05000454/FIN-2010003-05
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Finding | |
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| Title | Failure to Appropriately Analyse the Degraded Voltage Timer Settings |
| Description | A finding of very low safety significance and associated NCV of 10 CFR 50, Appendix B, Criterion III, Design Control, was identified by the inspectors for the licensees failure to have an appropriate analysis for the second level undervoltage (degraded voltage) relay timer settings. Specifically, Byrons analysis, Engineering Change 377631, Evaluation and Technical Basis for the AP System Second Level Undervoltage (Degraded Voltage) Time Delay Settings, dated February 3, 2010, failed to demonstrate the ability of the permanently connected safety-related loads to continue to operate for 5 minutes and 40 seconds without sustaining damage during a worst case, non-accident degraded voltage condition. The licensee entered this issue into their CAP as IR 1071667 and revised the affected procedures. The performance deficiency was determined to be more than minor because the finding affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, there was reasonable doubt as to whether the permanently connected safety-related loads would remain operable during a worst case, non-accident degraded voltage condition for the duration of the time delay chosen. This finding is of very low safety significance (Green) because the design deficiency was confirmed not to result in loss of operability or functionality. The primary cause of this finding is related to the decision making aspect of the Human Performance cross-cutting area (H.1(b)) because the licensee did not use conservative assumptions based on NRC approved changes to the licensing basis in choosing the worst case degraded voltage condition in their February 2010 analysis. |
| Site: | Byron  |
|---|---|
| Report | IR 05000454/2010003 Section 1R21 |
| Date counted | Jun 30, 2010 (2010Q2) |
| Type: | NCV: Green |
| cornerstone | Initiating Events, Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | T Bilik B Metrow D Jones T Go V Meghani R Skokowski J Bishop R Ng C Thompson B Bartlett J Robbins B Jose |
| CCA | H.14, Conservative Bias |
| INPO aspect | DM.2 |
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Finding - Byron - IR 05000454/2010003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2010Q2
Self-Identified List (Byron)
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