05000423/FIN-2016004-03
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Finding | |
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| Title | Untimely Corrective Action for Vital Inverters |
| Description | The inspectors identified a Green NCV of 10 CFR 50, Appendix B, Criterion XVI,Corrective Action, for Dominions failure to take timely corrective actions to replacedegraded diodes in Unit 3 vital inverters INV-1 and INV-2 upon receipt of information that called their reliability into question. Specifically, following two inverter failures, Dominion had not taken any corrective actions to replace degraded diodes in the Unit 3 vital inverters from the receipt of the Exelon Power Labs report on September 20 until the susceptible diodes were inspected and replaced on November 17 and 22. Dominion entered this issue into their CAP as CR1041301. The inspectors found that Dominions failure to take timely corrective action to replace degraded vital inverter diodes was a performance deficiency within Dominions ability to foresee and correct. This performance deficiency was considered to be more than minor because it would affect the Mitigating Systems cornerstone equipment performance attribute objective to ensure the availability and reliability of vital 120V power. Specifically,manufacturing defects in the diodes caused these subcomponents to fail when they were expected to last the life of the inverter. The finding was evaluated in accordance with IMC 0609, Appendix A, The Significance Determination Process for Findings At-Power, and determined to be of very low safety significance (Green) because although the failure challenged the reliability of the inverters, it did not result in a loss of operability or functionality. This finding has a cross-cutting aspect in the Human Performance crosscutting area associated with Work Management, in that Dominion focused on managing the risk associated with voluntarily entering a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> technical specifications (TS) limiting condition for operation (LCO) to replace the degraded diodes instead of the potential risk of another inverter failure. [H.5] |
| Site: | Millstone  |
|---|---|
| Report | IR 05000423/2016004 Section 4OA2 |
| Date counted | Dec 31, 2016 (2016Q4) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | C Highley E Dipaolo H. Anagnostopoulus J Ambrosini J Deboer J Schoppy L Mckown P Presby |
| Violation of: | 10 CFR 50 Appendix B Criterion XVI |
| CCA | H.5, Work Management |
| INPO aspect | WP.1 |
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Finding - Millstone - IR 05000423/2016004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Millstone) @ 2016Q4
Self-Identified List (Millstone)
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