New SMR LWR designs offer significantly enhanced safety, security and simplicity of design as describer earlier in this Handbook. Both the industry and the NRC recognize that many of the existing technical requirements would be applicable to these new designs. Traditionally, LWRs were licensed using deterministic engineering judgment and analysis to prove the safety case and establish the licensing basis. However, with the significant improvements in safety design, the NRC is permitting greater emphasis on the use of probabilistic risk assessment (PRA) techniques and risk insights to establish the licensing basis for SMRs. All US SMRs will develop and use design-specific PRAs to support their licensing basis.

While the NRC has indicated that it will permit greater use of PRAs to support and establish a licensing basis, the use of the PRA would be commensurate with the quality and completeness of the design and attendant PRA presented with the application. Depending on the quality and completeness, the NRC might use the PRA and risk-insights to complement a deterministic analysis to establish a licensing basis (including the selection of licensing basis events). Or, it might rely more heavily on the PRA and use a deterministic engineering judgment and analysis to complement the PRA. In the post-Fukushima environment, the quality of a design-specific PRA coupled with the use of deterministic engineering judgment and analysis becomes crucial for the licensing of SMRs that either seek relief from traditional LWR safety requirements, or are used to support revised licensing requirements. The use of PRA risk information for licensing of SMR LWR designs is particularly appropriate because the quality and completeness of the PRA is bolstered by the maturity of the LWR design, and the extent and richness of the operating history information.