Radiochemistry最新文献

The results obtained in the initial step of studying the effect of external proton irradiation on the properties and structure of simulated borosilicate and aluminophosphate glasses and of internal irradiation on the active glass arranged in the repository of the radiochemical plant of the Mayak Production Association are reported. These results show that the glass melting technologies used at the Mayak Production Association can reliably ensure the environmental safety of the glass incorporating the high-level waste.

Radiation resistance of diesel fuel with the addition of various percentages of toluene was studied. The experiments were carried out for a long time to study the postpolymerization processes. The kinetics of processes during irradiation of pure diesel fuel was studied at the temperature T = 20°C and dose rate P = 0.07 Gy/s in the range of absorbed doses D = 15–150 kGy, and a mixture of toluene with diesel fuel was irradiated within the absorbed dose range D = 24–90 kGy at a toluene concentration of 1, 3, and 5 vol %. Analysis by gas chromatography–mass spectrometric (GC/MS) was performed, and the density, viscosity, and iodine number of the diesel fuel before and after irradiation at various absorbed doses were determined. The kinetics of postpolymerization processes after the end of irradiation shows that the rate of the process and its share in the total polymerization depend on the irradiation time, initial mixture density, and dose. By adding additives (antirads), one can choose the composition of diesel fuel that will better withstand radiation exposure. It is necessary to find the optimal concentration of toluene in the composition of diesel fuel, at which the viscosity and density will not change with an increase in the absorbed dose.

Activated carbon (AC) decorated by silver (Ag/AC) and silica (Ag-Si/AC) nanoparticles was used in the treatment of crude phosphoric acid to remove some inorganic and organic impurities. The effect of time, solid/liquid ratio, temperature, and hydrogen peroxide dose on the phosphoric acid treatment was examined. The catalytic activity and uranium uptake efficiency are improved when carbon structures contain Ag and Si nanoparticles. Uranium and organic matter are removed from crude phosphoric acid more efficiently when crude phosphoric acid is treated with activated carbon decorated by silver (Ag/AC) and silica (Ag-Si/AC) nanoparticles with catalytic wet peroxide oxidation, compared to the treatment with activated carbon only, and at high acid concentration (8 M) and solid/liquid mass ratios (0.001), using unsurpassed H₂O₂. The higher removal efficiencies of uranium and organic matter (OM) were attributed to the increased adsorptive interactions between the AC-based adsorbent surfaces and the OM and uranium species.

The content of global ^239,240Pu in Caspian sea water (1996–2056) was calculated using the sorption–diffusion model of the radionuclide uptake by bottom sediments with the distribution coefficient K_d = 50 × 10³ and diffusion coefficient D = 0.1 × 10^–7 cm²/s. The ^239,240Pu global fallout on the sea was assumed to be equal to the experimental value for the mid-latitude belt of Russia, 60 Bq/m². At the plutonium fallout density on the sea surface of 58 Bq/m², its inventory in the sea Q as of the year 1964 is 21.9 TBq. In 1996, the experimentally determined ^239,240Pu concentration in Caspian sea water was ~20 μBq/L, and the calculation by the model gives 17.8 μBq/L. During the ~30-year migration of global ^239,240Pu, about 93% of the radionuclide passed from the aqueous phase to bottom soils. According to the calculations, the ^239,240Pu concentration in the seawater in the period 1996–2056 will decrease from 17.8 to 10.5 μBq/L, and the ^239,240Pu inventory in the seawater, from 6.3 to 3.7%, of the fallout value. The results were verified using an independent method for ⁹⁰Sr monitoring in Caspian sea water and determining the ^239,240Pu/⁹⁰Sr concentration ratio in the water. The results of estimating the ^239,240Pu concentrations in the seawater (2017–2020) by these two methods reasonably agree with each other.

The possibility of using ferrocyanide sorbents NPF-HTD, NPF-C, and T-35 for cesium concentration in the method of ¹³⁷Cs determination in natural and waste waters has been investigated. Differences in sorption characteristics of sorbents and conditions of cesium concentration to achieve a chemical yield of 98–99% in the concentrate have been revealed. A variable method for determination of ¹³⁷Cs in natural and waste waters has been developed, taking into account the ratio of sample volume and sorbent mass in the column, the efficiency of ¹³⁷Cs detection, and the time of concentrate measurement to achieve the minimum detectable activity of ¹³⁷Cs in the sample of 0.001–0.01 Bq/L. The method was tested for determination of ¹³⁷Cs in waters of natural reservoirs and rivers in the territories of Sverdlovsk oblast and Chelyabinsk oblast, as well as waters of monitoring wells in the territories of long-term storage and disposal of radioactive waste. The data on the composition of river and reservoir waters are presented, and the dependence of the cesium chemical yield into the concentrate on the concentration of macrocomponents in samples is shown.

Two new complex Np(VI) nitrates with carbamoylurea (biuret) and with a derivative of terpyridine (Ph-Terpy) of the composition [(NpO₂)(biuret)(NO₃)₂] (I) and [H₂(Ph-terpy)(NO₃)]₂[NpO₂(NO₃)₄] (II) have been synthesized and structurally characterized. The coordination environment of Np atoms in compounds are distorted hexagonal bipyramids with “yl” oxygen atoms in apical positions. The equatorial plane of the bipyramid in complex I is formed by oxygen atoms of two bidentate NO₃^– anions and an electroneutral ligand. The equatorial plane of the bipyramid in II is formed by oxygen atoms of two bidentate and two monodentate NO₃^– anions. The twice protonated Ph-terpy is the basis of the complex cation [H₂(Ph-terpy)(NO₃)]⁺.

NaUO₂(mia)₃ (I) crystals (mia: monoiodacetate ion CH₂ICOO⁻) were synthesized and studied by X-ray diffraction and IR spectroscopic analyses. Uranyl-containing complexes [UO₂(mia)₃]^– in the structure correspond to the crystal chemical formula A(B⁰¹)₃, where A = UO₂²⁺, B⁰¹ = mia. Using coordination sequences, we analyzed the features of the 3D framework, which is realized in the structure of crystals of I and contains 8 crystallographically nonequivalent U or Na atoms. A semiempirical calculation and comparison of the calculated and experimental vibration frequencies in the IR spectrum of I were performed.

¹⁰⁵Rh is one of the promising beta-emitters for therapeutic purposes in nuclear medicine, but its use is limited, due to in part its low availability, which dictates the search for new effective ways to produce it. In this work, the radionuclide composition of a PdCl₂ target irradiated by bremsstrahlung photons is determined and a method is proposed for recovery carrier free ¹⁰⁵Rh from it using a commercial DGA sorbent, which ensures a high degree of purification of the target isotope. In future, the studies carried out may contribute to the practical application of ¹⁰⁵Rh to nuclear medicine.

The properties of H₂O₂ and its reactions with lanthanide and actinide ions are considered. The potential values of pairs involving H₂O₂ in acidic and alkaline solutions are given. Depending on the oxidative potential of the f-element ion and pH, H₂O₂ exhibits oxidizing or reducing properties. The kinetics and mechanisms of reactions of H₂O₂ with lanthanides(II–IV) and with actinides(III–VII) in acidic, carbonate, and alkaline media have been analyzed. Ions of f-elements(III–VI) form peroxide complexes. The peroxo group occupies either one (OOH) or two (OO) coordination sites. U(VI), Np(IV) binds up to 3 peroxo groups. Oxidation or reduction reactions proceed intramolecularly. In the case of Yb²⁺, Sm²⁺, U³⁺, Ce⁴⁺ (in an acid solution), Pr(IV) and Am(IV) (in a weakly acidic medium), the bimolecular rate constants are 10⁵–n × 10⁶ L/(mol s), which exceeds the rate of ligand exchange in the coordination sphere of the f-element ion. Therefore, charge transfer occurs in the outer sphere. Coordination spheres of Ce(IV) oxalate, Tb(IV) with P₂W₁₇O₆₁^10–, and Np(VI) with NO₃^– slow down the charge transfer between H₂O₂ and the f-element ion. H₂O₂ arising during the radiolysis of aqueous solutions is in an excited state and is more active than H₂O₂ introduced from the outside. Of particular interest are the reactions of H₂O₂ with ions of f-elements in strongly complexing or nonaqueous (organic) media, as well as structural studies of solid compounds of peroxides of f-elements.

[³H]Hyaluronic acid with a molecular weight of 2.37 MDa and a specific radioactivity of 35 GBq/g was obtained using the tritium thermal activation method. Tritium labeled hyaluronic acid (HA) with a molecular weight of 2.37, 0.20, and 0.10 MDa were used to study their adsorption on hydroxyapatite (HAP) in two textural modifications: aqueous suspension and powder. Differences in adsorption kinetics and adsorption isotherms were observed due to variations in the interaction between polysaccharide molecules and the sorbent forms under consideration. The adsorption isotherms of HA on HAP were proven linear. It is shown that strong HA–HAP complexes are formed, and no desorption of HA into water and 0.9% NaCl solution were detected in 2 days.