process of gaseous diffusion, or in a gas centrifuge. This can produce low-enriched uranium containing up to 20% U-235 that is suitable for use in most large civilian electric-power reactors. With further processing, one obtains highly enriched uranium, containing 20% or more U-235, that is suitable for use in compact nuclear reactors—usually used to power naval warships and submarines. Further processing can yield weapons-grade uranium with U-235 levels usually above 90%, suitable for nuclear weapons. Radioactivity and safety The uranium in yellowcake is almost exclusively (>99%) U-238, with very low radioactivity. U-238 has an extremely long half-life, over 4 billion years, meaning that it emits radiation at a slow rate. This stage of processing is before the more radioactive U-235 is concentrated, so by definition, this stage of uranium has the same radioactivity as it did in nature when it was underground, as the proportions of isotopes are at their native relative concentration. Yellowcake is hazardous when inhaled. See also Uranium ore deposits Uranium mining Uraninite, an ore that is mostly uranium dioxide (UO2) Yellowcake forgery, fraudulently depicted Saddam Hussein trying to buy uranium powder Sequoyah Fuels Corporation, an American company involved in yellowcake processing COMINAK, a Niger uranium mining and processing company SOMAIR, a Niger uranium mining and processing company Vanadium(V) oxide, hydrous precipitates of which are known as "redcake" References Uranium compounds Oxides Nuclear materials