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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)
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.
Triuranium octoxide is (depending on conditions) the most stable compound of uranium and is the form most commonly found in nature. Uranium dioxide is the form in which uranium is most commonly used as a nuclear reactor fuel. [104] At ambient temperatures, UO 2 will gradually convert to U 3 O 8. Because of their stability, uranium oxides are ...
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]
No uranium oxyanion, such as [UO 4] 2− or [U 2 O 7] 2−, is known. Instead, all uranate structures are based on UO n polyhedra sharing oxygen atoms in an infinite lattice. [ 1 ] The structures of uranates(VI) are unlike the structure of any mixed oxide of elements other than actinide elements.
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]