Influence of the origin of H2O2 on the rate of its reaction with Pu(VI) and Am(V) in acid solutions

Analysis of published data shows that H₂O₂ arising in radiolysis of acidic aqueous solutions is in the excited state and reacts with Pu(VI) and Am(V) faster than in the case when in it is introduced into the system with actinide ions from the outside.     

Synthesis, crystal and molecular structure, and spectral properties of guanidinium salt of complex uranyl 2-methoxybenzoate

A crystalline uranyl 2-methoxybenzoate, [C(NH₂)₃][UO₂L₃]·H₂O, was synthesized. Its structure was determined by single crystal X-ray diffraction, and the electronic and IR spectra were recorded. The coordination number of the U atom is 8, with methoxyl O atom not involved in coordination bonding with uranyl. The structure contains a system of hydrogen bonds with water molecule of crystallization and guanidinium cation acting as proton donors. The electronic absorption spectrum of the crystalline complex has a pronounced vibronic structure, whereas in the solution spectrum all the lines are strongly broadened. This may be due to dissociation of the complex anion in solution, which leads to superposition of several spectra. In the IR spectrum, there is a set of band characteristic of guanidinium cations. The uranyl group in [C(NH₂)₃][UO₂L₃]·H₂O has almost symmetrical structure. Therefore, only the band of its antisymmetric vibrations is observed in the IR spectrum.     

Specific features of reactions of Am(V) with reductants in weakly acidic solutions

In EDTA solutions with pH ??5 at 25°C, Am(V) in a concentration of 5 × 10^?4?3 × 10^?3 M slowly transforms into Am(III). The Am(V) reduction and Am(III) accumulation follow the zero-order rate law. In the range 60?C80°C, the reaction is faster. In some cases, an induction period is observed, disappearing in acetate buffer solutions. In the range pH 3?C7, the rate somewhat increases with pH. In an acetate buffer solution, an increase in [EDTA] accelerates the process. The activation energy is 47 kJ mol^?1. Zero reaction order with respect to [Am(V)] is observed in solutions of ascorbic and tartaric acids, of Li₂SO₃ (pH > 3), and of hydrazine. The process starts with the reaction of Am(V) with the reductant. The Am(III) ion formed in the reaction is in the excited state, *Am(III). On collision of *Am(III) with Am(V), the excitation is transferred to Am(V), and it reacts with the reductant: *Am(V) + reductant ?? Am(IV) + R₁ and then Am(IV) + reductant ?? *Am(III) + R₁, Am(V) + R₁ ?? Am(IV) + R₂. A branched chain reaction arises. The decay of radicals in side reactions keeps the system in the steady state; therefore, zero reaction order is observed.     

Upgrading the Design of Cruciform Fuel Elements to Increase their Heat-Engineering Characteristics

The change occurring in the heat-engineering characteristics of a cruciform fuel element in a SM reactor as a result of the change in the characteristic dimensions of the fuel element, such as the diameter of the circumscribing circle, the indentation radius, and the rounding radius of a lobe, and as a result of the presence of a central displacer in the element is examined. The optimal values of the indentation radius and rounding radius of a lobe are determined to be 0.5 mm. It is shown that the presence of a central displacer in a fuel element substantially decreases the maximum temperature of the kernel and decreases the coefficient of nonuniformity of the heat flux density. For the same maximum kernel temperature in a standard fuel element and a fuel element with a displacer, the maximum heat flux density in the latter element gives an additional margin up to the crisis of heat transfer.__________Translated from Atomnaya Energiya, Vol. 98, No. 4, pp. 274–280, April, 2005.     

Comparison of the results of summer and winter measurements of atomospheric water vapor absorption at wavelengths 1.5 ÷ 1.55 mm

Instrumental data on the water vapor absorption coefficient at air temperatures 255 ÷ 272 K, as well as the equipment and measurement procedure are briefly desribed. A comparison is performed with the summer measurement and the data reported by other authors.     

Method for estimating lineature by scanned samples of documents

The paper considers an algorithm for estimating lineature of scanned digital images based on the calculation of series lengths and local directional fields. The results of an experiment are given and the efficiency of the algorithm is investigated. Vitalii Anatol’evich Mitekin. Born in 1983. Graduated from Samara State Aerospace University (SSAU) in 2006. At present, he is a post-graduate student in the Department of Geoinformatics at SSAU. His scientific interests include image processing, stenography, and cryptography. He is the author of three publications, including three articles. Viktor Andreevich Fedoseev. Born in 1986. Defended a degree thesis at the Samara State Aerospace University in 2007. Continues teaching at the SSAU at present, and also works as a technician at the Institute of Image Processing Systems at the Russian Academy of Sciences. His scientific interests include computer graphics, image processing, stenography, and cryptography. He is the author of 11 publications, including six articles.     

Extraction of U(VI), Th(IV), Pu(IV), Am(III), and rare-earth elements from nitric acid solutions with diphenyl(dialkylcarbamoylmethyl)phosphine oxides substituted in the methylene bridge

The extractive power and selectivity of diphenyl(dialkylcarbamoylmethyl)phosphine oxides in extraction of U(VI), Th(IV), Pu(IV), Am(III), and rare-earth elements from nitric acid solutions was studied, as influenced by substitution of one or two hydrogen atoms in the methylene bridge with alkyl, cycloalkyl, CH₂P(O)Ph₂, and CH₂C(O)NBu₂ groups.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 427–432.Original Russian Text Copyright © 2004 by Turanov, Karandashev, Yarkevich, Safronova, Kharitonov, Radygina, Fedoseev.     

Influence of the Redox Potential and Charge of <Emphasis Type="Italic">f</Emphasis> Element Ions on the Kinetics of Reactions Involving Them

Experimental data on the kinetics of reactions of lanthanide and actinide ions with ОН radicals, e _aq ^– , each other, and d element ions are analyzed. The reactions with ОН radicals are kinetically controlled, with the rate constants being independent of the redox potential of the ion. This is due to the fact that the ОН radical abstracts the H atom from Н₂О in the hydration shell, which is followed by the charge transfer. The An⁴⁺ ions are oxidized with the formation of the An⁵⁺ ions, followed by their hydrolysis. The hydrated electrons e _aq ^– react with f element ions whose potential is less negative than–2.0 V, with the reaction being diffusion-controlled. The reactions of e_aq^– with An⁴⁺ and AnO ₂ ²⁺ occur by the tunneling mechanism. The reactions of the ions with each other are kinetically controlled, with the rate constants depending on ΔЕ of the reaction. The correlation is broken in the case of formation of AnO ₂ ⁺ –An⁴⁺ cation–cation complexes or of reactions involving the structure rearrangement. The stability of heptavalent ions in an alkaline solution decreases with an increase in the oxidation potential and with a decrease in the ion charge.