PSA Conservatism Analysis and Quantification for the LOFW Accident

The conservatism was introduced in the probabilistic safety analysis (PSA) while successes criteria for the event tree were determined. The conservatism has strong relation with the uncertainty but independent with the uncertainty, and the conservatism could significantly influence the CDF results, contribution of dominant sequence, and sensitivity analysis. For methodology, the conservatism in PSA was identified, conservative numbers were defined to quantify the conservatism. Addressing the loss of feed water (LOFW) accident at the PWR, the probability distributions for the function events of the event tree were defined, and the conservatism was quantified based on the PSA insights and sensitivity analysis. The methodology and the application of the conservative numbers were discussed and conclusions were drawn.