Electrode Reaction of Pu³⁺/Pu Couple in LiCl-KCl Eutectic Melts: Comparison of the Electrode Reaction at the Surface of Liquid Bi with That at a Solid Mo Electrode

Abstract

The electrode reaction of Pu³⁺/Pu couple at the interface between LiCl-KCl eutectic melt containing PuCl₃ and liquid Bi phase was investigated by cyclic voltammetry at 723, 773 and 823 K. For comparison, the system was also studied using a solid Mo electrode in place of the liquid Bi electrode. It was found that the electrode reaction of Pu³⁺/Pu couple at the Bi electrode was almost reversible. The redox potentials of Pu³⁺/Pu couple at the liquid Bi electrode in the LiCl-KCl eutectic melt containing 0.87 wt% PuCl₃ (0.0014 mole fraction) at 723, 773 and 823 K were observed to be more positive by 0.575, 0.572 and 0.566 V, respectively, than those at the Mo electrode. These differences in potential were thermodynamically analyzed by assuming a lowering of the activity of Pu in Bi phase according to the alloy formation of PuBi₂.