Separation of Uranium and Zirconium in Alkali Chloride Melts Using Liquid Metal Cathodes

Abstract

Cyclic voltammetry and cathodic polarization measurements were employed to study zirconium and uranium electrochemical behavior in LiCl–KCl eutectic based melts on solid (tungsten) and liquid (zinc, gallium, indium, Gz–Zn eutectic alloy) working electrodes. Deposition potentials of zirconium and uranium were determined. Ga–Zn alloy showed a difference of ca. 0.9 V in U and Zr deposition potentials. Thermodynamically achievable Zr/U separation factor in a “LiCl–KCl salt melt – liquid Ga–Zn alloy” system was experimentally determined.

Reduction of ZrO2 during SNF Pyrochemical Reprocessing

“…This assumption is confirmed, firstly, by the data of the atomic emission analysis of the samples, according to which the zirconium content in the melt reaches 0.08-0.09 wt% (0.13-0.15 wt% in terms of ZrO 2 ), and, secondly, by the experimental data related to the potential of zirconium electrodeposition from the LiCl-KCl-ZrCl 4 melts, which is 1.0-1.2 V more positive than the potential for the lithium electroreduction. [31][32][33][34] The dissolution of ZrO 2 is facilitated by the presence of oxygen ions in the chloride melt. 35,36 At the same time, a clear inflection is seen in the dependence of the peak current density on the square root of the potential sweep rate (Fig.…”

Application of Low Melting Metals for Separation of Uranium and Zirconium in a “Fused Chloride—Liquid Alloy” System

“…Previous studies involving cyclic and differential pulse voltammetry measurements in zirconium and uranium chloride containing melts showed that the nature of the working electrode had the effect on the potential at which uranium and zirconium ions were reduced to the metallic state [17,18,22]. This work was aimed at more in depth studying the electroreduction processes by galvanostatic polarization technique.…”

“…Material of the cathode can have a noticeable effect on the deposition potential. Cyclic and differential pulse voltammetry experiments showed that using gallium, indium or zinc electrodes allowed shifting zirconium deposition potential to more positive values [17,18]. Maximum positive shift of the potential, ca.…”

“…Potentiostatic electrolysis on a zinc cathode at −(1.9-2.2) V vs. 2Cl − /Cl 2 reference couple yielded Zn 22 Zr phase [20]. Preliminary studies showed that cathodic polarization measurements could provide a valuable insight into zirconium and uranium deposition behavior on liquid metal cathodes [18,19]. Analysis of the polarization curves allowed determining the potentials at which the cathodic reactions took place, including U 4+ → U 3+ , U 3+ → U 0 and Zr n+ → Zr 0 reduction and evaluating applicability of various materials for separation of these two metals.…”

“…Electrochemistry of uranium on various liquid metal electrodes in chloride melts was studied [14][15][16] but substantially less attention was paid to reduction of zirconium chloro-species on liquid metals. Cyclic and differential pulse voltammetry was previously employed for assessing zirconium deposition on various liquid cathodes including gallium, indium and zinc [17][18][19]. A positive shift of zirconium deposition potential was observed on liquid "active" electrodes compare to an "inert" solid tungsten electrode due to formation of intermetallic compounds.…”