05000410/FIN-2014003-04
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Finding | |
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| Title | Failure to Identify Single-Point Vulnerabilities Results in a Manual Reactor Scram |
| Description | A self-revealing Green Finding (FIN) was identified at Unit 2 against procedure CNG-AM-1.01-2000, Scoping and Identification of Critical Components, Revision 00200. Specifically, Exelon staff performed an inadequate AP-913 evaluation in 2006. This evaluation failed to identify that reactor recirculation pump (RRP) switches S101A and S101B were single-point vulnerable components, so mitigating strategies to ensure proper operation to minimize plant risk were not developed. As a result, on December 2, 2013, both RRPs failed to properly shift from fast to slow speed resulting in a loss of all recirculation flow through the core and requiring operators to insert a manual reactor scram in accordance with plant procedures. Exelon generated CR-2013-009735, performed a root cause analysis (RCA), and developed corrective actions which included revising procedure N2-OP-29, Reactor Recirculation System, Revision 01801, to direct operators to manually start the low frequency motor generator sets, implementing a preventive maintenance activity for these switches, and developing plans to replace the switches during the next refueling outage (RFO). This finding is more than minor because it is associated with the equipment performance attribute of the Initiating Events cornerstone and adversely impacted the associated cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Additionally, the performance deficiency is similar to Example 4b of IMC 0612, Appendix E, Examples of Minor Issues, in that the error resulted in a plant trip. Specifically, the failure to identify switches S101A and S101B as single-point vulnerabilities and develop appropriate mitigating strategies resulted in the failure of the switches and a manual reactor scram on December 2, 2013. In accordance with IMC 0609.04, Initial Characterization of Findings, and Exhibit 1 of IMC 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power, issued June 19, 2012, the inspectors determined that this finding is of very low safety significance (Green); the performance deficiency did not cause both a reactor trip and the loss of mitigation equipment relied upon to transition the plant from the onset of the trip to a stable shutdown condition (e.g.; loss of condenser, loss of feedwater). The inspectors did not assign a cross-cutting aspect to this finding because the performance deficiency was determined to have occurred in 2006, and the guidance in the current revision of CNG-AM-1.01-2000, Appendix A, was sufficient for Exelons root cause team to determine the switches should have been screened in. Therefore, this finding is not indicative of current licensee performance and no cross-cutting issue was assigned. |
| Site: | Nine Mile Point  |
|---|---|
| Report | IR 05000410/2014003 Section 4OA3 |
| Date counted | Jun 30, 2014 (2014Q2) |
| Type: | Finding: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | A Bolger A Rosebrook C Graves D Schroeder E Burket E Miller G Stock J Furia K Kolaczyk N Floyd |
| INPO aspect | |
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Finding - Nine Mile Point - IR 05000410/2014003 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Nine Mile Point) @ 2014Q2
Self-Identified List (Nine Mile Point)
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