05000423/LER-2008-001, Regarding Postulated Fire Scenario Results in Unanalyzed Condition - Pressurizer Overfill

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Regarding Postulated Fire Scenario Results in Unanalyzed Condition - Pressurizer Overfill
ML083090386
Person / Time
Site: Millstone Dominion icon.png
Issue date: 10/26/2008
From: Jordan A
Dominion, Dominion Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0593 LER 08-001-00
Download: ML083090386 (6)


LER-2008-001, Regarding Postulated Fire Scenario Results in Unanalyzed Condition - Pressurizer Overfill
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
4232008001R00 - NRC Website

text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road, Waterford, CT 06385 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 OCT 2 6 Serial No.

MPS Lic/ITGC Docket No.

License No.

2000 08-0593 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2008-001-00, POSTULATED FIRE SCENARIO RESULTS IN UNANALYZED CONDITION - PRESSURIZER OVERFILL This letter forwards Licensee Event Report (LER) 2008-001-00, documenting a condition identified at Millstone Power Station Unit 3, on August 29, 2008. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(ii)(B).

If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.

Sincerely, A.

VJ.J rdean, Jr.

Site Vice President - Millstone

Serial No. 08-0593 Licensee Event Report 2008-001-00 Page 2 of 2 Attachments:

1 Commitments made in this letter: None.

cc:

U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders - Project Manager U.S. Nuclear Regulatory Commission, Mail Stop 08 B3 One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No. 08-0593 Licensee Event Report 2008-001-00 POSTULATED FIRE SCENARIO RESULTS IN UNANALYZED CONDITION PRESSURIZER OVERFILL MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

Abstract

On August 29, 2008 at 1007 while operating at 100% power, Millstone Power Station Unit 3 identified a potential vulnerability in the fire safe shutdown strategy which, under certain fire conditions, may challenge the ability to meet the performance criteria of the approved fire protection program. It is postulated that under certain fire conditions affecting the control room, the ability to maintain pressurizer level within the indicated range (high) may be challenged and lead to water relief through the pressurizer safety valves. The pressurizer safety valves are not qualified for water relief.

The apparent cause of this condition is a deficiency in the original fire protection evaluations to meet the requirements of Branch Technical Position (BTP) CMEB9.5-1 (NUREG-0800) as documented in the Millstone Unit 3 Fire Protection Evaluation Shutdown System Availability Report of 1985 (BTP Compliance Report). A modification is being implemented that will prevent this condition during plant power operations.

Additional corrective actions are being addressed in accordance with the station's corrective action program.

This condition has had no actual safety consequences as no fire has occurred to challenge the circuits in question. This event involves a postulated fire scenario and subsequent potential failure. This condition had no direct impact on the health and safety of the public or plant personnel. The event does involve an unanalyzed condition related to safe shutdown capability. This condition is being reported under 10 CFR 50.73(a)(2)(ii)(B),

"Any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded Plant safety."

(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17) could result in extensive damage. This is particularly the case for the control room (which is continuously staffed),

instrument rack room and cable spreading room in which the design features include multiple fire suppression options and no high voltage circuits or other significant ignition sources.

This condition had no direct impact on the health and safety of the public or plant personnel. This condition has had no actual safety consequences as no fire has ever occurred at MPS3 to challenge the circuits in question. Furthermore, a review of control room events in the Fire Events Database (Reference NUREG/CR-6850 Appendix L) reveals that none of the control room fires that had occurred in the industry affected components much beyond the point of ignition. In all cases, the fire was discovered by control room personnel and extinguished using hand-held extinguishers. Since the control room is occupied at all times, it is expected that the likelihood of a fire affecting a large number of items inside the main control board is low. It is expected that a detailed fire PRA analysis would show that a fire of this type is expected to contribute less than 1 E-6/year to core damage frequency (CDF) based on the low frequency of a fire in the control room with the specific qualities that would lead to nearly immediate evacuation and adverse system operation.

The event does involve an unanalyzed condition related to safe shutdown capability and operation.

4.

Corrective Actions

Compensatory actions were implemented that enhance the defense in depth philosophy to prevent, detect and rapidly extinguish fires to minimize the likelihood of a large scale fire affecting the control room. These include additional controls of combustible materials, hourly fire watches and increased monitoring of fire detection and suppression systems for the affected fire areas.

A modification is being implemented that will prevent pressurizer overfill from fire-induced failures during plant power operations. Beginning in Cycle 13 (scheduled for November 2008), a permissive on Low Pressurizer Pressure is being added to the reactor coolant system cold leg injection valves. This modification permits injection to the RCS from the charging pumps upon receipt of a safety injection signal only when the reactor coolant system pressure has dropped below the low pressurizer pressure setpoint.

Further evaluations are under way to ensure that the full scope of any other postulated fire scenarios that could result in pressurizer overfill have been identified. The compensatory actions will remain in place until that review is complete.

Additional corrective actions are being addressed in accordance with the station's corrective action program.

5.

Previous Occurrences

No previous similar events/conditions were identified.

Energy Industry Identification System (EIIS) codes are identified in the text as [XX].