Radiochemistry最新文献

The physicochemical and extraction properties of calixarene crown ethers, 1,3-alt-bis(octyloxy)-calix[4]arene-crown-6 (II) and its derivatives with o-phenylene (I), methylenepropoxy (IV) and methylene(2,2,3,3-tetrafluoropropoxy) (III) substituents in the crown ether ring, were studied. Solutions of compound II in bis(2,2,3,3-tetrafluoropropyl) carbonate (BK-1) effectively extract cesium from 3 M nitric acid already at a concentration of 0.001 M. The introduction of substituents into the crown ether ring significantly reduces the efficiency of the cesium extraction but increases the solubility of calixarene crown ethers in bis(2,2,3,3-tetrafluoropropyl) carbonate. Data on the solubility of calixarene crown ethers in water and 3 M nitric acid, on the distribution between the organic and aqueous phases, and on the rate of the reaction with nitric acid were obtained. Calixarene crown ether I with an o-phenylene substituent reacts with 3 M nitric acid approximately 2 times faster than dibenzo-21-crown-7 does. The other calixarene crown ethers studied do not react with nitric acid under the similar conditions. Quantum chemical modeling, including optimization of the structure geometry and calculation of vibrational frequencies, was performed for the molecules of calixarene crown ethers, DB21C7, and their complexes with the cesium cation. The calculated ΔG⁰ values for the complexation of ligands with the cesium cation correlate well with the experimental logD_Cs (except for compound III with a fluorinated substituent). Solutions of calixarene crown ethers in bis(2,2,3,3-tetrafluoropropyl) carbonate exhibit selectivity for cesium and extract neither ¹⁵²Eu nor ²⁴¹Am from nitric acid media.

The regularities of kinetics of Sr-90 sorption from a natural low saline water by Termoxid-3K inorganic sorbent have been studied. The effect of solution stirring rate, strontium concentration and temperature on the sorption rate constant, diffusion coefficients and kinetic regime was investigated, and the experimental results were modeled by diffusion and chemical kinetics models. The sorption of strontium by sorbent T-3K has a two-stage character, proceeds in the intra-diffusion mode with limiting contribution at stage 1 of the chemisorption process. Strontium diffusion coefficients were 10^–12–10^–13 m²/s, activation energy was 93.3 kJ/mol at stage 1 of sorption, and 23.8 kJ/mol at stage 2.

The ¹³⁷Cs migration from the upper reaches of the Vuoksa River, Lake Saimaa, to Lake Ladoga was studied to reveal the role of the river in the Ladoga contamination with ¹³⁷Cs from the emissions during the Chernobyl accident. The ¹³⁷Cs migration in 1988–2024 led to a decrease in its concentration in the river water from 113 to ≈4.0 Bq/m³. By 2015, the ¹³⁷Cs concentration in the Vuoksa River water approached the level of 4–5 Bq/m³, corresponding to the contamination of river waters with global ¹³⁷Cs prior to the accident. The decrease in the concentration of “Chernobyl” ¹³⁷Cs in the Vuoksa River is approximated by a two-component exponential dependence with the water half-clearance times Т₁ = 5 and Т₂ = 25 years, respectively. The runoff of “Chernobyl” ¹³⁷Cs from Lake Saimaa with the Vuoksa River water in 1986–2023 amounted to 22.5 TBq. This value is comparable in the order of magnitude with the fallout of “Chernobyl” ¹³⁷Cs on Lake Ladoga in 1986 (74.1 TBq). In 1986–1988, the runoff of “Chernobyl” ¹³⁷Cs from Lake Saimaa amounted to ≈30% of the total runoff in 1986–2024. The many-year transit of ¹³⁷Cs from Lake Saimaa caused increased accumulation of ¹³⁷Cs (≈300 Bq/kg) in the profile of silt sediments of the Vuoksa River and lakes of its catchment area.

The kinetics of 1,2-diformylhydrazine (reagent suggested for the reductive stripping of plutonium in the Purex process) oxidation with nitric acid was studied. The rate equation is first-order with respect to the reductant and third-order with respect to nitric acid in the interval [HNO₃] = 5.5–9.0 M. It is postulated that the reaction between diformylhydrazine and nitric acid involves their molecular undissociated forms. The activation energy of the reaction is 116 kJ/mol in temperature range 70–90°С.

The interference of Sr(II) and Y(III) cations and of cationic (dodecyltrimethylammonium bromide), anionic (sodium dodecyl sulfate), and nonionic (polyoxyethylene laurate, tradename Brij-35) surfactants in competitive adsorption onto activated carbon prepared from lignin was studied. The radiotracers ⁹⁰Sr/⁹⁰Y and tritium were used for determining the equilibrium and surface concentrations of metal cations and surfactants, respectively. The tritium-labeled surfactants were prepared by thermochemical activation of tritium. The concentrations of all the sorbates in solution were determined by liquid scintillation spectrometry. The SpectraDec software was used in joint measurement of the ⁹⁰Sr/⁹⁰Y and tritium activity. Surfactants affect the sorption of strontium and tritium onto activated carbon prepared by thermochemical activation with orthophosphoric acid. The formation of a poorly soluble precipitate with the anionic surfactant enhances the adsorption and prevents the desorption of both cations and favors the sorption of the anionic surfactant itself. The nonionic surfactant containing the oxyethyl groups does not affect the adsorption value of the strontium and yttrium cations but favors their retention on the carbon surface, preventing the desorption. The cationic surfactant competes with the strontium and yttrium cations for the active sites on the activated carbon surface: The adsorption of all the components decreases, whereas the desorption of cations from the surface increases.

Fragmentation of massive debris of the fuel and fuel-containing materials (FCMs) is one of important steps in the final decommissioning of the Fukushima Daiichi NPP. The generation and dissemination of radioactive microparticles in the course of the fragmentation largely depend on the cutting technology used. A previous study [1] dealt with the experimental cutting of simulated FCM and spent nuclear fuel (SNF) samples to justify the optimum configuration and operation conditions of the gas treatment system. To understand the properties of particles generated in the course of cutting FCM and SNF samples and to justify the methods for their localization, it is necessary to study in more detail the size, shape, and composition of the structures formed. This study deals with the microparticles formed by laser cutting of simulated FCMs from the Fukushima Daiichi NPP and of SNF samples. The microparticles formed were examined with a laser particle size analyzer and with a scanning electron microscope equipped with wave- and energy-dispersive spectrometers. The formation of particles of different size and morphology was noted. The laser cutting generates separate particles of submicron size and different morphology, which form agglomerates. Up to 35 wt % of particles formed by laser cutting of the simulated FDM passed into the vapor–gas phase. For the WWER (water-cooled water-moderated energy reactor) SNF, this fraction was 25 wt %. The major components of all kinds of particles formed by laser cutting of SNF are uranium, oxygen, and zirconium; their total fraction is in the range from 97.9 to 98.4%. The plutonium content ranges from 0.7 to 1.3%.

The extractive recovery of protactinium from irradiated thorium nitrate as applied to the conditions of the fusion neutron source blanket was studied using n-octanol and diisobutylcarbinol as extractants. The degree of recovery of ²³³Pa from a solution of irradiated thorium nitrate (600 g/dm³) in 3 М nitric acid in one contact exceeded 80%, and the separation factors from uranium and thorium were higher than 600 and 130000, respectively. To reduce the content of ²³²U in ²³³U (below 5 ppm), a flowsheet involving short irradiation of thorium nitrate and continuous extractive recovery of protactinium was suggested.

Scandium isotopes have attracted significant attention in nuclear medicine applications due to their favorable radiation and decay characteristics. This research is focused on the production of no-carrier-added (NCA) Sc isotopes through fast neutron irradiation (E_n > 1 MeV) of a natural titanium (^natTi) target in the Egyptian Second Research Reactor. Subsequently, the separation and purification of Sc isotopes were conducted using a newly developed method based on Amberlite IR-120 resin impregnated with Thorin. The modified resin, Amb-120-Thorin, was characterized using analytical techniques such as FTIR. The adsorption of Thorin onto the resin surface enhances the sorbent capacity for scandium ions. For the separation in the batch mode, the optimal pH was 5 and the equilibration time was 3 h. A chromatographic column filled with Amb-120-Thorin was employed to evaluate the separation and purification of the Sc radioisotope; a yield of 95.1 ± 1.2% was achieved.

The behavior of thorium, uranium, and REEs in oxalate and oxalate–formate media was studied. The thorium oxalate solubility in ammonium formate solutions was determined. Recommendations for the uranium separation from thorium and REEs were formulated. It is advisable to precipitate REE oxalates first and then to precipitate thorium oxalate with a nonisotopic carrier.