Thermodynamic modeling of the Th–U, Th–Zr and Th–U–Zr systems

The thermodynamic assessments of the Th–U, Th–Zr binary and Th–U–Zr ternary systems were carried out by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including phase equilibria and thermodynamic properties. The Gibbs free energies of the liquid, bcc, fcc, hcp, αU and βU phases were described by the subregular solution model with the Redlich–Kister equation, and that of the δ phase in the Th–U–Zr ternary system was described by the sublattice model. The thermodynamic parameters of each phase in the Th–U–Zr system were also evaluated by combining the experimental data of the phase equilibria with the parameters in three binary systems. The calculated phase equilibria are in good agreement with the experimental data.