Vol 66, No 1 (2024)

The method of obtaining a solid solution powder of uranium-plutonium oxides (with 38% plutonium content) from the AUPuC pulp of the process (ammonium uranyl-plutonyl carbonate) using microwave radiation in reducing and atmospheric environments was proposed and tested at the laboratory level. For research purposes, the pulp obtained by coprecipitation of uranium and plutonium from nitrate solution (stripping product simulator) was prepared in advance. The process consists of three main stages: oxidation of Pu(IV) to Pu(VI), precipitation, and conversion in a laboratory microwave unit. According to the X-ray phase analysis, the powder obtained in a reducing atmosphere is a solid cubic solution (U_xPu_1–x)O₂. The powder obtained in an atmospheric environment is a mixture of two oxides, PuO₂ and U₃O₈. Scanning electron microscopy and electron probe microanalysis of the powder obtained in an atmospheric environment showed a fairly uniform distribution of U, Pu, and O in the solid phase.

This work examines stone-cast matrices (SCM) obtained by fusing basalt with both uranium-containing pearlite grade M150 and U₃O₈ at a temperature of 1623 K in air for 5 h. As a result of fusing basalt with uranium-free M150 grade pearlite, matrices are obtained containing glass and spinel as the main phases. When basalt and uranium-containing pearlite of grade M150 are fused, SCMs are formed, the main phases of which are two Cr-spinels of different compositions, uranium-containing glass, and dendritic aluminosilicate crystals. When basalt and U₃O₈ taken in the initial mass ratio of 1:1 are alloyed, SCM is formed, the main phases of which are UO₃, CaU₃O₁₀, (Al, Cr, Fe)₂U₂O₉, plagioclase, and uranium-containing glass. The rate of uranium leaching from a basalt alloy with uranium-containing pearlite M150 containing ~7.2 wt% U and SCM obtained by fusing basalt with U3O8 and containing ~42.5 wt% U, in H₂O after 28 days of contact at 298 K was studied.

Results of centrifugal contactor rig trials of the flowsheet of the first solvent extraction cycle in protective glove boxes using simulated solutions of spent nuclear fuel and 30 and 45% TBP in isoparaffin as a solvent are compared. It was shown that an increase in the TBP concentration to 45% resulted in deterioration of the quality of the products obtained by the same flowsheets with 30% TBP in Isopar L as a solvent. Comparison of experimental and computer simulated profiles of component distribution across the stages of extraction units demonstrated satisfactory agreement in nitric acid and uranium concentrations. At the same time, it was found that simulation model of zirconium, technetium, and neptunium extraction requires improvement considering interaction of these elements with complexing agents.

The processes of sorption decontamination of aqueous solutions from TBP on the polymeric sorbent Polysorb-1, as well as of a 70% solution of TBP in dodecane from butylphosphoric acids using layered double oxides and Mg-Al hydroxides were studied. It has been established that the use of the polymeric sorbent Polysorb-1 makes it possible to decontaminate aqueous solutions from TBP in static and dynamic modes, and the use of the LDH-Mg-Al-CD-OH sorbent allows the decontamination of TBP solutions in dodecane from acid products of decomposition and hydrolysis of TBP.

The release of ¹³⁷Cs into an Ar flow during the interaction of ¹³⁷CsI and ¹³⁷CsOH—¹³⁷Cs₂CO₃ with molten lead at a temperature of ~852 K was studied. During the heating of Pb⁰ with ¹³⁷CsI, ¹³⁷CsOH—¹³⁷Cs₂CO₃, and ¹³⁷CsI—¹³⁷CsOH—¹³⁷Cs₂CO₃, from 2 to 8% of ¹³⁷Cs can pass into the gas flow. Based on the distribution of ¹³⁷Cs between the elements of the gas purification system, it was concluded that the chemical and disperse composition of compounds containing ¹³⁷Cs in the gas phase is quite heterogeneous. Volatile ¹³⁷Cs compounds formed upon heating ¹³⁷CsI, ¹³⁷CsOH—¹³⁷Cs₂CO₃, and ¹³⁷CsI—¹³⁷CsOH—¹³⁷Cs₂CO₃ with Pb⁰ in a gas flow at ~852 K can contain both charged aerosols and aerosols without electric charge.

Protecting soil from pollution by oil and petroleum products is an important environmental task. Sources of oil contamination of soil are not only oil fields, but also industrial facilities that directly or indirectly use petroleum products. Of interest are studies aimed at studying the processes of changes in oil during its degradation in the soil. When oil degrades, polycondensation processes occur on the soil surface, which leads to structural changes in the oil. We compared the composition and properties of oil after production and long-term presence on the soil surface. An analysis of oil-contaminated soils was carried out at a distance of 0–5 and 0–10 m from the source of pollution and from a depth of 0–15 cm. Oils degraded in the soil are also susceptible to the effects of natural radionuclide background. In this regard, the work investigated the impact of gamma radiation on oil degraded in the soil of the Surakhani oil field of Azerbaijan. Oil samples were taken from a well and from oil-contaminated soil and separated into three components: oils, resins, and asphaltenes. The results of mass spectrometric and IR spectrometric studies of the indicated fractions of crude and degraded oil samples are presented, and the patterns of formation of gaseous products during their radiolysis are established.

The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. When using D₂O at 200°C, about 0.5 deuterium atom was included in GABA on average. When using D₂O with trifluoroacetic acid (1 : 1) at 250°C, an average of 1.49 deuterium atoms with a yield of 15% were included. When using the solid-phase method, it was possible to introduce about 3 deuterium atoms per GABA molecule. During isotopic exchange with D₂O, the use of a palladium–rhodium mixture pretreated with gaseous deuterium made it possible to obtain [D]GABA with the deuterium content of 4.5–4.6 atoms. But in both cases, the yields of [D]GABA were low. Preparative amounts of [D]GABA were obtained using additional carriers. The best result was obtained when applying GABA to zeolite. Using D₂O and 5% Pd/BaSO₄–GABA–zeolite pretreated with deuterium gas, [D]GABA was obtained with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%.

The content of ²³⁷Np, ^239,240Pu, and ²⁴¹Am in seawater, suspended matter, and bottom sediment cores of the Ussuri and Amur Bays, sampled in July 2021 and August 2022, was analyzed. The activity concentrations of ²³⁷Np, ^239,240Pu, and ²⁴¹Am in the water of Peter the Great Bay were determined for the first time and were found to be equal to (19–105) × 10^–3, 2.0–5.3, and 24.1–33.5 mBq/m³, respectively. The activity concentrations as well as the ²³⁹Pu/²⁴⁰Pu isotope ratio (~0.18) in the bottom sediments definitely indicate that global fallout is the main source of plutonium in the investigated territory. The sedimentation rates were determined for the Amur Bay (in the Razdolnaya River estuary), 0.9 mm/year, and for the Ussuri Bay, 4.1 mm/year. Actinide transfer coefficients were determined for Peter the Great Bay in the system dissolved forms, including colloids–suspended matter–bottom sediment.