Mass Transfer Modeling of CsCl During Crystallization of Molten LiCl-KCl-CsCl Salt Mixture

Abstract

Metallic alloy fuels from fast reactors will be reprocessed by a non-aqueous electrochemical technique known as electrorefining. Electrorefining of spent metal fuel results in the accumulation of heat-generating fission products, especially ¹³⁷Cs in the eutectic salt. These fission products need to be removed from the salt so as to reduce the decay heat load and contamination. The melt crystallization technique is a simple separation process being pursued for the separation of fission products. This is a single-step process that utilizes the difference in solubility of fission products in the solid and liquid phase. This process is also less energy intensive. Crystallization involves the purification of a substance from a liquid mixture by solidification of the desired component. Since separation is based on selective solidification, which involves phase change, it is essential to evaluate the transient solidification pattern, liquid fraction distribution, solute distribution, and separation time and efficiency. Numerical modeling of the separation of CsCl from a LiCl-KCl eutectic mixture has been carried out using Ansys Fluent (19.2). The effect of crystallizer geometry and cooling rates on the separation of CsCl has been numerically simulated.