MOLECULAR DYNAMICS STUDY OF THE THERMAL CONDUCTIVITY OF THORIUM-BASED MIXED OXIDE FUEL

Abstract

A molecular dynamics (MD) simulation method of accurately calculating the thermal conductivity of thorium based mixed oxide fuel is introduced and two cases of ThO2 fuel doped with different Ce fraction and U fraction were considered, respectively. A random atomic distribution doping method was adopted, together with Coulomb-Buckingham potential adopted to describe the interaction of atoms. The calculated results indicate the Coulomb-Buckingham potential could accurately calculate the lattice parameter and thermal conductivity of ThO2, UO2 and CeO2 fuel，which is found to be consistent with experimental measurement. The thermal conductivity of thorium based mixed oxide fuel was further calculated based on this method. It was found that with the Ce doping fraction increased, the lattice parameter of (Th,Ce)O2 mixed oxide fuel was found to be decreased and the thermal conductivity was found to be increased gradually. While with the U doping fraction increased, the thermal conductivity of (Th,U)O2 mixed oxide fuel was found to have very tiny change and lattice parameter was found to be decreased gradually too. In addition, the calculated thermal conductivity of (Th0.8,Ce0.2)O2 fuel was found to be consistent with experimental measured data. Lastly, the effects of fission products on the thermal conductivity of ThO2 were also analyzed and discussed.