05000458/FIN-2012004-02
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Finding | |
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| Title | Untimely Corrective Actions to Ensure Reliability of the 480 Vac Molded Case Circuit Breakers and Unitized Motor Starters |
| Description | The inspectors identified a non-cited violation of 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, for the failure to correct within a reasonable period conditions adverse to quality associated with testing safety related molded-case circuit breaker and unitized motor starter circuit breakers. The licensees immediate corrective actions included increasing the rate of breaker preventive maintenance and testing to reduce the long-standing risk significant breaker backlog. The station documented the finding in Condition Report CR-RBS-2012-06364. The performance deficiency was more-than-minor and is therefore a finding because it is associated with the equipment performance attribute of the Mitigating Systems cornerstone objective of ensuring the availability, reliability, and capability of the safety-related molded-cased circuit breakers to respond to initiating events to prevent undesirable consequences. Specifically, failures of the affected breakers represent an increase in risk to safe plant operations, because to isolate a fault caused by a defective 480VAC breaker, the upstream feeder breaker would trip, thus causing a loss of power to additional safety related components. Using Inspection Manual Chapter 0609, Appendix A, the finding is associated with the loss of mitigation equipment (Service Water pumps A and C), and so screened to a detailed risk evaluation. That evaluation determined that the incremental conditional core damage probability (ICCDP) was 2.1E-8 for a fire in one of the standby cooling tower electrical rooms, resulting in a loss of one train of service water pumps (A and C, or B and D), as a consequence of the failure of the proximate 480 VAC breaker to open. The risk was low because normal service water would be unaffected by the fire, and it would be unlikely that offsite power would be lost concurrently. The fire could also affect control room ventilation, but the analyst qualitatively concluded that this would not add more than negligibly to the overall risk. Consequently, the finding has very low safety significance (Green). The inspectors determined that the apparent cause of the finding was a combination of two factors related to resources: station management did not ensure that each work group completed its actions to support timely resolution, and personnel vacancies from key positions hampered completion of the breaker testing program. The inspectors therefore determined the finding had a cross-cutting aspect in the human performance area associated with the resources component because station management did not ensure personnel resources were available to minimize long-standing equipment issues. |
| Site: | River Bend  |
|---|---|
| Report | IR 05000458/2012004 Section 1R04 |
| Date counted | Sep 30, 2012 (2012Q3) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.04 |
| Inspectors (proximate) | G Guerra P Elkmann A Barrett W Sifre J Laughlin R Hagar M Young G Larkin G Apger B Rice C Steely D Strickland |
| CCA | H.6, Design Margins |
| INPO aspect | WP.2 |
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Finding - River Bend - IR 05000458/2012004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (River Bend) @ 2012Q3
Self-Identified List (River Bend)
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