Molecular dynamics modelling of the thermal conductivity of off-stoichiometric UO2±x and (UyPu1−y)O2±x using equilibrium molecular dynamics

Thermal conductivities of off-stoichiometric single crystal mixed oxide nuclear fuels are estimated by equilibrium molecular dynamics simulations using the Green-Kubo method. The charge neutrality in non-stoichiometric systems is imposed using a charge rescaling method. The atomic charges are modified to account for charge removed or added depending on the defect concentration. The thermal conductivity for stoichiometric, hyperstoichiometric and hypostoichiometric nuclear fuels are estimated. A reduction in thermal conductivity is observed when the (U/Pu):O ratio deviates from 2.0, and the decrease is more pronounced in the hypostoichometric material. However, the U/Pu ratio had little effect on the thermal conductivity. The results are consistent with experimental and theoretically-determined values obtained elsewhere.