Separation of CsCl from a ternary CsCl–LiCl–KCl salt via a melt crystallization technique for pyroprocessing waste minimization

A parametric study has been conducted to identify the effects of several parameters on the separation of CsCl from molten LiCl–KCl salt via a melt crystallization process. A reverse vertical Bridgman technique was used to grow the salt ingots. The investigated parameters were: (1) the advancement rate, (2) the crucible lid configuration, (3) the amount of salt mixture, (4) the initial composition of CsCl, and (5) the temperature difference between the high and low furnace zones. From each grown salt ingot, samples were taken axially and analyzed using inductively coupled plasma mass spectrometry. Results show that CsCl concentrations at the top of the ingots were low and increased to a maximum at the bottom of the salt. Salt (LiCl–KCl) recycle percentages for the experiments ranged from 50% to 75% and the CsCl composition in the waste salt was low. To increase the recycle percentage and the concentration of CsCl in the waste form, multiple crystallization stages were explored showing that they were practical under the optimal experimental conditions at 5.0 mm/h rate with a lid configuration and temperature difference of 200 °C for a total of five crystallization stages. Up to 88% of the LiCl–KCl salt can be recycled under these proposed conditions.

► Separation of CsCl from a ternary CsCl–LiCl–KCl salt has been studied parametrically. ► A new buildup fraction method is used to determine recycle salt purity as a function of axial position. ► The optimal crystallization parameters and conditions are identified to minimize salt waste.