Electrochemical behaviour of americium ions in LiCl-KCl eutectic melt

This work presents a study on the electrochemical properties of AmCl3 in a molten LiCl-KCI eutectic, at a temperature rang e of 733-833 K. Transient electrochemical techniques, such as cyclic voltammetry and chronopotentiometry, on inert metallic tungsten working electrode have been used to investigate the reduction mechanism of Am3+ ions. The results show that Am3+ is reduced to Am metal by a two-step mechanism corresponding to the Am3+/Am2+ and Am2+/Am-0 transitions. Formal standard potentials of Am3+/Am2+ (E-Am3+/Am2+(0') =-2.695 V versus Cl-2/Cl- at 733 K) and Am2+/Am-0 (EA(M2+/AM0)(0') =-2.911 V versus Cl-2/Cl- at 733 K) redox couples as well as diffusion coefficients of Am3+ and Am2+ (2.4 x 10(-5) and 1.15 x 10(-5) cm(2) s(-1) at 733 K, respectively) have been calculated at three different temperatures. In the studied range of temperature, the DAM3+/DAM2+ ratio was found to be around 2. In addition, thermodynamic proper-ties have been calculated for Am3+ (Delta(infinity)(GAMCl3) =-933.7 + 0.152T) and Am2+ (Delta(infinity)(GAMCl2) =-623.9 + 0.085T) and compared to thermodynamic reference data in order to estimate activity coefficients (Am3+ =4.7 x 10(-3) and Am2+ =2.7 x 10(-2) at 733 K) in the molten LiCl-KCl eutectic. (c) 2005 Elsevier Ltd. All rights reserved.