Uranium(III) hydride

Last updated
Uranium(III) hydride
Names
Other names
Uranium(III) hydride [1]
Uranium trihydride [2] [3]
Hypouranous hydride
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/U.3H X mark.svgN
    Key: XOTGRWARRARRKM-UHFFFAOYSA-N X mark.svgN
  • [UH3]
  • [H-].[H-].[H-].[U+3]
Properties
UH
3
Molar mass 241.05273 g mol−1
Appearancebrownish grey to brownish black pyrophoric powder
Density 10.95 g cm−3
Reacts
Structure
Cubic, cP32
Pm3n, No. 223
a = 664.3 pm [4]
Hazards
Flash point Pyrophoric
Safety data sheet (SDS) ibilabs.com
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Uranium hydride, also called uranium trihydride (UH3), is an inorganic compound and a hydride of uranium.

Contents

Properties

Uranium hydride is a highly toxic, brownish grey to brownish black pyrophoric powder or brittle solid. Its density at 20 °C is 10.95 g cm−3, much lower than that of uranium (19.1 g cm−3). It has a metallic conductivity, is slightly soluble in hydrochloric acid and decomposes in nitric acid.

Two crystal modifications of uranium hydride exist, both cubic: an α form that is obtained at low temperatures and a β form that is grown when the formation temperature is above 250 °C. [5] After growth, both forms are metastable at room temperature and below, but the α form slowly converts to the β form upon heating to 100 °C. [3] Both α- and β-UH3 are ferromagnetic at temperatures below ~180 K. Above 180 K, they are paramagnetic. [6]

Formation in uranium metal

Hydrogen gas reaction

Exposure of uranium metal to hydrogen leads to hydrogen embrittlement. Hydrogen diffuses through metal and forms a network of brittle hydride over the grain boundaries. Hydrogen can be removed and ductility renewed by annealing in vacuum. [7]

Uranium metal heated to 250 to 300 °C (482 to 572 °F) reacts with hydrogen to form uranium hydride. Further heating to about 500 °C will reversibly remove the hydrogen. This property makes uranium hydrides convenient starting materials to create reactive uranium powder along with various uranium carbide, nitride, and halide compounds. [5] The reversible reaction proceeds as follows: [2]

2 U + 3 H2⇌ 2 UH3

Uranium hydride is not an interstitial compound, causing the metal to expand upon hydride formation. In its lattice, each uranium atom is surrounded by 6 other uranium atoms and 12 atoms of hydrogen; each hydrogen atom occupies a large tetrahedral hole in the lattice. [8] The density of hydrogen in uranium hydride is approximately the same as in liquid water or in liquid hydrogen. [9] The U-H-U linkage through a hydrogen atom is present in the structure. [10]

Water reaction

Uranium hydride forms when uranium metal (e.g. in Magnox fuel with corroded cladding) becomes exposed to water or steam, with uranium dioxide as byproduct: [8]

7 U + 6 H2O → 3 UO2 + 4 UH3

The resulting uranium hydride is pyrophoric; if the metal (e.g. a damaged fuel rod) is exposed to air afterwards, excessive heat may be generated and the bulk uranium metal itself can ignite. [11] Hydride-contaminated uranium can be passivated by exposure to a gaseous mixture of 98% helium with 2% oxygen. [12] Condensed moisture on uranium metal promotes formation of hydrogen and uranium hydride; a pyrophoric surface may be formed in absence of oxygen. [13] This poses a problem with underwater storage of very special spent nuclear fuel in spent fuel ponds (nuclear fuel from commercial nuclear plants does NOT contain any uranium metal). Depending on the size and distribution on the hydride particles, self-ignition can occur after an indeterminate length of exposure to air. [14] Such exposure poses risk of self-ignition of fuel debris in radioactive waste storage vaults. [15]

Uranium hydride exposed to water evolves hydrogen. In contact with strong oxidizers this may cause fire and explosions. Contact with halocarbons may cause a violent reaction. [16]

Other chemical reactions

Polystyrene-impregnated uranium hydride powder is non-pyrophoric and can be pressed, however its hydrogen-carbon ratio is unfavorable. Hydrogenated polystyrene was introduced in 1944 instead. [17]

Uranium deuteride is said to be usable for design of some types of neutron initiators.

Uranium hydride enriched to about 5% uranium-235 is proposed as a combined nuclear fuel/neutron moderator for the Hydrogen Moderated Self-regulating Nuclear Power Module. According to the aforementioned patent application, the reactor design in question begins producing power when hydrogen gas at a sufficient temperature and pressure is admitted to the core (made up of granulated uranium metal) and reacts with the uranium metal to form uranium hydride. [18] Uranium hydride is both a nuclear fuel and a neutron moderator; apparently it, like other neutron moderators, will slow neutrons sufficiently to allow for fission reactions to take place; the uranium-235 atoms within the hydride also serve as the nuclear fuel. Once the nuclear reaction has started, it will continue until it reaches a certain temperature, approximately 800 °C (1,500 °F), where, due to the chemical properties of uranium hydride, it chemically decomposes and turns into hydrogen gas and uranium metal. The loss of neutron moderation due to the chemical decomposition of the uranium hydride will consequently slow — and eventually halt — the reaction. When temperature returns to an acceptable level, the hydrogen will again combine with the uranium metal, forming uranium hydride, restoring moderation and the nuclear reaction will start again. [18]

On heating with diborane, uranium hydride produces uranium boride. [19] With bromine at 300 °C, uranium(IV) bromide is produced. With chlorine at 250 °C, uranium(IV) chloride is produced. Hydrogen fluoride at 20 °C produces uranium(IV) fluoride. Hydrogen chloride at 300 °C produces uranium(III) chloride. Hydrogen bromide at 300 °C produces uranium(III) bromide. Hydrogen iodide at 300 °C produces uranium(III) iodide. Ammonia at 250 °C produces uranium(III) nitride. Hydrogen sulfide at 400 °C produces uranium(IV) sulfide. Oxygen at 20 °C produces triuranium octoxide. Water at 350 °C produces uranium dioxide. [20]

Uranium hydride ion may interfere with some mass spectrometry measurements, appearing as a peak at mass 239, creating false increase of signal for plutonium-239. [21]

History

Uranium hydride slugs were used in the "tickling the dragon's tail" series of experiments to determine the critical mass of uranium. [22]

Uranium hydride and uranium deuteride were suggested as a fissile material for a uranium hydride bomb. The tests with uranium hydride and uranium deuteride during Operation Upshot–Knothole were disappointing, however. During the early phases of the Manhattan Project, in 1943, uranium hydride was investigated as a promising bomb material; it was abandoned by early 1944 as it turned out that such a design would be inefficient. [23]

Applications

Hydrogen, deuterium, and tritium can be purified by reacting with uranium, then thermally decomposing the resulting hydride/deuteride/tritide. [24] Extremely pure hydrogen has been prepared from beds of uranium hydride for decades. [25] Heating uranium hydride is a convenient way to introduce hydrogen into a vacuum system. [26]

The swelling and pulverization at uranium hydride synthesis can be used for preparation of very fine uranium metal, if the powdered hydride is thermally decomposed.

Uranium hydride can be used for isotope separation of hydrogen, preparing uranium metal powder, and as a reducing agent.

Related Research Articles

<span class="mw-page-title-main">Neptunium</span> Chemical element with atomic number 93 (Np)

Neptunium is a chemical element; it has symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar System, which uranium is named after. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. Like all actinides, it is radioactive, poisonous, pyrophoric, and capable of accumulating in bones, which makes the handling of neptunium dangerous.

<span class="mw-page-title-main">Protactinium</span> Chemical element with atomic number 91 (Pa)

Protactinium is a chemical element; it has symbol Pa and atomic number 91. It is a dense, radioactive, silvery-gray actinide metal which readily reacts with oxygen, water vapor, and inorganic acids. It forms various chemical compounds, in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. Because of its scarcity, high radioactivity, and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel.

<span class="mw-page-title-main">Hydride</span> Molecule with a hydrogen bound to a more electropositive element or group

In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen atom with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and more frequently in the past) been applied to all compounds containing covalently bound H atoms. In this broad and potentially archaic sense, water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. In covalent compounds, it implies hydrogen is attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.

A substance is pyrophoric if it ignites spontaneously in air at or below 54 °C (129 °F) or within 5 minutes after coming into contact with air. Examples are organolithium compounds and triethylborane. Pyrophoric materials are often water-reactive as well and will ignite when they contact water or humid air. They can be handled safely in atmospheres of argon or nitrogen. Class D fire extinguishers are designated for use in fires involving pyrophoric materials. A related concept is hypergolicity, in which two compounds spontaneously ignite when mixed.

<span class="mw-page-title-main">Neutron moderator</span> Substance that slows down particles with no electric charge

In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely more susceptible than fast neutrons to propagate a nuclear chain reaction of uranium-235 or other fissile isotope by colliding with their atomic nucleus.

<span class="mw-page-title-main">Lithium aluminium hydride</span> Chemical compound

Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li[AlH4] or LiAlH4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthesis, especially for the reduction of esters, carboxylic acids, and amides. The solid is dangerously reactive toward water, releasing gaseous hydrogen (H2). Some related derivatives have been discussed for hydrogen storage.

<span class="mw-page-title-main">Lithium hydride</span> Chemical compound

Lithium hydride is an inorganic compound with the formula LiH. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not soluble but reactive with all protic organic solvents. It is soluble and nonreactive with certain molten salts such as lithium fluoride, lithium borohydride, and sodium hydride. With a molar mass of 7.95 g/mol, it is the lightest ionic compound.

<span class="mw-page-title-main">Zirconium hydride</span> Alloy of zirconium and hydrogen

Zirconium hydride describes an alloy made by combining zirconium and hydrogen. Hydrogen acts as a hardening agent, preventing dislocations in the zirconium atom crystal lattice from sliding past one another. Varying the amount of hydrogen and the form of its presence in the zirconium hydride controls qualities such as the hardness, ductility, and tensile strength of the resulting zirconium hydride. Zirconium hydride with increased hydrogen content can be made harder and stronger than zirconium, but such zirconium hydride is also less ductile than zirconium.

<span class="mw-page-title-main">Uranium(III) chloride</span> Chemical compound

Uranium(III) chloride, UCl3, is a water soluble salt of uranium. UCl3 is used mostly to reprocess spent nuclear fuel. Uranium(III) chloride is synthesized in various ways from uranium(IV) chloride; however, UCl3 is less stable than UCl4.

<span class="mw-page-title-main">Titanium hydride</span> Chemical compound

Titanium hydride normally refers to the inorganic compound TiH2 and related nonstoichiometric materials. It is commercially available as a stable grey/black powder, which is used as an additive in the production of Alnico sintered magnets, in the sintering of powdered metals, the production of metal foam, the production of powdered titanium metal and in pyrotechnics.

<span class="mw-page-title-main">Uranium nitrides</span> Chemical compound

Uranium nitrides is any of a family of several ceramic materials: uranium mononitride (UN), uranium sesquinitride (U2N3) and uranium dinitride (UN2). The word nitride refers to the −3 oxidation state of the nitrogen bound to the uranium.

<span class="mw-page-title-main">Uranium hydride bomb</span> Type of atomic bomb

The uranium hydride bomb was a variant design of the atomic bomb first suggested by Robert Oppenheimer in 1939 and advocated and tested by Edward Teller. It used deuterium, an isotope of hydrogen, as a neutron moderator in a uranium-deuterium ceramic compact. Unlike all other fission-bomb types, the concept relies on a chain reaction of slow nuclear fission. Bomb efficiency was harmed by the slowing of neutrons since the latter delays the reaction, as delineated by Rob Serber in his 1992 extension of the original Los Alamos Primer.

Zinc hydride is an inorganic compound with the chemical formula ZnH2. It is a white, odourless solid which slowly decomposes into its elements at room temperature; despite this it is the most stable of the binary first row transition metal hydrides. A variety of coordination compounds containing Zn–H bonds are used as reducing agents, but ZnH2 itself has no common applications.

<span class="mw-page-title-main">Hydrogen-moderated self-regulating nuclear power module</span>

The hydrogen-moderated self-regulating nuclear power module (HPM), also referred to as the compact self-regulating transportable reactor (ComStar), is a type of nuclear power reactor using hydride as a neutron moderator. The design is inherently safe, as the fuel and the neutron moderator is uranium hydride UH3, which is reduced at high temperatures (500–800 °C) to uranium and hydrogen. The gaseous hydrogen exits the core, being absorbed by hydrogen absorbing material such as depleted uranium, thus making it less critical. This means that with rising temperature the neutron moderation drops and the nuclear fission reaction in the core is dampened, leading to a lower core temperature. This means as more energy is taken out of the core the moderation rises and the fission process is stoked to produce more heat.

<span class="mw-page-title-main">Thorium compounds</span> Chemical compounds

Many compounds of thorium are known: this is because thorium and uranium are the most stable and accessible actinides and are the only actinides that can be studied safely and legally in bulk in a normal laboratory. As such, they have the best-known chemistry of the actinides, along with that of plutonium, as the self-heating and radiation from them is not enough to cause radiolysis of chemical bonds as it is for the other actinides. While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium have relativistically destabilised and hence delocalised 5f and 6d electrons that participate in chemistry in a similar way to the early transition metals of group 3 through 8: thus, all their valence electrons can participate in chemical reactions, although this is not common for neptunium and plutonium.

Carbohydrides are solid compounds in one phase composed of a metal with carbon and hydrogen in the form of carbide and hydride ions. The term carbohydride can also refer to a hydrocarbon.

<span class="mw-page-title-main">Nitrogen pentahydride</span> Chemical compound

Nitrogen pentahydride, also known as ammonium hydride is a hypothetical compound with the chemical formula NH5. There are two theoretical structures of nitrogen pentahydride. One structure is trigonal bipyramidal molecular geometry type NH5 molecule. Its nitrogen atom and hydrogen atoms are covalently bounded, and its symmetry group is D3h. Another predicted structure of nitrogen pentahydride is an ionic compound, composed of an ammonium ion and a hydride ion (NH4+H−). Until now, no one has synthesized this substance, or proved its existence, and related experiments have not directly observed nitrogen pentahydride. It is only speculated that it may be a reactive intermediate based on reaction products. Theoretical calculations show this molecule is thermodynamically unstable. The reason might be similar to the instability of nitrogen pentafluoride, so the possibility of its existence is low. However, nitrogen pentahydride might exist in special conditions or high pressure. Nitrogen pentahydride was considered for use as a solid rocket fuel for research in 1966.

Lattice confinement fusion (LCF) is a type of nuclear fusion in which deuteron-saturated metals are exposed to gamma radiation or ion beams, such as in an IEC fusor, avoiding the confined high-temperature plasmas used in other methods of fusion.

Neptunium compounds are compounds containing the element neptunium (Np). Neptunium has five ionic oxidation states ranging from +3 to +7 when forming chemical compounds, which can be simultaneously observed in solutions. It is the heaviest actinide that can lose all its valence electrons in a stable compound. The most stable state in solution is +5, but the valence +4 is preferred in solid neptunium compounds. Neptunium metal is very reactive. Ions of neptunium are prone to hydrolysis and formation of coordination compounds.

<span class="mw-page-title-main">Plutonium compounds</span> Chemical compounds containing the element plutonium

Plutonium compounds are compounds containing the element plutonium (Pu). At room temperature, pure plutonium is silvery in color but gains a tarnish when oxidized. The element displays four common ionic oxidation states in aqueous solution and one rare one:

References

  1. ↑ Carl L. Yaws (2008). Thermophysical properties of chemicals and hydrocarbons. William Andrew. pp. 307–. ISBN   978-0-8155-1596-8 . Retrieved 11 October 2011.
  2. 1 2 Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. pp. 239–. ISBN   978-0-12-352651-9 . Retrieved 11 October 2011.
  3. 1 2 Gerd Meyer; Lester R. Morss (1991). Synthesis of lanthanide and actinide compounds. Springer. pp. 44–. ISBN   978-0-7923-1018-1 . Retrieved 11 October 2011.
  4. ↑ Bartscher W.; Boeuf A.; Caciuffo R.; Fournier J.M.; Kuhs W.F.; Rebizant J.; Rustichelli F (1985). "Neutron diffraction study of b-UD3 AND b-UH3". Solid State Commun. 53: 423–426. doi:10.1016/0038-1098(85)91000-2.
  5. 1 2 Seaborg, Glenn T. (1968). "Uranium". The Encyclopedia of the Chemical Elements. Skokie, Illinois: Reinhold Book Corporation. p. 782. LCCCN 68-29938.
  6. ↑ K. H. J. Buschow (2005). Concise encyclopedia of magnetic and superconducting materials. Elsevier. pp. 901–. ISBN   978-0-08-044586-1 . Retrieved 11 October 2011.
  7. ↑ I. N. Toumanov (2003). Plasma and high frequency processes for obtaining and processing materials in the nuclear fuel cycle. Nova Publishers. p. 232. ISBN   1-59033-009-9 . Retrieved 2010-02-07.
  8. 1 2 Amit Arora (2005). Text Book Of Inorganic Chemistry. Discovery Publishing House. p. 789. ISBN   81-8356-013-X . Retrieved 2010-02-07.
  9. ↑ Peter Gevorkian (2009). Alternative Energy Systems in Building Design (GreenSource Books). McGraw Hill Professional. p. 393. ISBN   978-0-07-162147-2 . Retrieved 2010-02-07.
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  12. ↑ "EMSP". Teton.if.uidaho.edu. Archived from the original on 2009-09-30. Retrieved 2010-02-07.
  13. ↑ OECD Nuclear Energy Agency (2006). Advanced nuclear fuel cycles and radioactive waste management. OECD Publishing. p. 176. ISBN   92-64-02485-9 . Retrieved 2010-02-07.
  14. ↑ Abir Al-Tabbaa; J. A. Stegemann (2005). Stabilisation/Solidification Treatment and Remediation: Proceedings of the International Conference on Stabilisation/Solidification Treatment and Remediation, 12–13 April 2005, Cambridge, UK. Taylor & Francis. p. 197. ISBN   0-415-37460-X . Retrieved 2010-02-07.
  15. ↑ International Conference on Nuclear Decom 2001: ensuring safe, secure and successful decommissioning: 16–18 October 2001 Commonwealth Conference and Events Centre, London UK, Issue 8. John Wiley and Sons. 2001. p. 278. ISBN   1-86058-329-6 . Retrieved 2010-02-07.
  16. ↑ "Uranium & Insoluble Compounds". Osha.gov. Archived from the original on 2010-03-22. Retrieved 2010-02-07.
  17. ↑ Lillian Hoddeson; et al. (2004). Critical Assembly: A Technical History of Los Alamos During the Oppenheimer Years, 1943–1945. Cambridge University Press. p. 211. ISBN   0-521-54117-4 . Retrieved 2010-02-07.
  18. 1 2 Peterson, Otis G. (2008-03-20). "Patent Application 11/804450: Self-regulating nuclear power module". United States Patent Application Publication. United States Patent and Trademark Office, Federal Government of the United States, Washington, DC, USA. Retrieved 2009-09-05.
  19. ↑ Harry Julius Emeléus (1974). Advances in inorganic chemistry and radiochemistry. Vol. 16. Academic Press. p. 235. ISBN   0-12-023616-8 . Retrieved 2010-02-07.
  20. ↑ Simon Cotton (2006). Lanthanide and actinide chemistry. John Wiley and Sons. p. 170. ISBN   0-470-01006-1 . Retrieved 2010-02-07.
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  22. ↑ "Photo – Tickling the Dragon's Tail". Mphpa.org. 2005-08-03. Archived from the original on 2010-02-18. Retrieved 2010-02-07.
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  24. ↑ E. E. Shpil'rain (1987). Thermophysical properties of lithium hydride, deuteride, and tritide and of their solutions with lithium. Springer. p. 104. ISBN   0-88318-532-6 . Retrieved 2010-02-07.
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  26. ↑ Fred Rosebury (1992). Handbook of electron tube and vacuum techniques. Springer. p. 121. ISBN   1-56396-121-0 . Retrieved 2010-02-07.
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