Yellow cake

To convert naturally occurring uranium oxide, yellow cake or U Og, to the gaseous UF, hydrofluoric acid is first used to convert the U Og to UF. Further fluorination using fluorine (generated from more HF) is employed to convert the UF to UF. The UF is then processed at gaseous diffusion enrichment plants. 

The raw material for nuclear reactor fuel, uranium, exits the mining—milling sequence as uranium oxide. Because of its color, it is called yellow cake. The yellow cake is converted to uranium hexafluoride and enriched in 235u... 

The throwaway fuel cycle does not recover the energy values present ia the irradiated fuel. Instead, all of the long-Hved actinides are routed to the final waste repository along with the fission products. Whether or not this is a desirable alternative is determined largely by the scope of the evaluation study. For instance, when only the value of the recovered yellow cake and SWU equivalents are considered, the world market values for these commodities do not fully cover the cost of reprocessing (2). However, when costs attributable to the disposal of large quantities of actinides are considered, the classical fuel cycle has been the choice of virtually all countries except the United States. 

The recycle weapons fuel cycle rehes on the reservoir of SWUs and yellow cake equivalents represented by the fissile materials in decommissioned nuclear weapons. This variation impacts the prereactor portion of the fuel cycle. The post-reactor portion can be either classical or throwaway. Because the avadabihty of weapons-grade fissile material for use as an energy source is a relatively recent phenomenon, it has not been fully implemented. As of early 1995 the United States had purchased highly enriched uranium from Russia, and France had initiated a modification and expansion of the breeder program to use plutonium as the primary fuel (3). AH U.S. reactor manufacturers were working on designs to use weapons-grade plutonium as fuel. 

Raffinate acid from the first cycle, containing approximately 7 to 14 g/L U Og is then reoxidized and re-extracted in the second, purification cycle using a solvent containing 0.3 Af D2EHPA and 0.075 AfTOPO. The loaded solvent is washed with iron-free acid to remove iron and then with water to remove extracted and entrained acid. The solvent is stripped with ammonium carbonate [506-87-6] to yield ammonium uranyl tricarbonate [18077-77-5] which is subsequendy calcined to U Og (yellow cake). The stripped solvent is regenerated with mineral acid before recycling (39). 

The acids are mixed in a flask (500 c.c.), and the nitrobenzene added in portions of 5—10 c.c. at a time. Heat is evolved, and the mass becomes somewhat deeper in colour. When the nitrobenzene has been added, the flask is heated for a shoit time on the water-bath. K few drops are then potiied into a test-tube of water. The dinitrobenzene should, if the reaction is complete, separate out as a hard pale yellow cake If it is semi-sohd, the heating" must be continued. The contents of the flask are then poured, whilst warm, into a large quantity of water. The dinitrobenzene, which separates out, is filteied at the punap and well washed with water. It is then dried. The yield is nearly theoretical. A few grams should be recrystallised from spirit. The remainder may be used for the next preparation without further puiification. 

Yellow cake is a complicated mixture of salts and oxides, the composition of which approximates to (NH4)2U207 but is dependent on the method by which it is produced (see p. 276 of ref 2). 

Uranium is a metal that is found naturally as a constituent of chemical compounds m minerals such as pitchblende. Uranium ore is mined much like coal Open pits are used to mine shallow deposits, deeper deposits require shaft mining. Commercial ores yield 3 to 5 lb of nranitim compounds per ton of ore. A material called yellow-cake is produced that is... 

Canada, are examples. These reactors do not use ordinai y water for the moderator. Most nuclear fission reactors use ordinaiy water for a moderator which requires that the fuel he about 3 percent and about 97 percent U. Achieving this enrichment requires that the solid uranium compounds in the yellow cake be converted to gaseous uranium hexafluoride (UF,). Following enrichment, gaseous UF is converted to solid uranium oxide (UO,) for fabrication of fuel elements for a nuclear reactor. 

Since the uranium from the milling process is still in an unusable form, the yellow cake is broken down once again. The uranium trioxide is reduced to uranium dioxide at veiy high temperatures. Refining of the product also takes place. Now the uranium product consists almost entirely of UO,. 

The principal member of the first class is tributyl phosphate (TBP). It is convenient to use this organic reagent in the refining of yellow cake consequent to nitric acid dissolution. After dilution, the solution is subjected to filtration through vacuum filters prior to intro-... 

Another, more modern, route of processing the yellow cake is shown in Figure 5.38, accomplishes the production of enriched uranium oxide entirely by pyroprocessing. Thus, uranium is finally obtained in three forms metallic uranium, enriched uranium dioxide, and natural uranium dioxide. As the flowsheet shows, and as briefly described herein, these are essentially the products of hydro and pyro-based processing schemes. 

Dapex [Di-alkylphosphoric acid extraction] A process for the solvent extraction of uranium from sulfuric acid solutions using di-(2-ethylhexyl) phosphoric acid (HDEHP). The HDEHP is dissolved in kerosene containing 4 percent of tributyl phosphate. The uranium is stripped from the organic phase by aqueous sodium carbonate and precipitated as uranyl peroxide (yellow cake). The process was no longer in use in 1988. See also Amex. 

Uranium is best known as a fuel for nuclear power plants. To prepare this fuel, uranium ores are processed to extract and enrich the uranium. The process begins by mining uranium-rich ores and then crushing the rock. The ore is mixed with water and thickened to form a slurry. The slurry is treated with sulfuric acid and the product reacted with amines in a series of reactions to give ammonium diuranate, (NH4)2U20 . Ammonium diuranate is heated to yield an enriched uranium oxide solid known as yellow cake. Yellow cake contains from 70—90% U3Og in the form of a mixture of U02 and U03. The yellow cake is then shipped to a conversion plant where it can be enriched. 

Natural uranium consists of different isotopes of uranium. Natural uranium is 0.7% U-235 and 99.3% U-238. Uranium-238 is nonfissionable, and therefore naturally occurring uranium must be enriched to a concentration of approximately 4% to be used as fuel for nuclear reactors or 90% for weapons-grade uranium. Yellow cake is shipped to conversion plants... 

Sufficient tri-n-butyl phosphate (TBP) or isodecanol is incorporated into the organic phase to prevent separation of the sodium salt of D2EHPA as a third phase. Uranium is precipitated from the strip solution by the addition of magnesium oxide or ammonia gas to give a product known as yellow cake . 

Figure 10 Outline flowsheet for the production of yellow cake from uranium ore...

Suckers Yellow cake French salad dressing Brownies Taco/tostada (FF)... 

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