A self-revealing
NCV of
10 CFR 50, Appendix B, Criterion XVI, Corrective Action, was identified because Entergy did not promptly correct an adverse condition resulting in the failure of the B
EDG. Specifically, Entergy personnel did not promptly replace a degraded jacket water
flange gasket prior to its subsequent failure. Entergys corrective actions included replacing the
gasket, visually inspecting the other jacket water connections, and initiating a condition report. The finding is more than minor because it is associated with the Equipment Performance attribute of the
Mitigating Systems cornerstone and affected the cornerstone objective to ensure the availability and reliability of systems that respond to
initiating events to prevent undesirable consequences (i.e., core damage). Specifically, the B
EDG failed in service due to a known degraded condition that affected the overall system redundancy and reliability and resulted in 37 days of unplanned unavailability. The inspectors and a Region I Senior Reactor Analyst (
SRA) completed the Detailed Risk Evaluation (
DRE) in accordance with
IMC 0609, Appendix A, The
Significance Determination Process for Findings At- Power, and determined this finding to be of very low safety significance (Green). The
DRE estimated the increase in core damage frequency (ACDF) for internal
initiating events in the range of 1 core damage accident in 2,000,000 years of reactor operation, in the mid-E-7 range per year. In addition, external
initiating events such as fire, seismic and flooding would not have increased the total ACDF above 1 E-6 per year, and the increase in the frequency of a large early release of radioactive material (ALERF) associated with the internal event ACDF core damage sequences would not be above
1E-7 per year. The finding had a cross-cutting aspect in the Human Performance, Decision-Making, because Entergy personnel did not use conservative assumptions in decision making in that the chosen action was to monitor the leak for a prolonged period of time.
