Electroseparation of Actinides from Lanthanides on Solid Aluminum Electrode in LiCl-KCl Eutectic Melts

This work presents a study on the electrochemical behavior of actinides and Pu) and lanthanides and Nd) onto solid aluminum cathodes in a molten LiCl-KCl eutectic at 733 K. Cyclic voltammetry of these elements onto Al working electrode is carried out to estimate the reduction potentials of An and Ln and to predict the efficiency of an An/Ln separation by electrolysis. Results show that the reduction of and ions leads to the formation of An-Al or Ln-Al surface alloys. Moreover, the difference in reduction potentials between An and Ln elements was found to be larger than on the classical molten cadmium or bismuth electrodes. Pu/Nd and Am/Nd electroseparations were carried out using Al foam as cathode and a plutonium rod as anode. Efficient and faradaic reduction of actinides was achieved at a cathodic potential preventing Nd coreduction. After electrolysis, a compact and adherent deposit covered the cathode surface, and scanning electron microscopy, energy-dispersive X-ray analysis of the deposit indicated the existence of or mixed Am-Pu-Al alloys. Analysis of the dissolved Al cathodes, after electrolytic separation of Am from Nd, showed that 536 mg of An (94% of the total Am present in the initial salt phase) had been deposited compared to less than 3 mg Nd. This work represents a breakthrough in the selective partitioning of An by electrorefining methods. © 2005 The Electrochemical Society. All rights reserved.