ML20086D958

AO 73-26:on 730903,apparent Detonation in Offgas Sys Caused Sufficient Back Pressure to Fracture Air Ejector Rupture Disc,Thereby Degrading Boundary Designed to Contain Radioactive Matls

ML20086D958
Person / Time
Site:	Vermont Yankee
Issue date:	09/04/1973
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20086D956	List: ML20086D950 ML20086D958
References
AO-73-26, RO-730904, VYV-3003, NUDOCS 8312050700
Download: ML20086D958 (3)

Text

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VCHNON. VcRMONT 05354 as September 4, 1973 m

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United States Atomic Energy Commission k

r Directorate of Regulatory Operations, Region 1 '

631 Park Avenue King of Prussin, Pennsylvania 19406 -

REFERENCE:

Operating License DPR-28 {

Docket No. 50-271  : m -

Abnormal occurrence No. A0-73-26 . t t

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Gentlemen: i As defined by Technical Specifications for the Vermont Yankee  ! J-Nucicar Power Station, Section 6.7.B.1, we are reporting the following l Abnormal Occurrence as A0-73-26 and confirming our telephone a

b conversation with your office.

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At 0250 on September 3,1973, while operating at approximately l @

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68% power, an apparent detonation in the Of f-1;as System caused nufficient back pressure to fracture the air ejector rupture disc, ,_

thereby degrading a boundary designed to contain radioactive materials as defined by Technical Specifications Section 1.A.5. 9 5

There was no evidence of lightning or electrical storm at the time of this incident. The operators became aware of this incident by the '

following events:

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1. Of f-gas flow recorder went downscale ~Z

2. liigh AP stack gas filter alarm

3. liigh steam pressure on SJAE alarm --

4. Off-gas radiation and stack gas radiation recorders indicated ,'

upscale s' pikes

5. Tr2,ediate visual inspection of SJAE rupture disc verified it $-

-L-vas fractured w

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K 05000271 PDR . 6 k

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VCRMONT YANKCC FJ LCAR POWCR CORPORATION 4

Directorate of Regulatory Operations Septether 4, 1973 Page 2 Turbine roof ventilation was innediately secured and an immediate orderly shutdown of the plant was initiated as well as effecting a temporary repair of the fractured disc to minimize turbine building gaseous activity. Air ejector roon air particulate samples taken at 0430 indicated a maximum particulate activity of 4.5x10-3 uc/cc. The Interin Of f-gas Systen was not in service as it had been previously isolated on August 31, 1973, and was verified isolated on September 3, 1973. The reactor was completely shutdown at 0950 on September 3,1973.

The immediate program will replace the rupture disc, test the cfficiency of the stack gas filter and replace if necessary. Additionally, ji detailed program of exploration has been initiated to determine the source of of f-gas ignition and apply appropriate corrective measures prior to resuming normal plant operation.

Very truly yours,  %,

VERMONT YANKEE NUCLEAR PO'4ER CORPORATION

. . l B.'J. Riley M Plant Superintendent BWR/kbd i

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3 orew AI C.9 % ( Rei. Alav 14,19 4 9 Al( M t'g Note ses retura For ti rastute. f or Information. -E INITI ALS ELMAArt

>O (Pdame . and *wast) w Licensee: Vermont Yankee ,huclear Power Corporation

<V Docket No.:

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11. D. Thornburg, oArt 50-271 Chief, FSLEB "

Abnormal Occurrence: A0-73-26 -m to cream. aos ..i) n.a: Ats .auAnis RO:1!Q (5)

DR Central Files (1) oArt The attached report from the subject licensee is Regulatory Standards :3)

Dir. of Licensing (13 i foniarded in accordance with R0 Manunt chanter 1000 10 (idame and unit; th4 TI AL5 REMARK 5 RO Files v The action taken by the licensee is considered oArt appropriate. Followup uill be performed during the next inspection as appronriate . Confes of _

FidOM (Pdame anj un.t) pluARKS

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• l, (d'ht. a- the report have been forwarded to the PDR, Local _

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R.,T. Carlson, Chief PDR, NSIC, DTIE and State representatives. The Facility Operations Branch licensee will siibmit a 10 day written report to '

FHONE h0, oATE 9/10/73 Licensing.

4/58 OlhER LIDE FOR ADDiflugaL plu ApKS Cm 8978 O 04b si)

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