Results 1 - 10 of 4385
Results 1 - 10 of 4385. Search took: 0.03 seconds
|Sort by: date | relevance|
[en] This study is concerned with direct crystallization of ammonium uranyl carbonate (AUC) from a uranium loaded organic phase (30% TBP in kerosene), with ammonium carbonate (NH4)2CO3. The effects of operating conditions ((NH4)2CO3 concentration, flow-ratio, residence time, temperature) on the physical properties of AUC crystals (particle size distribution, specific surface, density...) are reported. All products were identified (both by chemical analysis, X-Ray diffraction) as being ammonium uranyl carbonate crystals (AUC). The results show that a high phase ratio and (NH4)2CO3 concentration favor the formation of fine AUC grains and aggregates. This is due mainly to the high concentration of NH+4 in the system which leads to a high solution supersaturation and consequently to a rapid formation rate of crystal (germination). The reverse phenomenon is observed at low phase ratio and (NH4)2CO3 concentration, where germination and crystal growth are slow and the product is mainly monocrystal. In the intermediate range, a mixture of polycrystal and aggregates is obtained. Residence and temperature are also shown to have an effect on the processes (the effect of time being more important than temperature). In the course of this study a bench-scale stripper-crystallizer was developped and operated successfully. (author). tables, graphs
[en] Stripping nuclear reactions have proved to be a useful tool in studying nuclear structure and energy levels. These stripping reactions have been widely studied at different energies for the incident projectiles with values both above and below the Coulomb barrier between in interacting particles. In this article, the stripping nuclear reactions are introduced to show the success of stripping reactions in providing information on nuclear structure. The results presented are mainly concerned with stripping processes occurring at bombarding energies well below the Coulomb barrier. The one- and two-nucleon and cluster transfer reactions have been considered. Different projectiles have been considered in such reactions as deuterons, tritons, 3He, 6Li, 12C, 14N, 16O and 19F nuclei. The spectroscopic factors from these reactions have been extracted. (orig.)
[en] An analysis of stripping for unbound analog states was made, using a resonance form factor, calculated from the theory of analog resonances. (A.C.A.S.)
[pt]Uma analise do stripping para estados analogos nao ligados foi feita usando-se um fator de forma de ressonancia calculado a partir da teoria de ressonancias analogas. (A.C.A.S.)
[en] The kinetics of back-extraction of Pu(IV) from 30% Tri-Butyl-Phosphate/Odourless Kerosene (TBP/OK) into a nitric acid solution containing N,N-dimethylhydroxylamine (DMHAN) have been investigated using a Lewis cell. The different parameters affecting the back-extraction rate of Pu(IV) such as plutonium, nitric acid, DMHAN concentration in addition to temperature, stirring speed were separately studied and a rate equation was deduced. The activation energy of this process is 28.4 kJ/mol. (author)
[en] Equations for transverse emittance growth due to multiple passes of circulating proton beam through the H-minus stripping foil in Booster were developed in . These were based on simple principles of statistics and simple assumptions about the initial distribution of particles incident on the foil. It was assumed there that the foil dimensions and position of the incoming beam are such that all particles hit the foil on every turn around the machine. In the present note we assume only that all incoming H-minus ions from Linac hit the foil and are stripped of their electrons. The resulting protons circulate indefinitely around the machine. Setups in which the foil width is reduced so that not all protons hit the foil on every turn are studied here by simulation. The aim is to determine the effectiveness of such setups in reducing the emittance growth of circulating proton beam during the injection of H-minus beam. The simulations also serve as a check of the equations developed in , and vice versa. The particulars of the simulation setup are given in Sections 1 through 11. Figures 1 through 12 show simulation results for the case in which all particles hit the foil on every turn. The results are in good agreement with those obtained from the equations of reference . Figures 13 through 19 show simulation results for various setups in which the foil width is reduced. These results are summarized in Section 12. In all gures the horizontal axis gives the turn number. The unit of the vertical axis is micrometers ( m) in all plots of emittance.
[en] PNC has been promoting actinides partitioning studies as a part of advanced reprocessing system development efforts since 1990. Concurrently, the general TRUEX process was studied as a reference partitioning tool. In the counter-current flow-sheet tests using mixer-settler, some portion of U,Pu and Ru used to remain in the solvent by conventional stripping methods. Therefore a new 'Salt-free' solvent-washing methods were studied to remove these nuclides and Zr from TRUEX solvent. Hydrazine oxalate was tested for U. Hydrazine oxalate, hydrazine carbonate and TMAH (tetramethylammonium hydroxide) were tested for Ru and Zr. The stripping behavior of Pu by hydrazine oxalate was studied through the counter-current test. It was concluded that various 'Salt-free' reagents will be effective, if these are used in combination manner, for reducing- these nuclides retention in the solvent. (authors)
[en] FPEX contains a calixarene for Cs extraction, a crown ether for Sr extraction, Cs7SB modifier and TOA to aid in stripping, all in Isopar L diluent. The radiation stability of FPEX must be evaluated prior to process use. The radiolytic degradation of species in solution is due to reaction with the direct radiolysis products of the diluent. In Isopar L, the reactive species produced include solvated electrons (e-), hydrogen atoms (H) and alkane radicals, resulting in a reducing environment. However, when contacted with nitric acid, oxidising hydroxyl (OH) and nitrous (NO2) radicals dominate the system chemistry. Thus, the nature of the diluent and the presence of radical scavengers affect the results of irradiation. We report the preliminary results of a new programme to investigate the radiolysis of FPEX using the 60Co irradiation of FPEX neat solvent, acid pre-equilibrated solvent and mixed aerated phases. The Cs and Sr distribution ratios were used as metrics. (authors)
[en] The reductive stripping of Np using a n-butyraldehyde (NBA) from loaded organic solution containing Np, which was oxidative-extracted in a system of a 30 % TBP/NDD-2M HNO3and O/A=2 containing 0.005 M K2Cr2O7 as an oxidant of Np, was studied. The stripping yields of Np was increased with an increasing the NBA concentration, with a decreasing the nitric acid concentration of stripping solution and with a decreasing the reaction temperature. The apparent reductive stripping rate equation was shown by the following equation : -d [Np]-O-r-g/dt = 1,524 exp(-2,906/T) [NBA]0.92 [Np]Org. At 1.04 M NBA and 2 M HNO3, the stripping yield of Np and U was 70.1 %, and 7.1 %, respectively, and the separation factor of U over Np (=DU/DNp) was about 30.4. Therefore, it was found that U and Np co-extracted in a system of TBP-NHO3 could be effectively mutual-separated by the NBA.
[en] Investigations on uranium extraction from a representative mineralized granite sample (Gattar granite GII) by solvent-in-pulp (SIP) technique were carried out in the present study. For this purpose, the solvent (tri-butyl amine) (TBA) was mixed with the leaching slurry without prior filtration. The influence of various factors affecting the SIP process, such as contact time, solvent concentration, dilution factor, type of surfactant, surfactant/solid ratio were studied. About 91% uranium extraction efficiency was attained by the application of the chosen extraction SIP conditions. Also, about 96% of the loaded uranium could be stripped by using sulfuric acid as an effective stripping agent
[en] The basic principles of symmetric peaks modifications are considered in this work. Four types of modifications-two symmetric and two asymmetric are considered in detail. Double sequent peak modification was taken as example. The dependences of peak shape parameters on modification parameters were obtained for considered examples of modifications of three basic peaks. The methods of obtaining of common sequent modifications and techniques of suitable result function choice for adequate description of analytical signal series are developed. The approximation of groups of stripping voltammetry and chromatographic peaks with some single, double and triple modifications of elementary peaks has been get. The appreciable increasing of adequacy in description of more complicated modifications was shown