05000482/FIN-2008010-04
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Finding | |
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| Title | Operator Actions May Create the Potential for Secondary Fires |
| Description | The team identified an unresolved item concerning the potential that operator actions taken in response to fires in 14 fire areas may cause secondary fires and invalidate the safe shutdown analysis. Procedure OFN KC-016, Fire Response, Revision 19, specified operator actions to be taken in response to fires outside of the control room. This procedure provides the mitigating actions needed to maintain hot standby in the event of various failures and spurious actuations. The team identified the following 14 fire areas where the mitigating actions may cause secondary fires and invalidate the safe shutdown analysis: • Fire Area A-8 Auxiliary Building - 2000 Elevation, General Area • Fire Area A-11 Cable Chase (Room 1335) • Fire Area A-16 Auxiliary Building - 2026 Elevation, General Area • Fire Area A-17 South Electrical Penetration (Room 1409) • Fire Area A-18 North Electrical Penetration (Room 1410) • Fire Area A-27 Reactor Trip Switchgear (Room 1403) • Fire Area C-18 North Vertical Cable Chase (Room 3419) • Fire Area C-21 Lower Cable Spreading (Room 3501) • Fire Area C-22 Upper Cable Spreading (Room 3801) • Fire Area C-23 South Vertical Cable Chase (Room 3505) • Fire Area C-24 North Electrical Chase (Room 3504) • Fire Area C-30 South Vertical Cable Chase (Room 3617) • Fire Area C-33 South Vertical Cable Chase (Room 3804) • Fire Area RB Reactor Building (Containment) For these 14 fire areas, the procedure directs the operators to remove power to a power-operated relief valve if a fire causes the power-operated relief valve to spuriously open and operators are unable to close its associated block valve. Specifically, the procedure directs the operators to open circuit breakers on the associated 125 Vdc power supply. The inspectors noted that the failure of the block valve to close is considered fire damage and is not considered a spurious operation of the valve. The licensee specified this action in order to close the power-operated relief valve and preclude the potential for spurious opening due to inter-cable faults (i.e., cable-to-cable hot shorts). However, the team determined this action would also remove the control power used to operate 4160 Vac and 480 Vac circuit breakers. The removal of control power would prevent remote breaker operations and disable circuit breakers protective trips for the train affected by the fire. Removing control power to the circuit breaker results in a loss of its ability to automatically isolate faults before severe damage occurs. As a result, fire-induced faults (shorts to ground) in non-essential power cables of the affected 4160 Vac and 480 Vac supplies may not clear until after tripping an upstream feeder breaker to the supplies, which would remove power from equipment which was assumed by the safe shutdown analysis to be unaffected. This action would prevent breakers from automatically opening during an overload condition and has the potential to initiate secondary fires in plant locations outside of the initial fire area. The safe shutdown analysis assumed that a fire is present in only one fire area at any time. The team determined that the operator actions taken in response to fires in the listed fire areas had the potential to initiate secondary fires in other plant locations, which would invalidate the safe shutdown analysis and could impact the ability to achieve and maintain safe shutdown. The team was concerned that operator actions specified for responding to the fire-induced spurious opening of a pressurizer power-operated relief valve could remove electrical circuit protection and create the potential for secondary fires outside the initial fire area. Taking actions that could create secondary fires was potentially a performance deficiency. The team determined that this deficiency may be more than minor because it was associated with the Protection Against External Factors attribute of the Initiating Events Cornerstone and could affect the cornerstone objective to limit the likelihood of those events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Additional information is needed from the licensee to understand the potential for secondary fires and the possible locations of those fires based on the circuit design and remaining protection available. The licensee will provide the routing of power-operated relief valve cables in the 14 fire areas of concern and will identify the affected components where breaker coordination would be lost. The significance of this issue will be determined if this issue does involve a performance deficiency. As a compensatory measure, the licensee implemented an hourly fire watch in the affected fire areas, with the exception of the reactor building, which is not readily accessible during power operations. For the reactor building, the licensee is monitoring the containment temperature as a compensatory measure. The licensee entered this issue into their corrective action program as Condition Report 2008-005210. Enforcement. License Condition 2.C.(5) states, in part, that the licensee shall maintain in effect all provisions of the approved fire protection program as described in the SNUPPS Final Safety Analysis Report for the facility through Revision 17, the Wolf Creek Site Addendum through Revision 15, and as approved in the Safety Evaluation Report through Supplement 5. The Wolf Creek Updated Safety Analysis Report combined the SNUPPS Final Safety Analysis Report, Revision 17, and the Wolf Creek Site Addendum, Revision 15, into one document. Appendix 9.5B of the Updated Safety Analysis Report provides an area-by-area analysis of the power block that incorporated Drawing E-1F9905, Fire Hazards Analysis, Revision 2, by reference. Drawing E-1F9905 states that the overall intent is to demonstrate that a single plant fire will not negatively affect the post-fire safe shutdown capability and that if a circuit damaged by a fire is protected by an individual overcurrent protection device, that device is assumed to function to clear the fault. The team was concerned that operator actions specified for responding to the fire-induced spurious opening of a pressurizer power-operated relief valve could remove electrical circuit protection and create the potential for secondary fires outside the initial fire area. Specifically, removal of control power to 4160 Vac and 480 Vac circuit breakers prevents operation of the devices overcurrent protection function. Failure of circuit breakers to clear faults on power cables damaged by fire would create the potential for the overcurrent condition to start a secondary fire at another location. The plants post-fire safe shutdown capability has only been evaluated for damage due to a single fire. Additional information is needed from the licensee to understand whether there is a credible potential for secondary fires and the possible locations of those fires based on the circuit design and remaining protection available. The licensee will provide the routing of power-operated relief valve cables in the 14 fire areas of concern and will identify the affected components where breaker coordination would be lost. This information is needed to determine whether a violation existed for this issue. Therefore, this issue is being treated as an unresolved item: URI 05000482/2008010-04, Operator Actions May Create the Potential for Secondary Fires |
| Site: | Wolf Creek  |
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| Report | IR 05000482/2008010 Section 1R05 |
| Date counted | Dec 31, 2008 (2008Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | G Vasquez J Drake P Jayroe R Kopriva S Alferink A Fairbanks C Alldredge C Cauffman C Long C Peabody D Graves D Loveless G Millera Dahburj Adams J Mateychick N Okonkwo |
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Finding - Wolf Creek - IR 05000482/2008010 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Wolf Creek) @ 2008Q4
Self-Identified List (Wolf Creek)
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