A mesh-type assembly and stirrer assembly were developed to improve the performance of liquid cadmium cathodes for the electrodeposition of U and Ce from LiCl-KCl molten salt at 773 K. The thermodynamic basis for electrodepositing U and Ce was established through the calculation of equilibrium potentials and cyclic voltammograms, while also examining the co-deposition of Li. Thereafter, U and Ce electrodeposition was performed by galvanostatic electrolysis, and the current efficiency was determined. It was found that both assemblies effectively hampered the growth of U dendrites and Ce-Cd dendritic alloys. However, the utilization of the mesh-type assembly resulted in a greater current efficiency for U, with the maximum deposited amount attaining 7.7 wt% U/Cd without causing U dendrites formation. In contrast, the current efficiency for Ce was enhanced after using the stirrer assembly due to an improved diffusion flux of Ce ions. Finally, cathode deposits were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction, which revealed that disrupted fine U dendrites were randomly scattered in the Cd bulk, and that the CeCd11 dendritic alloys were also damaged, leading to an increased atomic ratio of Ce to Cd at the Cd bottom.
Pyroprocessing of spent nuclear fuels uses the LiCl–KCl molten salt as an electrolyte, which contains dissolved fission products and can be very corrosive to the structural alloys. This study investigates the effect of EuCl3 on the corrosion behavior of four commercial alloys: Haynes C276, Inconel 600, Incoloy 800, and 316L stainless steel. Static immersion tests and electrochemical polarization measurements were carried out in molten LiCl–KCl salts with and without EuCl3 additives at 500°C. The results showed that the presence of EuCl3 caused the severe dissolution of Ni, Fe, and Cr from alloys, accompanied by the cathodic reduction of EuCl3 to EuCl2. All alloys suffered from intergranular dissolution and cracking, with additional pitting and void attacks for Incoloy 800 and 316L stainless steel.
ABSRACT To extract lutetium (Lu) from LiCl-KCl fused salt, the electrode reaction mechanisms of Lu on W and liquid Zn electrodes were systematically investigated using a series of electrochemical methods such as cycle voltammetry (CV), square wave voltammetry (SWV), reverse chronopotentiometry (RCP), etc. The diffusion coefficient and diffusion activation energy of Lu(III) in LiCl-KCl fused salt were measured by CV. The results of CV, SWV and open circuit chronopotentiometry (OCP) confirmed that seven Lu-Zn intermetallic compounds were formed when Lu was deposited on Zn film electrode. Kinetic data of Lu(III)/Lu on W and liquid Zn electrodes, i.e., exchange current density, charge transfer resistance and reaction activation energy, were determined and compared by linear polarization (LP) at 773-848 K. Furthermore, the thermodynamic date such as equilibrium potential and formation Gibbs free energy of Lu-Zn alloys were also calculated and analyzed according to the OCP. The results demonstrate that the liquid Zn electrode is conducive to extract Lu from LiCl-KCl fused salt. Thus, constant potential electrolysis (CPE) was conducted at -1.58 V for 9 h on liquid Zn cathode to extract Lu from fused salt. The electrolytic product was composed of Zn and LuZn12 phases checked by XRD and SEM-EDS. The extraction rate of Lu is reached up to 98.37% based on the concentration change of Lu(III) in fused salt, which confirmed the feasibility to extract Lu employing liquid Zn electrode.
危险品化学品经营许可证（带存储）