Uranium trioxide conversion

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

Smiley, S. H. and Brater, D. C. Conversion of Uranium Trioxide to Uranium Tetrafluoride in vibrating tray reactors. Current Commission Methods for Producing UOs. UFi and UFs. U.S.A.E.C. Report, TID-5295 (1956). 

With regard to UO2 conversion supply, Cameco s plant is by far the largest supplier, with a licensed annual capacity of 2800 tU. In addition, smaller plants exist to meet the local needs in India, Argentina, and Romania. Cameco Corporation owns and operates ma-nium refinery and conversion facilities located respectively at Blind River and Port Hope. The Blind River plant refines natural uranium concentrates (U3O8) into uranium trioxide (UO3) and was commissioned in 1983. The intermediate product is shipped to the Port Hope plant (commissioned 1984) where further processing produces natural UFg. 

At a conversion facility, uranium trioxide is converted into a specific uranium end product according to the nuclear power reactor class. Actually, there are three uranium compounds used in nuclearpower reactors ... 

Weiss and Downs described the use of vanadium pentoxide for the catalytic oxidation of toluene and naphthalene. Subsequently, Graver suggested a mixed oxide catalyst derived from uranium oxide and molybdenum trioxide in molar ratios ranging from 3-13 1. Copper oxide was also suggested as a possible promoter. When using the vanadium pentoxide catalyst, benzoic acid was the main product at temperatures below 400°C, with some benzaldehyde formed at higher temperatures. Selectivity was only about 50% at 5% conversion. 

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