Thermodynamic properties of fission products (Pr, Ce, Er) in liquid bismuth by thermodynamic assessment

The binary systems of Bi-Pr, Bi-Ce, and Bi-Er were thermodynamically assessed by the CALPHAD method based on the available experimental data utilizing sub-regular model and the two-sublattice model. Enthalpies and entropies of formation of intermetallic compounds and enthalpies of mixing of liquid phase at different concentrations were calculated. The activity coefficients of fission products in liquid bismuth at different concentrations and temperatures were also obtained, which supplements the existing data that are limited to dilution cases. Additionally, the change patterns of the activity with concentration of these three systems were analyzed and discussed. Based on the phase diagram assessed in the study, the correlations for the temperature-dependent solubility of the fission products in liquid bismuth were also developed. The present study provides fundamental data in a broad concentration range when liquid bismuth is applied as extraction media for the separation of fission products from a molten salt.