical Specifications, Section,.1.A.5.

q There was no evidence of lightning or cicctrical storm at the time

'. ) of this incident. The station operators became aware of the incident by the following events:

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1. Off-gas flow recorder went downscale

2. liigh AP stack gas filter alarm

3. liigh stcan pressure en SJAE

4. Immediate visual inspection of the SJAE rupture disc verified .

it had fractured 8312050692 730917 PDR ADOCK 05000271 3 PDR I -

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• VERMONT YANKEC NUCLI*AR POWER CORPOR ATIC.'

Directorate of Regulatory Operations September 10, 1973 Page 2 Turbine roof ventilation was inmediately secured and an orderly shutdown of the plant wa9 initiated as well as effecting a temporary repair of the fractured disc to minimize turbine building gaseous activity. Turbine Building sumpics taken at 0347 indicated a maximum airborne activity of <1.1Sx10-6 pCi/ce. The Interim Off-gas System was not in service as it had been previously isolated on August 31, 1973. The reactor was completely shutdoun at 0723 on September 9,1973.

The immediate program will replace the rupture disc and test the efficiency of the stack gas filter and replace it if necessary.

The stack gas filter cartridge vill be modified to provide adequate grounding to the filter case. Additionally, a written emergency operating procedure addressed to detonation in the off-gas system will be established prior to resuming normal plant operation.

Very truly yours ,

VERMONT YM;KEE NUCLEAR POWER CORPORATION l.T D.O '

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Bradford U. Riley ~

Plant Superintendent WFC/kbd e

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