六氟化鈾

六氟化鈾
	IUPAC名; 六氟化鈾; 氟化鈾(VI)
识别
CAS号	7783-81-5
结构
晶体结构	六方紧密堆积 (HCP)
分子构型	八面体
偶极矩	0
热力学
ΔfHmo298K	-2317 kJ/mol
So298K	228 J.K−1.mol−1
相关物质
其他阴离子	氯化鈾（VI）
其他阳离子	氟化釷（IV）; 氟化鏷（V）; 氟化錼（VI）; 氟化鈽（VI）
相关化学品	三氟化鈾; 四氟化鈾; 五氟化鈾
	若非注明，所有数据来自25 ℃，100 kPa。

六氟化鈾是一个铀化合物，分子式为UF₆。六氟化铀被用于浓缩铀的制取，因此在核工业中有很重要的地位。标准状况下，六氟化铀为灰色的晶体。六氟化铀有很强的毒性，可与水剧烈反应，并且腐蚀大多数金属。它與鋁反應溫和，因為會在鋁的表面會形成一個AlF₃的薄層，阻止了進一步的反應。

[编辑] 制取

磨碎鈾礦（U₃O₈，或稱“黃餅”），并将其溶于硝酸，產生硝酸鈾酰UO₂(NO₃)₂溶液。萃取纯化后，使硝酸铀酰与氨反应，生成重铀酸铵(NH₄)₂U₂O₇。加氢还原得到二氧化铀，再与氢氟酸反应生成四氟化铀。四氟化铀與氟进行氧化反應產生UF₆。

[编辑] 核燃料循環中的應用

各种主要的铀浓缩方法都需要用到六氟化铀，不论是气体扩散法，还是气体离心法。这是由于六氟化铀的三相点为 147 °F （64 °C，337 K），且气压略高于大气压。氟在自然界只存在一种稳定核素也是一个原因，因此各种六氟化铀分子的相对分子质量差异可以完全归咎于各种铀核素相对原子质量的差异。^[1]

玻璃管中的六氟化鈾

其他所有的氟化鈾將產生固態的配位聚合物。

气相扩散法所需用的能量大约是气体离心法的60倍。尽管如此，其中仅仅有4%的能量被用于制取浓缩铀。

除此之外，捷克发展了一种循环使用核燃料的方法：用旧的氧化物核燃料与氟气反应生成各种氟化物的混合物，再用分馏分离各种组分。

[编辑] 储存

目前大约95%的贫化铀都以六氟化铀的形式被置于气体钢瓶中，储存在核工厂的附近。每个钢瓶大约含有12.7吨的固体六氟化铀。仅在美国，1993年至2005年期间，就有686,500吨的六氟化铀（57,122瓶）作为贫化铀的储存形式被生产出来。它们被储存在俄亥俄州樸茨茅夫，田納西州橡樹嶺和肯塔基州帕迪尤卡。^[2]^[3]六氟化铀不很稳定，与潮湿空气接触时即会反应生成极易溶于水并且毒性很大的 UO₂F₂ 和氟化氢，因此长期储存六氟化铀会对环境及人的健康造成损害，须定期检查是否有裂缝。^[4]

美国已经发生过数起涉及六氟化铀的事故。^[5]^[6]美国政府将 UF₆ 转化为固态的铀氧化物回收。^[7]但这种回收总共要花费大约1500万到4.5亿美元。^[8]

[编辑] 化學性質

固態時的結構由 J.H. Levy、J.C Taylor 和 A.B Waugh所描述。^[9]在該論文中，他們利用中子衍射測定UF₆、 MoF₆ 和 WF₆ 在77K下的結構。

六氟化铀的晶体结构

六氟化铀可作为氧化剂或路易斯酸，易于氟离子结合。如氟化铜与六氟化铀在乙腈中反应会生成 Cu[UF₇]₂.5MeCN。^[10]

含有有机阳离子的铀（VI）聚合物已经制得并用X光衍射分析。^[11]

[编辑] 其他铀氟化物

C.J. Howard，J.C. Taylor 和 A.B. Waugh 提出了五氟化铀（UF₅）和九氟化二铀（U₂F₉）的结构。^[12]三氟化铀的结构则由 J. Laveissiere 阐明。^[13]

J.H. Levy，J.C. Taylor 和 P.W. Wilson 提出了四氟氧铀的结构。^[14]

[编辑] 参见

[编辑] 参考资料

^ Uranium Enrichment and the Gaseous Diffusion Process. USEC Inc [2007-09-24].
^ How much depleted uranium hexafluoride is stored in the United States?. Depleted UF₆ FAQs. Argonne National Laboratory.
^ Documents
^ 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: Characteristics, Transport and Storage at the Siberian Chemical Combine (Sibkhimkombinat) Tomsk (briefing note). Large and Associates. 5 November 2005 [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. Neutron powder structural studies of UF₆, MoF₆ and WF₆ at 77 K. Journal of Fluorine Chemistry. 1983, 23: 29-36. doi:10.1016/S0022-1139(00)81276-2.
^ Berry JA, Poole RT, Prescott A, Sharp DWA, Winfield JM. The oxidising and fluoride ion acceptor properties of uranium hexafluoride in acetonitrile. J. Chem. Soc. Dalton Trans.. 1976: 272. doi:10.1039/DT9760000272. x
^ Walker SM, Halasyamani PS, Allen S, O'Hare D. 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.. 1999, 121: 10513. doi:10.1021/ja992145f. x
^ Howard CJ, Taylor JC, Waugh AB. Crystallographic parameters in α-UF₅ and U₂F₉ by multiphase refinement of high-resolution neutron powder data. Journal of Solid State Chemistry. 1982, 45: 396-398. doi:10.1016/0022-4596(82)90185-2. x
^ Laveissiere J. Bulletin de la Societe Francaise de Mineralogie et de Cristallographie. 1967, 90: 304-307.
^ Levy JH, Taylor JC, Wilson PW. Structure of fluorides .17. NEUTRON-DIFFRACTION STUDY OF ALPHA-URANIUM OXIDE TETRAFLUORIDE. Journal of Inorganic and Nuclear Chemistry. 1977, 39: 1989-1991.

[编辑] 延伸阅读

Levy JH. Structure of fluorides. Part XII. Single-crystal neutron diffraction study of uranium hexafluoride at 293 K. J. Chem. Soc. Dalton Trans.. 1976: 219. doi:10.1039/DT9760000219. x (xstal structure)
Olah GH, Welch J. Synthetic methods and reactions. 46. Oxidation of organic compounds with uranium hexafluoride in haloalkane solutions. J. Am. Chem. Soc.. 1978, 100: 5396. doi:10.1021/ja00485a024. x (selective oxidant of CFCs)

[0] Uranium Enrichment and the Gaseous Diffusion Process. USEC Inc [2007-09-24].

[1] How much depleted uranium hexafluoride is stored in the United States?. Depleted UF₆ FAQs. Argonne National Laboratory.

[2] Documents

[3] What is DUF₆? Is it dangerous and what should we do with it?. Institute for Energy and Environmental Research. 2007-09-24.

[4] Have there been accidents involving uranium hexafluoride?. Depleted UF₆ FAQs. Argonne National Laboratory.

[5] Uranium Hexafluoride (UF₆) Tailings: Characteristics, Transport and Storage at the Siberian Chemical Combine (Sibkhimkombinat) Tomsk (briefing note). Large and Associates. 5 November 2005 [2007-09-24].

[6] What is going to happen to the uranium hexafluoride stored in the United States?. Depleted UF₆ FAQs. Argonne National Laboratory.

[7] 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.

[8] J.H. Levy, J.C Taylor and A.B Waugh. Neutron powder structural studies of UF₆, MoF₆ and WF₆ at 77 K. Journal of Fluorine Chemistry. 1983, 23: 29-36. doi:10.1016/S0022-1139(00)81276-2.

[9] Berry JA, Poole RT, Prescott A, Sharp DWA, Winfield JM. The oxidising and fluoride ion acceptor properties of uranium hexafluoride in acetonitrile. J. Chem. Soc. Dalton Trans.. 1976: 272. doi:10.1039/DT9760000272. x

[10] Walker SM, Halasyamani PS, Allen S, O'Hare D. 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.. 1999, 121: 10513. doi:10.1021/ja992145f. x

[11] Howard CJ, Taylor JC, Waugh AB. Crystallographic parameters in α-UF₅ and U₂F₉ by multiphase refinement of high-resolution neutron powder data. Journal of Solid State Chemistry. 1982, 45: 396-398. doi:10.1016/0022-4596(82)90185-2. x

[12] Laveissiere J. Bulletin de la Societe Francaise de Mineralogie et de Cristallographie. 1967, 90: 304-307.

[13] Levy JH, Taylor JC, Wilson PW. Structure of fluorides .17. NEUTRON-DIFFRACTION STUDY OF ALPHA-URANIUM OXIDE TETRAFLUORIDE. Journal of Inorganic and Nuclear Chemistry. 1977, 39: 1989-1991.

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