Sensitivity of thermal transport in thorium dioxide to defects

Abstract In this research, the reverse non-equilibrium molecular dynamics is employed to investigate the effect of vacancy and substitutional defects on the thermal transport in thorium dioxide (ThO 2 ). Vacancy defects are shown to severely alter the thermal conductivity of ThO 2 . The thermal conductivity of ThO 2 decreases significantly with increasing the defect concentration of oxygen vacancy; the thermal conductivity of ThO 2 decreases by 20% when 0.1% oxygen vacancy defects are introduced in the 100 unit cells of ThO 2 . The effect of thorium vacancy defect on the thermal transport in ThO 2 is even more detrimental; ThO 2 with 0.1% thorium vacancy defect concentration exhibits a 38.2% reduction in its thermal conductivity and the thermal conductivity becomes only 8.2% of that of the pristine sample when the thorium vacancy defect concentration is increased to 5%. In addition, neutron activation of thorium produces uranium and this uranium substitutional defects in ThO 2 are observed to affect the thermal transport in ThO 2 marginally when compared to vacancy defects. This indicates that in the thorium fuel cycle, fissile products such as 233 U is not likely to alter the thermal transport in ThO 2 fuel.