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.: 050002770091407 Date: September 14, 2007 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE - PNO-I-07-008 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest 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.
Facility Licensee Emergency Classification Entergy Nuclear Operations, Inc. _ Notification of Unusual Event Vermont Yankee Nuclear Power Station Alert Unit 1 Site Area Emergency Brattleboro, VT General Emergency Docket: 50-271 X Not Applicable
Subject:
RESTORATION OF WEST COOLING TOWER Vermont Yankee returned the West cooling tower to service at approximately 11:00 p.m. on Thursday, 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 of eleven 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.
Entergys preliminary determination is that the collapse of cell 2-4 is attributable to several factors, including iron salt formation and fungal attack. The formation of iron salts in wood occurs where iron-containing hardware contacts the lumber, degrading the lumbers 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 water distribution pipe at the top of cell 2-4. Safety-related cell 2-1 is a more robust structure and uses stainless steel bolts, which is not susceptible to the iron salt formation associated with the carbon-steel connections used in some non-safety related cells.
The NRC Resident Inspectors permanently assigned to the Vermont Yankee site, as well as a structural 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 licensees 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. Powell B. Norris N. Sieller (610) 337-6967 (610) 337-5111 (610) 337-5380 rjp@nrc.gov bsn@nrc.gov nss@nrc.gov
DISTRIBUTIONS:
BY E-MAIL:
OWFN TWFN Chairman Klein NMSS Comm. Jaczko OIG Comm. Lyons RES OIP OCA OGC EDO OE NRR SECY Regional Offices BY FAX:
DOT:Trans INPO NSAC RI Resident Office Licensee: Entergy Nuclear Operations, Inc.
Vermont Yankee Nuclear Power Station ADAMS: ML SUNSI Review Complete: ____RJP (Reviewers Initials)
Document Name: C:\FileNet\ML072570337.wpd After 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: "C" = Copy without attachment/enclosure "E" = Copy with attachment/enclosure "N" = No copy OFFICE RI/DRP RI/POA RI/ORA RI/DRP NAME *RPowell *DScrenci/NSS for *NMcNamara *DLew DATE 09/14/07 09/14/07 09/14/07 09/14/07 OFFICE ORA NAME MDapas/MLD DATE 09/14/07 OFFICIAL RECORD COPY