UO₂-ZrO₂固溶体の融点および熱伝導率の分子動力学解析

Melting points of UO₂-ZrO₂ solid solutions and their thermal conductivities from solid to liquid state were evaluated using the classical molecular dynamics simulation with the interatomic potential function developed by Pedone et al. The one- and two-phase simulations have been performed to investigate the melting point with varying the chemical composition. Both approaches showed that the melting point was the lowest around 50 mol% ZrO₂ content and that the enthalpy of fusion also simultaneously was the smallest. However, the melting points calculated even by the two-phase simulation, which gave the better result than the one-phase simulation, were almost 300 K-600 K higher than the experimental ones. The thermal conductivities of the solid solutions were evaluated by the Green-Kubo approach in the equilibrium MD system. In the temperature region below the melting point, the thermal conductivity decreased with increasing temperature because of Umklapp scattering, and the solid solution with ZrO₂ content around 50 mol% had the lowest thermal conductivity at low temperatures where the impurity scattering had a maximum effect to lower the thermal conductivity. On the other hand, the thermal conductivity of liquid UO₂-ZrO₂ was relatively low, and it was almost independent of temperature and the chemical composition.