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, at a temperature range of 733-833 K. Transient electrochemical techniques, such as cyclic voltammetry and chrono-potentiometry, 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+ ∼2.10-5 cm2/s at 733 K. In addition the standard potential (-2796 V at 733 and vs. Cl2/Cl- reference electrode) and free enthalpy 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. (author)