Fission gas release behavior analysis of ThO2-UO2 fuel)

For the in-pile performance analysis of thoria-urania fuel, INFRA-Th version was developed by adding the pellet thermal conductivity, pellet radial power and burnup distribution, and fuel thermal expansion models for ThO2-UO2 fuel to INFRA of UO2 performance analysis code. By using INFRA-Th, fission gas release data base of ThO2-UO2 fuels which are produced by LWBR program is analyzed. Some of data gives low fission gas release due to relatively low burnup, so that mechanistic analysis of fission gas release by diffusion was not possible. In case of high fission gas release data, most of fission gas release came from the region where grain growth had occurred due to very high temperature irradiation. Therefore, it was not possible to apply conventional diffusional fission gas release model for those data with grain growth