05000255/LER-2006-001

LER-2006-001,

Docket Number
Event date:	02-14-2006
Report date:	04-14-2006
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
2552006001R00 - NRC Website

Palisades 05000-255 2006 -- 001 -- 00

EVENT DESCRIPTION

On February 14, 2006, during review of a 10 CFR 50, Appendix R analysis, a condition was identified that could challenge the ability to maintain the primary (reactor) coolant makeup function, as required by Appendix R, paragraph III.G, "Fire Protection of Safe Shutdown Capability.

In the analysis, the specific fire scenario is assumed to render all charging pumps [P;CB] unavailable for maintaining the primary coolant makeup function. To compensate for the loss of all charging pumps, the analysis credited high pressure safety injection (HPSI) pump P-66B [P;BQ] for supplying makeup. The analysis further recognized that the fire scenario could result in damage to the control circuit for the HPSI pump, resulting in a spurious start. A spurious start of the HPSI pump was deemed acceptable in the analysis since this would be consistent with the desired operating state of the pump for providing primary coolant makeup.

However, the review determined that the fire scenario could also result in damage to the control circuit for the HPSI pump's credited suction valve, CV-3031 [V;BP], resulting in a spurious closure of the valve. The spurious closure of the HPSI pump's suction valve with the HPSI pump in operation would likely render the HPSI pump inoperable, causing a loss of the ability to maintain the primary coolant makeup function.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition.

CAUSE OF THE EVENT

At the time this Appendix R analysis was developed, the coping strategy for the analysis assumed only one worst case spurious actuation or signal. Current guidance for Appendix R analyses requires the consideration of equipment failure combinations and multiple spurious actuations.

SAFETY SIGNIFICANCE

The safety significance of the event is considered to be minimal. Analysis has demonstrated that sufficient primary coolant inventory would be maintained to keep the core covered and prevent core damage for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> without makeup capability. A 24-hour period is considered sufficient time to complete proceduralized emergency repairs to a charging pump and to restore the primary coolant makeup function.

CORRECTIVE ACTIONS

Compensatory actions were established for this fire scenario to preserve the HPSI pump for primary coolant makeup capability. In the event of a spurious start of the HPSI pump, guidance directs operators to stop the HPSI pump. Guidance also directs isolation of control circuit power to CV-3031 to disable it in the open position, precluding HPSI pump damage caused by pump operation without a suction flow path. Once the suction valve is assured open, the HPSI pump may be operated as necessary to maintain the primary coolant makeup function.

An extent of condition evaluation of other Appendix R credited pumps with similar potential for pump damage resulting from spurious pump and valve operation is being conducted.

Final resolution of this condition is expected to be addressed with the planned transition to National Fire Protection Association (NFPA) 805, "Performance—Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants, 2001 Edition.

PREVIOUS SIMILAR EVENTS

Licensee Event Report 95-015, "Appendix R Scenario Results in Spurious Operation and Damage to Alternate Shutdown Motor Operated Valves" Licensee Event Report 97-008, "Spurious Valve Operation Could Result in Loss of Shutdown Capabilities Per 10 CFR 50, Appendix R, Section III.L" Licensee Event Report 97-010, "Inadequacy in Appendix R Analysis Results in a Condition Outside the Design Basis of the Plant" Palisades