Calorimetric measurements on plutonium rich (U,Pu)O2 solid solutions

Enthalpy increments of U(1−y)PuyO2 solid solutions with y = 0.45, 0.55 and 0.65 were measured using a high-temperature differential calorimeter by employing the method of inverse drop calorimetry in the temperature range 956–1803 K. From the fit equations for the enthalpy increments, other thermodynamic functions such as heat capacity, entropy and Gibbs energy function have been computed in the temperature range 298–1800 K. The results are presented and compared with the data available in the literature. The results indicate that the enthalpies of U(1−y)PuyO2 solid solutions with y = 0.45, 0.55 and 0.65 obey the Neumann–Koppʹs molar additivity rule.