Recovery of uranium from uranium refining waste water by using immobilized persimmon tannin

Some attempts were made to examine the practical conditions for uranium recovery from uranium refining waste water. The adsorbent was highly effective in recovering uranium. The uranium adsorption was affected by pH, temperature, and uranium concentration of the uranium refining waste water. The adsorbent also recovered uranium effectively in column system. It aquires better mechanical properties and can be used repeatedly in the uranium adsorption-desorption cycles.     

Reduction of uranium triiodide to metal by thermal decomposition

Uranium metal was successfully produced from uranium triiodide through thermal decomposition in a tetra-arc crystal furnace. The uranium triiodide was produced by reacting uranium and iodine at 600 °C for 24 h. After the uranium triiodide was heated in the arc furnace, a product was confirmed to be uranium metal through X-ray diffraction, density, and energy-dispersive X-ray spectroscopy measurements. Historically, uranium triiodide has been reduced after passing through a gaseous intermediate of uranium tetraiodide and reduced on a hot filament. This is the first report of directly reducing uranium triiodide to uranium metal, circumventing the uranium tetraiodide intermediary.

     

An investigation on the subcellular distribution and compartmentalization of uranium in Phaseolus vulgaris L.

Phaseolus vulgaris L. (bean) is a promising species for uranium rhizofiltration with high tolerance and accumulation ability. To further understand the mechanisms involved in uranium tolerance and detoxification, the present study investigated subcellular distribution and compartmentalization of uranium in bean. Subcellular fractionation of uranium containing tissues indicated that both in roots and shoots, the concentration of uranium in each subcellular fractions increased evidently with increasing solution uranium level, and the majority of uranium was located in cytosol and cell wall fraction, while a minor part of uranium associated with the organelle fraction. Meanwhile, with uranium concentration increasing from 100 to 1,000 μM, the proportion of uranium distribution in cytosol fraction was decreased but it was increased in cell wall fraction. However, the proportion of uranium distribution in organelle fraction is always less than 5 %. These results suggest that stored in the cytosol (such as uranium compartmentalization with organo-ligands in vacuole) and bound to the cell walls (may be integrated with polyose and protein) might play an important role in tolerance and detoxification of uranium in bean.     

Chronopotentiometry of uranium(iv)

The chronopotentiometry of uranium at platinum electrodes has been investigated. A determination of uranium has been devised based on the conversion of the uranium to uranium(IV) and the oxidation of the uranium (IV). The effect of several possible interfering substances has been checked.     

铀矿石中铀测量结果的不确定度评定

分析了容量法测定铀矿石中铀含量测量不确定度的影响因素。对样品质量、滴定样品溶液消耗的钒酸铵溶液的体积、钒酸铵对铀的滴定度等不确定度分量进行了分析和计算。铀矿石中铀含量为0．427％时,测量结果的扩展不确定度为0．020％。     

Influence of Acidity and Uranyl Nitrate Concentration on the Efficiency of Recovery of Uranium(VI) from Aqueous Solutions with Hydrolytic Wood Lignin

The efficiency of recovery of uranium(VI) from aqueous solutions with hydrolytic lignin and strength of binding of uranium to lignin were studied in relation to the uranium concentration and acidity. The mechanisms of sorption of uranium were analyzed by the methods of sequential leaching of uranium from lignin and IR spectroscopy.     

Determination of uranium metal concentration in irradiated fuel storage basin sludge using selective dissolution

Irradiated uranium metal fuel was stored underwater in the K East and K West storage basins at the US Department of Energy Hanford Site. The uranium metal under damaged cladding reacted with water to generate hydrogen gas, uranium oxides, and spalled uranium metal particles which intermingled with other particulates to form sludge. While the fuel has been removed, uranium metal in the sludge remains hazardous. An expeditious routine method to analyze 0.03 wt% uranium metal in the presence of >30 wt% total uranium was needed to support safe sludge management and processing. A selective dissolution method was designed based on the rapid uranium oxide dissolution but very low uranium metal corrosion rates in hot concentrated phosphoric acid. The uranium metal-bearing heel from the phosphoric acid step then is rinsed before the uranium metal is dissolved in hot concentrated nitric acid for analysis. Technical underpinnings of the selective dissolution method, including the influence of sludge components, were investigated to design the steps and define the reagents, quantities, concentrations, temperatures, and times within the selective dissolution analysis. Tests with simulant sludge proved the technique feasible. Tests with genuine sludge showed a 0.0028 ± 0.0037 wt% (at one standard deviation) uranium metal analytical background, a 0.011 wt% detection limit, and a 0.030 wt% quantitation limit in settled (wet) sludge. In tests using genuine K Basin sludge spiked with uranium metal at concentrations above the 0.030 wt% ± 25 % (relative) quantitation limit, uranium metal recoveries averaged 99.5 % with a relative standard deviation of 3.5 %.     

Recovery of uranium by polyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime

Sorption of uranium(VI) has been inbestigated using an open-cell plyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63). Above pH 4.5 more than 99% of uranium is sorbed onto the LIX 63 impregnated foam, and uranium can be desorbed with a dilute acid from the foam. The sorption capacity for uranium increases linearly with increasing concentration of impregnated LIX 63. Quantitative removal of uranium from salt solutions was accomplished.     

Solvent extraction of uranium from aqueous solutions by α-benzoinoxime

Solvent extraction of uranium with α-benzoinoxime from aqueous solutions has been systematically investigated. The extraction equilibration was very fast and achieved at 60 s for uranium. The extraction of uranium was pH-dependent using α-benzoinoxime as extractant. The effect concentration of uranium and α-benzoinoxime was studied. The uranium loaded in the organic phase can be stripped efficiently with 93 % yield using 0.1 M HCl as the stripping agent in a single stripping step. A good selectivity for uranium was observed through α-benzoinoxime as extractant from aqueous solution with other interfering cation ions. Present study suggested that α-benzoinoxime can be used as a potential extractant for separation of uranium from aqueous solution using centrifugal extractor in industrial application.     

Precise determination of uranium in pure uranium and uranium compounds by constant-current coulomeric titration

A procedure is described for very precise determination of uranium in high-purity uranium and uranium compounds. Uranium(VI) is reduced in a concentrated hydrochloric acid solution by metallic aluminium in the presence of cadmium ions to uranium(III). This is oxidized to uranium(IV) by protons on addition of an excess of orthophosphoric acid, and then oxidized to uranium(VI) by adding a weighed quantity of potassium dichromate in small excess. The excess of potassium dichromate is determined by constant-current coulometry. The coefficient of variation does not exceed 0.003%.     

Uranium sorption on oxyhydroxide minerals by surface complexation and precipitation

During the chemical weathering of the uranium mill tailings, released uranium could be immobilized by the newly formed secondary minerals such as oxyhydroxides. A deeper understanding of the interaction between uranium and common oxyhydroxides under environmental conditions is necessary. In this work, uranium sorption behaviors on Al-, Mn- and Fe-oxyhydroxide minerals (boehmite, manganite, goethite, and lepidocrocite) were investigated by batch experiments. Results showed that the uranium sorption on Al-oxyhydroxide behaved significantly differently from the other three minerals. The sorption edge of the Mn- and Fe-oxyhydroxides located around pH 5, while the sorption edge of boehmite shifted about 1.5 pH unit to near neutral. The sorption isotherms of uranium on manganite, goethite and lepidocrocite at pH 5.0 could be well fitted by the Langmuir model. Instead of surface complexation, sorption on boehmite happened mainly by uranium-bearing carbonates and hydroxides precipitation as illustrated by the characterization results. Both carbonate and phosphate strongly affected the uranium sorption behavior. The removal efficiency of uranium by boehmite exceeded 98% after three sorption-desorption cycles, indicating it may be a potential material for uranium removal and recovery.     

A titrimetric method for the sequential determination of thorium and uranium

A method for the sequential determination of thorium and uranium has been developed. In the sample solution containing thorium and uranium, thorium is first determined by complexometric titration with ethylenediaminetetraacetic acid (EDTA) and then in the same solution uranium is determined by redox titration employing potentiometry. As EDTA interferes in uranium determination giving positive bias, it is destroyed by fuming with HClO₄ prior to the determination of uranium. A precision and accuracy of better than ±0.15% is obtained for thorium at 10mg level and uranium ranging from 5 mg to 20 mg in the aliquot.     

Determination of uranium in wet phosphoric acid

A method for quantitative determination of uranium in wet phosphoric acid containing 0.001-0.02% of uranium has been developed. After reduction with Fe or FeSO(4) . H(2)O, uranium(IV) is extracted with a kerosene solution of an equimolar mixture of mono- and dinonylphenylphosphoric acids. The uranium is stripped with an oxidizing medium consisting of 10M H(3)PO(4) containing NaClO(3). The uranium stripped is determined spectrophotometrically with Arsenazo III.     

Resolution of uranium isotopes with kinetic phosphorescence analysis

This study was conducted to test the ability of the Chemchek? Kinetic Phosphorescence Analyzer Model KPA-11 with an auto-sampler to resolve the difference in phosphorescent decay rates of several different uranium isotopes, and therefore identify the uranium isotope ratios present in a sample. Kinetic phosphorescence analysis (KPA) is a technique that provides rapid, accurate, and precise determination of uranium concentration in aqueous solutions. Utilizing a pulsed-laser source to excite an aqueous solution of uranium, this technique measures the phosphorescent emission intensity over time to determine the phosphorescence decay profile. The phosphorescence intensity at the onset of decay is proportional to the uranium concentration in the sample. Calibration with uranium standards results in the accurate determination of actual concentration of the sample. Different isotopes of uranium, however, have unique properties which should result in different phosphorescence decay rates seen via KPA. Results show that a KPA is capable of resolving uranium isotopes.     

Uptake of uranium by various cell fractions of Chlorella regularis

To know what kinds of the cell components of Chlorella regularis are concerned with uranium binding, uptake of uranium by various cell fractions was examined. The uptake value (microgramU/mg starting dry cells) of the hot water-treated cells was almost the same as that of the starting dry Chlorella cells, showing that the cell components extracted with hot water were not so concerned with uranium binding. The cell components extracted with dilute alkali seemed to play an important role in uranium binding, and those extracted with chloroform-methanol seemed to be partly concerned with uranium binding. The cellulose fraction of the cells was scarcely concerned with uranium binding. In the dry cells, 34% of uranium taken up existed in the cell walls. However, in the living cells, 85% existed in the cell walls. The above results showed that the dry or the hot water-treated cells are the most convenient for uranium recovery from the aqueous systems.     

Ammonium uranyl carbonate (AUC) based process of simultaneous partitioning and reconversion for uranium and plutonium in fast breeder reactors (FBRs) fuel reprocessing

Ammonium uranyl carbonate (AUC) based process of simultaneous partitioning and reconversion for uranium and plutonium is developed for the recovery of uranium and plutonium present in spent fuel of fast breeder reactors (FBRs). Effect of pH on the solubility of carbonates of uranium and plutonium in ammonium carbonate medium is studied. Effect of mole ratios of uranium and plutonium as a function of uranium and plutonium concentration at pH 8.0–8.5 for effective separation of uranium and plutonium to each other is studied. Feasibility of reconversion of plutonium in carbonate medium is also studied. The studies indicate that uranium is selectively precipitated as AUC at pH 8.0–8.5 by adding ammonium carbonate solution leaving plutonium in the filtrate. Plutonium in the filtrate after acidified with concentrated nitric acid could also be precipitated as carbonate at pH 6.5–7.0 by adding ammonium carbonate solution. A flow sheet is proposed and evaluated for partitioning and reconversion of uranium and plutonium simultaneously in the FBR fuel reprocessing.     

Development of radiochemical analysis of uranium isotopes in highly contaminated soil samples

An accurate and reliable analytical technique of uranium isotopes in highly contaminated soil samples was developed and applied to the IAEA reference samples. The conventional TBP method of uranium isotopes is insufficient to completely purify uranium from actinides such as plutonium and americium isotopes in highly contaminated soil samples. For overcoming the demerits of the conventional TBP extraction method, sample materials were decomposed with HNO₃ and HF, and uranium isotopes were purified by TBP extraction and anion exchange columns and extraction chromatography. Among the purifying methods of uranium, with a TRU Spec resin column after TBP solvent extraction, uranium was completely separated from the radionuclides in a highly contaminated samples. With the modified TBP extraction method, it was found that the concentrations of uranium isotopes were consistent with the reference values reported by the IAEA.     

Uranium in pore water from coastal sediments determined by chemical activation analysis

Chemical neutron activation analysis was applied to determine trace uranium in estuarine pore water after a simple separation through coprecipitation with hydrated iron(III) oxide. The mean coprecipitation yield of uranium was found to be ~85% under pH ranged from 6 to 8.6. The distributions of uranium in both seawater and pore water were determined alongwith the variations of uranium content in oxidation and reduction conditions. Behaviors of uranium in pore water are also discussed.     

In situ spectroscopy and spectroelectrochemistry of uranium in high-temperature alkali chloride molten salts

Soluble uranium chloride species, in the oxidation states of III+, IV+, V+, and VI+, have been chemically generated in high-temperature alkali chloride melts. These reactions were monitored by in situ electronic absorption spectroscopy. In situ X-ray absorption spectroscopy of uranium(VI) in a molten LiCl-KCl eutectic was used to determine the immediate coordination environment about the uranium. The dominant species in the melt was [UO 2Cl 4] (2-). Further analysis of the extended X-ray absorption fine structure data and Raman spectroscopy of the melts quenched back to room temperature indicated the possibility of ordering beyond the first coordination sphere of [UO 2Cl 4] (2-). The electrolytic generation of uranium(III) in a molten LiCl-KCl eutectic was also investigated. Anodic dissolution of uranium metal was found to be more efficient at producing uranium(III) in high-temperature melts than the cathodic reduction of uranium(IV). These high-temperature electrolytic processes were studied by in situ electronic absorption spectroelectrochemistry, and we have also developed in situ X-ray absorption spectroelectrochemistry techniques to probe both the uranium oxidation state and the uranium coordination environment in these melts.     

<Superscript>99m</Superscript>Tc(CO)<Subscript>3</Subscript>-tosufloxacin dithiocarbamate complexation and radiobiological evaluation in male Wister rat model

The uranium ingot casting process is one of the steps which consolidate uranium deposits produced by electrorefiner in an ingot form in a pryprocessing technique. Since molten uranium metal reacts with a graphite crucible when the uranium is being dissolved, a graphite crucible cannot be used. Accordingly, a ceramic material must be selected which does not react with the dissolving uranium and this must be used as a coating material on the graphite crucible surface. As to this research, a reactivity experiments were performed between the coating layer and uranium by applying a thermal spray coating to the graphite material with alumina and YSZ ceramic material. As shown in the experimental result, the YSZ coating layer showed a stronger adhesive property on the side where there is no Ni–Al binding material. Moreover, no reaction was apparent between the YSZ coating layer and the uranium. Accordingly, the YSZ material and the process of thermal spray coating are considered to solve the reactive problem between uranium and a graphite crucible.