Uranium tetrafluoride production

Since a single furnace is used for three dryway operations, calcination, hydrogen reduction and hydrofluorination, the transfer of solids is minimized. The initial charging of trays and loading these into the furnace is relatively free from dust hazard since the ammonium di-uranate feed material is damp. Special precautions are needed, however, for removal of the final uranium tetrafluoride product from the trays, since it is a dry dusty powder and tends to adhere to the trays to some extent. This operation is therefore carried out in a small glove box , i.e. in a sealed and vented... 

Hawthorn, E., Shortis, L.R and Lloyd, J.E., Fluidised solids drying process for production of uranium tetrafluoride, Trans. Inst. Chem. Engrs., 38 (1960) 197-215. 

Mantz, E., Production of Uranium Tetrafluoride and Uranium Metal, USAEC Report NCLO 1068, U.S. Atomic... 

Uranium Tetrafluoride, Uranous Fluoride, UF, is the chief product obtained when the metal is acted upon by fluorine. It may be prepared by the action of hydrogen fluoride on urano-uranic oxide or on uranous oxide or by reduction of a solution of uranyl fluoride with stannous chloride. It is also formed with uranium hexafluoride when the pentachloride is acted upon by fluorine at —40° C. thus ... 

Uranium tetrafluoride is a key intermediate in the production of thermal reactor fuels. It may be prepared directly from uranyl solutions by reduction of the U to U and addition of HF to precipitate UF4. A number of processes have been developed to produce UF4 by this wet route, which may be used to produce UF4 at the ore processing site. These employ iron, S02/Cu or electrolysis for the reduction step, the latter being preferred since it introduces no contaminants into the solution. The reduction of u in various media has been studied to assess the effect of complexation on the reduction reaction. The standard potential for the reduction of U02 to in 1 M HCIO4 has been given as +0.32 V. " The overall formation constants of fluoride complexes in 1 M NaCl were found to be log 82= 13.12, logj83 = 17.46 and log/84 = 21.8. Although wet processes have been developed as a short cut to UF4, the most widely used process at present involves dry processing. 

A. A. Jonke, N. M. Levitz, and E. J. Petkus, Fluidized-Bed Process for the Production of Uranium Tetrafluoride (Green Salt) From Uranyl Nitrate, Interim Report, ANL-5363 (December 30, 1954). 

Figure 7—38. Direct decomposition of uranium fluorides in atmospheric-pressure thermal plasma. Energy cost of the process at different process and quenching modes (1) absolute quenching of uranium production from hexafluoride (UFe) (2) ideal quenching of uranium production from hexafluoride (UFo) (3) ideal quenching of (UF3) production from tetraflu-oride (UF4) (4) ideal quenching of uranium tetrafluoride (UF4) production from (UF5) (5) ideal quenching of (UF5) production from hexafluoride (UFe).

Electrochemical reactors are usually batch operated. Obviously energy is supplied in the form of electricity. In some cases, such as uranium production, the product can be prepared by both electrochemical and other methods, but other methods may then prove to be more economic in practice. Uranium, for example, is manufactured by heating a mixture of magnesium and uranium tetrafluoride ... 

The recently developed Excer process of the U.S.A.E.C. aims to extract uranium from low-grade ore, purify it up to nuclear specification and convert to uranium tetrafluoride ready for metal production. The process is shown in Fig. 3.15 and is based first upon a sulphuric acid leach of the ore and anion absorption of uranium from the pulp. Elution is then by 2M sulphuric acid to give a solution containing about 10 to 20 g U/1. The uranyl sulphate is then reduced by metallic iron to uranous sulphate, diluted to an acidity of 0-5M and a second cycle of anion-exchange carried out. Absorption behaves similarly to that with uranyl ion, but ferrous ion is not... 

The static bed dryway process for the production of uranium tetra-fluoride involves less advanced chemical engineering techniques than, for example, fluidization. With careful design and correctly optimized operating conditions, it has been difficult to supplant, however, on purely economic grounds. Many thousands of tons of uranium tetrafluoride have been produced by this method since the Second World War in the United Kingdom and the United States alone. 

The uranium tetrafluoride is cooled in a hydrogen atmosphere before opening the furnace, to prevent atmospheric oxidation. The product has a packing density of 2-2 g/cm and contains less than 2 per cent of uranyl fluoride (UO2F2) or uranium dioxide impurities. 

A residence time of 4-8 hr in the reactor leaves only about 1 to 2 per cent of the uranium dioxide unconverted. A temperature gradient in the top, middle and lower beds of 400°C, 500 C, and 600°C respectively gives the best results. The overall excess of hydrogen fluoride is of the order of 100 per cent, and this is recovered as a concentrated solution. The tetrafluoride product has a packing density of about 3-6 from dioxide feed material having a packing density of 4-4. 

Jonke, a. a. and Levitz, N. M. Development of a Fluidized Bed Process for the Production of Uranium Tetrafluoride. Progress in Nuclear Energy, Ser. Ill, Process Chemistry, vol. 2, p. 122. Pergamon Press (1958). 

Levitz, N. M. A fluidized bed process for the production of uranium tetrafluoride. Chem. Engng. Progr. 53, No. 4, 199 (April 1957). 

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