Radiochemistry最新文献

High-resolution georadiological assessment of 66 stratigraphically and lithologically varied rock samples from El Sheikh Soliman region (selected as the area of ground magnetic survey) was performed using gamma-ray spectrometry and multivariate statistical tools. The concentrations and distribution of natural radionuclides ²³⁸U, ²³⁸Ra, ²³²Th, and ⁴⁰K were measured, and the associated radiological hazards were evaluated. The activity levels of ²³⁸U ranged from 45.1 to 1073.2 Bq/kg (mean = 316.4 Bq/kg), with peak values in ferruginous siltstones (Um Bogma formation), organic-rich shales (Adedia formation), and micaceous shales (Abu Hamata formation). Over 70% of samples exhibited uranium-series disequilibrium (U/Ra >1.5), suggesting recent uranium remobilization under oxidizing-suboxic conditions. Radiological indices such as radium equivalent activity (Ra_eq), absorbed dose rate (D_r), and annual effective dose equivalent (AEDE) indicated that 36% of samples exceeded the Ra_eq safety limit of 370 Bq/kg, and 41% surpassed the global AEDE average (0.07 mSv/year), with strong correlations (r > 0.85) between ²³⁸U and hazard indicators. Although ²³²Th concentrations were lower (22.4–186.1 Bq/kg), significant contributions were found in felsic and metavolcanic rocks due to accessory minerals like monazite and zircon. The ⁴⁰K levels (54.3–1420.5 Bq/kg) were higher in granitic and clay-rich samples containing K-feldspar and muscovite. While ²³²Th and ⁴⁰K posed lower direct risks, their cumulative effects influenced Ra_eq and H_ex indices. Principal component analysis explained 87.3% of total variance, with uranium being the dominant factor. Hierarchical cluster analysis revealed four geochemically distinct groups, reflecting variations in lithology, mineralogy, and redox behavior. The study highlights the value of integrating radiometric and statistical data for effective radiological hazard mapping and environmental monitoring in uranium-rich arid zones.

Approaches to in situ decontamination were considered with a focus on techniques that minimize the time spent by personnel in the contaminated area but ensure highly efficient metal surface decontamination. A method of decontamination using removable polymer coatings was examined. Experiments aimed at increasing the efficiency of removing fixed radionuclides were carried out at the St. Petersburg State Institute of Technology (SPSIT). Based on advantages and shortcomings of using removable coatings, an alternative technology of in situ decontamination, consisting in treatment of the surface with a decontamination solution loaded onto a sorbent-based composite material, was developed at SPSIT. The decontamination method is briefly described, and the results demonstrating its efficiency are presented.

A technology was developed for processing Pu-containing nitric acid process solutions using tangential flow filtration. The technology of Pu recovery from solid waste of complex composition consists of the following stages: dissolution in nitric acid, stabilization of Pu in +4 oxidation state, hydroxide precipitation, and separation of the precipitate by tangential flow filtration. Laboratory and on-site trials of the technology developed were carried out. The efficiency of separating the plutonium(IV) hydroxide precipitate using tangential flow filtration in the stage of suspension clarification was demonstrated in comparison with the results of the previously used centrifugation.

This study describes the radiosynthesis and preclinical testing of ⁸⁹Zr-labeled conjugated durvalumab, a new immuno-PET probe aimed at improving in vivo stability and facilitating sensitive imaging of PD-L1 dynamics. Durvalumab was conjugated site-specifically to the bifunctional chelator 3,4,3-LI(1,2-HOPO) (LI-HOPO) and radiolabeled using ⁸⁹Zr under mild conditions. MALDI-TOF-MS and SDS-PAGE characterization validated successful conjugation with the chelator : antibody ratio of ~5 : 1 and the antibody integrity maintained. The radiolabeling efficiency reached 70.45 ± 1.8, with radiochemical purity >98.5%. The immunoreactivity, determined by Lindmo assay against PD-L1-positive CT26 cells, was 85.4 ± 1.2%. The radiotracer was highly serum stable in vitro (>96% intact at 120 h). PET/CT imaging in CT26 tumor-bearing mice revealed progressively higher tumor uptake, with the highest value at 120 h post injection. The tumor uptake correlated with the PD-L1 expression and immune modulation, particularly in mice receiving combination therapy with durvalumab and the epigenetic modulator I-BET762. Ex vivo biodistribution established the increased PD-L1 expression in tumors with high radiotracer accumulation. [⁸⁹Zr]Zr-3,4,3-LI(1,2-HOPO)-durvalumab is a promising immuno-PET tracer with high radiochemical stability, high specificity, and efficient tumor targeting. It permits quantitative noninvasive evaluation of PD-L1 expression and immune modulation, exhibiting significant potential as a new radiotracer for the guidance and monitoring of cancer immunotherapy.

The complexation of the [⁹⁹Tc(CO)₃(H₂O)₃]⁺ ion with phosphoric acid anions in aqueous solution was studied by ⁹⁹Тс NMR. In acid solutions, 1 : 1, 1 : 2, and 1 : 3 complexes with the H₂PO₄^– anion are formed; their stepwise stability constants are 1.0 ± 0.2, 0.20 ± 0.03, and 0.07 ± 0.03 L/mol, respectively. The complexation with the HPO₄^2– anion at pH 6–7 is complicated by the hydrolysis of the triaqua complex to form the stable tetramer [⁹⁹Tc(OH)(CO)₃]₄. The stability constant of the 1 : 1 complex with the HPO₄^2– ion is estimated at 10² L/mol. Higher-field signals assignable to the 1 : 2 and 1 : 3 complexes with the HPO₄^2– and H₂PO₄^– anions are also observed.

The results of studying the sorption equilibria of U(VI) ions with TiO₂||C oxide–graphene composite and with the oxide TiO₂ prepared from it were analyzed within the framework of the surface complexation theory. According to the established equilibrium mechanism, the following species participate in the sorption in the region of the Henry law at pH 2–11: UO₂²⁺, UO₂(OH)⁺, UO₂(OH)₂⁰, UO₂(OH)₃^–, and UO₂(CO₃)⁰; they react with the surface {≡Ti–OH} groups. Anionic carbonate complexes are not adsorbed onto titanium oxide. Oligomeric titanium complexes do not affect the resultant sorption because of a sharp decrease in the equilibrium analytical concentration of uranium due to the extremely high distribution coefficient K_d (mL/g) of the sorbent, exceeding 6 log units at рН 6.5. The linear correlation between the Henry constants of the sorption of uranium species onto titanium oxide and their stability constants in the electrolyte solution confirms the similarity of energy processes in the formation of U(VI) species in the contacting phases.

A response of zoobenthos communities to technogenic contamination of special industrial reservoirs of the Mayak Production Association is the biodiversity loss within soft zoobenthos (chironomids, oligochaetes, caddisflies, leeches), mainly at the expense of oligochaete species. An increase in the number and biomass of chironomids (at radiation exposure levels of up to 7.8 ± 0.9 mGy/day) and of oligochaetes (at radiation exposure levels of up to 10.0 ± 2.0 mGy/day) was recorded; however, as the radiation exposure increased further, these parameters decreased. Substitution of the zoobenthos community by a monospecific population of chironomids, accompanied by an increase in their number and biomass, was also observed at radiation doses ranging up to 4500 mGy/day.

Causes of the initiation of exothermic processes in nitric acid solutions containing reductants are analyzed. The required parameters of the occurring exothermic reactions are determined. The main conditions of the explosion safety of solution evaporation operations in commercial evaporators at radiochemical plants are formulated. The radiolysis of mixtures increases the onset temperature T_st of the exothermic reaction, and uranyl nitrate does not affect T_st. The explosion safety in evaporation of reductant solutions can be ensured even if their heating is accompanied by various exothermic reactions.

The concentration of ¹³⁷Cs originating from the Chernobyl accident in the Caspian water was estimated by subtracting the concentration of global ¹³⁷Cs from the total concentration of ¹³⁷Cs radionuclides in water at the monitoring date (1996). Late monitoring of the Caspian waters in 1996 made it impossible to determine the “Chernobyl” ¹³⁷Cs from the ¹³⁴Cs/¹³⁷Cs ratio because of the decay of the short-lived radionuclide. The concentration of global ¹³⁷Cs in the seawater was calculated using the sorption–diffusion model of the ¹³⁷Cs absorption by bottom sediments with sorption coefficients (K_d) and diffusion coefficients (D) equal to 2700 L/kg and 1.0 × 10^–7 cm²/s, respectively. By the monitoring date (1995–1996), the inventories of global and “Chernobyl” ¹³⁷Cs in the seawater were determined to be 312.6 and 93.8 TBq, respectively, with “Chernobyl” ¹³⁷Cs accounting for 23% of the total amount. With low fallout of “Chernobyl” ¹³⁷Cs on the Caspian Sea, ¹³⁷Cs of global fallout dominated in the marine pollution. During the 56-year exposure (1964–2020), the concentration of global ¹³⁷Cs in the Caspian water decreased from 23.7 to 1.8 Bq/m³, which is typical of the current level of ¹³⁷Cs in waters of the world ocean.