Application of the risk oriented accident analysis methodology (ROAAM) to severe accident management in the AP600 advanced light water reactor

Abstract An important part of the AP600 design, as well as of the design certification review by the US Nuclear Regulatory Commission, is devoted to ensuring defense in depth through deep consideration and management of severe accidents. Going beyond the traditional Level 2 PRA, in this article we show how this defense in depth was achieved and demonstrated in a consistent manner between prevention and mitigation, through application of the Integrated ROAAM approach. This requires the up-front integration of probabilistic and deterministic thought, which leads naturally to clear and coherent safety goals as an overall guide toward closure.