Uranium stripping from tri-n-butyl phosphate by hydrogen peroxide solutions

The processes of uranium stripping from 30% tri-n-butyl phosphate (TBP) in "odorless" kerosene by H2O2 solutions both with and without NH4OH added were investigated in the temperature range of 20-50 C and with a volumetric ratio of 1 between the organic and aqueous phases. The uranium was selectively precipitated in the form of uranium peroxide during stripping from the organic phase by hydrogen peroxide. The stripping of uranium increased with increasing H2O2 content, increasing temperature and increasing concentration of NH3 in the range of 0-15 g/L. The use of a heated solution (40 C) that contained 4 mol H 2O2/mol U and NH3 12 g/L resulted in 99.7% of the uranium being stripped from TBP in the form of uranium peroxide. The uranium peroxide obtained by stripping is a highly pure product that exists in two different hydrated forms: UO4в̂™4H2O (92 mass %) and UO4в̂™2H2O. The mean particle diameter was 20.75 μm. The effect of hydrogen peroxide on the organic phase was studied by IR spectroscopy. No structural changes in TBP were observed after 30 cycles of extraction/stripping; thus, the use of hydrogen peroxide in this application is unrestricted. © 2013 Elsevier B.V

Study of causes of film formation on the electrolyte surface during niobium electrorefining

Formation of a conducting film on the surface of fused electrolyte during electrorefining of niobium in chloride melts was investigated. It was found that this film has metallic nature and is formed as a result of disproportionation of niobium(III) ions at a liquid-gas interface. Decreasing temperature gradient along the heated part of the electrolyser can be used to limit the influence of the disproportionation onto film formation. The metal film formation on solid ceramics can be used for creation of conducting layers on various oxide materials. copyright The Electrochemical Society.Electrochemical Society, Phys. Anal. Electrochem. Div.;Electrochemical Society, Electrodeposition Division;Electrochemical Society, High Temperature Materials Division;Electrochemical Society, Battery Division;Electrochemical Society, Energy Technology Divisio

ВОЛОЧЕНИЕ СПЛОШНЫХ ПРОФИЛЕЙ ПРАВИЛЬНОГО МНОГОГРАННОГО СЕЧЕНИЯ

In designing the regular polygonal section shape drawing process, it is convenient to use analytical expressions allowing us to estimate effectively the effect of different process factors. A design procedure of stress calculation for this process is proposed. The ratios for calculation of drawing stress, optimum angle of the drawing tool hole, limit value of deformation degree in using the standard tool and index of stress state in the axial part of the deformation zone are obtained. The use of drawing tools with optimum angles reduces the accumulation rate in the metal structure and in case of repeated drawing allows us to cut down the number of intermediate heat treatments.При проектировании процесса волочения профилей правильного многогранного сечения удобно использовать аналитические выражения, позволяющие оперативно оценивать влияние разных технологических факторов. Предлагается методика расчета напряжения данного процесса. Получены соотношения для вычисления напряжения волочения, оптимального угла канала волочильного инструмента, предельного значения степени деформации при использовании стандартного инструмента и показателя напряженного состояния в осевой части зоны деформации. Применение волочильного инструмента с оптимальными углами снижает скорость накопления дефектов структуры металла и при многократном волочении дает возможность уменьшить число промежуточных термообработок

ОБ ОПТИМАЛЬНОЙ ГЕОМЕТРИИ КАНАЛА ВОЛОЧИЛЬНОГО ИНСТРУМЕНТА ПРИ ДЕФОРМИРОВАНИИ БИМЕТАЛЛИЧЕСКИХ КОМПОЗИТОВ

For designing the bimetallic product drawing process, analytical expressions are established for calculation of drawing stress and optimum die hole angle to estimate expeditiously the effect of different process factors on the process power parameters as well as on the value of longitudinal stresses in the layers of bimetallic composite. Disadvantages of the proposed formulas are noted.Для проектирования процесса волочения биметаллических изделий получены аналитические выражения для расчета напряжения волочения и оптимального угла канала волочильного инструмента, позволяющие оперативно оценивать влияние разных технологических факторов на энергосиловые параметры процесса, а также на величину продольных напряжений в слоях биметаллического композита. Отмечены недостатки предлагаемых формул

Triuranium octoxide dissolution by nitric acid solutions with addition of ammonium nitrate

The processes of triuranium octoxide dissolution by nitric acid with and without addition of ammonium nitrate were investigated in the temperature range 75-95 °C and in the acid concentration range 3.0-14.36 mol/L. The optimal effect of nitrogen oxide reduction to elementary nitrogen was obtained by adding of ammonium nitrate in the concentration range 1-2 mol/L and at temperature 75 °C. The kinetics of triuranium octoxide dissolution by nitric acid solutions (3.0 mol/L) with and without addition of ammonium nitrate were studied. The highest dissolution rate was obtained at concentration of ammonium nitrate 2 mol/L and temperature 368 K. The source of ammonium nitrate in the technology of uranium refining can be ammonium polyuranate. © 2012 Elsevier B.V