Assessment of Fuel Cladding Degradation for Small Modular Sodium-Cooled Fast Reactor in Deep Geological Repository Groundwater

Despite their many perceived advantages, one of the biggest challenges to the deployment of small modular reactors (SMRs) is the management of spent fuel and radioactive waste from their operation and decommissioning. Canada’s plan for the long-term management of nuclear fuel waste, including the spent fuel from SMRs, involves long-term disposal in a deep geological repository (DGR). The large variety of proposed SMR fuel forms, sizes, and compositions present significant challenges in assessing the requirements for long-term nuclear waste disposal, particularly the metallic fuels and fuel pins containing a sodium bond for sodium-cooled fast SMRs. In this work, the degradation of HT9 steel as a candidate fuel cladding for sodium-cooled fast SMRs in simulated DGR groundwater environment has been investigated using electrochemical testing and slow strain rate testing (SSRT) methods. The testing conditions are designed to simulate the groundwater ingress into a used fuel storage container under a DGR flood scenario for the assessment of corrosion and stress corrosion cracking susceptibility of the HT9 fuel cladding. The work addresses the knowledge gap in the safe long-term storage of spent SMR fuel in DGR, supporting the development and deployment of SMRs in Canada.