Direct calculation of concentration-dependent activity coefficient of UCl3 in molten LiCl-KCl

Abstract

In the present study, MD simulation using the thermodynamic integration for directly calculating the Gibbs energy, activity coefficient, and apparent potential of solute in molten LiCl-KCl was developed, which makes it possible to identify the effect of concentration of solute on its activity coefficient and other properties. As an example, the thermodynamic properties of UCl3 in the molten salt at 723 K were calculated for different concentrations. The simulation results agree well with the literature and indicate that the activity coefficient of U3+ in LiCl-KC1 eutectic at 723 K is indeed a function of concentration and will increase following it. Because the solute concentration is changeable during pyroprocessing, this phenomenon should be considered seriously in order to predict the process accurately. Present model demonstrates that the MD method could be a potential method to predict fundamental thermodynamic properties of actinides and fission products in molten salt in the applications of pyroprocessing for used nuclear fuel treatment.