05000269/LER-2002-002, Re Potential for Fire to Indirectly Damage Mitigation Component for Oconee Nuclear Station Unit 1
| ML021580287 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/28/2002 |
| From: | Mccollum W Duke Energy Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 02-002-00 | |
| Download: ML021580287 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2692002002R00 - NRC Website | |
text
Duke ar Energy.
Duke Energy Oconee Nuclear Station 7800 Rochester Highway Seneca, SC 29672 (864) 885-3107 OFFICE (864) 885-3564 FAx W. R. McCollum, Jr.
Vice President May 28, 2002 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555
Subject:
Oconee Nuclear Station Docket Nos. 50-269,-270, -287 Licensee Event Report 269/2002-02, Problem Investigation Process No.:
Revision 0 0-02-1357 Gentlemen:
Pursuant to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Event Report 269/2002-02, Revision 0, concerning discovery of a scenario for fire damage that could potentially result in inoperability of a component credited for Appendix R fire mitigation. As a result, the component was retroactively declared inoperable for a period longer than allowed by Technical Specifications.
This report is being submitted in accordance with 10CFR 50.73(a)(2)(i)(B), Conditions Prohibited By Technical Specification.
This event is considered to be of no significance with respect to the health and safety of the public.
Very truly yours, Attachellum J
Attachment aEL
Document Control Desk Date: May 28, 2002 Page 2 cc:
Mr. Luis A. Reyes Administrator, Region II U.S. Nuclear Regulatory Commission 61 Forsyth Street, S. W., Suite 23T85 Atlanta, GA 30303 Mr. L. N. Olshan Project Manager U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D.C.
20555 Mr. M. C. Shannon NRC Senior Resident Inspector Oconee Nuclear Station INPO (via E-mail)
Abstract
approximately 15 single-spaced typewritten lines)
On March 22, 2002, with all three Oconee units operating in Mode 1 at 100%
Rated Power, an engineering evaluation identified the potential for an adverse valve actuation during a design basis fire.
This valve actuation involves the inadvertent opening of either of two valves in the low pressure injection (LPI) system due to an assumed failure in the valve control circuitry.
The opening of either valve would cause the Borated Water Storage Tank (BWST) to empty its contents to the Reactor Building Emergency Sump.
The water from the BWST would flood the Reactor Coolant Make-Up (RCMU) Pump resulting in its failure.
The RCMU pump supplies reactor coolant pump seal and make-up flow during some design basis fire scenarios.
Roving fire watches have been implemented as compensatory measures in the area of the affected cables.
These fire watches are required while the unit is in Modes 1, 2, or 3 and will remain in place until modifications are implemented to mitigate this condition.
The apparent cause of this condition is a historic design deficiency.
An engineering risk assessment concludes that the likelihood of the actual spurious actuation of these valves is extremely low.
This event is considered to have minimal safety significance with respect to the health and safety of the public.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is Wequired, use additional copies of (if more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17) actuation cannot be ruled out, it is not expected to occur under
plant conditions
Based upon the conservatisms in test methodologies, it has been estimated that the cable must be exposed to a developed fire for a period in excess of 30 minutes in order to cause a fault in the LP-19 and 20 control circuit cables.
Fire brigade drills have been practiced in the areas in which LP-19 and 20 valve control circuit cables are subject to fire damage.
These drills have shown fire brigade response times of less than 30 minutes.
The brief response time allows the fire brigade to get positioned and initiate mitigating actions prior to fires becoming fully developed; therefore it is not expected that these cables will be exposed to the temperature at which cable degradation occurs (threshold temperatures greater than 700 degrees Fahrenheit) for any significant duration.
In summary, the likelihood of an actual spurious actuation occurring due to a "smart fire" causing the right two conductors to short together rather than shorting to ground has a very low probability.
The additional contribution to core damage frequency resulting from the issue of spurious actuation of LP-19 or LP-20 3
has been calculated to be less than 3E-8 per year Therefore, there was no impact on the health and safety of the public due to this event.
ADDITIONAL INFORMATION
There were no releases of radioactive materials, radiation exposures, or personnel injuries associated with this condition.
No actual equipment failure occurred, therefore this condition is not considered reportable under the Equipment Performance and Information Exchange (EPIX) Program.
3PRA Analysis of Spurious Operation of Oconee Valves LP-19 or 20