Uranium(III) hydride: Difference between revisions
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'''Uranium hydride''' (UH<sub>3</sub>) is an [[inorganic compound]], a [[transition metal hydride|hydride]] of [[uranium]]. |
'''Uranium hydride''', also called '''uranium trihydride''' (UH<sub>3</sub>) is an [[inorganic compound]], a [[transition metal hydride|hydride]] of [[uranium]]. It is a highly toxic, brownish gray to brownish black [[pyrophoric]] powder. It is electrically conductive.<ref name="ans">http://www.answers.com/topic/uranium-hydride</ref> Its [[CAS number]] is 7440-61-1 or 13598-56-6. Its [[specific gravity]] at 20 °C is 10.95, much lower than of uranium. It is slightly soluble in [[hydrochloric acid]] and decomposes in [[nitric acidd]]. |
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Uranium metal heated to 250 to 300 [[Celsius|°C]] (482 to 572 [[Fahrenheit|°F]]) reacts with [[hydrogen]] to form [[uranium hydride]]. Even higher temperatures 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.<ref name="EncyChem782">{{Harvnb|Seaborg|1968|p=782}}.</ref> Two crystal modifications of uranium hydride exist: an α form that is obtained at low temperatures and a β form that is created when the formation temperature is above 250 °C.<ref name="EncyChem782"/> |
Uranium metal heated to 250 to 300 [[Celsius|°C]] (482 to 572 [[Fahrenheit|°F]]) reacts with [[hydrogen]] to form [[uranium hydride]]. Even higher temperatures 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.<ref name="EncyChem782">{{Harvnb|Seaborg|1968|p=782}}.</ref> Two crystal modifications of uranium hydride exist: an α form that is obtained at low temperatures and a β form that is created when the formation temperature is above 250 °C.<ref name="EncyChem782"/> |
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Uranium hydride can be used for [[isotope separation]] of [[hydrogen]], preparing uranium metal powder, and as a [[reducing agent]].<ref name="ans" /> |
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Uranium hydride forms when uranium metal get sexposed to water; the reaction proceeds as follows: |
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:4 U + 6 H<sub>2</sub>O → 3 O<sub>2</sub> + 4 UH<sub>3</sub> |
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The formed uranium hydride is pyrophoric; when the metal (e.g. a damaged [[fuel rod]]) gets exposed to air afterwards, a lot of heat may be generated. Hydride-contaminated uranium can be [[passivated]] by exposition to a gaseous mixture of 98% [[helium]] with 2% [[oxygen]].<ref>http://teton.if.uidaho.edu/emsp/overviewflowviz.html</ref> |
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Uranium hydride exposed to water evolves hydrogen. In contact with strong oxidizers may cause fire and explosions. Contact with [[halocarbon]]s may cause violent reaction.<ref>http://www.osha.gov/SLTC/healthguidelines/uraniuminsolublecompounds/recognition.html</ref> |
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Uranium hydride and uranium [[deuterium|deuteride]] were suggested as a [[fissile material]] for an [[uranium hydride bomb]]. The tests with uranium hydride and uranium deuteride during the [[Operation Upshot-Knothole]] were however disappointing. |
Uranium hydride and uranium [[deuterium|deuteride]] were suggested as a [[fissile material]] for an [[uranium hydride bomb]]. The tests with uranium hydride and uranium deuteride during the [[Operation Upshot-Knothole]] were however disappointing. |
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Uranium deuteride is said to be usable for design of some types of [[neutron initiator]]s. |
Uranium deuteride is said to be usable for design of some types of [[neutron initiator]]s. |
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Uranium hydride is proposed as a combined [[nuclear fuel]]/[[neutron moderator]] for the [[Hydrogen Moderated Self-regulating Nuclear Power Module]] and the [[Hyperion Power Generation]] reactor. 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.<ref name="USPatApp11804450">{{cite web |url=http://www.google.com/patents?id=_WGoAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q=&f=false |title=Patent Application 11/804450: Self-regulating nuclear power module |last=Peterson|first=Otis G. |date=2008-03-20 |work=United States Patent Application Publication |publisher=United States Patent and Trademark Office, Federal Government of the United States, Washington, DC, USA |accessdate=2009-09-05}}</ref> 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 U-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 {{convert|800|°C|-2}}, 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 reaction|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.<ref name="USPatApp11804450" /> |
Uranium hydride [[enriched]] to about 10% [[uranium-235]] is proposed as a combined [[nuclear fuel]]/[[neutron moderator]] for the [[Hydrogen Moderated Self-regulating Nuclear Power Module]] and the [[Hyperion Power Generation]] [[nuclear reactor]]. 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.<ref name="USPatApp11804450">{{cite web |url=http://www.google.com/patents?id=_WGoAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q=&f=false |title=Patent Application 11/804450: Self-regulating nuclear power module |last=Peterson|first=Otis G. |date=2008-03-20 |work=United States Patent Application Publication |publisher=United States Patent and Trademark Office, Federal Government of the United States, Washington, DC, USA |accessdate=2009-09-05}}</ref> 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 U-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 {{convert|800|°C|-2}}, 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 reaction|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.<ref name="USPatApp11804450" /> |
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'''Uranium zirconium hydride''', a combination of uranium hydride and [[zirconium(II) hydride]], is used as a fuel/moderator in the [[TRIGA]]-class reactors. |
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[[Category:Nuclear fuels]] |
[[Category:Nuclear fuels]] |
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[[Category:Neutron moderators]] |
[[Category:Neutron moderators]] |
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[[Category:Reducing agents]] |
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Revision as of 00:23, 7 February 2010
Uranium hydride, also called uranium trihydride (UH3) is an inorganic compound, a hydride of uranium. It is a highly toxic, brownish gray to brownish black pyrophoric powder. It is electrically conductive.[1] Its CAS number is 7440-61-1 or 13598-56-6. Its specific gravity at 20 °C is 10.95, much lower than of uranium. It is slightly soluble in hydrochloric acid and decomposes in nitric acidd.
Uranium metal heated to 250 to 300 °C (482 to 572 °F) reacts with hydrogen to form uranium hydride. Even higher temperatures 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.[2] Two crystal modifications of uranium hydride exist: an α form that is obtained at low temperatures and a β form that is created when the formation temperature is above 250 °C.[2]
Uranium hydride can be used for isotope separation of hydrogen, preparing uranium metal powder, and as a reducing agent.[1]
Uranium hydride forms when uranium metal get sexposed to water; the reaction proceeds as follows:
- 4 U + 6 H2O → 3 O2 + 4 UH3
The formed uranium hydride is pyrophoric; when the metal (e.g. a damaged fuel rod) gets exposed to air afterwards, a lot of heat may be generated. Hydride-contaminated uranium can be passivated by exposition to a gaseous mixture of 98% helium with 2% oxygen.[3]
Uranium hydride exposed to water evolves hydrogen. In contact with strong oxidizers may cause fire and explosions. Contact with halocarbons may cause violent reaction.[4]
Uranium hydride and uranium deuteride were suggested as a fissile material for an uranium hydride bomb. The tests with uranium hydride and uranium deuteride during the Operation Upshot-Knothole were however disappointing.
Uranium deuteride is said to be usable for design of some types of neutron initiators.
Uranium hydride enriched to about 10% uranium-235 is proposed as a combined nuclear fuel/neutron moderator for the Hydrogen Moderated Self-regulating Nuclear Power Module and the Hyperion Power Generation nuclear reactor. 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.[5] 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 U-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.[5]
Uranium zirconium hydride, a combination of uranium hydride and zirconium(II) hydride, is used as a fuel/moderator in the TRIGA-class reactors.
References
- ^ a b http://www.answers.com/topic/uranium-hydride
- ^ a b Seaborg 1968, p. 782.
- ^ http://teton.if.uidaho.edu/emsp/overviewflowviz.html
- ^ http://www.osha.gov/SLTC/healthguidelines/uraniuminsolublecompounds/recognition.html
- ^ a b 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.