05000368/FIN-2015002-02
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Finding | |
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| Title | Failure to Protect Motor Control Center from Potential Pipe Spray |
| Description | The inspectors identified a Green non-cited violation of 10 CFR Part 50, Appendix B, Criterion III, Design Control, for the failure to select and review equipment for suitability of application that is essential to the safety-related function of Unit 2 motor control center (MCC) 2B-52. Specifically, the licensee failed to ensure that the safety-related electrical equipment inside the MCC was adequately protected from water spray in the event of a failure of overhead non-seismic category 1 pipes, in accordance with the safety analysis report. Inspectors identified that the installed spray curtain only protected the front of the cabinet, while a cooling water pipe that could break during a seismic event was located directly above the length of the MCC. This issue was entered into the licensees corrective action program as Condition Report CR-ANO-C-2015-01342. The failure to protect Unit 2 MCC 2B-52 from possible spray of overhead non-seismic category 1 pipes by installing a spray shield in accordance with the safety analysis report was a performance deficiency. The performance deficiency was more than minor because it was associated with the design control attribute of the Mitigating Systems Cornerstone and adversely affected the cornerstone objective to ensure the reliability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the performance deficiency could result in failure of one train of essential safety features during a seismic event, such as exhaust fans for the emergency diesel generators, containment spray isolation valves, and high pressure safety injection isolation valves. Using NRC Inspection Manual Chapter 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power, the inspectors determined to require a detailed risk evaluation because the finding involved degradation of equipment specifically designed to mitigate a seismic event and could degrade one train of a system that supports a risk significant function. A senior reactor analyst performed the detailed risk evaluation and estimated the change to the core damage frequency was 3.8E-8/year (Green). The dominant core damage sequences included seismically induced losses of offsite power. This finding did not have a cross-cutting aspect associated with it because the most significant contributing cause was not indicative of present performance. Specifically, the condition had existed since plant construction, with no recent substantial opportunities to identify the issue. |
| Site: | Arkansas Nuclear  |
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| Report | IR 05000368/2015002 Section 1R06 |
| Date counted | Jun 30, 2015 (2015Q2) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.06 |
| Inspectors (proximate) | B Tindell J Drake L Carson M Phalen M Williams M Young N O'Keefe Z Hollcraft |
| Violation of: | 10 CFR 50 Appendix B Criterion III, Design Control |
| INPO aspect | |
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Finding - Arkansas Nuclear - IR 05000368/2015002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Arkansas Nuclear) @ 2015Q2
Self-Identified List (Arkansas Nuclear)
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