Uranium tetrafluoride production at pilot scale using a mercury electrode cell

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 ℃. The maximum current efficiency achieved under these conditions was 80%. The UF₄ powders possessed spherical morphology, with diameters between 20 and 80 ㎛. 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%.