A self-revealing finding was identified for the licensees failure to implement adequate instructions for venting condensate booster pump (
CBP) emergency low suction pressure trip instrumentation which resulted in air entrainment causing a non-conservative shift in the trip setpoint. During a subsequent secondary side
transient involving a heater drain tank pump trip, the non-conservative trip setpoint resulted in a premature trip of all three
CBPs ultimately causing a
reactor trip. The performance deficiency was more than minor because it affected the Procedure Quality attribute of the
Initiating Events Cornerstone and adversely affected the cornerstone objective, in that, the inadequate venting allowed air entrainment in the instrumentation lines resulting in a
reactor trip. This finding was determined to have very low safety significance (Green) because it did not contribute to the likelihood of both a
reactor trip and that mitigation equipment or functions would not be available. No cross cutting aspect was identified.
