Vol 65, No 4 (2023)

Received January 16, 2023; revised March 21, 2023; accepted March 27, 2023 Extraction of U(VI), Th(IV), REE(III), and Sc(III) from nitrate and perchlorate solutions with solutions of phosphorylpodand 1,5-bis[di( p -tolyl)phosphoryl]-3-oxapentane (L) in 1,2-dichloroethane depending on the concentration of acids in the aqueous phase was studied. The stoichiometry of the extractable complexes was determined. It was found that, as the concentration of acids increases, the magnitude of the «perchlorate» e ect decreases, and at acid concentrations above 0.3 mol/L, REE(III) ions are extracted by podand L from HClO₄ solutions less e ciently than from HNO₃ solutions. During the extraction of Sc(III), the «perchlorate» e ect also manifests itself in the region of high acid concentration, which leads to an increase in the separation coe cients of Sc(III) and REE(III), U(VI), and Th(IV) during extraction with podand L from HClO₄ solutions.

The sorption of cesium from solutions of sodium and potassium nitrates, sodium hydroxide, and also from a model solution simulating alkaline high-level waste (HLW) of FSUE PO «Mayak» on various resorcinolformaldehyde sorbents (RFS), on sorbent based on a boron-containing polymer of the Clevasol brand and on sorbent of the Fersal brand based on modi ed nickel ferrocyanide was studied under batch conditions. It is shown that in all the media studied, the Fersal sorbent has the best sorption-selective characteristics with respect to cesium. During the sorption of cesium from a model solution of HLW under dynamic conditions, the volume of the passed solution to 1% breakthrough for the Fersal sorbent is 127 bed volumes (b.v.). The puri cation resource of the other studied sorbents is 3-4 times less. Desorption of cesium from the Fersal sorbent can be carried out by passing 9-10 b.v. 7.5 mol/dm³ HNO₃, however, in this case, the sorbent granules are destroyed, which does not allow it to be reused. It is concluded that the Fersal sorbent is the most promising for the treatment of alkaline HLW.

The in uence of various factors on the e ciency of introducing deuterium into3-(N-pyrrolyl)-propanoylL-histidine and 3-(N-salicyl)-propanoyl-L-histidine has been studied. Heavy water was used as a source of deuterium. It is shown that the content of deuterium atoms in the substance can be increased by pretreating the reaction mixture with deuterium gas. The new approach opens up additional possibilities both for obtaining highly puri ed preparations by introducing hydrogen isotopes into organic compounds, and theoretically for a deeper understanding of the participation in this process of activated deuterium or tritium particles solvated on the carrier and in the pool of the substance.

The through diffusion method at room temperature was used to study the migration of radionuclides (³H, ⁹⁹Tc, ¹³⁷Cs, ²³³U) in compacted samples of clay materials during pore diffusion from a model leachate of the RW phosphate matrix with a total salt content of about 400 mg/L. Based on the results of the experiments, the effective diffusion coeffcients and coeffcients of the sorption distribution of radionuclides for the studied barrier clay materials were determined. Regularities of the diffusion transfer of tritium, cesium and uranium depending on the structure, mineral composition of clay materials and the content of radionuclides in the pore solution are revealed. Numerical modeles are proposed for calculating the effective pore di usion coeffcients of these radionuclides. There are still insuffcient data to analyze the factors affecting the diffusion of technetium.

In bottom sediments of the Laptev and the Kara seas ¹³⁷Cs has been migrating with di usion coe cient ( D ) n ·(10-9-10-8) cm²/s during nearly 30 years. In the sediments pro le ¹³⁷Cs concentration gradient was persisting between the layers. The trend of concentration decrease from the upper to the lower layers of the core was not violated along the entire path of radionuclide migration. ¹³⁷Cs has been migrating in bottom sediments slowly; nearly 20% of the radionuclide stayed in the upper (0-1 cm) layer. In the Tsivolki Bay of Novaya Zemlya Archipelago 137Cs has been migrating in very low temperature conditions of water and bottom sediments (-1.0, -1.2°С). ¹³⁷Cs concentration in the upper layer of the Laptev Sea and Tsivolki Bay sediments was characterized by close values, 7-18 and 14-24 Bq/kg, which correlate with global level of sediments contamination. The Tsivolki bay is ice-covered for 10 months. ¹³⁷Cs pro le in the cores was forming due to radionuclide di usion in conditions of short warm period of terrigenic sedimentation. ¹³⁷Cs concentration in the bay sediments and a type of the concentration pro le demon rated an absence of radionuclide release from buried radioactive objects in the bay. ¹³⁷Cs di usion coe cients de nition computed with experimental data will be necessary in radionuclide migration models and scienti cally supported measures of damage minimization from exposure to the radiation factor.