GB858161A - Purification of uranium hexafluoride - Google Patents

Abstract

<PICT:0858161/III/1> Vaporized uranium hexafluoride is freed from vanadium oxytrifluoride impurity by passing it in contact with a cooled surface to condense uranium hexafluoride as a liquid, and deposit vanadium oxytrifluoride as a solid on the cooled surface. The condensed uranium hexafluoride is mixed with further impure uranium hexafluoride and the vaporized mixture is recycled in contact with the cooled surface until the vanadium oxytrifluoride has been substantially entirely eliminated from the uranium hexafluoride condensate. Any volatile impurities which are not condensed with the uranium hexafluoride may be continuously withdrawn, such withdrawal preferably constituting 0.5-10% by weight of the crude uranium hexafluoride feed. Non-volatile impurities remaining in the uranium hexafluoride after removal of vanadium oxyfluoride may be separated by distillation. In a continuous process (see Figure) crude uranium hexafluoride is vaporized in still 2 and passes via line 6 into fractionating column 7, which may have external heating means 57, from the top of which exit uranium hexafluoride, vanadium oxytrifluoride, and volatile impurities vapours, via line 8 into zone 12 containing a cooled coil 13, upon which solid vanadium oxytrifluoride is deposited; the uncondensed volatile impurities are removed via line 22, and the liquefied uranium hexafluoride is returned to the fractionating column 7 via lines 16 and 18, and optionally line 19. Some of the liquid uranium hexafluoride from the bottom of the column 7 may be returned to the still 2 via lines 45 and 47, or it may be sent to vaporizer 51, from which some may be returned to column 7 via line 55; the remaining vapour is passed via line 63 to fractionating column 65, which may have external heating means 66. Pure uranium hexafluoride vapour leaves column 65 via line 69 and is condensed by condenser 71. Liquid product may be withdrawn via line 76, and some may be cycled to the top of column 65 via line 79. The apparatus may be operated at superatmospheric pressure, e.g. 10-150 p.s.i.g.