GB824579A - Uranium and zirconium recovery as uranium hexafluoride and zirconium fluoride from alloys containing these elements - Google Patents

Abstract

<PICT:0824579/III/1> Fluorides of uranium and zirconium are prepared by dissolving a uranium-zirconium alloy in a molten zirconium tetrafluoride-sodium fluoride mixture and treating the molten mixture with a gaseous fluorinating agent. Zirconium fluoride remains in the melt and uranium hexafluoride; together with fluorides of niobium and ruthenium, for example, are volatilized. Equimolar amounts of zirconium and sodium fluoride are preferably employed and the temperature is normally between 500 DEG and 600 DEG C. Suitable fluorinating agents are bromine penta- and trichloride, chlorine trifluoride and fluorine. Alternatively a two-stage fluorination may be effected whereby the alloy in the molten fluoride bath is first treated with hydrogen fluoride at 500-800 DEG C. to form uranium and zirconium tetrafluorides and the bath is then treated with the above mentioned fluorinating agents to produce and volatilize uranium hexafluoride. If fluorine is employed to form the uranium hexafluoride from the tetrafluoride, lead fluoride may be added to the melt in an amount of about 5 mol. per cent. The fluorine may then be diluted with an inert gas such as helium. The apparatus may be as shown in the Figure where a refractory furnace 1 is provided with a nickel insert vessel 4 which contains the molten salt mixture 8. The alloy 9 is placed in the melt and hydrogen fluoride is passed in from line 12 thereby dissolving the alloy to form tetrafluorides. Excess hydrogen fluoride is collected in cold traps 17 and 18 and thereafter fresh traps are connected and bromine pentafluoride passed through the melt. Uranium hexafluoride and excess bromine pentafluoride and bromine trifluoride reaction products were condensed in condensers 17 and 18 whilst niobium and ruthenium condensed in the earlier portions of the pipe 16. The uranium hexafluoride condensate was freed from bromine compounds by passing fluorine gas through the condensate to convert bromine compounds to the pentafluoride which may be distilled off at 45 DEG C. The decontaminated uranium hexafluoride may be further purified by vaporizing it and passing the vapour thereof over a bed of solid sodium fluoride at 100-400 DEG C.