TRANSFER KINETICS OF METALS FROM MOLTEN FISSION-PRODUCT CHLORIDE TO LIQUID LEAD CATHODE DURING ELECTROLYSIS IN PYROMETALLURGICAL TREATMENT OF HIGHLY RADIOACTIVE-WASTE

It is sought to describe the interphase transfer kinetics governing th e electrolytic reduction of chloride salt mixtures in the process perf ormed for the purpose of recovering alkali, alkaline earth and rare ea rth metals from the salt mixture containing fission products generated during pyrometallurgical processing of highly radioactive waste from the Purer process of spent fuel. Data for analyzing the two-phase tran sfer kinetics of the metals of interest are acquired on simulated chlo ride mixtures submitted to experimental electrolysis in a system compr ising anode immersed in molten salt mixture and cathode of liquid lead . Approximating the concentrations of individual metals remaining in t he mixture as exponential functions of the duration of electrolysis, t he apparent overall transfer coefficients of the metals in reductive r eaction are estimated to range from 1.5x10(-6) to 3.8x10(-5) m/s. The metal ions prove to rank in descending order of transfer coefficient: Eu3+>Ba2+>Sr2+>Na+>Li+>K+>Cs+, thus indicating the likely effect of io nic valence influencing the interphanse transfer of metals.