The evolution of the U.S. nuclear regulatory process

This paper provides historical perspectives and insights on the early development of the U.S. nuclear regulatory process and its subsequent evolution towards risk-informed processes. After the landmark Reactor Safety Study (WASH-1400) and the TMI-2 accident, the U.S. Nuclear Regulatory Commission (NRC) began to use probabilistic risk assessment (PRA) methods and insights in regulatory applications as deemed necessary or useful. In 1995, the NRC adopted a policy that promotes increasing the use of probabilistic risk analysis in all regulatory matters to the extent supported by the state of the art to complement the deterministic approach. The NRC then started moving toward a much expanded use of PRAs in what is termed risk-informed regulatory approach. This paper discusses the challenges and the success stories of the use of probabilistic assessment of the risk to support and inform regulatory decisions.