Uranium tetrafluoride

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Uranium tetrafluoride

General
Systematic name	Uranium(IV) fluoride
Other names	Uranium(IV) fluoride
Molecular formula	UF₄
Molar mass	314.0226 g/mol
Appearance	Green crystalline solid.
CAS number	[[10049-14-6] [1]]
Properties
Density and phase	6.7 g/cm^-3, solid.
Solubility in water	Insoluable.
Melting point	1036°C
Boiling point	1417°C (Subl.)
Acidity (pK_a)	N/A
Hazards
MSDS	External MSDS
EU classification	Irritant (I), Very Toxic (+T)
NFPA 704	N/A
R-phrases	R14, R15/29. R29
S-phrases	Not listed.
Flash point	Non-flammable.
RTECS number	N/A
Supplementary data page
Structure & properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	None.
Related compounds	Uranium hexafluoride, uranium oxide.
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references

Uranium tetrafluoride (UF₄) is a green crystalline solid compound of uranium with an insignificant vapor pressure and very slight solubility in water. Uranium in its tetravalent (uranous) state is very important in different technological processes. In the uranium refining industry it is known as "Green salt"

UF₄ is generally an intermediate in the conversion of uranium hexafluoride (UF₆) to either uranium oxides (U₃O₈ or UO₂) or uranium metal. It is formed by the reaction of UF₆ with hydrogen gas in a vertical tube-type reactor or by the action of hydrogen fluoride(HF) on uranium dioxide. UF₄ is less stable than the uranium oxides and reacts slowly with moisture at ambient temperature, forming UO₂ and HF, which are very corrosive; it is thus a less favorable form for long-term disposal. The bulk density of UF₄ varies from about 2.0 g/cm3 to about 4.5 g/cm3 depending on the production process and the properties of the starting uranium compounds.

A molten salt reactor design, a type of nuclear reactor where the working fluid is a molten salt, would use UF₄ as the core material. UF₄ is generally chosen over other salts because of the usefulness of the elements without isotope separation, better neutron economy and moderating efficiency, lower vapor pressure and better chemical stability.

Like all uranium salts UF₄ is toxic and thus harmful by inhalation, ingestion and through skin contact. Being radioactive it may also cause cancer, probably through exposure to the breakdown product radon gas and its daughters.

[edit] References

Booth H. S., Krasny-Ergen W.,Heath R. E. (1946). "Uranium Tetrafluoride". Journal of the American Chemical Society 68: 1969-1970. DOI:10.1021/ja01214a028.
S. Kern, J. Hayward,S. Roberts, J. W. Richardson, F. J. Rotella, L. Soderholm, B. Cort, M. Tinkle, M. West, D. Hoisington, G. H. Lander (1994). "Temperature variation of the structural parameters in actinide tetrafluorides". Journal of Chemical Physics 101: 9333-9337. DOI:10.1063/1.467963.