A miscibility gap in LiF–BeF2 and LiF–BeF2–ThF4

LiF–BeF2 and LiF–BeF2–ThF4 are key systems for Molten Salt Reactor fuel. The liquid phase of these systems has been assessed using Redlich–Kister polynomials. The result shows a miscibility gap on the BeF2-rich side. This has never been proven experimentally. Nevertheless, evidence for a two liquids region is given by the fact that such a region exists in the analogous MgO–SiO2 system. Also the ternary system LiF–BeF2–ZrF4 contains such a miscibility gap in the BeF2 corner.