Uranium VI oxide

Urano-hydroxyd, n. uranous hydroxide, ura-nium(IV) hydroxide, -reihe, /. uranous series, -salz, n. uranous salt, -uranat, n. uranous uranate, uranium(IV,VI) oxide, UaOa. -verbindung, /. uranous compound, Uran-oxyd, n. uranium oxide, specif, uranic oxide, uranium(VI) oxide, UOa. -ozydhydrat, n. uranium hydroxide, -oxydoxydul, n. = Uranoxyduloxyd. -oxydrot, n. uranium oxide red- -oxydul, n. uranous oxide, ura-nium(IV) oxide, UO2. -oxyduloxyd, n. uranoso-uranic oxide, uranium (I V,VT) oxide, UaOa. -oxydulsalz, n. uranous salt, uranium-(IV) salt, -pechblende, /., -pecherz, n. pitchblende, -phosphat, n, uranium phosphate. -rot, n. uranium red. -salz, n. uranium salt. 

Dilute. sulfuric acid is generally u.sed as the acidic leaching agent. This digests the uranium(VI) oxide, which mainly occurs in secondary deposits, to uranyl sulfate ... 

In the production of uranium(lV) oxide in the wet process, the uranium concentrate is first converted into a uranyl nitrate solution with nitric acid. After the purification of the uranyl nitrate by solvent extraction, it can be converted into uranium(IV) oxide by two different routes either by thermal denitration to uranium(VI) oxide which is then reduced to uranium(IV) oxide or by conversion of uranyl nitrate into ammonium diuranate which is reduced to uranium(IV) oxide. Purification proceeds by extraction of the uranyl nitrate hydrate from the acidic solution with tri-n-butylphosphate in kerosene and stripping this organic phase with water, whereupon uranium goes into the aqueous phase. 

This diluted aqueous uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate, U02(N03)2 6H2O, which is then calcined to uranium(VI) oxide in a fluidized bed furnace ... 

The temperature must not exceed 400°C, to prevent the formation of U3O8. The nitrous gases produced are processed to nitrie aeid, whieh is recycled. The subsequent reduction of uranium(VI) oxide to uranium(IV) oxide with hydrogen at 500°C also proceeds in the fluidized bed furnace. 

Uranium(IV) oxide is the starting material for uranium(lV) fluoride production in which uranium(lV) oxide is generally reacted with anhydrous hydrogen fluoride. This difficult to carry out exothermic reaction proceeds either in a fluidized bed, in moving bed reactors, or in screw-reactors. To achieve as complete as possible reaction in fluidized bed reactors, two fluidized bed reactors are connected in series. Screw-reaetors are also preferably connected in series. In moving bed reactors the reduction zone and the hydrofluorination are arranged above one another in a plant. The uranium(IV) oxide produced by the reduction of uranium(VI) oxide with hydrogen is very reactive and is eompletely reaeted with HF at temperatures between 500 and 650°C to uranium(lV) fluoride. 

The further processing of the uranyl nitrate solution, which in some plants is postpurified with silica gel, is directed towards further enrichment of the uranium. If this is not worthwhile due to a too low - U-content, the product is converted into uranium(Vl) oxide, a storable compound. This can serve as a starting material for possible later utilization in fast breeder reactors. The uranium(VI) oxide is either produced indirectly by way of ammonium diuranate or by direct calcination. If further enrichment is foreseen, uranium(Vl) fluoride or uranium(lV) fiuoride is produced, the latter being fluorinated in the enrichment plant to uranium(VI) fluoride. 

The mol ratio of hexachloropropene to uranium (VI) oxide must be at least 5 1 to assure complete reaction of the hydrated uranium(VI) oxide. The equation given is an idealized one which does not account for the formation of other products such as hydrogen chloride and phosgene. 

Anhydrous uranyl chloride has been prepared by reaction of oxygen with uranium(IV) chloride at 300° to 350°. Other procedures for preparing uranyl chloride are reaction of chlorine with uranium(IV) oxide at 500° reaction of carbon tetrachloride with uranium (VI) oxide at 290° and reaction of hydrogen chloride mth partially hydrated... 

Fig. 326. Preparation of uranium (VI) oxide. r Inconel reactor q quartz Insert tube g graduated condensation trap f condensation trap m manometer and pressure-relief valve ...

---