Comparison of molten chloride and fluoride salts potentialities for An/Ln separation by electrodeposition

The objective of this paper is the comparison of molten fluoride and chloride salts potentialities for Am/Nd separation by electrodeposition on inert cathode, on a purely thermodynamic point of view. The molten LiF-CaF2 eutectic (77-23 mol.%, at 780 deg. C) was considered for this study. Cyclic voltammetry showed a one step Am(III)/Am reduction at a potential of ≅+0.5 V vs. Li+/Li. A potential difference of 290 mV between Am and Nd metallic deposition was estimated by square-wave voltammetry. This Am/Nd potential difference is more important than in molten chlorides (220 mV in the LiCl-KCl eutectic at 500 deg. C). Moreover in molten fluoride salt, the americium and neodymium (+II) oxidation state is not stable contrary to the molten chloride one where corrosion of deposited Am would be potential. However this larger potential difference in molten fluorides is quite balanced by the higher working temperature. (authors)