Electrochemical Behaviors Of Samarium, Erbium And Thorium In LiCl-KCl Molten Salts

The so-called partitioning and transmutation (P&T) strategy is one of the alternatives intended to reduce the inventory of highly radioactive long half-lived minor actinides (MA) and fission products (FP) in nuclear wastes. For the P&T based double-strata fuel cycle, highly efficient separations of actinides (An) over lanthanides (Ln) are always needed, otherwise the flagrant large neutron absorption cross-section of Ln will reduce the transmutation efficiency. However, due to the chemical similarities between Ln and An, successful separation of An from Ln is still one of the most challenging tasks in the spent fuel reprocessing. Pyrochemical reprocessing of nuclear fuels using molten salts has been considered to be a promising alternative to the traditional hydrometallurgical reprocessing technologies. This work presents an electrochemical study of the typical lanthanides and actinides in the LiCl-KCl molten salt to explore the appropriate electrode and deposition potentials for extraction.As the typical rare earth element, samarium (Sm) is one of the most abundant fission products and poison element for neutron, which has been extensively concerned in nuclear reactor physics and molten salt electrochemistry. Erbium(Er) has a large resonance in its thermal neutron absorption cross, which is absolutely troublesome for the future nuclear fuel cycle. In addition, erbium-dropped alloys have been widely applied as advanced functional materials in numerous industrial fields due to their specific functional properties. The typical Ans element, thorium, has been chosen as an analogue for uranium (U) and plutonium (Pu) on the electrochemistry study due to the chemical similarities between Th and U/Pu and the relatively lower radioactivity and toxicity of Th. Therefore, this paper choose these three element as the research object。 This paper mainly focused on the three part of investigation as following:1. Cyclic voltammetry, square wave voltammetry and chronopotentiometry were employed to investigate the reduction processes of Sm3+, Er3+and Th4+on the inert tungsten (W) or molybdenum (Mo) and active aluminum (Al) electrodes at773K. Furthermore, the diffusion coefficients of these elements in the molten salt were also calculated.2. The co-reduction behaviors of Al3+with Sm3+, Er3+and Th4+and formation mechanism of their alloys were also explored in various concentrations of the melts on the inert electrode by applying the transient technology of cyclic voltammetry, square wave voltammetry, chronopotentiometry and open circuit chronopotentiometry. A series of electrochemical signals were obtained corresponding to the Ln-Al/Th-Al alloys.3. Potentiostatic and gavanostastic electrolysis were both conducted at varies potentials and currents on an Al electrode to prepare the Ln-Al/Th-Al alloy samples. The obtained deposits were also characterized by SEM-EDS and XRD.