Radiochemistry最新文献

A method of coupled processes was proposed to maintain concentrations in the model leachate of the radioactive waste phosphate matrix, which served as a source of elements in the study of through-diffusion of P, Se, Br, Mo, Cs, and U in the pore solution of compacted clay materials. The method consisted in adding an leachatable solid phase to the solution in the source chamber of the diffusion cell. The use of this method made it possible to stabilize the boundary conditions and expand the range of element concentrations in the source chamber of diffusion cells. The new as-obtained data on the effective diffusion coefficients of radioactive waste elements in clay rocks were used to refine the empirical models of diffusion transfer. It is shown that in different geochemical systems (model groundwater and phosphate glass leachate) for some elements (Br, Mo, Cs) it is possible to use unified models in the form of effective diffusion coefficients as a function of factors influencing this process: sample porosity, smectite content in the sample, and concentration of radionuclide (element) in pore solution, while for Se and U, diffusion models for various geochemical systems differ. The specificity of diffusion behavior of elements is associated with structural features and physicochemical properties of particles of these elements in aqueous solutions.

The processes of localization of I₂, I^–, and [UO₂(CO₃)₃]^4– from aqueous solutions under static conditions on metal-containing clay powders from kaolin clays of the Kampanovskoye deposit and from bentonite clays of the 10th Khutor and Dinozavrovoe deposits were investigated. The studies were carried out with Cu-, Ni-, Zn-, and Fe-containing clay powders treated with a 2 M hydrazine hydrate solution. It was shown that the [UO₂(CO₃)₃]^4– complex is not sorbed on the synthesized clay materials from aqueous solutions under static conditions. It was established that the synthesized clay materials are capable of not only reducing the amount of the molecular form of iodine in an aqueous solution, but also sorbing the ionic form of iodine from an aqueous solution of KI to almost 100% at a concentration of I^– less than 10^–2 M.

The optimal conditions for the synthesis of a pelletized sorbent based on mixed Mn(III, IV) oxide by reacting aqueous solutions of MnSO₄ and KMnO₄ in an alkaline medium were determined: Mn²⁺/MnO₄^– molar ratio 1.70–1.80; pH of the reaction mixture 11.0–12.5; calcination temperature 220°C. For the sorbent fabricated under optimal conditions, the values ​​of the distribution coefficient (K_d) of ⁹⁰Sr in 0.01 M CaCl₂ solution, static exchange capacity for calcium, hydromechanical strength of granules, and K_d of ⁹⁰Sr as a function of the concentration of sodium and calcium ions were established. The sorbent afforded higher sorption characteristics with respect to strontium compared to known sorbents. A technology for producing pilot batches of the sorbent named MDM, was developed. Examples of the use of the MDM sorbent for the purification of various types of liquid radioactive waste from strontium and radium radionuclides are reported.

Archive data (1970–2024) on the results of monitoring the tritium content of surface liquid radioactive waste (LRW) storage reservoirs (special radioactive waste repositories) and of groundwater in the vicinity of the Mayak Production Association are analyzed. The tritium contamination existing today was formed before the 1970s and was initially accumulated (a) in V-2 reservoir (Kyzyl-Tash), which operated as a reservoir for recirculating direct-cooling of industrial uranium–graphite reactors (PUGRs) in case of failure of uranium slug cladding; (b) in V-9 (Karachay) and V-17 (Staroye Boloto) reservoirs, which were used for storage of intermediate-level tritium-containing liquid waste; (c) in groundwater as a result of tritium seepage from the reservoirs. After putting into operation the RT-1 radiochemical plant (1977), the major fraction of tritium was accumulated in a new LRW type, tritium condensate, which was stored in V-17 reservoir. The contaminated groundwater filtering from V-17 reservoir was discharged only into an inlet of V-10 reservoir of the Techa Cascade of Reservoirs (TCR). The maximal rate of tritium discharge was estimated at 0.11 TBq/year, and the specific activity of tritium in the TCR water, at 2 Bq/L. In the 2020s, the tritium discharge into the atmosphere from the RT-1 plant was ~34 TBq, which was ~2800 times lower than the maximum permissible discharge prescribed for the whole enterprise. The mean value of the annual effective dose from all the pathways of tritium intake by Ozyorsk inhabitants was 0.26 μSv, and the maximal value was 0.49 μSv, which is ~2000 times lower than the dose limit of 1 mSv for the population. The tritium emissions and discharges from the RT-1 plant are negligible and exert virtually no radiation impact on the population.

The study deals with U(VI) sorption from phosphoric acid media onto poly(hexamethylenesuccinamide) (PA46) (–CO(CH₂)₂)CO–NH(CH₂)₆NH–)_n as a cation-exchange resin. The process was studied using SEM, FT-IR, and surface area determination. The effect exerted on the process by the contact time, liquid to solid ratio, temperature, stirring rate, and initial U(VI) concentration was examined. The adsorption capacity for uranium under the optimum conditions was found to be 25 mg/g. The sorption data were described using Langmuir, Freundlich, and Temkin isotherm models. The thermodynamic equilibrium constant and the Gibbs free energy were determined: ΔG° from ‒19.08 to ‒22.49 kJ/mol, ΔH ‒78.63 kJ/mol, and ΔS ‒199.83 J/(mol K). These data show that the adsorption is spontaneous. The kinetic data are best described by the pseudo-second-order model.

An automated method has been developed for the synthesis of [N-methyl-¹¹C]choline, a radiopharmaceutical (RP) for the diagnosis of cancer using positron emission tomography (PET). The synthesis was carried out on a home-made module, using combined technology of on-line ¹¹C-methylation processes and solid-phase extraction methods. The radiochemical yield of [N-methyl-¹¹C]choline was 80% (based on the activity of the methylating agent, [¹¹C]CH₃I, decay corrected), which ensures the production of several clinical doses of radiopharmaceutical in one batch. [N-Methyl-¹¹C]choline was obtained with a radiochemical purity of more than 99% and an amount of 2-dimethylaminoethanol (the main chemical impurity) of 0.06 mg/mL, which meets the requirements of the Russian and European Pharmacopoeia.

A novel 12-step procedure was developed for preparing methyl 14-isocyano-3-methyltetradecanoate. “2+1_B” tricarbonyl complexes [^99mTc(CO)₃(N^N)CN(CH₂)₁₁CH(CH₃)CH₂COOMe]⁺, where N^N = 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen), were prepared by the reaction of [^99mTc(CO)₃(N^N)(H₂O,EtOH)]⁺ with methyl 14-isocyano-3-methyltetradecanoate in aqueous ethanol. The formation of technetium-99m complexes was confirmed by HPLC, and the partition coefficient (n-octanol/water) of these complexes was measured.

Synthesis, IR spectroscopic, and X-ray diffraction studies of R[UO₂(mia)₃]₂·2Hmia·4H₂O crystals, where R = Sr²⁺ (I) or Ba²⁺ (II), and mia is the monoiodacetate ion CH₂ICOO⁻, have been carried out. The [UO₂(mia)₃]^– complexes correspond to the crystal chemical formula A(B⁰¹)₃, where A = UO₂²⁺, B⁰¹ = mia. It has been established that a common feature of I and II is the presence of trinuclear electrically neutral clusters {R[UO₂(mia)₃]₂(Hmia)₂(H₂O)₂}. At the centers of the clusters there are trigonal RO₈ dodecahedra; half of their oxygen atoms belong to four different mia anions of two [UO₂(mia)₃]^– complexes. In addition, each R atom coordinates the oxygen atoms of two water molecules and the carbonyl oxygen atoms of two Hmia molecules. Using the method of molecular Voronoi–Dirichlet polyhedra, an analysis of noncovalent interactions in the structure of I was carried out.

The effect of the ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, on the extraction of lanthanides(III) from nitric acid solutions with phosphoryl-containing podands (2-(2-diphenylphosphoryl)-4-ethylphenoxy)methyl)diphenylphosphine oxide (1), (2-(2-diphenylphosphoryl)-4-ethylphenoxy)ethyl)diphenylphosphine oxide (2), and 2-[2-(diphenylphosphoryl)-4-ethylphenoxy]-N,N-dioctylacetamide (3) was studied. The stoichiometry of the extracted complexes was determined. The efficiency of extraction of lanthanides(III) with solutions of compounds 1–3 in dichloroethane from nitric acid solutions increases in the order 3 < 2 < 1. It has been established that, when replacing dichloroethane with an ionic liquid as a diluent, the extraction efficiency enhances. The magnitude of this effect decreases in the series of compounds 3 > 2 > 1. In the case of compound 1, the replacement of dichloroethane with an ionic liquid as a solvent is accompanied by a decrease in the extraction of lanthanides(III) at [HNO₃] > 1.5 M.

The possibility of introducing tritium into dexamethasone and dexamethasone phosphate using the thermal activation method was demonstrated. The affinity of ligands for glucocorticoid receptors has been successfully assessed using labeled compounds.