Radiochemistry最新文献

Materials and methods used for the analysis of physicochemical properties of submicron industrial aerosols are described. These approaches can be used at research centers and enterprises, including those of Rosatom, for studying the physicochemical properties of submicron and nanometer aerosols. The dispersity of industrial α-emitting submicron aerosols in air of working premises of Mayak Production Association was studied for ²³⁹Pu using the neutron-induced measurement method. The size distribution of ²³⁹PuO₂ nanoparticles in air of the oxalate precipitation department is the Pareto distribution. The result obtained can be used as a priori nanoparticle size distribution in the calculation of the ²³⁹Pu-caused internal irradiation dose load on the personnel of the oxalate precipitation department, RT Plant, Mayak Production Association, using the Bayesian method.

The crystal and molecular structures of the complex [⁹⁹TcCl(CO)₃(C₅H₈O₂)]₂ (C₅H₈O₂ = Hacac = acetylacetone) formed in the course of prolonged standing of a [⁹⁹Tc(acac)(CO)₄] solution in ССl₄/CDCl₃ and of its analog containing no organic ligand, [⁹⁹TcCl(CO)₄]₂, were determined. Both complexes contain a [Tc₂(μ-Cl)₂] four-membered ring. The remaining sites in the coordination sphere of the Tc atom are occupied by carbonyl ligands, and in the case of [⁹⁹TcCl(CO)₃(Hacac)]₂, also by the neutral acetylacetone molecule in the enol form. The Hacac molecules in the binuclear complex are in the cis position to the Cl atoms in the octahedral surrounding of the Тс atoms and in the trans position to each other relative to the [Tc₂(μ-Cl)₂] ring. A comparative analysis of the geometries of the complexes and their known analogs was performed.

The thermal stability of dibenzo-21-crown-7 (DB21C7) and its solution in 1,2-dichloroethane (DCE) after contact with nitrogen dioxide, which is a product of nitric acid degradation, was studied. It is shown that exothermic processes accompanied by the release of gaseous products are observed in inert and oxidizing atmosphere. The compounds formed after contact with nitrogen dioxide were determined by gas chromatography–mass spectrometry. Differences in gaseous products in the temperature range of 300℃ were defined for the initial crown ether and for DB21С7 and its solution in DСE after contact with NO₂.

The work examines the state of ¹⁰⁶Ru in solutions simulating technological media and liquid radioactive waste from nuclear power plants with a VVER reactor, as well as the influence of the physicochemical state of the radionuclide on the efficiency of ion exchange and ultrafiltration treatment methods. During the study, the regions of existence of ionic and nonionic states of the radionuclide were explored in solutions of complex composition. In addition, the size distribution of particles containing ¹⁰⁶Ru were established. The formation of complex compounds of ¹⁰⁶Ru with polyborate ions in the neutral and slightly alkaline pH region has been shown, which leads to a decrease in the efficiency of decontamination of liquid radioactive waste from ruthenium radionuclides.

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.