Triuranium octaoxide

CHEMICAL NAME = triuranium (V) octaoxide CAS NUMBER = 1344-59-8 MOLECULAR FORMULA = U508 MOLAR MASS = 842.1 g/mol COMPOSITION = U(84.8°/o) 0(15.2%) 

MELTING POINT = 1,150°C BOILING POINT = decomposes to U02 at 1300°C DENSITY = 8.4 g/cm3 

Uranium is best known as a fuel for nuclear power plants. To prepare this fuel, uranium ores are processed to extract and enrich the uranium. The process begins by mining uranium-rich ores and then crushing the rock. The ore is mixed with water and thickened to form a slurry. The slurry is treated with sulfuric acid and the product reacted with amines in a series of reactions to give ammonium diuranate, (NH4)2U20 . Ammonium diuranate is heated to yield an enriched uranium oxide solid known as yellow cake. Yellow cake contains from 70—90% U3Og in the form of a mixture of U02 and U03. The yellow cake is then shipped to a conversion plant where it can be enriched. 

Natural uranium consists of different isotopes of uranium. Natural uranium is 0.7% U-235 and 99.3% U-238. Uranium-238 is nonfissionable, and therefore naturally occurring uranium must be enriched to a concentration of approximately 4% to be used as fuel for nuclear reactors or 90% for weapons-grade uranium. Yellow cake is shipped to conversion plants 

is combined with fluorine gas to yield uranium hexafluoride, UF6 UF4(s) + F2fe) — UF6(g). Uranium hexafluoride is a white crystalline solid at standard temperature and pressure, but it sublimes to a gas at 57°C. The U-235 in uranium hexafluoride can be enriched by several methods based on the difference in masses of the uranium isotopes. Two common methods are gaseous diffusion and gas centrifuge. 

---

Malinin, G. V. et al., Russ. Chem. Rev., 1975, 44, 392-397 Thermal decomposition of metal oxides was reviewed. Some oxides (cobalt(II, III) oxide, copper(II) oxide, lead(II, IV) oxide, uranium dioxide, triuranium octaoxide) liberate quite a high proportion of atomic oxygen, with a correspondingly higher potential for oxidation of fuels than molecular oxygen. 

Thorium oxide sulfide, 4826 Tin(II) oxide, 4829 Tin(IV) oxide, 4840 Titanium(IV) oxide, 4842 Triuranium octaoxide, 4871 Tungsten(IV) oxide, 4844 Tungsten(VI) oxide, 4856... 

Heating the metal with ammonia at elevated temperatures (at about 700°C) yields nitrides of nonstoichiometric compositions. With nitric oxide, uranium is oxidized at about 400°C, forming triuranium octaoxide, UsOs-... 

One preparative method involves heating triuranium octaoxide, UsOs, with hydrogen fluoride and fluorine. The product hexafluoride is separated and purified by fractional distillation. 

Another preparative method involves converting triuranium octaoxide to uranyl nitrate, U02(N0s)2, by treatment with nitric acid. Uranyl nitrate then is decomposed to uranium trioxide, UO3, which is reduced to the dioxide, UO2, with hydrogen. A fluidized bed of uranium dioxide is treated with hydrogen fluoride to produce uranium tetrafluoride, UF4, which then is treated with fluorine to form hexafluoride. The preparation should be done in copper apparatus. 

Carbides of the Actinides, Uranium, and Thorium. The carbides of uranium and thorium are used as nuclear fuels and breeder materials for gas-cooled, graphite-moderated reactors (see Nuclear REACTORS). The actinide carbides are prepared by the reaction of metal or metal hydride powders with carbon or preferably by the reduction of the oxides uranium dioxide [1344-57-6], U02, triuranium octaoxide [1344-59-8], U,08, or thorium... 

Trithia[7]ferrocenophene—acetonitrilecopper(I) perchlorate, 3704 Trithorium tetranitride, 4768 Tri(4-tolyl)ammonium perchlorate, 3818 Triuranium octaoxide, 4865... 

OSHA PEL TWA 0.5 mg(Ba)/m3 ACGIH TLV TWA 0.5 mg(Ba)/m3 Not Classifiable as a Human Carcinogen DFG MAK 0.5 mg(Ba)/m3 DOT CLASSIFICATION 6.1 Label KEEP AWAY FROM FOOD SAFETY PROFILE A poison via subcutaneous route. See also BARIUM COMPOUNDS (soluble). Combustible by spontaneous chemical reaction produces heat on contact with water or steam. Reacts with H2O, Ba(OH)2. Incompatible with H2S, hydroxylamine, N2O4, triuranium octaoxide, SO3. 

Human and animal studies have shown that long-term retention in the lungs of large quantities of inhaled insoluble uranium particles (e.g., carnotite dust [4% uranium as uranium dioxide and triuranium octaoxide, 80-90% quartz, and <10% feldspar]) can lead to serious respiratory effects. However, animals exposed to... 

---