Thermodynamic properties of compounds of alkaline earth elements with other fission products

Abstract

The alkaline earth fission products barium and strontium can combine with other major fission product elements such as Mo, Ce and Zr in a mixed oxide fuel pin of a fast breeder reactor to form compounds such as molybdates. cerates and zirconates. In order to understand the condition of their formation in the fuel pin basic thermodynamic data on these compounds applicable to the relevant temperature range are required. In this work enthalpy increments of BaMoO₄, BaCeO₃ and (Ba, Sr)ZrO₃ were determined relative to room temperature using a high temperature differential calorimeter. The experimentally measured enthalpy data covered the temperature range of 985-1750 K. From these enthalpy values other thermodynamic functions such as heat capacities, entropies and free energy functions were generated using C_p298⁰ and S₂₉₈⁰ values of the compounds available in the literature. The free energies of formation of these compounds and the equilibrium barium partial pressures for the formation reactions have been computed in the temperature range of 500-2000 K and in the oxygen potential range of -376.56 kJ mol^-1 to -502.08 kJ mol^-1.