Separation and Extraction of Uranium from Leach Liquor Containing Uranium and Molybdenum by Solvent Extraction with LIX 622N

The leach liquor (0.5 g/L Mo, 0.05 g/L U) obtained from the leaching process of molybdenum-uranium ore material was treated using solvent extraction to recover U(VI) by LIX 622N, which is a salicylaldoxime derivative. The influence of various basic variables such as pH, concentration of LIX 622N, temperature, different stripping reagents, phase ratio, and diluents was examined. Using 10% LIX 622N with the aqueous solution of equilibrium pH 6.0 and a phase ratio organic phase:aqueous phase (O:A) = 1:1, a two-stage McCabe-Thiele plot was constructed, which showed 99.9% of U extraction with no co-extraction of molybdenum. This was confirmed by a 6-cycle counter current simulation (CCS) study. The obtained data of temperature on the extraction of uranium showed that the extraction process is exothermic with enthalpy change of ?20.949 kJ mol^?1. The stripping of U(VI) was quantitative using 4 M H₂SO₄. The stable complex UO₂(HSO₄)R_org formed during extraction, which supports the cation exchange mechanism, and was confirmed by FTIR spectral analysis.      

Isotopic analysis of single uranium and plutonium particles by chemical treatment and mass spectrometry

The isotopic composition of single uranium and plutonium particles was measured with an inductively coupled plasma mass spectrometer (ICP-MS) and a thermal ionization mass spectrometer (TIMS). Particles deposited on a carbon planchet were first analyzed with an energy dispersive X-ray spectrometer (EDX) attached to a scanning electron microscope (SEM) and then transferred on to a silicon wafer using a manipulator. The particle on the silicon wafer was dissolved with nitric acid and the isotopic ratios of U and Pu were measured with ICP-MS and TIMS. The results obtained by both methods for particles of certified reference materials showed good agreement with the certified values within the expected uncertainty. The measurement uncertainties obtained in this study were similar for both mass spectrometric methods. This study was performed to establish the method of particle analysis with SEM, EDX, the particle manipulation and chemical preparation technique, and the measurement of isotopic ratios of U and Pu in a single particle by mass spectrometry.     

Functional coatings of ternary alloys of cobalt with refractory metals

Finely crystalline cobalt–molybdenum–tungsten coatings were deposited in the nonsteady-state mode from a polyligand citrate-pyrophosphate electrolyte at a concentration ratio of the alloy-forming components Co²⁺/(WO ₄ ^2– + MoO ₄ ^2– ) = 1: 1 and citrate/pyrophosphate ligands of 1: 2. It was found that the quantitative composition and current efficiency by the ternary alloy depends on the current density. The effect of energy- and time-related parameters of the pulsed electrolysis on the surface morphology and roughness was studied. It was shown that, as the total content of refractory metals in Co–Mo–W coatings increases, the corrosion rate decreases in the acid medium and increases in the alkaline medium because of the instability of molybdenum and tungsten oxides.     

Thermodynamic investigations of uranium-rich binary and ternary alloys

Uranium–zirconium, uranium niobium, and uranium–zirconium–niobium alloys were synthesized by the arc melting technique and their phase transition temperatures were determined using a high temperature calorimeter. Heat capacities of U–7 wt%Zr, U–7 wt%Nb, U–5 wt%Zr–2 wt%Nb, U–3.5 wt%Nb–3.5 wt%Zr, and U–2 wt%Zr–5 wt%Nb were measured using a differential scanning calorimeter in the temperature range 303–921 K. A set of self-consistent thermodynamic functions such as entropy, enthalpy, and Gibbs energy function data for these binary and ternary alloys were reported for the first time using heat capacity data obtained in this study and required literature data.     

Enthalpies of mixing of Al-Ni-La ternary alloys

Partial (for nickel) and integral enthalpies of mixing of liquid alloys of the Al-Ni-La ternary system of three radial sections with a constant ratio of molar fractions of aluminum and lanthanum x _Al/x _La = 0.3/0.7 at 1770 ± 5 K and 0.5/0.5 and 0.8/0.2 at 1870 ± 5 K up to molar fractions of nickel in ternary alloys of approximately 0.5–0.6 are studied by means of high-temperature calorimetry in isoperibolic mode. It is found that the enthalpies of mixing of the melts are essentially exothermic values. Based on the energetics of alloy formation of this ternary system, it is concluded that the main contribution is made by interaction between the components of melts of the boundary Ni-Al binary system.     

The chemical characterization of silicon-germanium thermoelectric alloys

The performance of thermoelectric devices is sensitive to the chemical composition, the dopant concentration and the uniformity of the semiconductor materials used in their fabrication. Analytical methods for the determination of silicon, germanium, boron, and phosphorus in SiGe thermoelectric materials are described. These methods were developed because of the fragmentary data available in the literature regarding their chemical characterization. The methods are rapid, accurate, and, with the exception of boron, require a minimum of expensive apparatus. Germanium was determined acidimetrically by means of the mannitol complex after ion-exchange separation on Amberlite XE-243, silica by the conventional gravimetric method, phosphorus colorimetrically as the vanadomolybdophosphate, and boron by emission spectroscopy.     

Comparative thermodynamic study and characterization of ternary Ag-In-Sn alloys

The results of thermodynamics and characterization of alloys in ternary Ag-In-Sn system is presented in this paper. Thermodynamic properties, in three investigated sections with molar ratio In:Sn=1:1, 1:2 and 1:4, have been calculated at the temperature of 1423 K using different predicting methods (general solution model, Toop, Hillert, Muggianu, Kohler, Redlich-Kister), compared mutually and with literature experimental data. The alloys in investigated sections have been characterized using DTA, XRD, SEM and optic microscopy.     

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.     

Uranium/plutonium and uranium/neptunium separation by the Purex process using hydroxyurea

Hydroxyurea dissolved in nitric acid can strip plutonium and neptunium from tri-butyl phosphate efficiently and has little influence on the uranium distribution between the two phases. Simulating the 1B contactor of the Purex process by hydroxyurea with nitric acid solution as a stripping agent, the separation factors of uranium/plutonium and uranium/neptunium can reach values as high as 4.7·10⁴ and 260, respectively. This indicates that hydroxyurea is a promising salt free agent for uranium/plutonium and uranium/neptunium separations.     

Uranium/plutonium and uranium/neptunium separation by the Purex process using hydroxyurea

Hydroxyurea dissolved in nitric acid can strip plutonium and neptunium from tri-butyl phosphate efficiently and has little influence on the uranium distribution between the two phases. Simulating the 1B contactor of the Purex process by hydroxyurea with nitric acid solution as a stripping agent, the separation factors of uranium/plutonium and uranium/neptunium can reach values as high as 4.7·10⁴ and 260, respectively. This indicates that hydroxyurea is a promising salt free agent for uranium/plutonium and uranium/neptunium separations.     

Uranium and plutonium containing particles in a sea sediment sample from Thule, Greenland

Particles composed of radioactive materials and probably originating from US nuclear weapons were identified in sea sediment samples collected from Thule, Greenland, in 1997. The weapons were destroyed close to the Thule Air Base in 1968 in an aeroplane crash, which dispersed radioactive materials in the environment. The presence of particulate radioactive materials in the sediment samples was revealed by combining gamma-spectrometry and autoradiography. Isolation and separation of a radioactive particle from a bulk sample were performed using autoradiography, phosphor plate imaging and scanning electron microscopy. Using X-ray microanalysis as well as alpha and beta activity analysis, U and weapons-grade Pu were detected in the granular, brittle particle.     

Age determination of single plutonium particles after chemical separation

Age determination of single plutonium particles was demonstrated using five particles of the standard reference material, NBS 947 (Plutonium Isotopic Standard. National Bureau of Standards, Washington, D.C. 20234, August 19, 1982, currently distributed as NBL CRM-137) and the radioactive decay of ²⁴¹Pu into ²⁴¹Am. The elemental ratio of Am/Pu in Pu particles found on a carbon planchet was measured by wavelength dispersive X-ray spectrometry (WDX) coupled to a scanning electron microscope (SEM). After the WDX measurement, each plutonium particle, with an average size of a few μm, was picked up and relocated to a silicon wafer inside the SEM chamber using a micromanipulator. The silicon wafer was then transferred to a quartz tube for dissolution in an acid solution prior to chemical separation. After the Pu was chemically separated from Am and U, the isotopic ratios of Pu (²⁴⁰Pu/²³⁹Pu, ²⁴¹Pu/²³⁹Pu and ²⁴²Pu/²³⁹Pu) were measured with a thermal ionization mass spectrometer (TIMS) for the calculation of Pu age. The age of particles determined in this study was in good agreement with the expected age (35.9 a) of NBS 947 within the measurement uncertainty.     

Mechanical properties of high strength vanadium-base ternary alloys

High strength V-20wt.%Nb and V-10wt.%Ta base ternary alloys containing aluminium, chromium and molybdenum were studied. The fabricability and tensile properties at room temperature and in a temperature range 700–1000 °C were measured. The tensile strength values were estimated on the basis of the values for the corresponding vanadium-base binary alloys and compared with the experimental data. The estimated values are in good agreement with the experimental data. From these results, V-20wt.%Nb-5wt.%Al, V-20wt.%Nb-5wt.%Cr and V-20wt.%Nb 10wt.%Mo alloys were selected as alloys that could be recommended for their good high temperature mechanical properties.     

High-throughput synthesis and screening of ternary metal alloys for electrocatalysis

We report the application of a new method for the high-throughput synthesis and screening of thin film materials and its application to the discovery of electrocatalysts. Results are presented for the PtPdAu ternary alloy system with respect to activity for oxygen reduction. The results reveal an enhancement in activity for a range of PtPd alloy compositions over either of the pure elements. An optimum composition range of ternary alloys with significant activity was also identified. A correlation was also investigated between the surface reduction potential and the activity for oxygen reduction in both binary and ternary alloys. The results demonstrate the potential of the methodology for the discovery and optimization of electrocatalysts for a wide range of applications.     

The analysis of plutonium uranium carbide-iron cermets by electrochemical method

Summary Electrochemical methods have been developed for the direct determination of the main metallic constituents of 15 w/o (Pu, U) C — 10 w/o Fe cermets. Samples are dissolved in nitric acid, followed by wet oxidation with a mixture of sulphuric and nitric acids to destroy organic matter. Plutonium is determined by a potentiometric titration procedure based upon the reduction of Pu^VI to Pu^IV with ferrous iron added in slight excess, followed by the titration of this excess with ceric sulphate. The precision of this determination on 4 mg amounts of plutonium is 0.1%. Both uranium and iron are determined by controlled-potential coulometry, but the method for iron includes a contribution from plutonium and allowance has to be made for this. The precision of the uranium determination on 10 mg amounts is 0.25%, and the value for iron on 1 mg amounts is also 0.25%. Results for the complete analysis of typical cermet samples are given.

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Zusammenfassung Elektrochemische Verfahren wurden ausgearbeitet zur direkten Bestimmung der metallischen Hauptbestandteile in Metall-keramischen Materialien (Cermets) der Zusammensetzung 15% (Pu,U)C-10% Fe. Hierbei wird die Probe in Salpetersäure aufgelöst und anschließend zur Zerstörung organischer Substanz einer nassen Oxydation mit einem Gemisch von Schwefel- und Salpetersäure unterworfen. Plutonium wird mit Hilfe eines potentiometrischen Verfahrens bestimmt, das auf der Reduktion von Pu^VI zu Pu^IV mit Fe^II in geringem Überschluß und nachfolgender Titration des Überschusses mit Cer^IV-sulfatlösung beruht. Die Genauigkeit beträgt hierbei 0,1% bei Mengen von 4 mg Pu. Uran und Eisen werden durch Coulometrie mit Potentialkontrolle bestimmt; jedoch wird bei der Eisenbestimmung Plutonium miterfaßt und muß bei der Berechnung berücksichtigt werden. Die Genauigkeit der Uranbestimmung beträgt 0,25% bei 10 mg U, die der Eisenbestimmung 0,25% bei 1 mg Fe. Ergebnisse von vollständigen Analysen typischer Cermetproben werden angeführt.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.     

Application of plutonium radiochronometry to the analysis of plutonium age dating reference materials

Journal of Radioanalytical and Nuclear Chemistry - Radiochronometry is an important tool for nuclear forensic analysis. Plutonium has a wide array of parent/progeny pairs that can be measured to...     

Combinatorial screening of PtTiMe ternary alloys for oxygen electroreduction

The catalytic oxygen electroreduction properties of PtTiMe (Me = Co, Cr, Cu, Fe, Mn, Mo, Ni, Pd, Ta, V, W and Zr) ternary alloys were studied using an in-house developed thin film based combinatorial high throughput method. Libraries containing discrete alloy compositions were fabricated by plasma co-sputtering and the resulting alloys were electrochemically screened by the hydrodynamic rotating disk electrode technique. Candidate catalysts were identified by comparing the activity-stability-composition relationships between the platinum titanium alloys and pure platinum standard. Among the PtTiMe alloys studied, PtTiNi, PtTiCu and PtTiV, respectively, displayed the highest catalytic oxygen electroreduction activities with a tenfold, an eightfold and a sixfold enhancement as compared to the pure platinum standard and good chemical stabilities.     

Fluorescent ternary complexes of some biogenic amines and their metabolites with europium and oxytetracycline for applications in the chemical analysis

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HG-AFS法测定铀钼矿钼反萃取液、净化液中砷含量

建立氢化物发生-原子荧光光谱法(HG-AFS)测定铀钼矿钼反萃取液、净化液中砷含量的分析方法。仪器主要工作条件:负高压280 V,灯电流60 mA,原子化器高度9 mm,载气流量400 mL/min,屏蔽气流量1000 mL/min。砷的质量浓度在0～40μg/L范围内与荧光强度呈良好的线性,线性相关系数r=0.9998。方法测定砷的检出限为0.037μg/L,测定结果的相对标准偏差小于5%(n=6),加标回收率为90.5%～102.5%。针对溶液中的钼同多酸和杂多酸以及存在的其它氧化物,采取抗坏血酸-硫脲混合溶液进行预还原,溶液中铀含量约为0.1 g/L时,对砷的测定无影响。该法能满足铀钼矿钼反萃取液、净化液中砷含量0.005～4 g/L的测定要求。     

Differential Pulse Polarographic Determination of Trace Molybdenum in Uranium with α-Benzoinoxime Extraction

A method for the determination of trace molybdenum in uranium is described based on its specific catalytic reduction wave in the presence of nitric acid. Molybdenum is separated from uranium by α-benzoin oxime extraction and determined by differential pulse polarography. As lower as 1 ng/ml of Mo(VI) is determinable and 98% of recovery can be obtained at present work.