The expanding use of Zircaloy-clad zirconium-enriched uranium alloy fuel has suggested a need for higher capacity reprocessing facilities. The most urgent requirement is for continuous dissolution equipment to match the solvent extraction capacity already available at Idaho Chemical Processing Plant. Because of the rapid dissolution rates possible with aqueous hydrofluoric acid on clean metal as well as on oxidized fuels, and subsequent flowsheet economics, it is the reagent of choice.nLaboratory measurements and a survey of the properties of uranium tetrafluoride indicated highest solubility in the dissolver effluent was obtained at higher total fluoride concentrations and lower fluoride-to-zirconium mole ratios. Since zirconium salts have been shown to be susceptible to precipitation at higher fluoride and zirconium concen¬trations, an optimum dissolver effluent composition was selected for a Dilute Flowsheet at about 5M total fluoride and a 1.1M zirconium.nThe operation of two bench-scale dissolvers verified the feasibility of a continuous process, and Monel and Carpenter-20(Ob) were confirmed as suitable materials of construction for the dissolver. Using the Dilute Flowsheet, uranium solubility equivalent to the dissolution of fuels containing 2 per cent uranium, over-all, was achieved.nCorrelations of dissolver effluent flow rate with effluent compos¬ition and with total zirconium dissolved are given for guidance in engineering scale-up.
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