Radiochemistry最新文献

Thermal stability conditions and explosion and fire safety parameters were determined experimentally for promising extraction mixtures based on BC-1 and BC-2 fluorinated diluents. The results obtained allowed calculation of the specific gas release rate. The new diluents are resistant to nitric acid. Significant exothermic processes are noticeable only at nitric acid concentrations higher than 10 M. The studies performed allow a conclusion that the use of BC-1 and BC-2 fluorinated alcohol carbonates as tributyl phosphate diluents instead of hydrocarbon compounds does not impair the explosion and fire safety of the process.

Sorption of americium from nitric acid, neutral, and alkaline solutions onto commercial samples of detonation nanodiamonds (NDs) was studied. The sorption kinetics and the dependence of the degree of sorption on pH, ionic strength, m/V ratio, and temperature were examined. Thermodynamic parameters of americium adsorption onto NDs were determined. Conditions of quantitative sorption of americium onto ND samples were found. NDs are promising sorbents for decontamination of natural waters from possible americium impurities.

The radon and radium concentrations, mass and area radon exhalation rates, annual effective dose, and risk of an excess cancer fatality per million persons (CPPP) were measured for a total of twelve different types of powder and liquid milk samples collected randomly. CR-39 alpha track detectors were used to measure the concentrations. The average concentrations of radon and radium in the samples were 162 Bq/m³ and 0.47 Bq/kg, respectively. The average values of mass and area radon exhalation rates were 33 mBq/(kg day) and 396 mBq/(m² day), respectively. The average annual effective radon doses for adults, children, and infants across all samples were 7, 13, and 56 µSv/year, respectively. The average CPPP values were 0.13 × 10^–6, 0.24 × 10^–6, and 1.00 × 10^–6 for adults, children, and infants, respectively. The values were below the ICRP and UNSCEAR safe limit values. The results obtained indicate the absence of health risks.

The concentrations of natural and anthropogenic radionuclides in the atmospheric air over the coal-fired brick activity at the locations of Dhamrai, Savar, and Ashulia in Dhaka, Bangladesh, were measured. High-resolution HPGe gamma-ray spectrometry was used for analyzing 18 particulate samples collected from this area. The identified radioisotopes were ²²⁶Ra, ²³²Th, ¹³⁷Cs, and ⁴⁰K. The measured activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K ranged from 0.016 ± 0.002 to 10.1 ± 2.2, from 0.006 ± 0.002 to 1.8 ± 1.6, and from 1.2 ± 0.06 to 2.4 ± 0.08 mBq/m³, respectively, with the average values of 3.0 ± 0.7, 0.63 ± 0.4, and 1.1 ± 0.04 mBq/m³, respectively. The activity concentrations of ²²⁶Ra and ²³²Th exceed the word average values in atmospheric air. Anthropogenic radiocesium (¹³⁷Cs) was identified in several air samples. The average activity concentration of ¹³⁷Cs was found to be 0.026 ± 0.003 mBq/m³. The order of the radionuclides present in the air particulate matter is ²²⁶Ra > ²³²Th > ⁴⁰K > ¹³⁷Cs. The total annual effective inhalation dose due to natural radioisotopes was found to be 93 and 27 μSv/year for adults and infants, respectively, which was below the ICRP permissible limit of 2.4 mSv/year. The main contributor to the inhalation dosage in both adults and infants was ²³²Th.

The thermal stability of nitric acid solutions of acetohydroxamic acid, carbohydrazide, hydrazine nitrate, and their mixtures was studied. The onset temperature of the exothermic reaction was determined, and the thermal effects of the reactions were calculated. The effect of uranyl nitrate on the thermal stability of reducing agents and their mixtures was studied. Comparison of the characteristics of exothermic processes in solutions with and without uranyl nitrate showed that the introduction of uranyl nitrate reduced the intensity of exothermic processes in all the nitric acid solutions studied.

New approaches to the selective isolation of Am from the actinide–lanthanide fraction of high-level waste with preliminary oxidation of Am(III) to Am(V) and Am(VI) using ammonia and ammonia–carbonate media are proposed. When ammonium hydroxide is added to a 0.1 M HNO₃ solution containing Am(V), Cm(III), and Pr(III) (as a mimic of the behavior of lanthanides) to pH ~8, AmO₂⁺ shows increased stability and is retained in the solution to 80%, whereas Cm(III) and Pr(III) precipitate in the form of poorly soluble compounds. In ammonia–carbonate solutions at pH ~10, up to 96% of the initial amount of Am(VI) is retained in the solution, and Cm(III) and Pr(III) precipitate to 85%.

As demonstrated by the example of serotonin, 3-(N-pyrrolyl)propanoyl-L-histidine, sodium p-phenylbenzoate, and Pro–Gly–Pro, activation of the isotope exchange with D₂O also occurred when a solution of an organic compound in D₂O was mixed with 5% Pd/Al₂O₃ or 5% Pd/С (after preliminary treatment of catalysts with deuterium gas on heating). When implementing this technique, 2–3 atoms of deuterium were incorporated in serotonin, 4–5 atoms, in Pro–Gly–Pro, 7–8 atoms, in 3-(N-pyrrolyl)propanoyl-L-histidine, and 3–4 atoms, in sodium p-phenylbenzoate. In the latter case, as judged from the composition of the reaction products, atomic deuterium takes part in the activation of isotope exchange with D₂O. The participation of atomic deuterium in these reactions follows from the intensification of the degradation of the compounds during deuteration. When using compounds that do not contain labile fragments, isotope exchange with D₂O can be activated by keeping the catalyst at room temperature and heating.

The Тс(VII) reduction with 1,2-diformylhydrazine in nitric acid solutions in the presence of uranyl nitrate was studied by spectrophotometry. Tc(VII) is reduced to Тс(IV) via intermediate Tc(V) species. The optical spectra were resolved into two components by mathematical deconvolution. The kinetic curves are S-shaped. Presumably, the induction period is associated with the formation of Тс(V). The rate equation of the Тс(IV) formation under these conditions was obtained. The Tc(V) formation rate increases with an increase in the diformylhydrazine and U(VI) concentrations, initial Тс(VII) concentration, and temperature but decreases with an increase in the nitric acid concentration. From the data obtained, the reaction constants were calculated and the partial reaction orders with respect to components were found.

The effect of the cobalt(II) speciation on its distribution parameters was studied for different types of sorbents. Inorganic sorbents based on hydrolyzable elements have shown the highest selectivity to Co in neutral and alkaline media (pH 7–10). The experiments on the cobalt sorption onto KU-2 strong acid cation-exchange resin at pH 3–5 have demonstrated the presence of Co²⁺, which shows high affinity for all the sorbents studied. In neutral and weakly alkaline media, the inorganic sorbents adsorbed Со(ОН)⁺ and Со(ОН)₂⁰ hydroxo complexes due to heterogeneous ion-exchange reaction (surface complex formation). The appearance of the S–pH dependences for the inorganic sorbents suggests higher stability of cobalt hydroxo complexes at microconcentrations as compared to the published data. In the whole pH range studied, cobalt(II) showed a behavior of an inert sorbate with all the inorganic sorbents studied.

A process was developed for the extraction and separation of actinides and REEs from PUREX process raffinates using TODGA in meta-nitrobenzotrifluoride (F-3). The flowsheet proposed was tested under dynamic conditions using simulated raffinates of the PUREX process. The process includes joint extraction of actinides and REEs, nitric acid scrubbing, actinide stripping, and REE stripping. The conditions of selective stripping of minor actinides with a DTPA solution in the presence of a salting-out agent were determined.