The team identified a finding of very low safety significance (Green) involving a non-cited violation of
10 CFR 50.63, Loss of all Alternating Current Power, in that, Entergy did not ensure that adequate battery capacity would be available during a station blackout (
SBO), as assumed in the stations
SBO analysis. Specifically, unrecognized delays in performing a credited manual direct current (
DC) load shedding operator action, as well as an incorrectly translated minimum battery voltage referenced in the stations
SBO procedure, could have resulted in the B station battery capacity being insufficient during an
SBO. Entergy entered the issue into the corrective action program. Entergy also recalculated the B station battery capacity and determined that sufficient battery capacity existed when realistic load shedding assumptions were applied (battery remained
operable). The finding is more than minor because it is associated with the procedure quality attribute of the
Mitigating Systems Cornerstone and affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to
initiating events to prevent undesirable consequences. This finding was determined to be of very low safety significance (Green) because it was not a design or qualification deficiency, did not represent a loss of system safety function, and did not screen as potentially risk significant due to a seismic, flooding, or severe weather initiating event. (1R21.2.2.1
