ML20112F800

Special Rept:On 960424,fire Protection Sys Declared Inoperable as Conservative Precaution for Greater than 14 Days.Calculations for Sys May Not Accurately Reflect Pressure Loss.Mods Being Developed

ML20112F800
Person / Time
Site:	Vermont Yankee
Issue date:	06/07/1996
From:	Wanczyk R VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-96-75, NUDOCS 9606100124
Download: ML20112F800 (2)

Text

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VERMONT YANKEE NUCLEAR POWER CORPORATION Ferry Road, Brattleboro, VT 05301-7002

) ENGINEERING OFFICE I M

• 580 MAIN STREET

, BOLTON. MA 01740 (508)779-6711 l

June 7 1996 BVY 9,6-75 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 l

l Attn: Document Control Center l

References:

a) License No. DPR-28 (Docket No. 50-271)

! b) Licensee Event Report, LER 96-013, dated May 23,1996 1 j

Subject:

Vermont Yankee Special Report, Fire Protection i System Out of Service Greater Than 14 Days l l The purpose of this letter is to report the inoperability of part of the Vermont Yankee Fire Protection l System in accordance with Vermont Yankee Technical Specification 3.13.F.

l Originally installed and tested as a result of the Fire Hazards Survey recommendation in response to

! NUREG 75/87, the Vermont Yankee Reactor Building elevation 252' suppression system was modified l in 1984 to provide extended coverage above the cable trays and to provide protection for the elevation 232' corner room.

In 1995, Vermont Yankee formed the Fire Protection Improvement Project (FPIP) to review existing fire protection systems and equipment to verify bases and continued compliance with the requirements of 10CFR50, Appendix R. During the review of the Reactor Building 252'/232' suppression system bases, the FPIP Assessment Team determined that the hydraulic calculations for the system may not accurately reflect the pressure loss through the 4 inch feed main located in the Turbine building. This omission l

changes the amount of water calculated for delivery by each system sprirAler, resulting in the systems failing to meet its design requirements.

As a conservative precaution, the suppression system was declared inoperable on April 24,1996. At that time the Control Room Shift Engineer was notified, the Technical Specification compensatory measure g hourly fire watch was established within one hour, and the NRC resident inspector was advised. This fire watch will be maintained until modifications and confirmatory calculations are made such that the system can be declared operable.

This system is installed at the Reactor Building cable penetration area from the Cable Vault at elevation 252', providing protection for the safety related cable trays in the area where they enter the Reactor Building. Two layers of sprinkler heads are provided, one to suppress a fire at the floor level, the other

, above the trays to suppress a fire in the trays. The calculation assumes that all 46 of the sprinkler heads are fully open. In an actual fire situation not all of the heads would be expected to open. The existing water supply can meet the minimum design flow per sprinkler if most, but not all of the sprinklers are 9606100124 960607 PDR ADOCK 05000271 S PDR q

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• U.S. Nuclear Regulatory Commission

• VERMONT YANKEE NUCLEAR POWER CORPORATION June 7,1996 Page 2 1

open. Since the postulated fire (s) are not expected to open all sprinkler heads at once, an adequate water supply exists to suppress or retard the growth of a fire.

Modifications are currently being developed for implementation and acceptance testing no later than the end of the 1996 refuel outage in order to reestablish confidence that the system will provide and maintain the design required discharge.

We trust you will find this submittal satisfactory. However, should you desire additional information, please feel free to contact us.

Very Truly Yours, Vermont Yankee Nuclear Power Corporation

}f4M( YkW /

Robert J. anczyk Plant Manager 1

RJW/dm i

cc: USNRC Region 1 Administrator USNRC Resident limpector,VYNPS USNRC Project Manager, VYNPS