Development of Processes for the Solubilization of Uranium from Waste Leach Residue

摘要

Two processes, capable of solubilizing enriched uranium from refractory leach residue solids generated at the Y-12 processing facility, have been developed and tested on a laboratory scale. Both processes take advantage of a sinter step, followed by leaching with nitric acid. One process, designated the Calsinter method, uses a source of CaO as a sintering media to react with refractory metal silicates and provide subsequent solubilization of uranium from the sinter matrix by an acid leach. The sintering step in this case requires a temperature of approximately 1200 exp 0 C. The second process employs fluoride in the sinter media to free the uranium from any refractory silicate, thus rendering it soluble in subsequent acid leaching. A sintering temperature of 700 to 900 exp 0 C is used in this process. Both methods are capable of solubilizing 90 to 99% of the uranium remaining in the leach residue which, after current solids leaching treatment at the Y-12 Plant, still contains 1 to 3% enriched uranium. Uranium concentrations in final leached residues (after the sinter/leach techniques) have been reduced to as low as 500 to 1000 mu g U/g. Physical and chemical characterizations of the Y-12 leach residue are discussed. Inconel trays or high-magnesia refractory material have been shown to be potential materials of containment for the Calsinter step. Sinter reaction and leaching parameters are presented and discussed. 9 tables. (ERA citation 09:018177)