THREE COMPOSITIONS OF HIGH-ENTROPY MELTS OF LITHIUM, SODIUM AND POTASSIUM FLUORIDES AND CHLORIDES AS PROMISING COOLANTS FOR MOLTEN SALT REACTORS

Suggestions are made for potentially promising solvent melts for molten salt reactors from a mixture of six lithium, sodium, and potassium fluoride and chloride salts having high mixing entropy. These compositions, containing less lithium salts, should have higher thermodynamic stability than FLiNaK or FLiBe because of their high entropy. Chemical formula of maximum high-entropy solution may result from mixing the variety of alkali halides like MX (M=Li, Na, K and X=F, Cl) taken in an equimolar ratio. The configurational part of the mixing entropy of such a mixture equal to 1/2Rln24 (1.59R), which is very close to Rln5. At the same time, this is much larger than for standard compositions like FLiNaK-eutectic (0.83R). On the basis of the experimental phase diagram for the quasi-ternary salt mixture (LiF)1/2(LiCl)1/2 - (NaF)1/2(NaCl)1/2 - (KF)1/2(KCl)1/2 two more high-entropy compositions with reduced lithium content can be considered, namely, Li(0.1)Na(0.2)K(0.2)F(0.25)Cl(0.25) and Li(0.08)Na(0.1625)K(0.2575)F(0.25)Cl(0.25) , having a liquidus temperature of 606 and 630 Celsius. Their configurational entropy is equal to 1.57R and 1.54R, correspondingly.