Electrochemistry of uranium in molten LiCl-LiF

Abstract

This work is focused on the electrochemical behaviour of uranium in molten eutectic LiCl-LiF (70-30 mol%) in the 550-650 °C temperature range. On tungsten electrode, U(III) ions were reduced in one step to U metal exchanging 3 electrons and oxidized also in one step to U(IV) exchanging one electron. Both systems were studied by cyclic and square wave voltammetries and chronopotentiometry. The reduction and oxidation mechanisms of U(III) ions were found to be diffusion controlled processes. The diffusion coefficient of U(III) was measured at different temperatures, and it followed an Arrhenius "type law". Apparent standard potentials were measured in chloride-fluoride (LiCl-LiF eutectic) and pure chloride media (LiC-KCl eutectic). The addition of fluoride ions into a chloride salt leads to the formation of more stable complexes reduced at more negative potentials. This shift of reduction potentials is more pronounced for the U(IV)/U(III) transition ( ~5 00 mV) than for the U(III)/U system ( ~1 00 mV).

Review—Fundamental Uranium Electrochemistry and Spectroscopy in Molten Salt Systems

“…2 and 1, respectively. 76 Figure 5, from Reddy et al 81 shows a cyclic voltammogram of UCl 3 in LiCl-KCl at 482 °C (755 K) with scan rates ranging from 50 mV s −1 to 500 mV s −1 . The electrode potential is given with respect to the Ag/AgCl reference electrode.…”

“…For the case of another actinide, americium, there were more oxidation states accessible (Am metal, Am(II), Am(III)) in the chloride solvents, whereas the fluoride solvents limited the number of oxidation states (Am metal, Am(III)). 76,116 Fewer stable oxidation states during molten salt electrolysis improves the quantitative recovery. 76 This is not seen in the case of U mixed molten salt chemistry, but it would simplify the U separation processes because it would increase the recovery of the metals.…”

Production of Metallic Titanium by Electrowinning in Molten Salts of Titanium Oxycarbide Anode

“…All RE potentials were referred to Cl 2 /Cl − redox couple. The conversion was obtained by graphical estimation of the potential at zero current in the linear variation region during the positive scan of voltammograms, as shown in reference [19].…”

Potential Application of Ionic Liquids for Electrodeposition of the Material Targets for Production of Diagnostic Radioisotopes

“…therein. For instance, recent publication of Geran et al [ 134 ] delivered the information on the electrochemical properties of uranium in molten LiCl-LiF salts. In this context the structure of obtained uranium films plays a minor role.…”