Modification of UO 2 Fuel Thermal Conductivity Model at High Burnup Structure

The thermal conductivity of UO2 under in-pile irradiation changes due to produced porosity. This paper has calculated evolution of fuel swelling and porosity by using a model of fuel matrix swelling due to fission gases that is valid for range of low temperature and burnups up to 120 MWd/KgU where high burnup structure (HBS) is formed. The HALDEN thermal conductivity correlation is selected for study of the fuel swelling and porosity evolution effect on irradiated UO2 thermal conductivity. In addition, the correlation is completed with a proposed porosity factor. With considering porosity evolution by burnup, is seen a reduction about 25% in the thermal conductivity which increases the fuel temperature. Calculation results indicate a good agreement with experimental data.