A pragmatic approach to modelling thermal conductivity of irradiated UO2 fuel: Review and recommendations

Abstract The thermal conductivity of irradiated UO 2 fuel is discussed considering the effects of burnup (dissolved and precipitated solid fission products), porosity and fission-gas bubbles, deviation from stoichiometry and radiation damage based on single-effect results previously published on SIMFUEL (simulated extended burnup UO 2 fuel) and on radiation damage measurements. An analytical expression including factors describing the above effects is applied to the expression for unirradiated UO 2 thermal conductivity; it reflects the knowledge available today, and it is recommended for use with irradiated fuel. The expression is validated against available published data on thermal conductivity of irradiated fuel. This expression can be incorporated into fuel modelling codes to improve calculations of operating temperatures and predictions of behaviour of irradiated fuel under normal and accident conditions, including the extended burnup.