Том 61, № 1 (2019)

Gas-phase conversion of UN to water-soluble compounds in NO_x-air, NO_x-H₂O (vapor)-air, or HNO₃ (vapor)-air atmosphere (hereinafter, nitrating atmosphere) at temperatures from 298 to 673 K was studied. The use of the oxidizing atmosphere based on NO_x gases allows the conversion to be performed at a lower temperature. The process yields both UO₃ and hydrates of UO₂(NO₃)₂. The highest conversion of UN to water-soluble compounds, ∼80%, is reached at ∼565 K. In the course of gas-phase conversion in NO_x-H₂O (vapor)-air and HNO₃ (vapor)-air atmospheres, UN transforms into water-soluble compounds (nitrates, hydroxynitrates). The gas-phase conversion of UN in an NO_x-H₂O (vapor)-air atmosphere occurs less efficiently than that in an HNO₃ (vapor)-air atmosphere.

Sorption of radionuclides (⁹⁰Sr, ⁹⁰Y, ¹³⁷Cs, ¹⁵²Eu) and nonferrous metals (Cu, Ni, Zn, Pb) from aqueous solutions onto granulated sorbents based on coarsely porous silica gel of KSKG and MSKG grades and on BAU-A activated carbon was studied. The granulated sorbents based on coarsely porous silica gel of KSKG and MSKG grades, modified with Cu, Zn, and Ni ferrocyanides, efficiently take up ⁹⁰Sr and ⁹⁰Y from distilled water. In tap water, the sorption efficiency for all the sorbents based on KSKG and MSKG does not exceed 70%. The surface of BAU-A was modified by keeping it in a nitrating atmosphere [NO_x-air or HNO₃ (vapor)-air] at 90–110°C for 4 h, and also by impregnating it with 10 wt % triethanolamine (TEA), triethylenediamine (TEDA), or urea (CH₄N₂O). The sorbents based on BAU-A activated carbon efficiently take up ⁹⁰Y (analog of trivalent actinides and lanthanides) and nonferrous metal ions from various aqueous solutions. Modification of BAU-A decreases its sorption capacity for Cu²⁺, Ni²⁺, and Zn²⁺ but increases its sorption capacity for Pb²⁺.

Methodical approach to evaluation of the relative efficiency of various rock minerals in radionuclide sorption is suggested. The approach involves sorption experiments on the surface of polished rock samples, radiographic analysis of the rock surface before and after sorption, determination of mineral phases mainly responsible for the radionuclide sorption and of phases with low sorption ability, and calculation of the relative sorption coefficient taking into account the surface area occupied by the given mineral phase. The approach is applied to evaluation of the performance of mineral phases from rocks of the exocontact of the Nizhnekansky granitoid massif in sorption of Ra, Pu, and Am. The suggested approach allows obtaining data for long-term predictive simulation of the radionuclide migration taking into account variations in the composition of rocks and of the mineral filling of fractures in hard rocks surrounding the radioactive waste repository.

An idea of developing domestic solid-state radioluminescent light sources (RLSs) based on bound tritium is put forward, and the existing ways of its implementation are described. Materials for the development of solid-state RLSs were chosen, and their comparative tests were performed. The emission intensity and brightness for different phosphors under excitation with bound tritium were determined, and comparative statistical data on the surface density of the phosphor distribution were obtained.

Isotope exchange between dalargine applied onto various supports [glass, activated carbon, few-layer graphite (FLG)] and molecular tritium, performed with activation on a tungsten wire and on 5% Pd/C, 10% Pd/C, and 5% Pt/FLG catalysts was studied. Depending on the experiment conditions, the molar radioactivity of [³H]dalargine varied from 0.47 to 31 Ci mmol⁻¹ with activation on a tungsten wire and from 0.63 to 5.5 Ci mmol⁻¹ under the conditions of heating to 335 K in the presence of noble metal catalysts. Significant difference in the tritium distribution between amino acid residues of the peptide depending on the support and on the activation method is observed. Reactions of tritium atoms generated on tungsten led to the tritium incorporation mainly into aliphatic acid residues upon application of the peptide onto glass and into aromatic residues upon application onto activated carbon. The use of FLG as a support influenced the tritium redistribution between aliphatic and aromatic residues to a lesser extent. Upon tritium activation on 5% Pd/C, 10% Pd/C, and 5% Pt/FLD, tritium was mainly incorporated into aromatic residues, which is typical of electrophilic reactions. The study revealed strong effect of the support on the mechanism of the isotope exchange of hydrogen for tritium in dalargine. The intramolecular distribution of tritium in preparation of labeled compounds using thermal activation can be controlled by properly choosing a support onto which the substrate is applied.

A new production method of ^99mTc using a high-current solid target was tested. The separation and purification setup was developed to produce high quantity and high specific activity of ^99mTcO₄⁻ suitable for labeling various ligands for nuclear medicine imaging. A semiautomated target dissolution and separation system has been developed for ^99mTcO₄⁻ production. The separation is based on a chromatographic column system. The chemical and radiochemical purity was found to be in accordance with the US and European Pharmacopoeia specifications. 99% of activity in the final product belonged to ^99mTc. Less than 1% of the ^99mTc activity was not incorporated in the target product with MDP kits. Biodistribution data for the labeled MDP kits show that the quality of the produced ^99mTc-pertechnetate is identical to that of the pertechnetate from ⁹⁹Mo/^99mTc generators. The application of ^99mTc-ethylenedicysteine in human proves the good quality of the produced Na^99mTcO₄.

Trazodone was labeled with ^99mTc by indirect method. More than 97% radiochemical yield was reached under the following optimized conditions: 100 µg of Trazodone, pH 7, 10 mg of glucoheptonate, 35 µg of stannous chloride, 185 MBq of ^99mTc eluate, 20 min, room temperature. The in vitro stability and also the retention of the complex in the brain tissue allow the use of this complex as a potential brain imaging agent.

The results of five-year studies in Shelter subreactor rooms are summarized. At height elevations from 0 to 12 m, the mean volume activity (VA) of ²¹²Pb-bearing aerosols is about 10 Bq m⁻³. The main source of ²²⁰Rn and of its daughter ²¹²Pb is ²³²Th contained in the building structures. The maximal ²¹²Pb VA is observed in the warm period of a year, and the minimal VA, in the cold period. In ventilation releases through the Bypass system, VA of ²¹²Pb is 4–5 times lower than in subreactor room. The activity median aerodynamic diameter (AMAD) of ²¹²Pb-bearing aerosols in most cases was within the range 0.06–0.4 µm. During works in subreactor space, the irradiation via ²¹²Pb inhalation can amount to 3–5% of the annual effective dose limit (20 mSv) adopted in Ukraine.

The 5–17-year migration of ¹³⁷Cs in bottom sediments (BSs) of five oligotrophic lakes located on the “Chernobyl” ¹³⁷Cs fallout plume was studied. The layer-by-layer analysis of the ¹³⁷Cs levels in BS cores allowed determination of the ¹³⁷Cs migration mechanism and of the numerical characteristics of its transfer into the thickness of BSs of low-trophy water bodies. The exponential decrease in the ¹³⁷Cs concentration from the core surface to the BS depth was evaluated by the half-loss layer h. The value of h for “Chernobyl” ¹³⁷Cs for BSs of oligotropic lakes was 1.2–2.3 cm. The ¹³⁷Cs transfer in BSs of oligotrophic lakes occurred by the diffusion mechanism. The diffusion coefficients (D) of “Chernobyl” ¹³⁷Cs in the lake BS columns were (2.0–4.7) × 10⁻⁸ cm² s⁻¹. The diffusion coefficients in ¹³⁷Cs migration increased from the near-surface layer of bottom sediments (∼0–2 cm) to the depth of the bottom soil in the range n × (10⁻⁹–10⁻⁸) cm² s⁻¹. The numerical characteristics of the ¹³⁷Cs migration (h and D) refer to BSs of oligotrophic lakes in which the flow of sediments to the lake bottom did not exceed 1.8 mm year⁻¹. In Lake Sukhodol’skoe at a sedimentation rate of 6 mm year⁻¹ and radionuclide exposure of 31 years, the bulk of BSs was contaminated with ¹³⁷Cs by the mixed mechanism: diffusion from the primary accumulation site and sedimentation of suspended matter with ¹³⁷Cs.