Uranyl nitrate solution

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

These can be converted to their uranyl nitrate addition compounds. The crude or partially purified ester is saturated with uranyl nitrate solution and the adduct filtered off. It is recrystallised from -hexane, toluene or ethanol. For the more soluble members crystallisation from hexane using low temperatures (-40°) has been successful. The adduct is decomposed by shaking with sodium carbonate solution and water, the solvent is steam distilled (if hexane or toluene is used) and the ester is collected by filtration. Alternatively, after decomposition, the organic layer is separated, dried with CaCl or BaO, filtered, and fractionally distilled under high vacuum. 

The analytical use of cellulose fibre to absorb uranyl nitrate solution prior to ignition has led to explosions dining ignition, owing to formation of cellulose nitrate. An alternative method is described. 

Uranyl Nitrate. Acquaint yourself with the appearance of uranyl nitrate. Find the solubility products of uranyl nitrate in water and ether in a reference book. What is the reaction of solutions of ammonium sulphide, potassium hexacyanoferratefll), and potassium phosphate with a uranyl nitrate solution What is obtained Write the equations of the reactions. 

Ammonium Diuranate. Pour 5 ml of a uranyl nitrate solution into a 50-ml beaker. Heat the solution to 80 °C and add several drops of a methyl orange solution to it. What causes the colour of the indicator to change Carefully pour in a 10% ammonia solution containing no carbon dioxide dropwise until the colour of the indicator changes. What substance precipitates Write the equation of the reaction. 

Uranium Peroxide Hydrate. Add a 3% hydrogen peroxide solution dropwise to 5 ml of a 10% uranyl nitrate solution up to complete precipitation. Filter off the product on a small filter, wash it with water, and dry it in a drying cabinet at 70 °C. What is the composition of the product Test the reaction of uranium peroxide hydrate with 10% solutions of acids and alkalies in the cold and when heated. 

Uranium Compounds with Lower Oxidation States. Pour 5 ml of a uranyl nitrate solution into a test tube, add 1 ml of a 10% hydrochloric acid solution, and drop one or two small pieces of zinc into the tube. How can the change in the solution s colour be explained Pour the solution into three test tubes. Pour a potassium permanganate solution dropwise into one tube. What happens What properties do uranium(lV) compounds have ... 

The purification of uranium by precipitation may involve the formation of insoluble oxalate or peroxide complexes.50 In the oxalate method the ore concentrate is dissolved in nitric acid to give a uranyl nitrate solution from which uranyl oxalate is precipitated according to equation (101), leaving the bulk of the impurities in solution. This approach is favoured over dissolution in hydrochloric acid and reduction to UIV prior to U(C204)2 precipitation since it is simpler and... 

The peroxide method involves the precipitation of uranyl peroxide by addition of H202 to uranyl nitrate solutions according to equation (103). Below 50 °C, U04-4H20 precipitates, while... 

ASTM C788-98 Standard specification for nuclear-grade uranyl nitrate solution or crystals. 

Uranium solution Uranyl nitrate solution, 0.02 M U02+ Dissolve 10.0 g U02(N03)2.6H20 in water and dilute in a volumetric flask to 1 L. 

Step 1. Pipette 1.0 mL of the uranyl nitrate solution into a clean 50 mL beaker. Place under a heat lamp or on a hot plate at low setting and evaporate to near dryness. Remove from heat and cool. Add 5 mL of saturated ammonium nitrate solution. Carefully swirl to dissolve any dried uranium salt. 

Solvent Extraction. The yellow cake is dissolved in nitric acid and extracted from this aqueous phase by 5 percent tributyl phosphate (TBP) in a hydrocarbon diluent. The diluent reduces the density and viscosity of the TBP, enhancing the aqueous/solvent phase separation. The extraction is very specific for uranium, with separation factors of 103 to 105. The product thus obtained is an aqueous uranyl nitrate solution (Fig. 21.14). 

Denitration. The uranyl nitrate solution from solvent extraction is converted to U03 by evaporating the solution to a final boiling point of 120 to 140°C, followed by calcination at 620°C. The product characteristics are dependent on the type of calciner (pot, trough, or fluid bed) and significantly affect the subsequent steps (see Fig. 21.15). 

La Touche, Y.D., Willis, D.L., Dawydiak, O.L (1987). Absorption and biokinetics of U in rats following an oral administration of uranyl nitrate solution. Health Phys. 53 147-62. 

In a much earlier patent, the removal of organics from exhaust gases by oxidation over a supported uranium oxide catalyst was reported by Hofer and Anderson [39]. The catalyst was 4% U3O8 supported on alumina spheres. The authors used the incipient wetness technique to impregnate alumina with uranyl nitrate solution. In this case the catalyst precursors were calcined at 700°C for 3 h to decompose the uranium salt. The use of other uranium compounds as starting materials was mentioned and these included uranyl acetate, uranium ammonium carbonate and uranyl chloride. The alumina-supported catalyst had a surface area of ca 400m g and further added components, such as copper, chromium and iron, were highlighted as efficient additives to increase activity. 

Figure 1, Dependence of the electron concentration on the cube root of the molarity of uranyl nitrate solution sprayed into a flame...

Uranium Molybdates.—Uranyl nioh bdate, UO2M0O4, is obtained as a white amorphous precipitate when ammonium molybdate is added to uranyl nitrate solution in the dark. It is reduced to uranous molybdate. U(Mo04)2, becoming green by the action of ethyl or methyl alcohol or acetic acid, and dissolves in mineral acids with a yellovush-... 

Barium Diuranate, BaUjO, is obtained by heating barium uranyl acetate, or by heating together the green oxide and barium chlorate. It is obtained in a hydrated condition when ammonia is added to mixed solutions of barium chloride and uranyl nitrate, or when excess of baryta water is added to uranyl nitrate solution. It is a deep yellow crystalline powder. 

Since oxygen is one of the products of electrolysis, if the electrolytic cell is undivided, reoxidation of U " ion takes place which hampers the production of uranyl with higher concentration. Cation-selective membrane spacers are effective in improving the production of uranyl nitrate solution. 

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 second route to uranium(IV) oxide eonsists of precipitation of ammonium diuranate from the solvent extraetion-purified aqueous uranyl nitrate solution by adding ammonia and then reducing it with hydrogen to uranium(lV) oxide (Comurhex process developed in France). 

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. 

This paper deals with three different oxidation states of plutonium Pu(III), Pu(IV), and Pu(VI) in HNO3-HF systems. The chromatographic column method using alumina has been applied success-fuly to the separation of plutonium when uranyl nitrate solution containing 0.1-0.3M HF was percolated through the column. 

Removal of Residual Nitrate From UO Uranium trioxide produced by thermal decomposition of uranyl nitrate solution in a fluidized-bed contains a small amount (usually about 0.4 to 1.0 wt%) of residual nitrate. If UO is to be converted to UF for feed to a gaseous diffusion enrichment plant, the nitrate content of the UO must be reduced to meet UF purity specifications. Fluorination of UO in the presence of nitrate results in formation of nitrosyl and nitryl hexafluorouranates and heptafluorou-ranates (NO UF where x = 1 or 2 and y = 6 or 7) (2). These compounds form potentially troublesome solids. 

Derivation Finely ground ore is leached under oxidizing conditions to give uranyl nitrate solution. The uranyl nitrate, purified by solvent extraction (ether, alkyl phosphate esters), is then reduced with hydrogen to uranium dioxide. This is treated with hydrogen fluoride to obtain uranium tetrafluoride, followed by either electrolysis in fused salts or by reduction with calcium or magnesium. Uranium can also be recovered from phosphate sand. 

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