Thermodynamics of the LiF–NaF–BeF2 system at high temperatures

Molten mixtures of LiF, NaF, and BeF2 may be useful as a liquid first wall in a fusion-energy reactor. For design, it is necessary to know the thermodynamic properties of these mixtures, in particular, the total pressure as a function of temperature and composition. For successful application inside fusion chambers, the total pressure normally should be small, on the order of 0.1 Pa or less. This work presents a simple molecular-thermodynamic model based on the “chemical” theory of solutions with corrections for physical interactions. Parameters in this model are obtained from experimental binary and ternary data reported previously. The simple model, with only a few adjustable parameters, provides a good description of the thermodynamic properties for this system. For the temperature range 600–650  ° C at BeF2 mole fractions between 0.3 and 0.4, the total pressure is in the region 0.01–0.1 Pa.