Effect of fission products on the thermal conductivity of ThO2-A molecular dynamics study

Abstract

Thermal conductivity (k), as an important thermal property of nuclear fuels, would be deteriorated due to fission products. Therefore, to investigate the effect of fission products on the thermal conductivity of nuclear fuels is essential. Two typical fission products: Xe and Kr with 0–2 % concentration are considered in this work. The lattice constants (L) of ThO2 increase due to fission products at all testing temperatures. The extent of increase in L due to Xe interstitials is the maximum. The fission products significantly reduce the thermal conductivity of ThO2. The extent of reduction in thermal conductivity of ThO2 by the defects follows the trend Xe (interstitials) > Xe (substitutional defects) > Kr (substitutional defects) > Kr (interstitials). Finally, the full-filled Xe/Kr bubble has a nearly identical thermal conductivity as an empty void or half-filled Xe/Kr bubble. The underlying reason may be that the thorium atoms have a lower mobility than uranium atoms. These calculated values can be used to predict the thermal properties of the irradiated ThO2.

Keywords

• Thorium dioxide
• Fission products
• Molecular dynamics
• Thermal conductivity
• Theoretical models
• Dislocation loops