Uranium tetrafluoride production at pilot scale using a mercury electrode cell

Abstract

This work shows the technical feasibility to obtain uranium tetrafluoride through an electrochemical mercury cell. This technique represents a custom scaling-up methodology from our previous studies to obtain UF4 using the dropping mercury electrode cell. The UF4 products were obtained from natural UF6 gas, which was hydrolyzed to obtain a 50 g/L UO2F2 solution. The electrolysis cell was made using a mercury reservoir, to reach UF4 production rates of 1 Kg UF4/day. This custom design allowed a stable UF4 production thanks to the mercury cathode, which do not permit the accumulation of solid products in its surface. The cell was tested using current densities from 5.000 to 17.500 A/m2 and temperatures from 25 to 65 °C. The maximum current efficiency achieved under these conditions was 80%. The UF4 powders possessed spherical morphology, with diameters between 20 and 80 μm. Compared to the SnCl2 precipitation, this process did not allow preferential growth of the precipitates. This improved the compaction of the UF4 – Mg powders mixtures, with densities between 3.0 and 3.5 g/cm3. The purity of the UF4 products was over 98%.

Keywords

• Uranium tetrafluoride
• Electrolysis
• Mercury electrode