Uranium pentafluoride
Uranium pentafluoride
Pale blue to pale gray crystals
Fixed
- 5.81 g · cm -3 ( α )
- 6.45 g · cm -3 ( β )
348 ° C
Risk
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U ( V ) fluoride is a chemical compound consisting of the elements of uranium and fluorine. It has the formula UF5 and belongs to the class of fluorides.
Production and representation
U ( V ) fluoride can be obtained by reaction of uranium (VI) or uranium chloride (V ) chloride with anhydrous hydrogen fluoride.
It is also possible comproportionation of uranium (IV ) fluoride and uranium (VI ) fluoride
Or the fluorination of uranium (IV ) fluoride.
Also possible is the representation by reduction of uranium (VI ) fluoride with hydrogen bromide.
Properties
U ( V ) fluoride exists in two modifications, the high-temperature α - modification, and the low-temperature β - modification. The transition temperature is 125 ° C. The α - modification has a tetragonal crystal structure with space group I4 / m ( a = 651.2 pm and c = 446.3 pm ). She is in the vacuum above 500 ° C sublimed, with temperatures above 150 ° C, disproportionation starts. It forms pale blue to pale gray crystals and melts ( under UF6 pressure) at 348 ° C. The connection consists of UF5 units forming linear chains by fluorine bridges. The β - modification is pale yellow and has a tetragonal crystal structure with space group I42d (a = 115.0 pm and c = 519.8 pm ).
Use
U ( V) fluoride is applied to the laser enrichment. Here, the 235U containing molecule 235UF6 is first selectively excited by a first laser, before a fluorine atom is cleaved by a second laser. The resulting solid 235UF5 can be easily filtered from the gas. The 238UF6 is not implemented, so that a simple separation of isotopes occurs. After the initial euphoria about the advantages of this method over conventional, established enrichment method is presented later greater skepticism regarding an industrial feasibility. Many research and development programs have been set back because it was found that the technical problems ( corrosion of the equipment ) are almost insurmountable.