What are the properties of uranium hexafluoride?
Uranium hexafluoride can be a solid, liquid, or gas, depending on its temperature and pressure. At atmospheric pressure (14.7 psia), UF6 is a solid below a temperature of 134° F (57° C) and a gas at temperatures above 134° F. Solid UF6 is a white, dense, crystalline material that resembles rock salt. Liquid UF6 is formed only at temperatures greater than 147° F (64° C) and at pressures greater than 1.5 times atmospheric pressure (about 22 psia). At atmospheric pressure, solid UF6 will transform directly to UF6 gas (sublimation) when the temperature is raised to 134° F (57° C), without going through a liquid phase. These properties are shown in the phase diagram below, which presents the different physical forms of UF6 as a function of temperature and pressure.
Uranium hexafluoride does not react with oxygen, nitrogen, carbon dioxide, or dry air, but it does react with water. When UF6 comes into contact with water, such as water vapor in the air, the UF6 and water react, forming corrosive hydrogen fluoride (HF) and a uranium-fluoride compound called uranyl fluoride (UO2F2).
Additional information can be found in the "Properties of Uranium and Its Compounds" section of this web site: ( http://web.ead.anl.gov/uranium/guide/uf6/propertiesuf6/index.cfm).