Insights from the AP600 probabilistic safety study

Abstract A full Probabilistic Safety Study (PSS), including Levels 1, 2 and 3, has been performed for the AP600, a Westinghouse design midsize, advanced passive light-water reactor plant. This study was part of an interactive process in the development of the AP600 design. As a result of frequent interaction between PSS analysts and design engineers, many potential safety concerns were addressed early in the evolution of the AP600 design that led to the incorporation of beneficial design modifications procedures and analyses. As a consequence of this process, the AP600 design that was submitted to the U.S. Nuclear Regulatory Commission (NRC) for certification presents a very low core damage frequency and severe accident frequency. Very effective severe accident mitigating features are also demonstrated. The frequency of exceeding the Protective Action Guideline limit of 1 rem effective dose equivalent at the site boundary within 24 hours of the onset of core damage is negligibly small. Therefore, simplification of emergency planning required for the AP600 is justified.