Radiochemistry最新文献

The results of monitoring the contamination of air, soil, and plants in the region of location of the Mayak Production Association with ¹³⁷Cs, ⁹⁰Sr, and plutonium isotopes (^239,240Pu and ²³⁸Pu), obtained in 2023 by specialists of Mayak and of the Federal Service for Hydrometeorology and Environmental Monitoring of Russia, are reported. The volume activity (VA) of ¹³⁷Cs and ⁹⁰Sr in the surface layer of the atmosphere in the Mayak surveillance zone is lower than the limits prescribed by the sanitary regulations by 6–7 orders of magnitude, and the VA of ^239,240Pu and ²³⁸Pu is lower by 3–5 orders of magnitude. The radiation situation near the enterprise is stable, and the monitoring results obtained in 2023 correspond to the measurement results obtained in the previous years and confirm the previously revealed trends.

The photolytic reactions of U(VI), Np(VI, V), and Pu(VI) in 0.5–13 M C₂H₅COOH solutions were studied. Under UV irradiation, U(VI) is reduced to U(IV); Np(VI), to Np(V); Np(V), to Np(IV); and Pu(VI), to Pu(IV) and Pu(III). The photochemical reduction of U(VI) in concentrated propionic acid to U(IV) under UV irradiation is fast and complete. The Np(V) reduction proceeds with an induction period, after which the reaction accelerates. This is due to the fact that Np(V) weakly absorbs in the UV range. The appearance of Np(IV) leads to the formation of a Np(V)–Np(IV) cation–cation complex. The complex absorbs light, its energy excites Np(V), and Np(V) reacts with the acid. The photoreduction of Np(VI) proceeds without an induction period, because Np(VI) significantly absorbs UV light. Pu(VI) under UV irradiation is reduced to Pu(IV) and finally to Pu(III).

The results of regular hydrological and radiochemical monitoring of open liquid radioactive waste storage reservoirs (OLRWSRs) of the Mayak Production Association in 2021–2023 in the period of reduced water content are summarized. Changes in the water level in OLRWSRs are, as a rule, seasonal with intermediate maxima in the spring flood period. The concentration of contaminants and radionuclides in water of the storage reservoirs shows virtually no seasonal variations and tends to decrease. The condition of all the OLRWSRs with respect to all the parameters monitored remains stable.

The extraction of U(VI), Th(IV), and lanthanide(III) ions with mixtures of diphenyl-N,N-dioctylcarbamoylmethylphosphine oxide (Ph₂Oct₂) and lithium bis[(trifluoromethyl)sulfonyl]imide (LiTf₂N) in dodecane containing 10% octanol was studied. A synergistic effect was discovered during the extraction of metal ions with such mixtures. When extracting Ln(III) from solutions of 3 M HNO₃, the D_Ln values in the system with Ph₂Oct₂–LiTf₂N are more than three orders of magnitude higher than when extracting with a solution of Ph₂Oct₂. The stoichiometry of the extracted complexes was determined, and the effect of HNO₃ concentration on the extraction of metal ions was studied. It has been established that actinide and lanthanide(III) ions are extracted with a mixture of Ph₂Oct₂ and LiTf₂N from nitric acid solutions via a cation-exchange mechanism.

The regular trends in the formation of gaseous products from petroleum bitumen of BN grade and bitumen mastic obtained from Absheron oil upon exposure to gamma radiation to the absorbed dose of up to 200 kGy were examined. The total radiation-chemical yield of gases does not exceed 0.43 molec/100 eV; i.e., bituminous materials are highly resistant to the generation of gaseous products.

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.