05000445/FIN-2013004-05
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Finding | |
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| Title | Potential Motor-Operated Valve Single Spurious Operation Vulnerability |
| Description | The inspectors identified an unresolved item associated with fire-induced single spurious operations. The inspectors were concerned that a single hot short could cause the spurious operation of motor-operated valves and bypass their torque/limit switch, resulting in damage to the pressure boundary. On February 28, 1992, the NRC issued Information Notice 92-18, Potential for Loss of Remote Shutdown Capability During a Control Room Fire, to alert licensees of conditions that could result in the loss of capability to maintain the reactor in a safe shutdown condition in the event that a control room fire forced operators to evacuate the control room (i.e., alternative shutdown scenarios). Information Notice 92-18 was primarily concerned with the loss of control of valves required for alternative shutdown. Specifically, the Information Notice was concerned with the potential for hot shorts to cause the spurious operation of these motor-operated valves and bypass their torque/limit switch, potentially damaging the valves before operators could transfer control to the remote shutdown panel. In this situation, the valves may not be able to be operated manually or from the remote shutdown panel. The licensee evaluated this issue in Engineering Report ER-ME-089, Resolution of NRC Information Notice 92-18, Potential Loss of Remote Shutdown Capability Following Control Room Fire, Revision 0, dated December 29, 1993. The licensee evaluated the population of motor-operated valves that were required to be operated manually or remotely from the remote shutdown panel for alternative shutdown scenarios. This population consisted of 86 motor-operated valves. The licensee made modifications as necessary to ensure that these valves could be operated manually or remotely from the remote shutdown panel for all alternative shutdown scenarios. In 2010, the licensee began their evaluation of multiple spurious operations in accordance with Nuclear Energy Institute Document NEI 00-01, Guidance for Post-Fire Safe-Shutdown Circuit Analysis, Revision 2. Appendix G to NEI 00-01 contained the generic list of multiple spurious operations scenarios applicable to pressurized water reactors. This appendix contained a scenario (MSO-55) that considered valve failure due to a spurious motor-operated valve operation in conjunction with a short that bypassed the torque/limit switch. This scenario was described as follows: General scenario is that fire damage to motor-operated valve circuitry causes spurious operation. If the same fire causes wire-to-wire short(s) such that the valve torque and limit switches are bypassed, then the valve motor may stall at the end of the valve cycle. This can cause excess current in the valve motor windings as well as valve mechanical damage. This mechanical damage may be sufficient to prevent manual operation of the valve. Scenario only applies to motor-operated valves. Note this generic issue may have already been addressed during disposition of the NRC Information Notice 92-18. This disposition should be reviewed in the context of multiple spurious operations and multiple hot shorts. The licensee formed a multiple spurious operations expert panel, which met in March 2010, to review the generic list of multiple spurious operations contained in NEI 00-01. The multiple spurious operations expert panel meeting results were documented in Engineering Report ER-ME-130, Summary of Expert Panel Activities Related to Postulation of Multiple Spurious Operations for the CPNPP Fire Safe Shutdown Analysis, Revision 0, dated April 2010. The licensee initially concluded that scenario MSO-55 was already addressed in the fire safe shutdown analysis. On August 17, 2010, the licensee convened a supplemental meeting of the multiple spurious operations expert panel. The expert panel reconsidered multiple spurious operations scenario MSO-55 and concluded that a nonconformance existed. Specifically, the expert panel concluded that the licensee had addressed the concerns raised in Information Notice 92-18 for alternative shutdown scenarios, but did not address the concerns for scenarios where operators did not need to evacuate the control room. The licensee subsequently evaluated the larger population of motor-operated valves that are used or must remain intact for post-fire safe shutdown. The licensee concluded that modifications were needed for 57 valves. Ten of the valves required a mechanical modification, while the remaining 47 valves required an electrical modification. The licensee entered this issue into their corrective action program as Condition Report CR-2010-007806 and implemented compensatory measures. The inspectors identified an issue of concern with the potential for single spurious operations to damage the pressure boundary. The inspectors determined that additional inspection is required to determine if a performance deficiency exists. This issue of concern is being treated as an unresolved item URI 05000445/2013004-06; 05000446/2013004-06, Potential Motor-Operated Valve Single Spurious Operation Vulnerability. |
| Site: | Comanche Peak  |
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| Report | IR 05000445/2013004 Section 4OA2 |
| Date counted | Sep 30, 2013 (2013Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | B Correll E Uribe J Dixon J Watkins S Alferinkd Proulxi Anchando J Kramer M Williams R Kumana S Alferink S Graves W Walkers Gravesw Walker D Proulx I Anchando J Kramer M Williams S Alferink |
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Finding - Comanche Peak - IR 05000445/2013004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Comanche Peak) @ 2013Q3
Self-Identified List (Comanche Peak)
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