[[Uranium dioxide]] is converted with [[hydrofluoric acid]] (HF) to [[uranium tetrafluoride]]:<ref name=Ull>{{cite book |doi=10.1002/14356007.a27_281.pub2 |chapter=Uranium, Uranium Alloys, and Uranium Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2007 |last1=Peehs |first1=Martin |last2=Walter |first2=Thomas |last3=Walter |first3=Sabine |last4=Zemek |first4=Martin |isbn=978-3-527-30385-4 }}</ref>
[[Uranium dioxide]] is converted with [[hydrofluoric acid]] (HF) to [[uranium tetrafluoride]]:<ref name=Ull>{{cite book |doi=10.1002/14356007.a27_281.pub2 |chapter=Uranium, Uranium Alloys, and Uranium Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2007 |last1=Peehs |first1=Martin |last2=Walter |first2=Thomas |last3=Walter |first3=Sabine |last4=Zemek |first4=Martin |isbn=978-3-527-30385-4 }}</ref>
:{{chem2|UO2 + 4 HF -> UF4 + 2 H2O}}
:{{chem2|UO2 + 4 HF -> UF4 + 2 H2O}}
In samples contaminated with [[uranium trioxide]], the [[oxyfluoride]] is produced in the HF step:
:{{chem2|UO3 + 2 HF -> UF2O2 + H2O}}
The resulting {{chem2|UF4}} is subsequently oxidized with [[fluorine]] to give the hexafluoride:
The resulting {{chem2|UF4}} is subsequently oxidized with [[fluorine]] to give the hexafluoride:
:{{chem2|UF4 + F2 -> UF6}}
:{{chem2|UF4 + F2 -> UF6}}
In samples contaminated with [[uranium trioxide]], [[uranyl fluoride]], an [[oxyfluoride]] compound is produced in the HF step:
:{{chem2|UO3 + 2 HF -> UO2F2 + H2O}}
which can be fluorinated to produce the same product, uranium hexafluoride.
:{{chem2|UO2F2 + 5 F2 -> UF6 + O2}}
The fluorination step in both reactions above are highly exothermic.
==Properties==
==Properties==
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In addition to its use in enrichment, uranium hexafluoride has been used in an advanced reprocessing method ([[fluoride volatility]]), which was developed in the [[Czech Republic]]. In this process, [[spent nuclear fuel]] is treated with fluorine gas to transform the oxides or elemental metals into a mixture of fluorides. This mixture is then distilled to separate the different classes of material. Some [[fission product]]s form nonvolatile fluorides which remain as solids and can then either be prepared for storage as nuclear waste or further processed either by [[solvation]]-based methods or [[electrochemistry|electrochemically]].
In addition to its use in enrichment, uranium hexafluoride has been used in an advanced reprocessing method ([[fluoride volatility]]), which was developed in the [[Czech Republic]]. In this process, [[spent nuclear fuel]] is treated with fluorine gas to transform the oxides or elemental metals into a mixture of fluorides. This mixture is then distilled to separate the different classes of material. Some [[fission product]]s form nonvolatile fluorides which remain as solids and can then either be prepared for storage as nuclear waste or further processed either by [[solvation]]-based methods or [[electrochemistry|electrochemically]].
Uranium enrichment produces large quantities of [[depleted uranium hexafluoride]] (D{{chem2|UF6}} or D-{{chem2|UF6}}) as a waste product. The long-term storage of D-{{chem2|UF6}} presents environmental, health, and safety risks because of its chemical instability. When {{chem2|UF6}} is exposed to moist air, it reacts with the water in the air to produce {{chem2|UO2F2}} ([[uranyl fluoride]]) and HF ([[hydrogen fluoride]]) both of which are highly corrosive and toxic. In 2005, 686,500 tonnes of D-{{chem2|UF6}} was housed in 57,122 storage cylinders located near [[Portsmouth, Ohio]]; [[Oak Ridge, Tennessee]]; and [[Paducah, Kentucky]].<ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=How much depleted uranium hexafluoride is stored in the United States? |url=https://web.evs.anl.gov/uranium/faq/mgmt/faq23.cfm |publisher=[[Argonne National Laboratory]]}}</ref><ref>{{cite web |title=Depleted UF<sub>6</sub> Management Program Documents |url=https://web.evs.anl.gov/uranium/documents/ |access-date=2006-05-17 |url-status=live |archive-url=https://web.archive.org/web/20080216013118/http://web.ead.anl.gov/uranium/documents/index.cfm |archive-date=2008-02-16}}</ref> Storage cylinders must be regularly inspected for signs of corrosion and leaks. The estimated lifetime of the steel cylinders is measured in decades.<ref>{{cite web |publisher=Institute for Energy and Environmental Research |date=2007-09-24 |title=What is DUF<sub>6</sub>? Is it dangerous and what should we do with it? |url=http://www.ieer.org/sdafiles/vol_5/5-2/deararj.html}}</ref>
Uranium enrichment produces large quantities of [[depleted uranium hexafluoride]] (D{{chem2|UF6}} or D-{{chem2|UF6}}) as a waste product. The long-term storage of D-{{chem2|UF6}} presents environmental, health, and safety risks because of its chemical instability. When {{chem2|UF6}} is exposed to moist air, it reacts with the water in the air to produce {{chem2|UO2F2}} ([[uranyl fluoride]]) and HF ([[hydrogen fluoride]]) both of which are highly corrosive and toxic. In 2005, 686,500 tonnes of D-{{chem2|UF6}} was housed in 57,122 storage cylinders located near [[Portsmouth, Ohio|Portsmouth]], Ohio; [[Oak Ridge, Tennessee|Oak Ridge]], Tennessee; and [[Paducah, Kentucky|Paducah]], Kentucky.<ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=How much depleted uranium hexafluoride is stored in the United States? |url=https://web.evs.anl.gov/uranium/faq/mgmt/faq23.cfm |publisher=[[Argonne National Laboratory]]}}</ref><ref>{{cite web |title=Depleted UF<sub>6</sub> Management Program Documents |url=https://web.evs.anl.gov/uranium/documents/ |access-date=2006-05-17 |url-status=live |archive-url=https://web.archive.org/web/20080216013118/http://web.ead.anl.gov/uranium/documents/index.cfm |archive-date=2008-02-16}}</ref> Storage cylinders must be regularly inspected for signs of corrosion and leaks. The estimated lifetime of the steel cylinders is measured in decades.<ref>{{cite web |publisher=Institute for Energy and Environmental Research |date=2007-09-24 |title=What is DUF<sub>6</sub>? Is it dangerous and what should we do with it? |url=http://www.ieer.org/sdafiles/vol_5/5-2/deararj.html| archive-url=https://web.archive.org/web/20071014065307/http://www.ieer.org/sdafiles/vol_5/5-2/deararj.html| archive-date = 14 October 2007}}</ref>
== Accidents and disposal ==
== Accidents and disposal ==
There have been several accidents involving uranium hexafluoride in the US, including a cylinder-filling accident and material release at the [[Sequoyah Fuels Corporation]] in 1986 where an estimated 29 500 pounds of gaseous {{chem2|UF6}} escaped.<ref>{{cite journal | pmc=1963288 | date=2007 | last1=Brugge | first1=D. | last2=Delemos | first2=J. L. | last3=Bui | first3=C. | title=The Sequoyah Corporation Fuels Release and the Church Rock Spill: Unpublicized Nuclear Releases in American Indian Communities | journal=American Journal of Public Health | volume=97 | issue=9 | pages=1595–1600 | doi=10.2105/AJPH.2006.103044 | pmid=17666688 }}</ref><ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=Have there been accidents involving uranium hexafluoride? |url=http://web.ead.anl.gov/uranium/faq/health/faq30.cfm |publisher=Argonne National Laboratory |archive-url=https://web.archive.org/web/20170609171651/http://web.ead.anl.gov/uranium/faq/health/faq30.cfm |archive-date=2017-06-09}}</ref> The U.S. government has been converting D{{chem2|UF6}} to solid [[uranium oxides]] for disposal.<ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=What is going to happen to the uranium hexafluoride stored in the United States? |url=https://web.evs.anl.gov/uranium/faq/storage/faq22.cfm |publisher=Argonne National Laboratory}}</ref> Such disposal of the entire D{{chem2|UF6}} stockpile could cost anywhere from $15 million to $450 million.<ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=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 UF<sub>6</sub> inventory? |url=http://web.evs.anl.gov/uranium/faq/mgmt/faq27.cfm |publisher=Argonne National Laboratory}}</ref>
There have been several accidents involving uranium hexafluoride in the US, including a cylinder-filling accident and material release at the [[Sequoyah Fuels Corporation]] in 1986 where an estimated 29 500 pounds of gaseous {{chem2|UF6}} escaped.<ref>{{cite journal | pmc=1963288 | date=2007 | last1=Brugge | first1=D. | last2=Delemos | first2=J. L. | last3=Bui | first3=C. | title=The Sequoyah Corporation Fuels Release and the Church Rock Spill: Unpublicized Nuclear Releases in American Indian Communities | journal=American Journal of Public Health | volume=97 | issue=9 | pages=1595–1600 | doi=10.2105/AJPH.2006.103044 | pmid=17666688 }}</ref><ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=Have there been accidents involving uranium hexafluoride? |url=http://web.ead.anl.gov/uranium/faq/health/faq30.cfm |publisher=Argonne National Laboratory |archive-url=https://web.archive.org/web/20170609171651/http://web.ead.anl.gov/uranium/faq/health/faq30.cfm |archive-date=2017-06-09}}</ref> The US government has been converting D{{chem2|UF6}} to solid [[uranium oxides]] for disposal.<ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=What is going to happen to the uranium hexafluoride stored in the United States? |url=https://web.evs.anl.gov/uranium/faq/storage/faq22.cfm |publisher=Argonne National Laboratory}}</ref> Such disposal of the entire D{{chem2|UF6}} stockpile could cost anywhere from $15 million to $450 million.<ref>{{cite web |work=Depleted UF<sub>6</sub> FAQs |title=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 UF<sub>6</sub> inventory? |url=http://web.evs.anl.gov/uranium/faq/mgmt/faq27.cfm |publisher=Argonne National Laboratory}}</ref>
{{Gallery
{{Gallery
|width=250
|width=250
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}}
}}
==See also==
* [[Enriched uranium]]
==References==
==References==
{{Reflist}}
{{Reflist}}
==Further reading==
==Further reading==
* ''[[Gmelins Handbuch der anorganischen Chemie]]'', System Nr. 55, Uran, Teil A, p. 121–123.
{{refbegin|30em}}
* ''Gmelins Handbuch der anorganischen Chemie'', System Nr. 55, Uran, Teil C 8, p. 71–163.
* {{cite book
* R. DeWitt: ''Uranium hexafluoride: A survey of the physico-chemical properties'', Technical report, GAT-280; Goodyear Atomic Corp., Portsmouth, Ohio; 12. August 1960; {{doi|10.2172/4025868}}.
| title = [[Gmelins Handbuch der anorganischen Chemie]]
* Ingmar Grenthe, Janusz Drożdżynński, Takeo Fujino, Edgar C. Buck, [[Thomas E. Albrecht-Schmitt]], Stephen F. Wolf: [http://radchem.nevada.edu/classes/rdch710/files/Uranium.pdf Uranium] {{Webarchive|url=https://web.archive.org/web/20120118213655/http://radchem.nevada.edu/classes/rdch710/files/Uranium.pdf |date=2012-01-18}}, in: Lester R. Morss, Norman M. Edelstein, Jean Fuger (Hrsg.): ''The Chemistry of the Actinide and Transactinide Elements'', Springer, Dordrecht 2006; {{ISBN|1-4020-3555-1}}, p. 253–698; {{doi|10.1007/1-4020-3598-5_5}} (p. 530–531, 557–564).
| volume = System Nr. 55, Uran, Teil A
* US-Patent 2535572: [https://www.freepatentsonline.com/2535572.html Preparation of UF<sub>6</sub>]; 26. December 1950.
| pages = 121–123
* US-Patent 5723837: [https://www.freepatentsonline.com/5723837.html Uranium Hexafluoride Purification]; 3. March 1998.
| publisher = Verlag Chemie, Gmelin-Institut für Anorganische
| location = Weinheim
| year = 1955
|orig-year=1817
| language = de
| editor-first= Leopold
|editor-last =Gmelin
}}
* {{cite book
| title = [[Gmelins Handbuch der anorganischen Chemie]]
| volume = System Nr. 55, Uran, Teil C
| pages = 71–163
| publisher = Verlag Chemie, Gmelin-Institut für Anorganische
| location = Weinheim
|orig-year=1817
| language = de
| editor-first= Leopold
|editor-last =Gmelin
}}
* {{cite report
| last = DeWitt
| first = R.
| title = Uranium hexafluoride: A survey of the physico-chemical properties
* Simon Cotton (Uppingham School, Rutland, UK): [http://www.chm.bris.ac.uk/motm/uf6/uf6v.htm Uranium Hexafluoride].
* Simon Cotton (Uppingham School, Rutland, UK): [http://www.chm.bris.ac.uk/motm/uf6/uf6v.htm Uranium Hexafluoride].
* [https://web.evs.anl.gov/uranium/guide/uf6/ Uranium Hexafluoride (UF<sub>6</sub>) – Physical and chemical properties of UF<sub>6</sub>, and its use in uranium processing – Uranium Hexafluoride and Its Properties]
* [https://web.evs.anl.gov/uranium/guide/uf6/ Uranium Hexafluoride (UF<sub>6</sub>) – Physical and chemical properties of UF<sub>6</sub>, and its use in uranium processing – Uranium Hexafluoride and Its Properties]
As one of the most volatile compounds of uranium, uranium hexafluoride is relatively convenient to process and is used in both of the main uranium enrichment methods, namely gaseous diffusion and the gas centrifuge method. Since the triple point of Template:Chem2; 64 °C(147 °F; 337 K) and 152 kPa (22 psi; 1.5 atm);[10] is close to ambient conditions, phase transitions can be achieved with little thermodynamic work.
Fluorine has only a single naturally occurring stable isotope, so isotopologues of Template:Chem2 differ in their molecular weight based solely on the uranium isotope present.[11] This difference is the basis for the physical separation of isotopes in enrichment.
All the other uranium fluorides are nonvolatile solids that are coordination polymers.
Gaseous diffusion requires about 60 times as much energy as the gas centrifuge process: gaseous diffusion-produced nuclear fuel produces 25 times more energy than is used in the diffusion process, while centrifuge-produced fuel produces 1,500 times more energy than is used in the centrifuge process.
In addition to its use in enrichment, uranium hexafluoride has been used in an advanced reprocessing method (fluoride volatility), which was developed in the Czech Republic. In this process, spent nuclear fuel is treated with fluorine gas to transform the oxides or elemental metals into a mixture of fluorides. This mixture is then distilled to separate the different classes of material. Some fission products form nonvolatile fluorides which remain as solids and can then either be prepared for storage as nuclear waste or further processed either by solvation-based methods or electrochemically.
Uranium enrichment produces large quantities of depleted uranium hexafluoride (DTemplate:Chem2 or D-Template:Chem2) as a waste product. The long-term storage of D-Template:Chem2 presents environmental, health, and safety risks because of its chemical instability. When Template:Chem2 is exposed to moist air, it reacts with the water in the air to produce Template:Chem2 (uranyl fluoride) and HF (hydrogen fluoride) both of which are highly corrosive and toxic. In 2005, 686,500 tonnes of D-Template:Chem2 was housed in 57,122 storage cylinders located near Portsmouth, Ohio; Oak Ridge, Tennessee; and Paducah, Kentucky.[13][14] Storage cylinders must be regularly inspected for signs of corrosion and leaks. The estimated lifetime of the steel cylinders is measured in decades.[15]
Accidents and disposal
There have been several accidents involving uranium hexafluoride in the US, including a cylinder-filling accident and material release at the Sequoyah Fuels Corporation in 1986 where an estimated 29 500 pounds of gaseous Template:Chem2 escaped.[16][17] The US government has been converting DTemplate:Chem2 to solid uranium oxides for disposal.[18] Such disposal of the entire DTemplate:Chem2 stockpile could cost anywhere from $15 million to $450 million.[19]Script error: No such module "Gallery".
↑J. C. Taylor, P. W. Wilson, J. W. Kelly: „The structures of fluorides. I. Deviations from ideal symmetry in the structure of crystalline UF6: a neutron diffraction analysis", Acta Crystallogr., 1973, B29, p. 7–12; Script error: No such module "doi"..
