Molecular dynamics study of oxygen transport and thermal properties of mixed oxide fuels

Evaluation of thermal and transport properties of actinide mixed oxide fuels is a problem of high importance for the development of new generation reactors. Molecular dynamics provides a powerful tool, that can be used for this goal. In this work molecular dynamic simulations have been performed with the purpose to evaluate thermal and diffusion properties of UO2, PuO2 and (Pu0.3U0.7)O2 oxide nuclear fuels. Specific heat, thermal conductivity and thermal expansion of these materials were estimated in the temperature range of 300–2500 K and compared with available recommendations. Migration energies of the anion defects via the interstitial and vacancy mechanisms have been estimated together with oxygen self-diffusion coefficients. The presence of a strong interaction between point defects and Pu atoms in (Pu0.3U0.7)O2 oxide has been revealed and this interaction alters the diffusivity of point defects in comparison with the pure uranium and plutonium dioxides.