Separation of plutonium from lanthanum by electrolysis in LiCl–KCl onto molten bismuth electrode

Abstract This work presents a study on the electroseparation of plutonium from lanthanum using molten bismuth electrodes in LiCl–KCl eutectic at 733 K. The reduction potentials of Pu 3+ and La 3+ ions were measured on a Bi thin film electrode using cyclic voltammetry (CV). A difference between the peak potentials for the formation of PuBi 2 and LaBi 2 of approximately 100 mV was found. Separation tests were then carried out using different current densities and salt phase compositions between a plutonium rod anode and an unstirred molten Bi cathode in order to evaluate the efficiency of an electrolytic separation process. At a current density of 12 mA/cm 2 /wt% (Pu 3+ ), only Pu 3+ ions are reduced into the molten Bi electrode, leaving La 3+ ions in the salt melt. Similar results were found at two different Pu/La concentration ratios ([Pu]/[La] = 4 and 10). At a current density of 26 mA/cm 2 /wt% (Pu 3+ ), co-reduction of Pu and La was observed as expected by the large negative potential of the Bi cathode during the separation test.