Yellowcake
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Yellowcakes (also known as urania) are uranium concentrates obtained from leach solutions, they represent an intermediate step in the processing of uranium ores. Yellowcake concentrates are prepared by various extraction and refining methods, depending on the types of ores. Typically yellowcakes are obtained through the milling and chemical processing of uranium ore forming a coarse powder which is insoluble in water and contains about 80% uranium oxide, and which melts at approximately 2878°C.
The ore is first crushed to a fine powder by passing raw uranium ore through crushers and grinders to produce "pulped" ore. This is further processed with concentrated acid, alkaline, or peroxide solutions to leach out the uranium. Yellowcake is what remains after drying and filtering. The yellowcake produced by most modern mills is actually brown or black, not yellow; the name comes from the colour and texture of the concentrates produced by early mining operations.
Initially, the compounds formed in yellowcakes were not identified; in 1970, the U.S. Bureau of Mines still referred to yellowcakes as the final precipitate formed in the milling process and considered it to be ammonium diuranate or sodium diuranate. The compositions were variable and depended upon the leachant and subsequent precipitating conditions. Among the compounds identified in yellowcakes include: uranyl hydroxide, uranyl sulfate, sodium para-uranate, and uranyl peroxide, along with various uranium oxides. Modern yellowcake typically contains 70 to 90 percent triuranium octaoxide (U3O8) by weight. (Other uranium oxides, such as uranium dioxide (UO2) and uranium trioxide (UO3), exist)
Yellowcake is used in the preparation of fuel for nuclear reactors, where it is processed into purified UO2 for use in fuel rods for PHWR and other systems using unenriched uranium. It may also be enriched, by being converted to uranium hexafluoride gas (UF6), by isotope separation though gaseous diffusion or in a gas centrifuge to produce enriched uranium suitable for use in weapons and reactors.
Yellowcake is produced by all countries in which uranium is mined.
References
Characterizing and Classifying Uranium Yellow Cakes: A Background by Donald M. Hausen JOM-9812-45FSee also
External links
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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