| 摘要 |
<p>Volatile fluoride values of technetium, neptunium, molybdenum and/or vanadium may be separated from uranium hexafluoride containing the same by contacting with magnesium fluoride. The uranium hexafluoride may have been obtained directly from ore concentrates or from reprocessed, irradiated uranium. Specified fluoride values are NpF6, MoF6, VF5, and VOF3. The impure uranium hexafluoride may be contacted with magnesium fluoride either in the gaseous or the liquid state. Preferably the gaseous UF6 is passed through either a stationary or fluidized bed of magnesium fluoride pellets. Pellets within the size range of 0.09 inch to 0.25 inch diameter are preferred. In a typical embodiment, UF6 is passed through a pellet bed, 32 inches deep and 16 inches diameter, at 900-1200 ft./hr. at a temperature of 200 DEG to 250 DEG F. The gas phase sorption capacity of MgF2 pellets is about 0.004 to 0.008 g. impurity (e.g. technetium) per g. MgF2. The used pellets may be regenerated by drying at room temperature to about 6% moisture content, heating to 400 DEG F. in air, and contacting with air containing 20% gaseous fluorine for 8 hours. Water washing of the MgF2 pellets desorbs over 98% technetium and from 10 to 40% neptunium. An alkaline reagent, e.g. aqueous KOH, may be added to the above eluate to precipitate neptunium, uranium, and other metallic impurities, e.g. aluminium, chromium, iron, manganese, molybdenum, nickel. Technetium may be recovered from the filtrate by ion exchange, e.g. using a strongly basic anion exchanger with a trimethyl benzyl ammonium group for sorption, eluting with 8MHNO3, neutralizing the eluate to remove fluoride ions, and repeating the ion exchange process. Neptunium may be further eluted from the MgF2 pellets by contacting with hot nitric acid, e.g. 0.1-1.0 Molar solution, at a temperature of at least 160 DEG F. The acidity of the neptunium eluate may be adjusted to 8MHNO3, ferrous sulphamate added, and the resulting solution contacted with an anion exchange resin to sorb neptunium. After washing, neptunium may be recovered by eluting with 0.3 MHNO3. Neptunium may also be recovered from the precipitate obtained when neutralizing the aqueous technetium-bearing eluate by dissolving it in nitric acid, adding ferrous sulphamate, and proceeding as just described. Molybdenum is removed with technetium in the initial aqueous eluate, whereas vanadium is removed with neptunium in the nitric acid eluate. These elements are separated from technetium and neptunium in the above-mentioned recovery procedures.</p> |
