[en] Dihydrate of oxovanadium (4) perrhenate is prepared by VO(OH)₂ solution in rhenic acid. Stability boundaries of VO(ReO₄)₂x2H₂O and VO(ReO₄)₂ are determined by means of thermal analysis. Change of the structure during vanadyl perrhenate dehydration is established by X-ray phase analysis and proved by the method of IR spectroscopy

[en] Practically all experimental data on the separation of U(VI) and Pu(IV) between HNO₃ solutions and 30% TBP in n-paraffins are processed. Data are presented as regression functions of the separation coefficients on component concentrations. The accuracy is 8%

[en] Extraction equilibria are studied for aqueous (UO₂)(NO₃)₂-Pu(NO₃)₄-HNO₃ and 20% and 30% TBP in n-dodecane at 25 and 60 degrees C. Data are obtained for the stable two-phase systems. Regions near the critical point [formation of a second organic phase at high Pu(NO₃)₄ concentration] are also investigated. The behavior of Pa in the system is studied

[en] Lead (2) hydroxoperrhenate has been synthesized and investigated, using the methods of chemical, thermographical, thermogravimetric, X-ray diffraction phase, PMR and IR spectroscopic analyses. By means of thermal analysis it has been established, that the process of dehydration of basic lead perrhenate takes place according to the scheme: PbOHReO₄→Pb₂O(ReO₄)₂+H₂O. On the basis of X-ray diffraction phase and IR spectroscopic methods of analysis the difference in the structure of PbOHReO₄ and Pb₂O(ReO₄)₂ is detected. Using PMR, quantitative content of hydroxyl groups in basic lead perrhenate is determined and it is shown, that interproton distapce for OH^--groups equals 2.52+-0.12 A

[en] The properties of isoparaffin TBP diluents such as the density, dynamic viscosity, and their temperature dependence are studied. The capacity of the extractant for Pu can be increased. Empirical functions for calculating the maximal extractant capacity (TBP in isoparaffin diluents) as a function of mobility are proposed

[en] Method for decreasing plutonium losses during Pu(6) to Pu(4) reduction by nitrogen oxides in nitric acid solutions at temperatures above 60 deg C is suggested. Nitric acid solution (4-5 mol/l), saturated preliminary by nitrogen oxides at 22-25 deg C is used as source of nitrogen oxides at that. This results to sufficient decrease of plutonium losses with aerosol and 5-30 time decrease of the flow-rate of gaseous nitrogen oxides. The method can be used for reprocessing of plutonium-containing materials and for reprocessing of NPP spent fuel in particular

[en] A study was made on the dependence of the rate of Pu⁶⁺ macroconcentration reduction to Pu⁴⁺ (2-40 g/l) when bubbling mixture of gaseous nitrogen oxides (oxide and dioxide) on nitric acid concentration (3-8 mol/l, initial Pu⁶⁺ content (20-95 %) total plutonium concentration in processable solution temperature (50-80 deg C), the rate of gaseous nitrogen oxides and composition of the given gaseous mixture, as well as the presence of uranium (6) and stable isotopes of some fission products in processable solution. Empirical kinetic equation for the rate of studied process enabling to calculate the apparent rate constants of gas-chemical reduction of Pu⁶⁺ to Pu⁴⁺ using experimental data is suggested. Applicability of derived equation for decribing the studied process under steady conditions during regeneration of NPP spent fuel is shown

[en] A one-cycle scheme for extractive reprocessing of spent breeder-reactor fuel with co-extraction of U and Pu at elevated temperature is modeled mathematically. The optimal configuration of the processing scheme with the most stable regime is found. The prospects and possibilities of automated design for reprocessing fuel with a high Pu content are demonstrated

[en] Short note

[en] The use of n-paraffins as diluents for extractants in extraction processes for handling solutions of spent nuclear fuel from nuclear power stations is complicated by phase separation or the metal-containing extractants at a certain metal concentration, which hinders the performance of technological extraction processes, because of possible upsets of the hydrodynamics and nuclear safety. It is possible to increase the capacity of the extractants by raising the temperature, or by the introduction of aromatic compounds and alcohols, and also isoparaffins. The synthetic C₁₀-C₁₆ isoparaffins prepared by the authors, having a teriary carbon atom, were just as suitable as n-paraffins with respect to the basic requirements for a diluent to dilute an extractant in radiochemical practice. Although slightly inferior to the n-paraffins inflammability and stability toward nitration, yet they surpass them in resistance to freezing, and, on the whole, they also have a substantially higher capacity for extractants used to extract Th(IV), Pu(IV), and Sr(II). These isoparaffin hydrocarbons, prepared by the simple technological operation of catalytic hydrogenation of an n-paraffin feedstock, when used instead of n-paraffin diluents in the radiochemical operations of extracting thorium, Pu, or strontium, improve the essential operating properties of the diluent, including its radiolytic stability, and substantially increase the capacity of the extractants for metals, whereby the operating capabilities of the extraction apparatus are expanded through increased productivity, through less danger of phase-separation of the organic phases, and in the case of plutonium, through enhanced nuclear safety of the extraction process. The correlation established between the fine structure and composition of isoparaffin diluents and their solubilizing effect in relation to the solvation of metals makes it possible to conduct a targeted search, and synthetic program, for new diluents