Calorimetric studies on urania-thoria solid solutions

The enthalpy increments of (UyTh1-y)O-2 solid solutions With y=0.1, 0.5 and 0.9 were measured by using a drop calorimeter of isoperibol type. The expe rimental data cover the temperature range 473-973 K relative to 298 K. Othe r thermodynamic functions such as heat capacity, entropy and free energy fu nction of these solid solutions were derived from the measured enthalpy inc rement values. The results indicate that the enthalpies of (UyThy-1)O-2 sol id solutions in the temperature range 373-973 K obey the Neumann-Kopp molar additivity rule. (C) 2000 Elsevier Science S.A. All rights reserved.