A study on the integrity and behavior of nuclear fuel in temporary storage

Due to the saturation of spent fuel pools of nuclear power plant in Korea, spent fuel will be stored in dry casks for a considerable period. Since spent fuel must withstand continuous decay heat, radiation, and high internal pressure of the fuel rod in the cask, behavior of spent nuclear fuel is needed to be reviewed. It is very important to evaluate the behavior of nuclear fuel with realistic modeling. In this study, the behavior of spent nuclear fuel after being burned in a reactor for three cycles and subsequently cooled in a spent fuel pool was analyzed by FALCON -1.5.0 which is a computational code for mechanical and thermal analysis of nuclear fuel. For code analysis, three burnup levels of 42,000 MWD/MTU, 50,000 MWD/MTU, and 58,000 MWD/MTU were considered. The hoop stress, strain, and other parameters were analyzed for each burnup level. Furthermore, the cooling periods in the spent fuel pool are set to 5, 10, 15, and 30 years, allowing for an evaluation of nuclear fuel behavior consistent with the burnup levels. Additionally, nuclear fuel behavior with normal and high thickness of oxidation is reviewed as well. The behavior of various nuclear fuels during the temporary storage period is studied with FALCON and the factors affecting the integrity of nuclear fuel are analyzed for up to 50 years of the temporary storage. This evaluation will contribute to demonstrating the safe storage of nuclear fuel in dry storage.