Scoping studies on recovery of uranium from man-made ores

The potential for recovery of enriched uranium from spent nuclear fuel which has been consolidated into a nuclear waste form was explored in the studies reported here. The waste form of interest is iron-enriched basalt (IEB), a silicate-based, fused-cast ceramic. The IEB samples, or man-made uranium ores (MMUO), are in two different mineralogical forms. From the results of the scoping tests, it is suggested that there is little difference in the two samples in terms of recovery of uranium. It is also suggested that the ore can be opened and the uranium recovered by either a sodium hydroxide fusion or sulfuric acid leaching. The sodium hydroxide fusion method gave the best recovery but requires the most energy and has the greatest operational complexity. The sulfuric acid/hydrogen peroxide leach gave intermediate results but is easier to handle. The sodium carbonate/sodium bicarbonate/hydrogen peroxide gave unacceptable recovery. Improved uranium recovery using the sodium hydroxide fusion method could probably be achieved by using a strong oxidant such as sodium peroxide or sodium nitrate in the fusion step. The fusion method relied on air oxidation of the uranium and was controlled by either the rate of dissolution of oxygen in the melt or by diffusion of the dissolved oxygen. Increasing the oxygen overpressure may offer an alternative to air oxidation. The recommendation made in regard to the oxidants is that other oxidants be tested, in terms of species, as well as concentration. The beneficial effect of increasing the sodium hydroxide to ore ratio is evident from the data. The use of sodium hydroxide beyond that required for fusion at 8000C should be studied. Sulfuric acid leaching could probably be improved by control of acid and oxidant concentrations and by reducing the particle size