Thermodynamic investigations of ThO2–UO2 solid solutions

Thermodynamic properties of Th U1−O2 (0 <x< 1) based on quantum–mechanical calculations and Monte-Carlo simulations

“…Calorimetric measurements can measure enthalpies of formation and, in turn, enthalpies of mixing (e.g., [47,48]); however, such measurements for intermediate compositions across the ThO 2 -UO 2 solid solution are not yet available. Alternatively, enthalpy increments and heat capacities are calorimetric measurements that are commonly available for intermediate compositions across the ThO 2 -UO 2 solid solution [38,[49][50][51][52][53]; however, enthalpy increments and heat capacities cannot be compared with the results of the calculations in this study. Dash et al [53] compute Gibbs free energies of mixing from old vapor pressure data [54], which have since been disregarded [51].…”

“…Alternatively, enthalpy increments and heat capacities are calorimetric measurements that are commonly available for intermediate compositions across the ThO 2 -UO 2 solid solution [38,[49][50][51][52][53]; however, enthalpy increments and heat capacities cannot be compared with the results of the calculations in this study. Dash et al [53] compute Gibbs free energies of mixing from old vapor pressure data [54], which have since been disregarded [51]. The computed Gibbs free energy of mixing from Dash et al [53] is less than À15 kJ/mol at x = 0.5 and T = 1500 K for Th x U 1Àx O 2 .…”

“…Dash et al [53] compute Gibbs free energies of mixing from old vapor pressure data [54], which have since been disregarded [51]. The computed Gibbs free energy of mixing from Dash et al [53] is less than À15 kJ/mol at x = 0.5 and T = 1500 K for Th x U 1Àx O 2 . When compared with the maximum configurational entropy (i.e., TDS = ÀRT(xlnx + (1 À x)ln(1 À x), using the point entropy where no ordering is considered), their DH data is roughly À6.4 kJ/mol.…”

Theoretical analysis of uranium-doped thorium dioxide: Introduction of a thoria force field with explicit polarization

“…3 Since a neutron source is required for its application as a nuclear fuel, and as ThO 2 and UO 2 are isostructural, there is significant interest in thoria-urania solid solutions and both experimental and theoretical investigations have been carried out. [5][6][7][8] As it is useful to study thoria in the context of uranium-doping, it is advantageous to have a reliable computational method to model these materials due to the safety hazards and high costs of conducting experiments on radioactive materials.…”

Melting behavior of (Th,U)O2 and (Th,Pu)O2 mixed oxides

“…Important thermodynamic quantities such as density and enthalpy increment of both solid and liquid phases as well as heat of fusion are only available for pure UO2 [25,27,28]. For ThO2, these thermodynamic quantities for the solid phase are available only over a limited temperature range [21][22][23][24]26] and no data is available for the liquid phase. Recently, Böhler et al [18] and Bruycker et al [20] determined melting temperatures of PuO2 using a laser heating method and pyrometry.…”