Calorimetric measurements on (U,Th)O2 solid solutions

Enthalpy increments of urania – thoria solid solutions, (U0.10Th0.90)O2, (U0.50Th0.50)O2 and (U0.90Th0.10)O2 were measured by drop calorimetry in the temperature range 479 – 1805 K. Heat capacity, entropy and Gibbs energy function were computed. The heat capacity measurements were carried out also with differential scanning calorimetry in the temperature range 298 – 800 K. The heat capacity values of (U0.10Th0.90)O2, (U0.50Th0.50)O2 and (U0.90Th0.10)O2 at 298 K are 59.62, 61.02, 63.56 J K−1 mol−1, respectively. The results were compared with the data available in the literature. From the study, the heat capacity of (U,Th)O2 solid solutions was shown to obey the Neumann – Kopp’s rule.