05000287/LER-2005-001, Regarding TS LCO Condition Allowed Outage Time and Required Action Completion Time Exceeded Due to Blockage of Lpi/Bs Pump Room Air Flow Path
| ML053120367 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/31/2005 |
| From: | Rosalyn Jones Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 05-001-00 | |
| Download: ML053120367 (9) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2872005001R00 - NRC Website | |
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RONALD A JONES
_Duke Vice President ltoftwern Oconee Nuclear Site Duke Power ONOI VP / 7800 Rochester Hwy.
Seneca, SC 29672 864 885 3158 864 885 3564 fax October 31, 2005 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555 Subject: Oconee Nuclear Station Docket No. 50-287 Licensee Event Report 287/2005-01, Revision 0 Problem Investigation Process No.: 0-05-05564 Gentlemen:
Pursuant to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Event Report 287/2005-01, Revision 0. This report addresses failure to meet Technical Specification required action completion times for LCO 3.5.3 Conditions A and C and 3.6.5 Conditions A and D due to a blocked air flow path in Unit 3 Low Pressure Injection/Building Spray Pump Room.
This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(i)(B), operation or condition which was prohibited by the plant's Technical Specifications.
This event is considered to be of no significance with respect to the health and safety of the public.
Very truly yours, R. A. Jones Attachment www. dukepower. corn
Document Control Desk Date: October 31, 2005 Page 2 cc:
Mr. William D. Travers 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
On August 30, 2005, while at 100% power, the stairwell into Room 81 on Unit 3 was found to be covered with a tent enclosure. Room 81 contains the B train pumps for the Low Pressure Injection System (LPI) and the Building Spray System (BS).
Calculations credit an air flow path through the stairwell to ensure acceptable environmental conditions within the room. The tent enclosure blocked this air flow path. Another adverse condition was identified, involving temporary filters installed in the inlet and exhaust grilles for the air handling units serving the room.
Consequently, for certain design basis accidents, the room temperature could have exceeded the qualification limits for the 3B LPI Pump and 3B BS Pump and their associated motors.
The enclosure had been in place approximately 34 days, thus exceeding Technical Specification required action times for these systems.
There was no loss of function, as redundant trains of LPI and BS were not affected. This event was cauqsed by failure to provide adequate controls on critical inputs to safety analyses.
Corrective actions included removal of the tent from the stairwell outside Room 81, removal of filters from ventilation grilles in Room 81, and placement of signs outside of all HPI, LPI, and BS pump rooms cautioning against blockage of these air flow paths.
This event has no significance with respect to public health and safety.
NRC FORM 366 (7-2001)
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The incremental conditional core damage probability (ICCDP) associated with this event is estimated to be 7.6E-07, and the incremental conditional large early release probability (ICLERP) is estimated to be 4.3E-09.
These results indicate that this event is of low risk significance.
The dominant accident sequences involve either a loss of off-site power or loss of 3TC bus (4kV) initiating event.
These events are important because power to the normal ventilation system is lost.
A loss of all emergency feedwater sources leads to HPI forced cooling which later requires alignment to the containment sump when the BWST inventory is depleted.
Note:
This analysis did not take credit for restoration of normal ventilation flow following a loss of power.
Additional human reliability analysis of these recovery actions or further enhancement of the temperature analysis could be expected to further reduce the estimated risk impact of this event.
Therefore, these risk results are considered to be conservative.
The failure of Reactor Building Spray (RBS) System does not play an important role in the large early release frequency (LERF) and is not modeled in the OR3 Simplified LERF model.
The long-term nature of this failure mode for the 3B RBS pump also means that the containment temperature and pressure control functions should be able to perform as intended for most LOCA initiating events.
Further, the Reactor Building Cooling Units (RBCUs) were not affected by the ventilation problem. Therefore, the impact of the inoperability of the 3B RBS pump is not considered in the analysis of the ICCDP and ICLERP because it is not expected to have any measurable risk impact.
ADDITIONAL INFORMATION
There were no releases of radioactive materials, radiation exposures or personnel injuries associated with this event.
This event is not considered reportable under the Equipment Performance and Information Exchange (EPIX) program.