Recent advances in uranium ore processing

The paper reviews the major technological improvements in uranium ore processing in recent years. Semi-autogenous grinding, where applicable, has proven to be a significant innovation that has resulted in lower capital and operating costs. Preconcentration of ores has been successful only in a few instances. Pressure leaching has been used in treating ores with a uranium content in the range of 0.5 to 2.5% and ores containing refractory uranium minerals. In situ, in place and heap leaching techniques have found favour in the treatment of very low-grade porous or fissured ores. Uranium plants have been turning to high-capacity thickeners and horizontal belt filters in an effort to improve the efficiency of solid-liquid separation and to reduce capital and operating costs. Ion exchange and solvent extraction processes have received much attention, probably more than any other unit operation in uranium ore processing. Continuous ion exchange (CIX), in its various forms, is the most recent innovation in ion exchange technology. New developments in the design of mixer-settlers for solvent extracton have been directed to reducing the shear in mixers and to reduce the area required for phase separation in order to reduce the size of the plant and the solvent inventory. Regarding precipitation, there has been a move from the use of ammonia and nitrates to strong sulphuric acid elution and stripping to reduce environmental problems. The technology for recovering uranium from wet-process phosphoric acid and from copper heap-leaching solutions continues to be improved. Research is also being done on the recovery of uranium from seawater and from coal, although suitable technology may not be available for several decades