Том 61, № 4 (2019)

Papers dealing with the ¹⁷⁷Lu production technology are analyzed with the aim of evaluating the readiness of the existing processes to setting up regular large-scale production, which is the necessary condition for the progress of the market of ¹⁷⁷Lu-based radiopharmaceuticals. This is now on the initial step of its development. The ¹⁷⁷Lu production processes are based on irradiation of isotopically enriched ¹⁷⁶Lu or ¹⁷⁶Yb with reactor neutrons, followed by radiochemical processing of the irradiated targets. Specific production features are analyzed with emphasis on process aspects of the reactor and radiochemical stages. The evaluation shows that the presently reached level of the ¹⁷⁷Lu production technology allows only the current demand of nuclear medicine for this radionuclide, corresponding to the initial step of its clinical use, to be met. Further growth of the market of ¹⁷⁷Lu radiopharmaceuticals requires the upgrading of existing or construction of new facilities, which is possible only with significant improvement of both reactor and radiochemical processes.

The actinide contraction effect in the structures of 55 crystals containing \(\rm{AnO}_2^{2+}\) dioxocations (An = U, Np, Pu, Am) and belonging to 18 series of isostructural An(VI) compounds was analyzed using Voronoi-Dirichlet (VD) polyhedra. Analysis shows that the actinide contraction, as a rule, is accompanied by a regular decrease in the radii of the spherical domains (R_sd) of the volume equal to that of the VD polyhedra of the An(VI) atoms in the crystal structures. In the series U-Np-Pu, such contraction is accompanied by a regular increase in the second moment of inertia (G₃) of the VD polyhedra, suggesting a decrease in the extent of their sphericity (due to stronger flattening of the coordination polyhedron in the form of bipyramid), whereas in going from Pu to Am the extent of sphericity of the VD polyhedron increases instead of decreasing. The results obtained confirm the viewpoint that the contraction and localization of the 5f shell start specifically from Am. The lack of correlation between the actinide contraction and relative strength of An-O bonds in the series U-Np-Pu-Am is noted.

The Np(V) complex Na[NpO₂(cbc)₂] was isolated in the crystalline form and studied by single crystal X-ray diffraction. The coordination surrounding of the Np(1) atom is a pentagonal bipyramid with the O atoms of the NpO₂ group in apical positions. The equatorial plane of the bipyramid is constituted by one O atom of the adjacent NpO₂ group and four O atoms of three C₄H₇COO_– anions. Cation–cation (CC) interaction (mutual coordination of linear \(\rm{NpO}_2^+\) dioxocations) observed in the structure leads to the formation of chains of \(\rm{NpO}_2^+\) cations. The bridging anions link the \(\rm{NpO}_2^+\) cations along the chains with the formation of infinite anionic chains \(\left[ {\rm{Np}{O_2}{{(cbc)}_2}} \right]_{\rm{n}}^{{\rm{n -}} }\) oriented along [001] in the crystal. The Na₊ cations arranged between the \(\left[ {\rm{Np}{O_2}{{(cbc)}_2}} \right]_{\rm{n}}^{{\rm{n -}} }\) anionic chains link them in the [010] direction. As a result, electrically neutral layers parallel to the (011) plane are formed in the crystal.

Oxidation of Pu(III) in a diaphragmless cell with a Ti cathode and a Pt anode in 1.0–3.9 M HNO₃ solutions containing 4.5 × 10⁻²–1.8 × 10⁻¹ M hydrazine was studied. The final solutions contain, along with Pu(IV), also a small amount of Pu(VI), increasing with an increase in the current density. Methods allowing minimization of the Pu(VI) amount in the solutions after the electrolysis were suggested. The possible process mechanism involving reactions of Pu ions at the electrodes and in the bulk of the solution with HNO₂ was considered.

The sorption ability of an aluminosilicate sorbent prepared from clay-salt slimes (Belaruskalii production waste, Belarus) was studied. The ¹³⁷Cs sorption is the most efficient at pH 2.5-10.5. At the sorbent dosage of 4 g dm³ and sorption time of 1 h, the degree of the ¹³⁷Cs sorption from aqueous solution is 98.8%. The sorbent performance in the ¹³⁷Cs removal is mainly determined by the kind (Na⁺, K⁺, Ca²⁺) and concentrations of macrocomponents in surface and groundwater. The aluminosilicate sorbent selectively takes up ¹³⁷Cs from an aqueous solution in the presence of Na⁺ and Ca²⁺ cations, but in the presence of K⁺ cations the selective sorption of ¹³⁷Cs is observed at K⁺ concentrations lower than 1 mM.

Gamma and alpha spectrometry techniques were applied to determine the activity concentrations of ²³⁸U and ²³²Th (Bq kg^–1) as well as the ²³⁴U/²³⁸U and ²³⁰Th/²³⁴U isotopic ratios for commercial grade monazite (purity ≈50%) supplied from the Egypt nuclear materials authority. A method for total dissolution of monazite followed by the sequential radiochemical separation using anion-exchange chromatography is presented. The average activity concentrations of ²³⁸U and ²³²Th, measured by α-ray spectrometry, are 2.49 g kg^–1 (0.24 wt %) and 30.09 g kg^–1 (3.1 wt %), respectively. The calculated ²³⁴U/²³⁸U and ²³⁰Th/²³⁴U isotopic ratios are close to unity, suggesting closed system equilibrium. The possibility of using leaching of monazite with water at different pH values for gaining information about the masses of uranium and thorium that pass into the solution and remain fixed in the crystal lattice was examined.

The possibility of reprocessing of irradiated [¹⁸O]H₂O after isolation of [¹⁸F]fluoride ion from it (regenerate) under the conditions of the cyclotron-radiochemical laboratory of an operating PET center was examined. The radionuclide and chemical composition of [¹⁸O]H₂O and the degree of its enrichment in ¹⁸O before and after distillation at atmospheric pressure were studied comprehensively. The suggested method allows efficient removal of long-lived γ-emitting radionuclides (⁵⁶Co, ⁵⁷Co, ⁵⁸Co, ⁶⁵Zn, ⁵⁴Mn, ⁵¹Cr) from the [¹⁸O]H₂O regenerate. The distillation reduces the content of residual solvents (acetaldehyde, acetone, isopropanol, ethanol, acetonitrile), whereas the content of 3H and ¹⁸O in [¹⁸O]H₂O changes within the measurement uncertainty. The distillation residues and decontamination solutions after neutralization can be jointly cemented to incorporate the γ-emitters into a compact matrix with the aim of its subsequent delivery to specialized organizations performing long-term storage and disposal of solid radioactive waste.

Uranium contents were measured in the siltstones and siliceous limestone interbeds within sandstone of Kubaca member of the Eocene of Ayhan formation, with chemical values ranging from 175 to 2537 ppm and radiometric values ranging from 85.40 to 660.40 cps. The highest chemical values of uranium and Th/U were obtained from the siltstones. Mineralogical studies were also conducted, and these indicated that uranium is associated with fluorapatite and hydroxyapatite in the siltstone and as discrete rutherfordine in fractures of siliceous limestone. The uranium contents in the siltstones are higher than those in the siliceous limestones due to the cation-exchange capacity and adsorption of smectite/kaolinite group clay minerals. The D-factor determination of the equilibrium state of the studied rocks indicated that chemically analyzed uranium values are greater than radiometrically determined uranium values, reflecting a disequilibrium state characterized by the addition of uranium into the system. The study shows two types of the uranium mineralization: (1) syngenetic phosphate cement controlled and (2) epigenetic, fluid driven, fracture controlled. The potentiality of the area with respect to uranium is enhanced in view of the addition of uranium into fractures and fault planes, after remobilization from the overlying phosphatic siltstone unit and other deep-seated sources.