ML20148B870

Special Rept:On 970123,periodic Source Leakage Test of 150 Uci Cs-137 Source Revealed Presence of Greater than 0.005 Uci of Removable Contamination.Source Removed from Svc & Will Be Disposed of IAW Applicable Regulatory Requirements

ML20148B870
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	04/22/1997
From:	Duffy J VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-97-50, NUDOCS 9705130394
Download: ML20148B870 (2)

Text

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i; VERMONT YANKEE -

nucle ^R POWER CORPORATION

• ek Ferry Road, Brattleboro, VT 05301-7002 ENGINEERING OFFICE

%0 VA!N STREE Y BOLTON MA01?d0 (SCP) 779 6711 April 22,1997 BVY 97-50 United States Nuclear Regulatory Commission

! ATTN: Documcnt Control Desk Washington, DC 20555

References:

(a) License No. DPR-2.5 (Docket No. 50-271)

Subject:

Vermont Yankee Spec'.al Report - Sealed Scurce Leakage The purpose of this letter is to sport, in accordance with Vermont Yankee Technical Specification 6.5.F. that on January 23,1997, a periodic source leakage test of a 150-microcurie (gCI) Cesium-137 source revealed the presence of greater then 0.005 Cl of removable contamination. Specifically, a survey of the outer surface of the source indicated 0.18 Cl of removable contamination. At the time of discovery, the source was in its shieldsd storage location. The storage location was surveyed for internal smearable contamination and none was found. In accordance with Vermont Yankee Technical Specifications, the source was removed from service and will be disposed of in accordance with '

applicable regulatory requirements.

Sources of the type found to have greater than 0.005pCi of removable contamination have been used as check sources in electronic dosimeter reader units. Our root cause investigation deterniined that sources of this design are dimensionally too large to be used with the electronic dosimeter reader. As a result, the sources tended to become stuck in the reader's source holder and the difficulty of removing the sources from the reader could cause the plastic covering of the source to peel off, i exposing the radioactive source materla!. Vermont Yankee also determined that the sources design and construction were not durable enough for this intended use. The leaking source is manufactured ,

from a plastic disc with the radioactive material deposited in its geometric center. The source is sealed l In place by a thin layer of plastic glued to the disc. When the source was removed from the storage /use location, the plastic covering the source material could be dislodged, exposing the source l, material. 1 l

In response to this event, Vermont Yankee has discontinued the use of sources of similar design for this application. In addition, Vermont Yankee has removed from service all 150 pCi Cesium-137 sources with model numbers MED 3503, Custom Cal 2600 and Custom Cal 2601. These sources will be disposed of in accordance with applicable regulatory requirements. Vermont Yankee is also p i evaluating all other " button" sources used at Vermont Yankee Nuclear Power Station for susceptibility '

to this type of failure. Finally, Vermont Yankee is reviewing this event with staff Rad!ation Protection personnel as part of our accredited RP training curriculum.

9705130394 970422 PDR ADOCK 05000271 1 S PDR

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• VI.RMONT YANKLt NUCLEAR POWER CORPORATION I

U.S. Nuclear Regulatory Commission April 22,- 1997 .l

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Should you have any questions or require additionalinformation regarding this matter, please contact this office.

l Sincerely,  !

VERMONT YANKEE NUCLEAR POWER CORPORATION pfffff.47 -

James J. Duffy  ;

Licensing Engineer ,

i c: USNRC Region 1 Administrator ,

USNRC Project Manager - WNPS l USNRC Resident inspector WNPS  !

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