Uranium(III) chloride, UCl<sub>3</sub>, is a water soluble salt of uranium. UCl<sub>3</sub> is used mostly to reprocess spent nuclear fuel. Uranium(III) chloride is synthesized in various ways from uranium(IV) chloride; however, UCl<sub>3</sub> is less stable than UCl<sub>4</sub>.
There are two ways to synthesize uranium(III) chloride. The following processes describe how to produce uranium(III) chloride.
(1) In a mixture of NaCl-KCl at 670âÂÂ710 ðC, add uranium tetrachloride with uranium metal.
(2) Heat uranium(IV) chloride in hydrogen gas.
In solid uranium(III) chloride each uranium atom has nine chlorine atoms as near neighbours, at approximately the same distance, in a tricapped trigonal prismatic configuration.
Uranium(III) chloride is a green crystalline solid at room temperature. UCl<sub>3</sub> melts at 837 ðC and boils at 1657 ðC. Uranium(III) chloride has a density of 5500 kg/m<sup>3</sup> or 5.500 g/cm<sup>3</sup>.
Its composition by weight:
Its formal oxidative states:
This salt is very soluble in water and is also very hygroscopic. UCl<sub>3</sub> is more stable in a solution of hydrochloric acid.
Uranium(III) chloride is used in reactions with tetrahydrofuran (THF) and sodium methylcyclopentadiene to prepare various uranium metallocene complexes.
Uranium(III) chloride is used as a catalyst during reactions between lithium aluminium hydride (LiAlH<sub>4</sub>) and olefins to produce alkyl aluminate compounds.
Molten uranium(III) chloride is an important component of liquid nuclear fuel used in molten-salt reactors. Neutron scattering and computational studies point to the presence of unusual heterogeneous bonding environment around U(III) at high temperatures, with distinct inner- and outer-coordination subshells. The molten form of uranium(III) chloride is also a typical compound in pyrochemical processes as it is important in the reprocessing of spent nuclear fuels. UCl<sub>3</sub> is usually the form that uranium takes as spent fuel in electrorefining processes.
There are three hydrates of uranium(III) chloride:
Each are synthesized by the reduction of uranium(IV) chloride in methylcyanide (acetonitrile), with specific amounts of water and propionic acid.
While there are no long-term data on the toxic effects thas UCl<sub>3</sub>, it is important to minimize exposure to this compound when possible.
Similar to other uranium compounds that are soluble in water, UCl<sub>3</sub> is likely absorbed into the blood through the alveolar pockets of the lungs within days of exposure. Exposure to uranium(III) chloride leads to toxicity of the renal system.