Microstructural Evolution and Radionuclide Release Behavior of SIMFUEL Under Coupled Effects of Burn-up, Sintering, and Leaching Temperature

Abstract: Understanding the long-term behavior of spent nuclear fuel (SNF) is crucial for safe radioactive waste management. This study evaluates how burn-up, sintering temperature, and leaching temperature impact the leaching and microstructural stability of SIMulated FUEL (SIMFUEL) pellets designed to simulate SNF characteristics. Pellets with burn-up levels of 35 and 55 GWd/tU were sintered at 1550 °C and 1700 °C and subjected to leaching tests over one year at 25 °C, 60 °C, and 90 °C. Radionuclide release and microstructural changes were investigated using ICP-MS, SEM, XRD, and EDS. Results show that higher sintering temperatures enhance microstructural stability and reduce radionuclide release. Burn-up influences release behaviors in an element-dependent and time-sensitive manner. Leaching temperature generally accelerates release rates and surface corrosion. Despite subtle compositional and size changes at elevated temperatures, key metallic inclusions remain largely stable. These findings highlight the combined effects of fabrication and environmental factors on SIMFUEL durability and radionuclide mobility. This improved understanding aids in predicting long-term SNF performance and informs approaches for ensuring disposal safety.