Thermodynamic assessment of the LiF–CeF3–ThF4 system: Prediction of PuF3 concentration in a molten salt reactor fuel

A thermodynamic description of the LiF–CeF3–ThF4 system is made in this study using a two-sublattice model for the description of the solid solution and a quasi-chemical model based on quadruplet approximation for the liquid phase. New calorimetric experimental data of the binary LiF–CeF3, CeF3–ThF4 and ternary LiF–CeF3–ThF4 systems have been obtained in this work justifying the calculated phase diagrams. Using the obtained thermodynamic assessment the concentration of PuF3 in the LiF–ThF4 melt was estimated based on the similarities with CeF3 and the melting behaviour of the initial molten salt fast reactor fuel was discussed.