URANIUM IX - PAST, PRESENT AND FUTURE

摘要

Ion exchange has played an important role in nuclear power generation. The development of resins in particular was spurred by the challenges posed by the recovery of uranium from leach liquors on the one hand and the purification of water used for reactor cooling on the other. The application of ion exchange resins for the separation, concentration and purification of uranium leach liquors is the subject of this paper. Major developments of this technology, which has come in waves in response to the fluctuating prices and demand for uranium, are highlighted.The first wave of uranium mining activity occurred in the nineteen fifties, underpinned by military applications and interest in nuclear power. These plants used strong base polystyrene-divinylbenzene gel resins in fixed bed systems with nitrate based elution. The uptake and construction of new nuclear power plants in the sixties was slower than projected and a decline in uranium demand ensued. This was reversed by the oil crisis in the seventies which brought about increased uranium production and a series of innovations to the uranium hydrometallurgical flowsheet, including the coupled ion exchange/solvent extraction or Bufflex/Eluex processes, using sulfate elution, and the adoption of fluidized continuous ion exchange to treat unclarified liquors. Two decades of sustained low uranium prices, reduced demand and draw down of military inventories, resulted in virtually no new uranium developments. Second generation plants, which commenced operation in the eighties treating higher grade ores, tended to use solvent extraction as the preferred separation technology. Ion exchange has maintained its relevance with technologies such as resin-in-pulp and in-situ recovery processes that are applied to lower grade deposits. Ion exchange has been adopted by three of the most recently built tank leaching operations, Langer Heinrich, Kayelekera and Husab, and continues to be used in all operating ISR projects in the USA, Kazakhstan and Australia. Looking to future innovations, this paper discusses the potential of ion exchange to address particular challenges and niche areas in uranium processing such as: The use of resins with functionalities other than conventional strong base for recovery of uranium from saline and phosphoric acid liquors; The use of ion exchange to facilitate reagent re-cycle; Improvements in elution to target more concentrated eluates; and Coupling ion exchange with other technologies.