A self-revealing finding was identified when one of the
115 kV offsite power transformer
71T-3 surge arresters failed in-service. Specifically, Entergy did not adequately implement maintenance program expectations outlined in
EN-DC-324, Preventive Maintenance Program, Revision 4 and ensure replacement of the surge arrester upon exceeding its reliable service life. The surge arrester failure contributed to a
loss of offsite power. The inspectors determined that this finding is more than minor because it is associated with the protection against external factors attribute (grid stability) of the
Initiating Events cornerstone and affected the cornerstone objective to limit the likelihood of those events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. The inspectors evaluated the significance of this finding using Phase 1 of
IMC 0609, Appendix A, Significance Determination of Reactor Inspection Findings for At Power Situations, and determined it to be of very low safety significance (Green) because the finding did not contribute to both the likelihood of a
reactor trip and the likelihood that mitigation equipment or functions will not be available. This finding had a cross-cutting aspect in the area of problem identification and resolution because Entergy did not take appropriate corrective actions to promptly replace the surge arrester when it was identified to be past its reliable service life. (
P.1(d)