An assessment of the risk significane of human errors in selected PSAs and operating events

Sensitivity studies based on Probabilistic Safety Assessments (PSAs) for a PWR and a BWR are described. In each case, human errors modeled in the PSAs were categorized according to such factors as error type, location, timing, and plant personnel involved. Sensitivity studies were then conducted by varying the error rates in each category and evaluating the corresponding change in total core damage frequency and accident sequence frequency. Insights obtained are discussed and reasons for differences in risk sensitivity between plants are explored. A separate investigation into the role of human error in risk-important operating events is also described. (orig.)