Thermodynamic assessment of lithium halide reciprocal salt systems for energy applications

Lithium halides are of interest because of their unique applications as fuel or coolants in molten salt reac-tors (MSRs) and electrolytes in thermally activated batteries. Because iodine is an important fission pro-duct for MSRs, the Molten Salt Thermal Properties Database-Thermochemical (MSTDB-TC) is being expanded to include relevant iodide reciprocal salt systems. In this work, we assess the thermochemical properties of lithium halide pseudobinary systems based on reported experimental phase diagrams, eutectic tem-peratures, and enthalpies of mixing. Within the framework of the modified quasi-chemical model in the quadruplet approximation (MQMQA), extrapolations to the related pseudoternary and pseudoquater-nary systems have been performed. The pseudoquaternary representations of phase equilibria, enthalpy, entropy, and heat capacity are represented in the resultant models. Of interest for generating source terms for accident analysis is the ability to compute the vapor pressures of the dominant iodide species for the systems at any composition. An example of such calculations is provided for the LiF-LiI system at xLiI = 0.01 and xLiI = 0.70, in this case indicating that the LiI vapor species are predominant.(c) 2022 Published by Elsevier B.V.

Automated summary

The thermochemical properties of lithium halide pseudobinary systems were assessed and calculations for related pseudoternary and pseudoquaternary systems were performed using a modified quasi-chemical model. The ability to compute the vapor pressures of the dominant iodide species is of interest for accident analysis.