NationMaster - Encyclopedia: Uranium hexafluoride

Uranium hexafluoride (UF₆), referred to as "hex" in industry, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and nuclear weapons. It forms solid grey crystals at standard temperature and pressure (STP), is highly toxic, reacts violently with water and is corrosive to most metals. It reacts mildly with aluminum, forming a thin surface layer of AlF₃ that resists further reaction. Image File history File links Download high-resolution version (993x1079, 8 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Uranium hexafluoride ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... In crystallography, the hexagonal crystal system is one of the 7 lattice point groups. ... Close-packing of spheres refers to arranging an infinite lattice of spheres so that they take up the greatest possible fraction of an infinite 3-dimensional space. ... The coordination geometry of an atom is the geometrical pattern formed by its neighbors in a molecule or a crystal. ... four spÂ³ orbitals three spÂ² orbitals In chemistry, hybridisation or hybridization (see also spelling differences) is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the qualitative description of atomic bonding properties. ... An octahedron (plural: octahedra) is a polyhedron with eight faces. ... The Earths magnetic field, which is approximately a dipole. ... The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 atmosphere... In chemistry, the standard molar entropy is the entropy content of one mole of substance, under conditions of standard temperature and pressure. ... This article is about the electrically charged particle. ... This article is about the electrically charged particle. ... This article lacks information on the importance of the subject matter. ... Uranium tetrafluoride (UF4) is a green crystalline solid that melts at about 1,760Â°F (960Â°C) and has an insignificant vapor pressure and is very slightly soluble in water. ... Uranium pentafluoride is a coordination polymer which consists of UF5 units linked by bridging fluorides forming linear chains. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... General Name, symbol, number uranium, U, 92 Chemical series actinides Group, period, block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Standard atomic weight 238. ... Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. ... Core of a small nuclear reactor used for research. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ...

Milled uranium ore — U₃O₈, or "yellowcake" — is dissolved in nitric acid, yielding a solution of uranyl nitrate UO₂(NO₃)₂. Pure uranyl nitrate is obtained by solvent extraction, then treated with ammonia to produce ammonium diuranate ("ADU", (NH₄)₂U₂O₇). Reduction with hydrogen gives UO₂, which is converted with hydrofluoric acid (HF) to uranium tetrafluoride, UF₄. Oxidation with fluorine finally yields UF₆. Powdered yellowcake in a drum Yellowcakes (also known as urania) are uranium concentrates obtained from leach solutions. ... The chemical compound nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is an aqueous solution of hydrogen nitrate (anhydrous nitric acid). ... Uranyl nitrate (UO2(NO3)2) is a water soluble yellow uranium salt. ... In chemistry, liquid-liquid extraction (or more briefly, solvent extraction) is a useful method to separate components (compounds) of a mixture. ... For other uses, see Ammonia (disambiguation). ... Ammonium diuranate or (ADU) (NH4U2O7), is one of the intermediate chemical forms of uranium produced during yellowcake production. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Hydrofluoric acid is a solution of hydrogen fluoride in water. ... Uranium tetrafluoride (UF4) is a green crystalline solid that melts at about 1,760Â°F (960Â°C) and has an insignificant vapor pressure and is very slightly soluble in water. ... Distinguished from fluorene and fluorone. ...

Application in the nuclear fuel cycle

It is used in both of the main uranium enrichment methods, gaseous diffusion and the gas centrifuge method, because it has a triple point at 147 °F (64 °C, 337 K) and slightly higher than normal atmospheric pressure. Additionally, fluorine has only a single stable naturally occurring isotope, so isotopomers of UF₆ differ in their molecular weight based solely on the uranium isotope present.^[1] Uranium hexafluoride phase diagram. ... Uranium hexafluoride phase diagram. ... In physical chemistry, mineralogy, and materials science, a phase diagram is a type of graph used to show the equilibrium conditions between the thermodynamically-distinct phases. ... -1... A cascade of gas centrifuges at a United States enrichment plant. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ... Distinguished from fluorene and fluorone. ... Isotopomers (isotopic isomers) are isomers having the same number of each isotopic atom but differing in their positions. ... For other uses, see Isotope (disambiguation). ...

It is important to note that all the other uranium fluorides are involatile solids which are coordination polymers. Coordination polymer is the term given in inorganic chemistry to a metal coordination compound where a ligand bridges between metal centres, where each metal centre binds to more than one ligand to create a infinite array of metal centres. ...

Gaseous diffusion requires ca. 60 times as much energy as the gas centrifuge process; even so, this is just 4% of the energy that can be produced by the resulting enriched uranium. These pie-graphs showing the relative proportions of uranium-238 (blue) and uranium-235 (red) at different levels of enrichment. ...

In addition to its use in enrichment, uranium hexafluoride has been used in an advanced reprocessing method which was developed in the Czech Republic. In this process used oxide nuclear fuel is treated with fluorine gas to form a mixture of fluorides. This is then distilled to separate the different classes of material. Enrichment may mean: Education. ... An oxide is a chemical compound containing an oxygen atom and other elements. ... Nuclear Fuel Process A graph compairing nucleon number against binding energy Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. ...

Storage in gas cylinders

About 95% of the depleted uranium produced to date is stored as uranium hexafluoride, (D)UF₆, in steel cylinders in open air yards close to enrichment plants. Each cylinder contains up to 12.7 tonnes (or 14 US tons) of solid UF₆. In the U.S. alone, 560,000 tonnes of depleted UF₆ had accumulated by 1993. In 2005, 686,500 tonnes in 57,122 storage cylinders were located near Portsmouth, Ohio, Oak Ridge, Tennessee, and Paducah, Kentucky.^[2]^[3] The long-term storage of DUF₆ presents environmental, health, and safety risks because of its chemical instability. When UF₆ is exposed to moist air, it reacts with the water in the air to produce UO₂F₂ (uranyl fluoride) and HF (hydrogen fluoride) both of which are highly soluble and toxic. Storage cylinders must be regularly inspected for signs of corrosion and leaks. The estimated life time of the steel cylinders is measured in decades.^[4] Image File history File links DUF6_cylinder_leak. ... Depleted uranium storage yard. ... Uranyl fluoride (UO2F2) a compound of uranium ,is an intermediate in the conversion of uranium hexafluoride UF6 to an uranium oxide or metal form and is a direct product of the reaction of UO2F2 with moisture in the air. ... Hydrogen fluoride is a chemical compound with the formula HF. Together with hydrofluoric acid, it is the principal industrial source of fluorine and hence the precursor to many important compounds including pharmaceuticals and polymers (e. ...

There have been several accidents involving uranium hexafluoride in the United States.^[5]^[6] The U.S. government has been converting DUF₆ to solid uranium oxides for disposal.^[7] Such disposal of the entire DUF₆ inventory could cost anywhere from 15 million to 450 million US dollars.^[8] The United States dollar is the official currency of the United States. ...

Chemistry

The solid state structure was reported by J.H. Levy, J.C Taylor and A.B Waugh.^[9] In this paper neutron diffraction was used to determine the structures of UF₆, MoF₆ and WF₆ at 77K. Neutron diffraction is a crystallography technique that uses neutrons to determine the atomic structure of a material. ...

It has been shown that uranium hexafluoride is an oxidant and a lewis acid which is able to bind to fluoride, for instance the reaction of copper fluoride with uranium hexafluoride in acetonitrile is reported to form Cu[UF₇]₂.5MeCN.^[10] An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... In chemistry, a Lewis acid can accept a pair of electrons and form a coordinate covalent bond, after the American chemist Gilbert Lewis. ... Fluoride is the ionic form of fluorine. ... For other uses, see Copper (disambiguation). ... Acetonitrile is an organic molecule, often used as a solvent, with the chemical formula of CH3CN. Also known as methyl cyanide, it is the simplest of the organic nitriles. ...

It is interesting to note that polymeric uranium(VI) fluorides containing organic cations have been isolated and characterised by X-ray diffraction.^[11] A polymer (from Greek: Ï€Î¿Î»Ï…, polu, many; and Î¼ÎÏÎ¿Ï‚, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ...

Other uranium fluorides

The pentafluoride of uranium (UF₅) and diuranium nonafluoride (U₂F₉) has been characterised by C.J. Howard, J.C Taylor and A.B. Waugh.^[12]

It is clear that the solid is a 1D coordination polymer

This is U2F9 which is a coordination polymer

This is UF4 which is a coordination polymer

Image File history File links Download high-resolution version (1024x768, 64 KB) The solid state lattice I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high-resolution version (1024x768, 67 KB) The solid state lattice I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high-resolution version (1024x768, 110 KB) The solid state lattice I, the creator of this work, hereby release it into the public domain. ...

This is UF3 which is a coordination polymer

Image File history File links Download high-resolution version (827x473, 50 KB) UF3 solid I, the creator of this work, hereby release it into the public domain. ...

The structure of UOF₄ was reported by J.H. Levy, J.C. Taylor, and P.W. Wilson.^[14]

See also

Depleted uranium storage yard. ... General Name, symbol, number uranium, U, 92 Chemical series actinides Group, period, block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Standard atomic weight 238. ...

External links

References

^ Uranium Enrichment and the Gaseous Diffusion Process. USEC Inc. Retrieved on 2007-09-24.
^ How much depleted uranium hexafluoride is stored in the United States?. Depleted UF₆ FAQs. Argonne National Laboratory.
^ http://web.ead.anl.gov/uranium/documents/index.cfm
^ What is DUF₆? Is it dangerous and what should we do with it?. Institute for Energy and Environmental Research (2007-09-24).
^ Have there been accidents involving uranium hexafluoride?. Depleted UF₆ FAQs. Argonne National Laboratory.
^ Uranium Hexafluoride (UF₆) Tailings: Characteritics, Transport and Storage at the Siberian Chemical Combine (Sibkhimkombinat) Tomsk (briefing note). Large and Associates (5 Nov 2005). Retrieved on 2007-09-24.
^ What is going to happen to the uranium hexafluoride stored in the United States?. Depleted UF₆ FAQs. Argonne National Laboratory.
^ Are there any currently-operating disposal facilities that can accept all of the depleted uranium oxide that would be generated from conversion of DOE's depleted UF6 inventory?. Depleted UF₆ FAQs. Argonne National Laboratory.
^ J.H. Levy, J.C Taylor and A.B Waugh (1983). "Neutron powder structural studies of UF₆, MoF₆ and WF₆ at 77 K". Journal of Fluorine Chemistry 23: 29-36. DOI:10.1016/S0022-1139(00)81276-2.
^ Berry JA, Poole RT, Prescott A, Sharp DWA, Winfield JM (1976). "The oxidising and fluoride ion acceptor properties of uranium hexafluoride in acetonitrile". J. Chem. Soc. Dalton Trans.: 272. DOI:10.1039/DT9760000272. x
^ Walker SM, Halasyamani PS, Allen S, O'Hare D (1999). "From Molecules to Frameworks: Variable Dimensionality in the UO₂(CH₃COO)₂·2H₂O/HF(aq)/Piperazine System. Syntheses, Structures, and Characterization of Zero-Dimensional (C₄N₂H₁₂)UO₂F₄·3H₂O, One-Dimensional (C₄N₂H₁₂)₂U₂F₁₂·H2O, Two-Dimensional (C₄N₂H₁₂)₂(U₂O₄F₅)₄·11H₂O, and Three-Dimensional (C₄N₂H₁₂)U₂O₄F₆". J. Am. Chem. Soc. 121: 10513. DOI:10.1021/ja992145f. x
^ Howard CJ, Taylor JC, Waugh AB (1982). "Crystallographic parameters in α-UF₅ and U₂F₉ by multiphase refinement of high-resolution neutron powder data". Journal of Solid State Chemistry 45: 396-398. DOI:10.1016/0022-4596(82)90185-2. x
^ Laveissiere J (1967). "". Bulletin de la Societe Francaise de Mineralogie et de Cristallographie 90: 304-307.
^ Levy JH, Taylor JC, Wilson PW (1977). "Structure of fluorides .17. NEUTRON-DIFFRACTION STUDY OF ALPHA-URANIUM OXIDE TETRAFLUORIDE". Journal of Inorganic and Nuclear Chemistry 39: 1989-1991.

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Contents

Application in the nuclear fuel cycle

Storage in gas cylinders

Chemistry

Other uranium fluorides

See also

External links

References

Further reading

Contents

Application in the nuclear fuel cycle var ACE_AR = {Site: '756743', Size: '300250'};

Storage in gas cylinders

Chemistry

Other uranium fluorides

See also

External links

References

Further reading

Application in the nuclear fuel cycle