Radionuclide Inventory Calculations for Structural Materials of Small Modular Reactors (SMR)

Abstract

In support of the Pan-Canadian Small Modular Reactor (SMR) roadmap activities, radionuclide inventory calculations for structural materials of various SMR types are performed. The calculations provide essential data for improving the understanding of reactor safety, radioactive material management, and environmental impacts. The Monte Carlo code SERPENT is used to model five major types of SMR, based on the latest published design data, to obtain neutron flux distributions in space and energy as functions of operating schedule, and the SCALE/ORIGEN code is then used for time-dependent neutron activation and decay calculations. Radionuclide inventories have been comprehensively estimated for principal structures of five SMRs: integral pressurized water reactor (iPWR), molten salt reactor (MSR), high-temperature gas-cooled reactor (HTGR), lead-cooled fast reactor (LFR), and heat pipe based reactors. The primary contributing reactor components, the dominating radionuclides to the total activity, and the radioactivity evolution with time after reactor shutdown, are discussed.