Carbon uranium processing

AUC [Ammonium uranyl carbonate] A process for converting uranium hexafluoride into uranium dioxide for use as a nuclear reactor fuel. The hexafluoride vapor, together with carbon dioxide and ammonia, are passed into aqueous ammonium carbonate at 70°C, precipitating ammonium uranyl carbonate ... 

Molybdenum can also be recovered economically from some uranium leach liquors, particularly those of the USA. When uranium is stripped from amine extractants by solutions of sodium chloride, any molybdenum present remains in the organic phase, and can be subsequently recovered by being stripped into a solution of sodium carbonate. A process has been operated in which the strip liquor is acidified to a pH value of 4.5 and the molybdenum is reextracted into a solution of quaternary amine chloride in kerosene.218 The extracted metal is stripped into a solution containing sodium hydroxide and sodium chloride to produce liquors containing 30-40 g of molybdenum per litre, from which calcium molybdate can be precipitated by the addition of calcium chloride. 

Weak-base resins have been tested from time to time but have not found wide acceptance in the uranium industry, The main reason for this is that the major advantage of weak- over strong-base resins, viz. elution by neutralization, cannot be utilized in uranium processing since it is not possible for the weak-base resin to be converted to the free-base form without diuranate precipitating within the pores of the resin (unless a complexing agent such as carbonate is added to the eluate). In the presence of carbonate, uranium remains in solution as the uranyl carbonate anion, even in very alkaline solution, so is readily eluted from a weak-base resin in the free-base form. This eluate would then be treated as depicted in equations (105) and (106) for the recovery of uranium. Alternatively, weak-base resins can be eluted by ion-exchange mass action. 

Amine reagents also extract thorium from carbonate solutions and the use of a primary amine, RNH3C1, where R = C10 to Cl3 alkyl, as a 20% solution in kerosene allowed the concentrations of impurities in the extracted thorium to be reduced by factors of 33.8 for UVI, 111.4 for MoVI, 18.9 for Zrlv and 6167 for Mg11.177 The extracted thorium species was shown to be of the composition (RNH3)4Th(C03)4(H20)x. Di(tridecyl)amine has been used to extract thorium from barren uranium process liquors in the Blind River plant in Canada147 and flowsheets for the recovery of lanthanides, U03 and high-purity Th(S04)2 from the Elliot Lake area in Ontario using Primene/isodecanol have been described.178... 

Leaching with alkali always takes place at high temperatures, either under pressure (5 to 6 bar, 95 to 120°C) or at atmospheric pressure (75 to 80°C). The leaching agent used is sodium carbonate, sodium hydrogen carbonate or ammonium carbonate. Uranium(Vl) oxide is converted in this process into uranyl tricarbonato-complexes ... 

Ammonium uranyl carbonate (AUC) process This process was developed in the 1960 s in the Federal Republic of Germany. It comprises the simultaneous feeding of uranium(Vl) fluoride, carbon dioxide and ammonia into an aqueous ammonium carbonate solution at 70°C, whereupon tetra-ammonium tricarbonato-dioxo-uranate (ammonium uranyl carbonate) precipitates out ... 

A more constrained opportunity for nitrate bioremediation arose at the US-DoE Weldon Spring Site near St. Louis, Missouri. This site had been a uranium and thorium processing faciUty, and treatment of the metal had involved nitric acid. The wastestream, known as raffinate, was discharged to surface inpoundments and neutralized with lime to precipitate the metals. Two pits had nitrate levels that requited treatment before discharge, but heavy rains in 1993 threatened to cause the pits to overflow. Bioremediation by the addition of calcium acetate as a carbon source successfully treated more than 19 million liters of water at a reasonable cost (75). 

Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

Ion Excha.nge, The recovery of uranium from leach solutions using ion exchange is a very important process (42). The uranium(VI) is selectively adsorbed to an anion-exchange resin as either the anionic sulfato or carbonato complexes. In carbonate solutions, the uranyl species is thought to be the tris carbonato complex, U02(C03) 3 [24646-13-7] and from sulfate solutions the anion is likely to be U02(S0 , where nis ) [56959-61-6] or 2 [27190-85-8], The uranium is eluted from the resin with a salt or acid solution of 1 AfMCl or MNO (M = H", Na", The sulfate solution is... 

Solvent Extraction. Solvent extraction has widespread appHcation for uranium recovery from ores. In contrast to ion exchange, which is a batch process, solvent extraction can be operated in a continuous countercurrent-fiow manner. However, solvent extraction has a large disadvantage, owing to incomplete phase separation because of solubihty and the formation of emulsions. These effects, as well as solvent losses, result in financial losses and a potential pollution problem inherent in the disposal of spent leach solutions. For leach solutions with a concentration greater than 1 g U/L, solvent extraction is preferred. For low grade solutions with <1 g U/L and carbonate leach solutions, ion exchange is preferred (23). Solvent extraction has not proven economically useful for carbonate solutions. 

Chemical Precipitation. The product of the extraction processes, whether derived from acid or carbonate leach, is a purified uranium solution that may or may not have been upgraded by ion exchange or solvent extraction. The uranium ia such a solution is concentrated by precipitation and must be dried before shipment. Solutions resulting from carbonate leaching are usually precipitated directly from clarified leach Hquors with caustic soda without a concentration step, as shown ia equation 9. 

Ryon and Lowrie (U.S. AEC ORNL-3.381, 1960). Batch and continuous extraction of uranium from aqueous sulfate solutions into kerosine -t- amines, stripping of extract with aqueous sodium carbonate baffled vessels, turbine agitated. A detailed process study. 

Nuclear power reactors cause the transmutation of chemicals (uranium and plutonium) to fission products using neutrons as the catalyst to produce heat. Fossil furnaces use the chemical reaction of carbon and oxygen to produce CO2 and other wastes to produce heat. There is only one reaction and one purpose for nuclear power reactors there is one reaction but many puiposes for fossil-burning furnaces there are myriad chemical processes and purposes. 

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