PNO-I-07-008, Vermont Yankee, Restoration of West Cooling Towers
| ML072570337 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee  |
| Issue date: | 09/14/2007 |
| From: | Norris B, Racquel Powell, Sieller N NRC Region 1 |
| To: | |
| Powell R, RI/DRP/610-337-6967 | |
| References | |
| DCS 050002770091407 PNO-I-07-008 | |
| Download: ML072570337 (3) | |
DCS No.: 050002770091407Date: September 14, 2007PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE - PNO-I-07-008This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or publicinterest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region I staff on this date.FacilityLicensee Emergency ClassificationEntergy Nuclear Operations, Inc. _ Notification of Unusual EventVermont Yankee Nuclear Power Station Alert Unit 1 Site Area EmergencyBrattleboro, VT General EmergencyDocket: 50-271 X Not Applicable
Subject:
RESTORATION OF WEST COOLING TOWERVermont Yankee returned the West cooling tower to service at approximately 11:00 p.m. onThursday, September 13. The cooling tower, which is comprised of eleven cells, was taken out-of-service on August 21, 2007 following the collapse of a non-safety related cell. This cell, designated cell 2-4, was not returned to service with the rest of the tower. Structural repairs have been completed, but the cell's non-structural fill material has not been re-installed.Vermont Yankee has two cooling towers, which as previously noted, each tower consists ofeleven cells. Only one cell, designated cell 2-1, is considered to be safety-related. This safety-related cell has a more robust construction than the non-safety related cells, and was unaffected by the collapse of cell 2-4.Entergy's preliminary determination is that the collapse of cell 2-4 is attributable to severalfactors, including iron salt formation and fungal attack. The formation of iron salts in wood occurs where iron-containing hardware contacts the lumber, degrading the lumber's structure.
The growth of fungus at this site can also damage the wood. This degradation resulted in the weakening and deformation of the heavily loaded vertical timbers that supported the waterdistribution pipe at the top of cell 2-4.
Safety-related cell 2-1 is a more robust structure anduses stainless steel bolts, which is not susceptible to the iron salt formation associated with thecarbon-steel connections used in some non-safety related cells. The NRC Resident Inspectors permanently assigned to the Vermont Yankee site, as well as astructural expert from the NRC's headquarter's office, independently inspected the exterior of the cooling towers and accessible internal portions of the safety-related cell. The NRC determined that cell 2-1 appeared to be in good condition. The NRC monitored the licensee's investigation, assessed Entergy's preliminary root cause analysis, and verified key assumptions in determining the continued operability of cell 2-1. The adequacy and thoroughness of Entergy's past inspections of the cooling towers are currently under review.Inquiries have been received from select Congressional offices in Vermont and Massachusetts.
The NRC Region I office has notified the State of Vermont, the Commonwealth of Massachusetts, and the State of New Hampshire regarding the restoration of the cooling tower. This preliminary notification is being issued for information only.ADAMS Accession Number: ML072570337 Contacts:R. PowellB. NorrisN. Sieller(610) 337-6967(610) 337-5111(610) 337-5380 rjp@nrc.govbsn@nrc.govnss@nrc.gov DISTRIBUTIONS
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OIP OCA OGC EDO OE NRR SECY Regional OfficesBY FAX: DOT:Trans INPO NSAC RI Resident Office Licensee:Entergy Nuclear Operations, Inc. Vermont Yankee Nuclear Power StationADAMS: ML SUNSI Review Complete: ____RJP (Reviewer's Initials)Document Name: C:\FileNet\ML072570337.wpdAfter declaring this document "An Official Agency Record" it will be released to the Public.To receive a copy of this document, indicate in the box:
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" N" = No copyOFFICERI/DRPRI/POARI/ORARI/DRPNAME*RPowell*DScrenci/NSS for*NMcNamara*DLewDATE09/14/0709/14/0709/14/0709/14/07OFFICEORANAMEMDapas/MLDDATE09/14/07OFFICIAL RECORD COPY