Radiochemistry最新文献

Abstract

According results of a theoretical analysis of the countercurrent column operation for the liquid phase catalytic exchange (LPCE) between hydrogen and water in a mode with independent flows of hydrogen and water, it is shown that there are temperature-dependent maximum values of the molar ratio of hydrogen and water flows, at which the separation performance of the column towards isotope mixtures of protium–tritium and protium–deuterium diminishes. Options for the operation of a chemical treatment column were experimentally studied provided that water vapor condensate is returned to the column from the output steam–gas flow or without it. The experimental results are consistent with the theoretical analysis performed.

Abstract

The comparison of the speciations of ²³⁹Pu and chemical elements, including rare earth elements (REE), in the bottom sediments of the Kara Sea and the Laptev Sea is given. The speciations were investigated by three different methods of selective leaching. Data were obtained on the content of chemical elements and ²³⁹Pu in the composition of complexes with different lability: easily soluble, bound to organic matter, including groups of humic acids (HA) and fulvic acids (FA), as well as to amorphous oxides of Fe and Mn. It is shown that humic and low molecular weight organic acids and their compounds with chemical elements can influence the behavior of plutonium in the seawater–bottom sediments system in the waters of the Arctic seas. The possibility of using a number of REE as a marker for predicting the migration behavior of plutonium is evaluated.

Abstract

Modern contamination of lake–river systems bottom sediments with global and “Chernobyl” ¹³⁷Cs is estimated. Drainage lakes of North-Western Russia were investigated. Lake Kopanskoe, located south of the Gulf of Finland, is on the “Chernobyl” ¹³⁷Cs fallout plume, whereas Ladoga, Sukhodolskoe, Vuoksa, Imandra lakes are located at its periphery, in Karelia and Kola Peninsula. Following parameters are distinguished: lakes bottom ¹³⁷Cs contamination density (kBq/m²), distribution of ¹³⁷Cs in the profile of bottom sediments, ¹³⁷Cs diffusion coefficients (D) in bottom sediments and content of the exchange chemical form of the radionuclide. ¹³⁷Cs contamination of the lakes was formed due to suspended matter sedimentation with ¹³⁷Cs, ¹³⁷Cs sorption and diffusion in bottom sediments. With sedimentation ≥3 mm/year, the concentration of ¹³⁷Cs increased from the top to the bottom of the core (lakes Vuoksa, Ekostrovskaya Imandra), reflecting the gradual process of ¹³⁷Cs migration into the sediments. The opposite trend of ¹³⁷Cs concentration was observed in the bottom sediments of lakes Ladoga and Sukhodolskoe with sedimentation ≤0.5 mm/year. Here ¹³⁷Cs diffusion with D = (0.5–6.2) × 10^–8 cm²/s caused slow radionuclide transfer in the bottom sediments. The main inventory of ¹³⁷Cs was contained in the top layer 0–5 cm. In Lake Sukhodolskoye bottom sediments an absorbed ¹³⁷Cs in an exchange chemical form, extracted into 1 М NH₄Aс solution, amount only 14.4–20%.

Abstract

The ⁸²Sr/⁸²Rb generator is used to produce a radiopharmaceutical rubidium-82 chloride in saline solution for PET imaging. In this work, we studied the effect of the amount of stable strontium and calcium delivered to the sorbent (on the basis of hydrated tin dioxide) on the maximum volume of radiopharmaceutical solution that can be obtained from the generator. Sr and Ca may be delivered to the sorbent from the initial solution of strontium-82 chloride or from the eluent (0.9% NaCl) during medical application of the generator. It is shown that this volume depends on the value C_Sr + 0.11C_Ca, where C_Sr and C_Ca are molar concentrations of the elements in 1 g of the sorbent. The obtained results make it possible to increase significantly the productivity and reliability of the used generators.

Abstract

The effect of the ionic liquid—1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide—on the extraction of lanthanides(III), U(VI) and Th(IV) from nitric acid solutions with 1,2-bis(diphenylphosphinyl)-ethane I and 1,2-bis(diphenylphosphinyl)benzene II was studied. The stoichiometry of the extracted complexes was determined. A solution of dioxide II in dichloroethane extracts metal ions much more efficiently than a solution of dioxide I. It was established that in the presence of an ionic liquid in the organic phase, the efficiency of extraction of metal ions from nitrate solutions with solutions of dioxide I increases significantly, and that of dioxide II decreases. Thus, in the presence of an ionic liquid in the organic phase, dioxide II is significantly inferior to dioxide I in terms of the efficiency of Ln(III), U(VI) and Th(IV) extraction from nitric acid solutions, which is attributed to a significantly greater ability of dioxide II to extract HTf₂N.

Extraction of U(VI), Th(IV), REE(III), and Sc(III) from nitrate and perchlorate solutions with solutions of phosphorylpodand 1,5-bis[di(p-tolyl)phosphoryl]-3-oxapentane (L) in 1,2-dichloroethane depending on the concentration of acids in the aqueous phase was studied. The stoichiometry of the extractable complexes was determined. The magnitude of the “perchlorate” effect was shown to diminish upon an increase in the acid concentration, and REE(III) ions, to be extracted by podand L from HClO₄ solutions less efficiently than from HNO₃ solutions at acid concentrations above 0.3 M. During the extraction of Sc(III) the “perchlorate” effect also manifests itself in the region of high acid concentration, which leads to an increase in the separation factors of Sc(III) and REE(III), U(VI), and Th(IV) during extraction with podand L from HClO₄ solutions.

The processes of solvent extraction of cesium and strontium stable isotopes using solutions of macrocyclic polyethers in organic solvents from nitric acid solutions were studied. The influence of crown ether structure and solvent type on the distribution coefficients of cesium (D_Cs) and strontium (D_Sr) was investigated. Extraction systems for the co-extraction of cesium and strontium were tested, in which 1,1,7-trihydrododecafluoroheptanol and chlorine-substituted hydrocarbons were used as solvents. It was shown that there are highest D_Cs and D_Sr during co-extraction of metals when using a mixture of DTBDB18C6 and DCH18C6. Experimental data prove high selectivity of crown ethers for the extraction of cesium and strontium into a separate fraction when managing radioactive waste.

Using the through diffusion method at room temperature, the migration of radionuclides (³H, ⁹⁹Tc, ¹³⁷Cs, ²³³U) in compacted samples of clay materials was studied through pore diffusion from a model leachates of phosphate matrix of radioactive waste with a total salt content of about 400 mg/L. The effective diffusion coefficients and sorption distribution coefficients of radionuclides for the studied clay barrier materials were determined based on the experimental results. The patterns of diffusion transfer of tritium, cesium and uranium were revealed depending on the structure, mineral composition of clay materials and the content of radionuclides in the pore solution. Numerical solutions are proposed for calculating the effective pore diffusion coefficients of these radionuclides. There are not yet enough data to analyze the factors influencing the diffusion of technetium.