Correlational Approach to Predict the Enthalpy of Mixing for Chloride Melt Systems

A methodology to estimate the heat of mixing (Δ_mix H) for salt liquids in unexplored AkCl-AnCl /LnCl (Ak = alkali, An = actinide, Ln = lanthanide) systems is developed. It improves upon previous empirical approaches by eliminating the need for arbitrarily choosing the required composition at maximum short-range ordering, the minimum Δ_mix H prior to performing the estimation, which avoids the intrinsic ambiguity of that approach. This semiempirical method has computationally reproduced the behavior of NaCl-UCl₃ and KCl-UCl₃ systems, providing Δ_mix H values that agree well with the reported measurements within a propagated two standard deviations (2σ). The capability of the approach is demonstrated in its application to the entirety of the AkCl-UCl₃ and AkCl-PuCl₃ systems, the results from which have facilitated the accurate thermodynamic modeling of these and other AkCl-AnCl₃/LnCl₃ systems. The resultant assessed Gibbs energy functions and models have been incorporated in the Molten Salt Thermal Properties Database-Thermochemical (MSTDB-TC).