Proposed Review Framework for Design of Pressure Retaining Systems and Components (PRSC) in Small Modular Reactor (SMR)

A recent surge of nuclear industry interest in the development of smaller, modular/factory-built nuclear reactors has been underway for the last few years. Recently, the Canadian Nuclear Safety Commission (CNSC), which is the Canadian nuclear regulatory authority, has been reviewing a number of proposed Small Modular Reactor (SMR) designs through the pre-licensing Vendor Design Review (VDR) process. Some of these SMR designs propose to operate under relatively high neutron fluxes and at elevated temperatures to achieve high thermal efficiency compared to current operating power reactors. Other designs employ a highly corrosive coolant medium. Such operating conditions could accelerate or present unforeseen degradation mechanisms that could adversely affect the integrity and service life of the pressure boundary. It is therefore crucial to understand the material behavior under these conditions to devise appropriate design rules for metallic and non-metallic components. Thus, a systematic approach and a well-designed research and development program to address any knowledge gaps in material behavior at the early design stage for a SMR is crucial, so that potential/plausible degradation mechanisms are accounted for and the structural integrity of Pressure Retaining Systems and Components (PRSC) is maintained over the design life. This paper discusses a proposed framework based on key review findings from the pre-licensing VDR of several SMR designs in Canada.