05000361/FIN-2010006-01
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Finding | |
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Title | Inadequate Operability Determination for Turbine-Driven Auxiliary Feedwater Pump Steam Admission Valves |
Description | The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criterion V, \\\"Instructions, Procedures, and Drawings,\\\" involving the failure to follow procedural requirements for performing operability determinations. Specifically, the licensee\\\'s operability evaluation for a degraded turbine-driven auxiliary feedwater pump steam admission valve failed to address all the specified safety functions of the affected component as described in the Final Safety Analysis Report and design basis documents. For exampie, the operabiiity determination incorrectly stated that manual closure of the valves was not a credited safety function and incorrectly assumed nonsafety-related instrument air would always be available to close the valves. This finding was entered into the licensee\\\'s corrective action program as Nuclear Notifications 200869281 and 200887620. The licensee\\\'s corrective actions included re-performing the evaluation and emphasizing with licensee staff the importance of ensuring ali design basis information is considered in operability evaluations. The finding was more than minor because it impacted the Mitigating Systems Cornerstones and its objective to ensure the availability and reliability of equipment that responds to initiating events. Using Inspection Manual Chapter 0609 the issue screened to a Phase 3 analysis because it represented a loss of safety function for greater than the allowed technical specification allowed outage time and it screened to greater than Green using the Phase 2 pre-solved worksheet. The senior reactor analyst determined that this finding was of very low safety significance (Green) based on a bounding calculation which assumed inoperability of the component for a year. The senior reactor analyst determined that the combined significance of these scenarios was a delta-core damage frequency of 1.3E-7/yr and a delta-large early release frequency of 4.2E-8/yr. Therefore the violation was determined to be of very low safety significance (Green). The analyst determined that the cause of the finding has a crosscutting aspect in the area of human performance associated with decision making. Specifically, the licensee utilized unsupportable assumptions in its evaluation that were not consistent with the Final Safety Analysis Report or the valve vendor manual. |
Site: | San Onofre |
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Report | IR 05000361/2010006 Section 4OA2 |
Date counted | Jun 30, 2010 (2010Q2) |
Type: | NCV: Green |
cornerstone | Mitigating Systems |
Identified by: | NRC identified |
Inspection Procedure: | IP 71152 |
Inspectors (proximate) | C Long E Ruesch G Tutak G Wilson M Hay R Smith S Marquez S Matharu S Walker |
CCA | H.14, Conservative Bias |
INPO aspect | DM.2 |
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Finding - San Onofre - IR 05000361/2010006 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (San Onofre) @ 2010Q2
Self-Identified List (San Onofre)
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