Thermodynamic assessment of the Th-U-Pu system

Thermodynamic assessments of the Th-U and Th-Pu binary systems are performed in this study according to CALPHAD method and together with the data on the U-Pu system, which has been already published in the literature, the Th-U-Pu ternary system is determined. All available experimental data from the literature were used for the binary system assessments and based on them the Gibbs energy properties of the unknown phases have been optimized. For the excess Gibbs energy of the liquid phase the ionic liquid model has been used, whereas for solid solutions the Redlich-Kister description was selected. In case of the Th-U and Th-Pu binary systems a very good agreement between the assessment and the experimental equilibrium data has been achieved, with 80% of equilibrium data reproduced within ±20 K.