Possible Electrochemical Imitators for AmCl2 and CmCl3 in the Molten LiCl–KCl Eutectic

Published data are examined, and the choice of possible imitators for studying the electrochemical partitioning of americium and curium in molten salts is substantiated. Since the direct study of americium and curium is difficult because of their high radioactivity, the corresponding lanthanides (europium and gadolinium) are proposed for the use as imitators. The structures of their external electron shells are very similar, and the oxidation levels are also similar. The electrochemical partitioning in molten salts is concluded to be most promising, since similar media make it possible to conduct the process at elevated temperatures and they are more resistant to radiation than aqueous and organic solvents. The calculation results show that AmCl 3 is easily reduced to AmCl 2 at elevated temperatures in chloride melts. The conventional standard potentials of Am 2+ /Am and Cm 3+ /Cm in the molten LiCl–KCl eutectic according to the data of independent authors are presented. In the melts based on the LiCl–KCl eutectic, the electrode potentials of americium and curium are found to nearly coincide; hence, the direct electrochemical partitioning of these elements is theoretically impossible. The electroreduction potentials of the Eu/Gd couple are additionally estimated more precisely. The data obtained show that the conventional standard potentials of Eu 2+ /Eu significantly differ from those of Gd 3+ /Gd, unlike the pair of Am 2+ /Am and Cm 3+ /Cm, because of which europium and gadolinium cannot serve as imitators for studying the partitioning of americium and curium. In addition, the Eu 2+ /Eu couple cannot be used in the LiCl–KCl melt, because the reduction potential of europium is more negative than the reduction potential of lithium. The conventional electroreduction potentials of Mg, Sc, Sr, Ba, Pr, and Nd in the LiCl–KCl melt at different temperatures are examined. The data obtained show that, among the chosen elements, the potentials of magnesium are closest to the potentials of americium and the scandium potentials are close to those of curium, which makes them more preferable for studying americium and curium partitioning in the LiCl–KCl melt.