Vol 58, No 1 (2016)

Thermal deformations of Na₆(UO₂)₂O(MoO₄)₄ were studied by high-temperature powder X-ray diffraction. The compound crystallizes in the triclinic system, space group Р\(\bar 1\), a = 7.636(7), b = 8.163(6), c = 8.746(4) Å, α = 72.32(9)°, β = 79.36(4)°, γ = 65.79(5)°, V = 472.74(4) ų. It is stable in the temperature interval 20–700°С. The thermal expansion coefficients (TECs) are α₁₁ = 25.5 × 10^–6, α₂₂ = 7.8 × 10^–6, and α₃₃ = 1.1 × 10^–6 (°C)^–1. The orientation of the TEC pattern relative to the crystallographic axes is a₃₃^Z = 45°, a₃₃^X = 122°, a₂₂^Z = 59°, and a₂₂^X = 66°. The anisotropy of the thermal expansion is due to specific features of the crystal structure of the compound.

The gas-phase conversion of U₃O₈, MoO₃, SrO, and their mechanical mixtures, and also of ZrO₂ into water-soluble compounds in the NO_x–H₂O (vapor)–air atmosphere was studied. In the course of gas-phase conversion, U₃O₈ and SrO transform into water-soluble compounds (nitrates, hydroxonitrates), whereas MoO₃ and ZrO₂ undergo no changes. The principal possibility of separating U from Mo and Zr by gas-phase conversion of the oxides in the NO_x–H₂O (vapor)–air atmosphere was demonstrated.

Extraction of La and Ln(III) (except Pm) from HNO₃ solutions with mixtures of acidic zirconium salts of dibutyl hydrogen phosphate (ZS HDBP) with chlorinated cobalt dicarbollide (CCD) in a polar diluent, 1: 1 mixture of о-chloronitrobenzene and CCl₄, was studied. A synergistic effect is observed at definite ratios of CCD and ZS HDBP in the mixture. The magnitude of the synergistic effect increases with an increase in the Zr to HDBP molar ratio. The maximal synergistic effect equal to 360 was reached for Dy in the ZS HDBP (1: 6)–CCD extraction system. The maximal REE distribution ratio (D_max) is observed for elements from La to Dy at the HDBP to CCD molar ratio of 2 in all the extraction systems. For elements of the Ho–Lu series, D_max is observed at the HDBP to CCD molar ratio from 2 to 6. The HDBP to CCD molar ratio at which D_max is reached increases with an increase in the Zr content of the extraction system. For some pairs of elements, the separation factor considerably increases in the extractant mixture relative to the extractants taken separately. The largest increase in the separation factor (by a factor of 8.3) was noted for the Tm–Er pair in the CCD–ZS HDBP (1: 6) system. The synergistic effect in some cases is preserved at least up to the HDBP to CCD molar ratio of 670: 1, and at higher ratios the magnitude of the synergistic effect does not exceed the uncertainty of its determination. This fact suggests the formation of so-called hypercomplexes containing tens and hundreds of HDBP molecules in the CCD–ZS HDBP systems, similarly to the CCD–HDBP system. The largest number of HDBP molecules was noted in the Ln–CCD–[(ZS HDBP (1: 6)]_n complexes. The CCD–ZS HDBP (1: 6) and CCD–ZS HDBP (1: 12) systems are promising for the separation of REE and TPE, and small addition of CCD to the ZS HDBP (1: 6) system in a polar diluent allows the development of a cheap solvent efficiently recovering all the REE and TPE from a 3 M HNO₃ solution.

A procedure was developed for removing uranium, thorium, and potassium from a liquid organic scintillator based on linear alkylbenzene (LAB) by stripping with water. The volume ratio of the scintillator and water in the process should be no less than 1: 5. The attenuation length (L₄₂₀) of LAB after treatment with water does not change and is as high as 13.0 ± 1.8 m. The solubility of water in LAB and of LAB in water was determined to be 46 and 5.1 ppm, respectively.

The results of the first experimental study on the sorption of molybdenum microamounts onto Termoxid- 5 sorbent in relation to the solution acidity and specific amount of the sorbent, varied in a wide range, are reported. The dependences obtained are correlated with changes in the molybdenum speciation depending on pH of the aqueous solution and with the data calculated using different sorption models. The experimental data are described most adequately with the model of the sorbent in the form of the supporting electrolyte cation, with possible sorption of cationic, neutral, and anionic molybdenum species. The experimental dependences of the molybdenum sorption onto Termoksid-5 sorbent on the specific amount of the sorbent show that molybdenum exists in a strongly acidic solution (3 M HNO₃) in the form of several labile species.

The distribution coefficients of a number of chemical elements between live and dead plankton and aquatic medium were determined experimentally. The sorption isotherms of macro- (Mg, Ca) and microelements (Sr, Ba, Mn, Fe, REE, Th, U) on plankton as biosorbent under the conditions when their level exceeds the natural background in water follow the Langmuir equation. The equation parameters for samples of live and dead plankton differ statistically significantly. In the sorption affinity level (logK_d [mL g^–1] ~3–5), freshwater plankton can be considered as effective biosorbent. Electron microscopic examination with local multielement analysis revealed abnormally high content of manganese in the form of adsorption colloid for Trachelomonas acanthostoma var. acanthostoma plankton alga in separate water samples taken from the cooling pond of the Beloyarsk NPP.

A new reactive species, fluorinated phenyl cation generated by β-decay of tritium in difluoroditritiobenzene, was used for introducing fluorinated phenyl fragment into organic compounds. Studies of ion–molecule reactions have shown that, similarly to the unsubstituted nucleogenic phenyl cation, p-difluorophenyl cation directly phenylates the N atom in the heterocyclic ring of quinoline. The nuclear-chemical method allows not only generation of nucleogenic species of various structures, but also one-step synthesis of previously unknown and difficultly accessible heterocyclic derivatives labeled with tritium.

The ²¹⁰Ро content in various grades of tea sold in St. Petersburg shops was determined, and the effective annual dose of internal irradiation from ²¹⁰Ро at daily tea drinking was estimated. As shown by α-ray spectrometry, the activity concentration of ²¹⁰Ро in tea leaves varies from 1.1 to 25 Bq kg^–1. The ²¹⁰Po content in black teas is, on the average, 1.7 times higher than in green teas. This difference is accounted for by specific features of processes for the production of black and green teas. From 1.5 to 56% of ²¹⁰Ро passes into aqueous extracts. Despite higher polonium content in black teas, the amount of ²¹⁰Po extracted from green teas is, on the average, 6.3 times higher than that extracted from black teas. This effect may be associated with the formation of water-soluble organic polonium compounds on the surface of tea leaves in the course of tea processing. The effective annual dose of internal irradiation from polonium at daily use of 10 g of dry tea is estimated at 0.8–9.5 μSv year^–1 depending on the tea grade, or 0.5–5.8% of the average annual dose of irradiation of the Russian Federation population from the sum of the nuclides (²¹⁰Pb, ²¹⁰Po, ²²⁸Rа, ²²⁶Rа, etc., except ⁴⁰K) getting into a human body with food and water.