(418d) Monitoring of Actinide Concentrations in Molten LiCl-KCl Salt Using Alpha Spectroscopy

In order to develop a sensor for measuring actinide concentrations in molten electrorefiner salt, a process for electrodeposition of U and Th from LiCl-KCl-UCl₃-ThCl₄ onto Pt-coated surfaces has been developed. To facilitate the counting of alpha particles by the sensor, the objective is to electrodeposit a uniform, one micron thick layer of actinides. Such a deposit was accomplished using repeating chronoamperometry (RCA) tests in LiCl-KCl-UCl₃, LiCl-KCl-ThCl₄, and LiCl-KCl-UCl₃-ThCl₄ molten salt mixtures at 500°C. Uniformity of the deposits was verified using scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDXS). Time to pass a fixed amount of electric charge through the cell was correlated with concentrations of UCl₃ and ThCl₄ in the salt mixtures. As expected, the deposition time was inversely proportional to actinide concentration in the salt. The actinides could be stripped and re-deposited multiple times on a given Pt-coated coupon with repeatable time results. This method shows great promise for simultaneously measuring concentrations of multiple actinides with very close electrochemical reduction potentials. It thus offers potential functionality beyond what is possible with only electrochemical methods such as cyclic or normal pulse voltammetry.