05000285/FIN-2011007-01
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Finding | |
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| Title | Failure to Correct a Degraded Contactor in the Reactor Protective System |
| Description | The inspectors identified an apparent violation of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix B, Criterion XVI, Corrective Action, for the licensees failure to ensure that the cause of a significant condition adverse to quality was determined and corrective actions taken to preclude repetition. Specifically, the licensee failed to identify the cause and preclude the shading coils from becoming loose material in the M2 trip contactor assembly of the reactor protection system that subsequently resulted in a failed contactor. The inspectors determined that the licensees failure to preclude shading coils from repetitively becoming loose material in the M2 reactor trip contactor was a performance deficiency. The finding is more than minor because it affected the Mitigating Systems Cornerstone, and it directly affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. The inspectors evaluated the issue using the Significance Determination Process Phase 1 Screening Worksheet for the Initiating Events, Mitigating Systems, and Barriers Cornerstones provided in Manual Chapter 0609, Attachment 4, Phase 1 Initial Screening and Characterization of Findings. The inspectors determined that the finding represented the actual loss of a single train (i.e., each of the four contactors are considered a train) of non-Technical Specification equipment, designated as risk-significant per 10 CFR 50.65, for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Therefore, the finding was potentially risk significant and a Phase 2 analysis was required. The inspectors determined that the pre-solved table does not contain a target suitable for evaluating the finding of interest and informed the regional senior reactor analyst that use of the risk-informed notebook would be necessary. The senior reactor analyst completed a Phase 3 analysis using the plant-specific Standardized Plant Analysis Risk Model for Fort Calhoun, Revision 3.50 modified to include a detailed modeling of the reactor protection system. The exposure period of 64 days represented the 63 days from the last verification of contactor operation, which is most likely the time of failure, until the failure of the quarterly surveillance plus the 1-day repair time until de-energization of half the reactor protection system. External events impacting the risk included seismic and internal fire initiators. The resulting risk was calculated to be 2.6 x 10-5 indicating that the finding was of preliminarily substantial safety significance (Yellow). The final significance of this finding is to be determined (TBD). This finding has a crosscutting aspect in the area of human performance, decision making component, because the licensee did not use conservative assumptions in the evaluation of the ongoing problems with the trip contactors. |
| Site: | Fort Calhoun  |
|---|---|
| Report | IR 05000285/2011007 Section 4OA2 |
| Date counted | Jun 30, 2011 (2011Q2) |
| Type: | Violation: White |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | C Steely J Kirkland J Wingebach K Kennedy L Micewski |
| CCA | H.14, Conservative Bias |
| INPO aspect | DM.2 |
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Finding - Fort Calhoun - IR 05000285/2011007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Fort Calhoun) @ 2011Q2
Self-Identified List (Fort Calhoun)
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