Radiochemistry最新文献

The applicability of bentonite clay-based ceramics for immobilization of waste from pyrochemical reprocessing of spent nuclear fuel–spent electrolyte, which consists of alkali metal chlorides, was studied. Main matrix characteristics such as the phase composition, mechanical durability, leaching rate and microstructure were studied. The results obtained were compared to the requirements to the cement compound, formulated in NP-019-15 document. The matrix was considered to be suitable for the radioactive waste disposal.

Zirconium is one of critical high-level waste components that get into the glass and affect its properties. There are various zirconium sources such as partial corrosion damage of fuel rod clads in the course of SNF reprocessing or dissolution of the zirconium-containing refractory material of the glass-making furnace in the glass melt. Furthermore, zirconium is present in SNF as a fission product. Dissolution of zirconium in aluminoborosilicate glasses developed as a host material for high-level waste vitrification was studied by electron microscopy. The zirconium distribution between the glass and crystalline phases was studied. The optimum component ratio ensuring maximal incorporation of zirconium into the glass-containing fraction of the host material was determined. The results obtained can serve as a basis for adjusting the synthesis parameters of glass-containing borosilicate host materials used for immobilization of zirconium-containing high-level waste.

The paper is focused on the problem of groundwater flow and transport modeling applied to safety assessment of nuclear facilities and development of relevant computational codes. The classification of typical tasks of the nuclear industry is provided, and specific features typical of different classes of simulated objects are analyzed, including their near and far fields. The most radioecologically relevant radionuclides are identified for each class. GeRa computational code is used as an example to analyze current trends of the development of hydrogeological modeling software.

Alternative procedures for the dissolution of the solid phase (filter cake) of sludge formed by filtration of a spent nuclear fuel solution through cartridge and bulk filters were tested. Quite successful dissolution of the filter cake from the cartridge filter regeneration is ensured by successive treatment with alkali and acid solutions. Attempts to dissolve the filter cake from the bulk filter regeneration failed. The chemical and radiochemical composition of the filter cakes was evaluated. The results obtained will be used for assessing the nuclear and radiation safety and for developing procedures for the management of filter cakes from the filter regeneration.

The radiation-chemical resistance of Fersal, RFR-i, RFR-Ca, and Clevasol sorbents was determined. The effect of the absorbed dose on the ¹³⁷Cs distribution coefficient in sorption from an alkaline solution simulating the accumulated high-level waste solutions was studied. The sorbent samples were examined by electron microscopy. The mechanism of the degradation and oxidation of the sorbents on heating in air was determined.

The study is aimed at the source-term reconstruction for the exposure of people to ionizing radiation who lived in 1949–1956 on the Techa riverside. It deals with the migration of γ-emitting nuclides (GENs), and specifically ⁹⁵Zr and ⁹⁵Nb, in the river system. It is known that ⁹⁵Zr exhibits abnormally high sorption properties and is virtually completely and irreversibly sorbed onto bottom sediments (BSs) and suspended material already near the liquid radioactive waste (LRW) discharge site. Therefore, its further migration is possible only with the solid runoff. It was shown previously that the large-scale radioactive contamination of the river occurred in the relatively short period from July to October 1951, when the water flow rate in the upper section was varied from 8 to 30 m³/s. Under such water runoff conditions, the most contaminated BSs near the LRW discharge site undergo intense stirring-up (erosion), and the resulting suspensions are transferred with gradual sedimentation of the suspended material throughout the river stretch. After October 1951, when the LRW discharge into the river decreased by 2–3 orders of magnitude, the ⁹⁵Zr distribution in BSs was determined only by the radioactive decay and transfer of suspended matters and saltation loads. Specific features of methods used in the 1950s for measuring the specific activity of the sum of β-emitting nuclides (BENs, A_Σ, μCi/kg) and sum of GENs (М_Σ, μg-equiv Ra/kg) are discussed. The use of the ratio R_Σ = М_Σ/А_Σ as a criterion furnishes new information on the ⁹⁵Zr activity concentration in BSs and allows picking out BS samples with prevalent contributions of ⁹⁵Zr (М_Zr) и ⁹⁵Nb (М_Nb) to М_Σ from the whole set of the archive data. Analysis of the measured archive data on the specific activity of BS samples taken from different sections of the Techa River in 1952, 1954, and 1955 using the criterion R_Σ = М_Σ/А_Σ allowed estimation of М_Σ ≈ М_Zr + М_Nb and recalculation of these results taking into account the radioactive decay as of November 1, 1951. The results of M_Σ measurements performed in 1952, 1954, and 1955 and converted to the level of November 1, 1951 appeared to be close, although the absolute activity level decreased by a factor of up to ~10 mln owing to radioactive decay. The ⁹⁵Zr specific activity in the river BSs as of November 1951 remained virtually constant throughout the river stretch. These results provide a new approach to reconstruction of the external dose for the Techa riverside population.

The paper is aimed at reconstruction of a source term for external exposure of population that inhabited the banks of the Techa River from 1949 to 1956. The composition of γ-emitting nuclides contributing to radiation environment of the river banks and floodplain is also studied. The γ-emitting nuclides entered the river system both in solutions and as industrial and natural suspended matter. The paper considers archive data on measured parameters of radiation contamination of the Techa bottom sediments and riverside area. Results of the present-day radiation surveys of the Techa River show that the distribution of the exposure dose rate has a pronounced spotted and non-monotonic character along the entire river stretch and is due to sedimentation of suspended particles contaminated with the γ-emitting nuclides on the soil surface. The activity of γ-emitting nuclides accumulated in the upper reaches of the river due to sorption of water-soluble radionuclides onto bottom sediments and to sedimentation of contaminated suspended matter on the surface of bottom sediments was calculated using a stationary sorption model and a hydrodynamic model of settling ponds. Until July 1951, when the river runoff did not exceed 1 m³/s, practically all industrial and natural suspended particles settled to and accumulated at the bottom of Metlinsky Pond. Only a small portion of clay particles could enter the river below the dam of Metlinsky Pond. ⁹⁵Zr and ⁹⁵Nb are of high importance for reconstruction of the radiation environment in the Techa riverside area, because before 1953 the activity of the bottom sediments in all segments of the river was predominantly determined by these γ-emitting nuclides. There is practically no sorption of ⁹⁵Nb onto bottom sediments and suspended matter, and the river flow carries predominantly soluble ⁹⁵Nb species. ⁹⁵Zr, on the contrary, is strongly sorbed onto bottom sediments and can be transferred for long distances only as suspended matter or bed silt. Until October 1951, the radiation environment along the entire river stretch below Metlinsky Pond was contributed predominantly by ⁹⁵Nb and was characterized by uniform and stable contamination level in all swampy areas of the floodplain. Vast contamination of the bottom sediments and the floodplain along the entire river stretch by other γ-emitting nuclides (⁹⁵Zr, ¹³⁷Cs, ^141,144Ce, ^103,106Ru, etc.) could result only from “washing” of Metlinsky Pond in October 1951, when the flow rate in the upper reaches of the river was up to 30 m³/s. This was accompanied by intensive stirring-up of the bottom sediments and activity transfer out of Metlinsky Pond.

Procedure of tritium labeling vancomycin synthesis using tritium thermal activation method was developed. The influence of target mass on the specific and total radioactivity was revealed. [³H]Vancomycin was used for studying its equilibrium adsorption on nanodiamonds as well as its amount that tightly bonded to surface and did not remove with water. It was found that vancomycin is adsorbed from aqueous solution via strong bonding to nanodiamonds and is not washed out with water. Application of 0.028 M phosphate buffer (pH 6.7 and 2.7) increased the equilibrium vancomycin adsorption about one and a half times, while vancomycin amount in the adsorption complex with nanodiamonds after washing with water was significantly reduced. Such behavior of vancomycin is due to the presence of phosphate-ions that contribute to vancomycin adsorption but are washed out with water. Molecular mechanics simulation allows the suggestion that the formation of multiple hydrogen bonds is required for generation of a durable adsorption complex of vancomycin with nanodiamonds.

“2+1_B” tricarbonyl complexes of the general formula [M(CO)₃(N^N)CN(CH₂)₄CH(COOMe)SC₁₀H₂₁]-ClO₄, where M = ^99mTc or Re, N^N = 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen), were prepared by the reaction of [M(CO)₃(N^N)(MeOH)]ClO₄ with methyl 2-(decylthio)-6-isocyanohexanoate in methanol. The rhenium complexes were isolated and characterized by ¹H NMR and IR spectroscopy. The formation of technetium-99m complexes was confirmed by HPLC. The lipophilicity of the technetium complexes was measured.

The extraction of U(VI), Th(IV), Am(III), and lanthanides(III) from nitric acid solutions with solutions of phosphorylated pyrazines in organic solvents was studied. The stoichiometry of the extracted complexes was determined, and the influence of the structure of the extractant and an HNO₃ concentration in the aqueous phase on the efficiency of the extraction of metal ions into the organic phase was considered. It was established that among the studied compounds, bis(diphenylphosphine)quinoxaline dioxide has the highest extraction ability with respect to actinides and lanthanides in nitric acid media.