Electrochemical behaviour of plutonium ion in LiCl–KCl eutectic melts

This work presents a study on the electrochemical properties of PuCl3 in a molten LiCl–KCl eutectic, in a temperature range of 733–833 K. Transient electrochemical techniques, such as cyclic voltammetry and chronopotentiometry, on inert metallic tungsten and molybdenum working electrodes have been used in order to investigate the reduction mechanism and transport parameters. The results show that Pu3+ is reduced to Pu metal by a single step mechanism and that the diffusion coefficient of Pu3+ ion is DPu3+∼1.6×10−5 cm2/s at 733 K. In addition the standard potential (−2.796 V at 733 K vs. a Cl2 | Cl− reference electrode) and Gibbs energy of formation for the Pu(III)/Pu(0) system have been measured and compared to thermodynamic data in order to estimate the activity coefficient of Pu3+ in the molten LiCl–KCl eutectic.