Enhancing FRAPCON fuel performance code for physical phenomena at high temperature and high burnup

Advanced LWR fuel designs aim for higher burnup and heating rates. Operating at higher fuel temperatures and burnups involve several physical phenomena typically ignored in LWR fuel performance codes. To accurately analyze the fuel rod behavior at such conditions, the modification of existing LWR fuel performance code is necessary. This paper describes the enhancement of FRAPCON, a fuel performance code used by US NRC. In this study, mechanistic models describing porosity, cesium and hydrogen migration and precipitation kinetics were added into FRAPCON-3.5, referred to as FRAPCON 3.5 Enhanced Performance (EP). A survey of MOX fuel thermal conductivity models vs. experimental data was performed and multiplying factors to account for plutonium weight fraction were derived. Overall, the comparison of these revised models showed reasonable agreement with in-pile experiments.