A self-revealing non-cited violation (
NCV) was identified for a human performance error associated with inadvertently racking out the 2B
emergency diesel generator (
EDG) output breaker. The system operator racked out the incorrect breaker while performing lockout 2-DT-09-1217-00289 on the Auxiliary Component Cooling Water (
ACCW) system. As a result, the 2B
EDG was temporarily rendered
inoperable. Licensee immediately restored the 2B
EDG to
operable status by returning the output breaker to the connect position. The licensee entered the issue into their corrective action program. This issue is more than minor because it is associated with a cornerstone attribute and adversely affected the objective of the
Mitigating Systems cornerstone. Specifically, the performance deficiency is a human performance error which affected the availability, reliability, and capability of the B train
emergency core cooling system to respond to a loss of coolant accident during a loss of off-site power. The finding was determined to be of very low safety significance (Green) because the event did not represent an actual loss of safety function of a single train for greater than its Technical Specification (TS) allowed outage time. The inspectors determined that the cause of this finding was related to the Work Practices component of the Human Performance cross-cutting area due to less-than-adequate human error prevention techniques
H.4(a). Specifically, peer checking techniques were less than adequate
