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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]
According to the International Nuclear Safety Center [22] the thermal conductivity of uranium dioxide can be predicted under different conditions by a series of equations. The bulk density of the fuel can be related to the thermal conductivity. Where ρ is the bulk density of the fuel and ρ td is the theoretical density of the uranium dioxide.
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.
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]
Ammonium diuranate or (ADU) ((NH 4) 2 U 2 O 7), is one of the intermediate chemical forms of uranium produced during yellowcake production. The name "yellowcake" originally given to this bright yellow salt, now applies to mixtures of uranium oxides which are actually hardly ever yellow. It also is an intermediate in mixed-oxide fuel fabrication.