Comparison Between Canadian Probabilistic Safety Assessment Methods Formulated by Atomic Energy of Canada Limited and Probabilistic Risk Assessment Methods

Abstract

The procedures used by Atomic Energy of Canada Limited (AECL) to perform probabilistic safety assessments (PSAs) differ somewhat from conventionally accepted probabilistic risk assessment (PRA) procedures used elsewhere. In Canada, PSA is used by AECL as an audit tool for an evolving design. The purpose is to assess the safety of the plant in engineering terms. Thus, the PSA procedures are geared toward providing engineering feedback so that necessary changes can be made to the design at an early stage, input can be made to operating procedures, and test and maintenance programs can be optimized in terms of costs.Most PRAs, by contrast, are performed in plants that are already built. Their main purpose is to establish the core melt frequency and the risk to the public due to core melt. Also, any design modification is very expensive.The differences in purpose and timing between PSA and PRA have resulted in differences in methodology and scope.The PSA procedures are used on all plants being designed by AECL.