Radiochemistry最新文献

In solutions with рН 1.5–2.5, terbium(IV) stabilized with unsaturated phosphotungstate anions P₂W₁₇O₆₁^10– slowly oxidizes NpO₂²⁺·5H₂O. The Np(VII) cation arising in the process preserves the surrounding of Np(VI), i.e., remains a pentagonal bipyramid. Therefore, the oxidation potential of the Np(VII)/(VI) couple is higher than that of the couple in which Np(VII) generated by acidification of the Np(VII) anion preserves the octahedral surrounding. High potential of Np(VII) with the structure of a pentagonal bipyramid makes Np(VII) unstable. We failed to obtain it using such strong oxidants as persulfate, perxenate, and xenon difluoride. Flash radiolysis may become an effective tool for oxidizing Np(VI) in deaerated solutions containing persulfate or ХеО₃ at рН 1.5–3.

The diffusion of manmade radionuclides in pore solutions of compacted clay materials is accompanied not only by the sorption retention on the surface of clay minerals, which is typical for many radionuclides, but also by other physicochemical processes occurring simultaneously. These processes, termed coupled, are associated mainly with the precipitation–dissolution of radionuclide compounds in pore solutions, as well as with the sorption–desorption of radionuclide particles on the surface of solid phases as a result of their diffusion transfer in the pore medium together with chemically contrasting components of leachates of technogenic materials used in the radioactive waste disposal. Without taking into account the coupled processes, it is impossible to correctly interpret the experimental results, as well as to reliably predict the migration of manmade radionuclides and justify the safety of radioactive waste disposal facilities.

This study deals with radon concentrations and associated radiological hazard parameters due to ingestion of radon in vegetable samples collected randomly from eleven sites in the Ranya district, Iraq. An active detector (RAD7) was employed to monitor radon levels. The concentration of radon in the analyzed vegetable samples ranged from 6.23 to 33.20 Bq/m³ with a mean value of 15.38 Bq/m³. These concentrations were significantly below the global average recommended by the International Commission on Radiological Protection (ICRP). The estimated mean annual effective doses for children and adults were 0.336 and 0.308 μSv/year, respectively, which were also lower than the global reference values. The mean excess lifetime cancer risks were calculated as 1.293 × 10^–6 for children and 1.186 × 10^–6 for adults, indicating levels within internationally accepted safety limits for human consumption. The findings highlight the importance of ongoing monitoring and suggest further research needed to assess the transfer mechanisms of radionuclides from soil to edible crops.

The release of radionuclides into the gas phase from a LiCl–Li₂O salt melt in the “metallization” operations in the course of pyrochemical reprocessing of spent nuclear fuel was studied. The experiments were performed at three temperatures characterizing the normal operation and violation of the normal conditions: 650, 750, and 850°С. Alkali and alkaline-earth elements showed the highest rate of the release into the gas phase, of the order of 10²–10³ g/(m² h), whereas the target components (uranium, plutonium, and minor actinides) quantitatively remained in the form of insoluble oxides in the salt melt. The major fraction of the radionuclides released into the gas phase was adsorbed on the walls of the pumping system. In the case of violation of the normal operation conditions, cesium and strontium make the major contribution to the gas phase activity.

The conjugation of N-succinimidyl-4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB), a widely used radiosynthon for labeling biologically complex molecules for use as radiopharmaceuticals (RPs) in positron emission tomography (PET), with a model tripeptide, glutathione (GSH), was studied. [¹⁸F]SFB was prepared using the previously developed method of direct copper(II)-mediated radiofluorination of pinacol arylboronate as a labeling precursor. The efficiency of the conjugation of [¹⁸F]SFB, which was recovered from the reaction mixture by solid-phase extraction (SPE) on disposable cartridges, with GSH in an acetonitrile/phosphate buffered mixture with pH 8.4 depended on the ratio of the aqueous and nonaqueous phases and the peptide concentration. With equal volumes of the components (0.5 mL) and a GSH concentration of 1.0 mg/mL, the conjugation yield of 97% was achieved. This serves as further evidence of the efficiency of SPE purification, which removes chemical impurities that could otherwise compete in the conjugation reaction. This purification method using disposable cartridges can be easily adapted to any automated modules, including cassette ones. This contributes to the more effective use of [¹⁸F]SFB in synthesizing radiopharmaceuticals based on complex biomolecules.

The extraction of lutetium with 0.5–2 M solutions of 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (HEH[EHP]) in hexane from 0.5–2 M solutions of nitric acid containing ytterbium at a lutetium concentration of 0.57 mM (0.1 g/L) and lutetium to ytterbium concentration ratios from 1 : 1 to 1 : 50 was studied. The extraction mechanisms of both lanthanides are identical under the conditions studied. The effect of excess ytterbium on the distribution of lutetium during extraction is due to a decrease in the concentration of the free extractant. A model describing the dependence of the lutetium distribution ratio on the ytterbium concentration in the aqueous phase at various concentrations of the extractant and nitric acid is proposed; it satisfactorily agrees with the experimental data.

Extraction of lanthanides(III) from aqueous solutions of nitric and perchloric acids and bis[(trifluoromethyl)sulfonyl]imide with solutions of N,N '-dimethyl-N,N '-dicyclohexyldiglycolamide in organic solvents was studied in relation to the concentration of acids in the aqueous phase. The stoichiometry of the extracted complexes was determined. It was found that the transformation of N,N '-dimethyl-N,N '-dicyclohexyldiglycolamide into a complex with bis[(trifluoromethyl)sulfonyl]imide leads to a significant increase in the extraction of lanthanide(III) ions from solutions of nitric, hydrochloric, sulfuric, and phosphoric acids.

The influence of the content of structure-forming components of sodium aluminum iron phosphate glass on its phase composition, structure, and resistance to leaching at elevated temperatures as necessary characteristics of vitrified iron-containing high-level waste during its deep disposal was studied. It was found that the samples studied (mol %), 40.0Na₂O–12.5Al₂O₃–12.5Fe₂O₃–35.0P₂O₅, 35.0Na₂O–12.5Al₂O₃–12.5Fe₂O₃–40.0P₂O₅, and 35.0Na₂O–10.0Al₂O₃–10.0Fe₂O₃–45.0P₂O₅, consist of a single amorphous glass phase and have high hydrothermal stability. The leach rate of sodium and phosphorus from the above samples under semidynamic (on the 28th day) and dynamic (on the 10th day) conditions at 90 and 95°C, respectively, was about 10⁻⁵ g (cm² day), that of aluminum, within the range (2–10) × 10⁻⁶ and (0.6–2) × 10⁻⁵ g/(cm² day), respectively, and that of iron, within the range (7–12) × 10⁻⁷ and (0.4–3) × 10⁻⁶ g/(cm² day), respectively.

The possibility and efficiency of sorption of artificial (¹³⁷Cs), natural (²¹⁰Pb, ²¹⁰Po, ²²⁶Ra, ²²⁸Ra, ²³⁴Th), and cosmogenic (⁷Be, ³²P, ³³P) radionuclides from large volumes of seawater using various types of sorbents were evaluated. The sorption of the radionuclides studied was scaled up and optimized, and the optimal parameters of the sorption preconcentration were established. Based on the data obtained, a comprehensive method for simultaneous preconcentration of a wide range of radionuclides from seawater using the most efficient sorbents was developed and tested. By this method, diverse radionuclides can be concentrated from a single sample, which significantly simplifies the sampling procedures and field research.