The inspectors documented a self-revealing finding involving the failure to follow
LS-AA-125, Corrective Action Program, Revision 14. Specifically, the licensee failed to take appropriate corrective actions to correct degraded
control rod drive mechanism cable connections identified during a 2010 stuck rod event. This resulted in a
rod drop event on October 10, 2017, that caused a turbine runback to 55 percent and required a plant shutdown to repair. As an immediate corrective action, the licensee replaced the Bendix 7-pin electrical connector for the
control rod drive mechanism (
CRDM) and performed extent of condition visual and resistance checks on the other
CRDM cables. The issue was entered into their corrective action program (
CAP) as
issue report (IR) 04061160.The performance deficiency is more-than-minor because it was associated with the equipment performance attribute of the
Initiating Events cornerstone and adversely affected the objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during power operations. Specifically, a
transient resulting from a dropped rod challenged the critical safety function of reactivity control. The inspectors determined that this finding was of very low safety significance (Green) since it did not cause both a
reactor trip and the loss of mitigation equipment relied upon to transition the plant to a stable shutdown condition. This finding has a cross-cutting aspect in the area of Problem Identification and Resolution, Evaluation, because despite indications of degradation during inspections in 2013 and 2015, the site failed to ensure that a resolution addressed the cause commensurate with its safety significance (P.2).
