Thermodynamic and Physical Properties of Molten LiF-ThF4-UF4 Salts Mixture

Abstract The comprehensive information on LiF-ThF4-UF4 system is necessary for the development of new design molten salt reactors. LiF–ThF4 system has been established to be the most appropriate solvent for the fissile isotope 233U. Based on this pseudo-binary phase diagram and reactor criticality data, the composition of fuel carrier salts has been calculated as: F1.675Li0.775Th 0.1995U0.0255. The thermo-physical and thermodynamic properties of this fuel salts mixture were measured using thermal analysis, Archimedes and Rheometric techniques. The solidus, liquidus temperature and enthalpy of fusion values were determined for molten F1.675Li0.775Th 0.1995U0.0255.salts mixture to be 825 ± 3 K, 838 ± 4 K and (15.9 ± 4) kJ mol-1, respectively. The dynamic and kinematic viscosities, density and thermodynamic function as a function of temperature of molten fuel carrier salts F1.675Li0.775Th 0.1995U0.0255 mixture have been determined. The activities of LiF, ThF4 and UF4 over the molten F1+3zLi1-zTh xUy (z = x + y, 1 ≤ x ≤ 0, 0 ≤ y ≤ 1) salts mixture have been computed using FTsalt-FACT salt phase diagrams database.