The significance of sequence timing to human factors modeling

The authors examine the special significance of probabilistic safety assessment (PSA) event sequence timing among all the factors affecting human performance. It is concluded that because of the nature of the recovery actions modeled in PSA and the inherent characteristics of commercial nuclear plant design, the time available for recovery is the basic criterion for evaluation of human performance, whether the time is an explicit parameter of the operator actions analysis or not. Examples taken from the author's work in support of the more than 20 PSA studies illustrate how the time enters alternative human-factors models recovery for actions.<>