Uranium calcination

The objectives of the uranium calcination development program were to ... 

Test the performance of a rectangular uranium calcination vessel. 

Behavior of Technetium and Ruthenium A pilot plant test was conducted to study the behavior of technetium and ruthenium in the uranium calcination process. The U0- product from these tests was used i subsequent fluorination studies. The UNH feed was spiked with xc (as ammonium pertechnetate) and nonradioac-tive ruthenium (as ruthenium nitrate), and then denitrated under normal run conditions. As expected, most of the technetium was found in the UO product as technetium oxide. Over half of the ruthenium (RuO )° was volatilized and found in the condensate from the off-gas. 

U02(C02) 3. The pregnant solution is concentrated and purified by ion exchange or solvent extraction, yielding a stripping solution of ca 50 kg/m U Og. Uranium is then precipitated chemically. Pure U Og is obtained by calcination (see Uraniumand URANIUM COMPOUNDS). 

Oxides and hydroxides Bauxite laterites copper oxide ores uranium ores zinc ores and calcines manganese ores and nodules... 

Solids in contact with fluids may be catalysts or they may be reactants as in combustion or calcination or coal liquefaction or uranium chlorination, etc. 

Spectral parameters of the structured green luminescence (Fig. 4.4d) are absolutely similar to those of luminescence in fluorite after thermal treatment (Tarashchan 1978). Principally, during the calcination of the sedimentary phosphates new mineralogical phases, including fluorite, may be formed. Taking these data into accoimt, it is possible to conclude that after thermal treatment uranium is concentrated in the fluorite lattice in the form of... 

Alkaline leach mills will use NaOH for final product recovery (in the form of sodium uranate, Na2U207). Often these uranium ore concentrates (yellowcake) are transformed into U3Os by drying at 200°C to remove water and calcining, that is, heating until decomposition. 

The precipitate is filtered and then calcined at 600 °C to yield high-grade U3Og. Alternatively, stripping with a more dilute solution of ammonium carbonate allows the uranium to remain in solution in the strip liquor and to be precipitated subsequently as U042H20 by the addition of hydrogen peroxide.130... 

Ammonia is used to precipitate the final uranium concentrate salt (yellowcake) prior to drying or calcination. It is generally economically preferred over sodium hydroxide or hydrogen peroxide57. 

Co-extraction of Np and Pu The waste from the uranium extraction battery is adjusted to 5 M LiNO and then passed through an IRA-400 column at a high flow rate (30 L/h). The americium is not sorbed. Neptunium and plutonium are stripped by a dilute nitric acid solution and precipitated as a hydroxide, and calcined to yield mixture of oxides. 

Conversion to Uranium Hexafluoride. The calcined U03 is reduced to U02 with hydrogen, then converted first to UF4 with hydrogen fluoride and finally to UF6 using fluorine. These steps usually are carried out in fluidized-bed reactors, but the conversion to UF4 sometimes is done in a stirred trough reactor.34... 

Finally, some DOE sites also have stored hexavalent uranium fluoride (UFs). The approach to stabilize this compound is to calcine it to form stable uranium oxide. There is no study reported in the literature on treatment of fluorides using a CBPC matrix, but considering that fluroapatites are stable minerals, they should be applicable to stabilization of actinide compounds. 

In a much earlier patent, the removal of organics from exhaust gases by oxidation over a supported uranium oxide catalyst was reported by Hofer and Anderson [39]. The catalyst was 4% U3O8 supported on alumina spheres. The authors used the incipient wetness technique to impregnate alumina with uranyl nitrate solution. In this case the catalyst precursors were calcined at 700°C for 3 h to decompose the uranium salt. The use of other uranium compounds as starting materials was mentioned and these included uranyl acetate, uranium ammonium carbonate and uranyl chloride. The alumina-supported catalyst had a surface area of ca 400m g and further added components, such as copper, chromium and iron, were highlighted as efficient additives to increase activity. 

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