Thermal conductivities of (U, Pu, Am)O2 solid solutions

The thermal conductivities of (U0.7−zPu0.3Amz)O2 solid solutions (z = 0.007–0.03) were studied by the laser flash method at temperatures from 900 to 1773 K. First, the thermal conductivities of (U0.68Pu0.3Am0.02)O2 solid solutions were measured as a function of density (ρ = 85–95% of theoretical density). The dependence of the thermal conductivities on the effective porosity (1 − ρ) was evaluated by the correction equations of Loeb, Maxwell–Eucken and Shultz, and then the experimental values were best-fitted with the correction coefficient of β = 0.5 in the Maxwell–Eucken equation.The thermal conductivities of (U0.7−zPu0.3Amz)O2 solid solutions were found to decrease slightly with increasing Am-content. The thermal conductivities satisfied the classical phonon transport model, λ = (A + BT)−1 up to about 1500 K. The coefficient A increased linearly with increasing Am-content, and little variation was observed in the coefficient B.The dependencies of the coefficients A and B on the Am-content were evaluated by the phonon scattering model. The coefficients obtained in the experiment could be theoretically well explained, assuming that the chemical formula of Am-MOX was U(0.7−2z)4+Uz5+Pu0.34+Amz3+O22−.