U3O8

U3O8, triuranium oct oxide, is the chemical compound that represents the most common form of uranium concentrate produced from mined ore. Commonly called yellowcake, it is a yellow to orange powder that serves as the initial feedstock in the nuclear fuel cycle. The composition is predominantly U3O8 with various impurities, and its exact grade depends on ore quality and processing.

Production and occurrence: Uranium ore is milled to produce a slurry of ground rock and uranium compounds. Through chemical leaching, uranium is dissolved and subsequently recovered as a concentrate—often as ammonium diuranate or related intermediates—that is calcined to yield U3O8. The product is shipped to conversion facilities and typically contains a high proportion of U3O8 by weight, with remaining material consisting of oxides, silicates, and trace radionuclides.

Properties: In U3O8, uranium is in the +6 oxidation state. The solid is a stable oxide, with relatively low solubility in water but solubility in acids, notably nitric acid, which forms uranyl complexes. It is radioactive; the primary hazard is inhalation or ingestion of dust, and long-term exposure requires shielding, containment, and monitoring.

Use in the fuel cycle: U3O8 is not directly usable as fuel. It is converted to uranium hexafluoride (UF6) for enrichment, after which the material can be fabricated into reactor fuel assemblies.

Safety and regulation: Because it contains natural radioactivity and chemical hazards, U3O8 production, handling, transport, and disposition are subject to strict regulatory controls and international safeguards to prevent diversion and protect worker health and the environment.

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