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Uranium dioxide or uranium(IV) oxide (UO 2), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used as MOX fuel.
Uranium dioxide is the form in which uranium is most commonly used as a nuclear reactor fuel. [3] At ambient temperatures, UO 2 will gradually convert to U 3 O 8. Because of their stability, uranium oxides are generally considered the preferred chemical form for storage or disposal. [3]
The metal uranium forms several oxides: Uranium dioxide or uranium(IV) oxide (UO 2, the mineral uraninite or pitchblende) Diuranium pentoxide or uranium(V) oxide (U 2 O 5) Uranium trioxide or uranium(VI) oxide (UO 3) Triuranium octoxide (U 3 O 8), the most stable uranium oxide; yellowcake typically contains 70 to 90 percent triuranium octoxide)
Ammonium uranyl carbonate (UO 2 CO 3 ·2(NH 4) 2 CO 3) is known in the uranium processing industry as AUC [2] and is also called uranyl ammonium carbonate.This compound is important as a component in the conversion process of uranium hexafluoride (UF 6) to uranium dioxide (UO 2). [3]
Uraninite, also known as pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO 2 but because of oxidation typically contains variable proportions of U 3 O 8.
Uranium dioxide (UO 2) can be oxidised to an oxygen rich hyperstoichiometric oxide (UO 2+x) which can be further oxidised to U 4 O 9, U 3 O 7, U 3 O 8 and UO 3.2H 2 O. Because used fuel contains alpha emitters (plutonium and the minor actinides), the effect of adding an alpha emitter (238 Pu) to uranium dioxide on the leaching rate of the oxide ...
Natural uranium (NU or U nat [1]) is uranium with the same isotopic ratio as found in nature. It contains 0.711% uranium-235 , 99.284% uranium-238 , and a trace of uranium-234 by weight (0.0055%). Approximately 2.2% of its radioactivity comes from uranium-235, 48.6% from uranium-238, and 49.2% from uranium-234.
The authors report that a layer of U 3 O 7 was present on the uranium dioxide surface during this induction time. They report that 3 to 8% of the krypton-85 was released, and that much less of the ruthenium (0.5%) and caesium (2.6 x 10 −3 %) occurred during the oxidation of the uranium dioxide. [5]