A milling and conversion pilot plant at Ningyo Toge, Japan

Operation of the milling and conversion pilot plant using a Power Reactor and Nuclear Fuel Development Corporation (PNC) process started in March 1982. The plant which has a producing capacity of 290 t uranium hexafluoride (approximately 200 t uranium per year) is now operating satisfactorily. It has been considerably improved on the basis of experience gained from continuous operation. The raw materials are the pregnant solution in the form of uranyl sulphate solution from heap leaching and/or yellow cake followed by dissolution into sulphuric acid solution. Tri-n-octylamine (TNOA) is used as the extraction reagent in the solvent extraction section. Uranium is transferred in the form of solution to the uranium tetrafluoride precipitation section. In the conventional refining process, yellow cake is dissolved in nitric acid solution, and uranium in the solution is extracted by tributyl phosphate (TBP). In all sections, except for the TBP extraction section, uranium is transferred in the form of solid. The PNC process differs considerably from the conventional refining process. In the conventional process, the impurities in the nitric acid solution dissolved yellow cake are nearly removed at the TBP extraction section; in the PNC process, the specific elements such as molybdenum are not removed by amine extraction however, they are, in particular molybdenum, almost removed at the uranium tetrafluoride precipitation section. Therefore, uranium tetrafluoride produced by the PNC process bears a comparison with that produced by the conventional process. Ninety tonnes of uranium hexafluoride (approximately 60 t uranium) were produced in 1984 in addition to renewing or improving the uranium tetrafluoride precipitation vessel and other equipment. (author). 1 ref., 4 figs, 2 tabs