05000315/FIN-2015004-02
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Finding | |
|---|---|
| Title | Probabilistic Risk Assessment Model Errors |
| Description | The inspectors identified a finding of very low safety significance for the failure of the licensee to follow procedure 12EHP9010PRA001, PRA Model Update. Procedure 12EHP9010PRA001 establishes requirements to ensure that Donald C. Cook Probabilistic Risk Analysis (PRA) models represent the as-built, as-operated plant in a manner sufficient to support the applications for which they are used. One of the requirements is to perform an update every four years. The updates include activities such as reviewing internal and external operating experience, reviewing procedures that have an impact on human error probabilities or equipment test frequencies, and updating basic event data resulting from current reliability and unavailability data. Contrary to these requirements, the Donald C. Cook internal events model was not updated for six years following the last update in 2008. The inspectors also determined the licensee did not have a formal process to ensure all of the update items were being met. Additionally, the procedure required that any needed peer reviews are performed and that any significant model issues are addressed prior to any use of the revised model for risk-informed applications. Specifically, formal peer reviews are to be performed for changes that constitute PRA upgrades. Contrary to the procedure, a formal peer review was not completed for a change to certain test and maintenance modeling factors that met the definition of a PRA upgrade. The change resulted in an error that affected the license amendment request for National Fire Protection Association (NFPA)805 fire regulations and several risk-informed applications onsite. The issue was more than minor because if left uncorrected, it could become a more significant safety concern. Specifically, the failure to ensure peer reviews were performed and the failure to perform updates as required were reflective of programmatic weaknesses. Per IMC 0612 Appendix E, Examples of Minor Issues, evidence of programmatic weaknesses constitute an example of a more than minor issue. The inspectors determined the Mitigating Systems cornerstone was adversely affected by the finding since it was associated with maintenance of PRA models, which could impact probabilities of mitigating systems ability to perform their functions. The finding screened as Green, or very low safety significance, utilizing IMC 0609 Appendix A, The Significance Determination Process for Findings at Power. Specifically, the inspectors answered no to questions under both the Mitigating Structures, Systems, and Components, and Functionality and External Event Mitigation Systems sections. The finding had an associated cross cutting aspect in the Human Performance area, namely, Avoid Complacency (H.12), because of the lack of rigor applied in ensuring procedural requirements were met. |
| Site: | Cook  |
|---|---|
| Report | IR 05000315/2015004 Section 4OA1 |
| Date counted | Dec 31, 2015 (2015Q4) |
| Type: | Finding: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71151 |
| Inspectors (proximate) | G Edwards J Ellegood J Mancuso K Riemer T Go T Taylor |
| CCA | H.12, Avoid Complacency |
| INPO aspect | QA.4 |
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Finding - Cook - IR 05000315/2015004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Cook) @ 2015Q4
Self-Identified List (Cook)
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