05000280/FIN-2015003-04
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Finding | |
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Title | Licensee-Identified Violation |
Description | 10 CFR 50, Appendix B, Criterion III requires, in part, that measures shall be established to assure that applicable regulatory requirements and the design basis for those SSCs are correctly translated into specifications, drawings, procedures, and instructions. Contrary to the above, on January 27, 2015, the licensee discovered that abnormal procedure, 0-AP-37.01, Abnormal Environmental Conditions, used when there is a tornado watch or warning declared for Surry County or when hurricane force winds are expected in Surry County within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, did not have specific steps to shut the four total sliding missile shield doors on the Unit 1 and Unit 2 MSVHs. The shields are necessary to meet the design function of the MSVH for protection of the equipment inside the MSVH which includes the AFW pumps and other safety-related components in the main steam and AFW systems. This issue was discovered during a procedure revision walk-through. Using IMC 0609.04, Initial Characterization of Findings, Table 2, dated June 19, 2012, and IMC 0609 Appendix A, Significance Determination Process for Findings at-Power, dated June 19, 2012, the inspectors determined that a detailed risk evaluation was required because the finding could involve the total loss of any safety function, identified by the licensee through probability risk analysis (PRA) that contributes to external event initiated core damage accident sequences (i.e., severe weather event). A detailed risk assessment was performed by a regional SRA in accordance with NRC IMC 0609 Appendix A using the NRC Surry SPAR model. The major analysis assumptions included: a one year exposure period, the performance deficiency was modelled as a non-recoverable weather-related loss of offsite power (LOOP) with the Station Blackout DG and all AFW pumps on one unit failed, damage assumed if F2-F5 tornado winds occurred within the 100 square mile radius including the site, and no recovery credit for AFW or for closing the missile shield doors prior to damage. The dominant sequence was a success of the reactor protection system and the electric power system, late failure of AFW and failure of feed and bleed. The risk was mitigated by the low frequency of events requiring use of the sliding missile shields and the remaining mitigation equipment including the AFW unit cross-tie. The result of the risk evaluation was an increase in core damage frequency of <1.0E-6/year, a GREEN finding of very low safety significance. This issue was entered into the licensees CAP as CR 570365 and the abnormal procedure 0-AP-37.01 was revised with the correct operator actions. |
Site: | Surry |
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Report | IR 05000280/2015003 Section 4OA7 |
Date counted | Sep 30, 2015 (2015Q3) |
Type: | NCV: Green |
cornerstone | Mitigating Systems |
Identified by: | Licensee-identified |
Inspection Procedure: | |
Inspectors (proximate) | A Masters C Jones E Stamm P Mckenna T Fanelli |
Violation of: | 10 CFR 50 Appendix B Criterion III, Design Control |
INPO aspect | |
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Finding - Surry - IR 05000280/2015003 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Surry) @ 2015Q3
Self-Identified List (Surry)
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