Radiochemistry最新文献

Thermochemical denitration of nitric acid solutions of U and Pu to obtain mixed uranium–plutonium formates was performed. It was followed by the reduction of the mixture in Ar–H₂ (5 vol %) to obtain a powder of mixed U–Pu dioxide. The products obtained were studied and characterized by X-ray diffraction, X-ray fluorescence analysis, and Raman spectroscopy. The analysis of the powder revealed the formation of a (U,Pu)O₂ solid solution containing 5 wt % Pu and of UO₂. After the powder treatment by vortex mixing, high-density pellets of homogeneous structure were fabricated.

The extraction of ytterbium from nitric acid solutions with solutions of 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (HEH[EHP]) in hexane was studied. The HEH[EHP] concentration was varied from 0.5 to 2.0 M; acidity, from 0.1 to 2.0 M; and lanthanide concentration, from 0.1 to 5 g/L. The dependences of the ytterbium distribution ratio on the solution acidity are described by equations of the type log D = a log[H⁺] + b, where the coefficient a depends on the extractant and lanthanide concentrations and varies from –1.26 to –3.0. Its variation is probably caused by the occurrence of the extraction by both cation-exchange and solvation mechanism. The model describing the dependence of the ytterbium distribution ratio on its concentration in the aqueous phase at different concentrations of the extractant and acid was suggested. The data predicted by the model reasonably agree with the experimental data.

The possibility of using new anion-exchange resins AM-4VP, AM_pu, AMP-p, AM-p, and AM-2B produced by Smoly Group of Enterprises for plutonium recovery from nitric acid process solutions was examined. The physicochemical characteristics of the resins, the thorium distribution coefficients as functions of the nitric acid concentration, and the static exchange capacities of the resins were determined. The plutonium recovery from process solutions was studied in column experiments. The physicochemical properties and sorption ability of the anion-exchange resins were compared to those of the previously used VP-1Ap resin. AM-4VP resin shows promise for plutonium recovery from nitric acid process solutions.

The suitability of a matrix based on an iron phosphate ceramic (IPC) for immobilization of waste from pyrochemical reprocessing of spent nuclear fuel (spent electrolyte, a readily water-soluble fusion cake of alkali metal chlorides) was examined. The phase composition, chemical durability, and mechanical strength of the matrix material were studied. The matrix meets the requirements to a cement compound formulated in NP-019-15 regulation document and is suitable for radioactive waste disposal.

The study deals with the effect exerted by adding various zirconium amounts on the heat resistance and chemical durability of aluminoborosilicate glass-containing host materials prepared by rapid cooling (quenching) of melts with different ratios of sodium and cesium. The specific features of the anionic structure of the glass-containing part of these materials were studied by vibrational spectroscopy. The Na/Cs ratio and zirconium additions influence the softening/glass transition point and the rate of dissolution of the major components on prolonged keeping in an aqueous medium. The results obtained are recommended for use in evaluation and correction of properties of borosilicate host materials for high-level waste immobilization.

The efficiency of the extraction of lanthanide(III), americium(III), and thorium(IV) ions from nitric acid solutions with tetraoctyldiglycolamide significantly increases in the presence of an ionic liquid, didecylammonium di-2-ethylhexyl sulfosuccinate, in the organic phase. The effect of the aqueous phase acidity on the distribution ratios of the extracted elements was considered, and the stoichiometry of the extractable complexes was determined.

The concentration of radon gas was measured in human blood samples for smokers and non-smokers collected randomly in Kurdistan region, Iraq. The study was carried out using a CR-39 detector. The average ²²²Rn concentrations in powdered blood samples for cigarette, vape, and hookah smokers and for non-smokers were 228, 275, 290, and 21.9 Bq/m³, respectively. Thus, the hookah smokers had greater average values of ²²²Rn concentration in blood samples than the other smokers. The average values of ²²²Rn concentration for smokers were slightly higher than the global permissibility limit of exposure to radon (200 Bq/m³) recommended by the International Commission on Radiological Protection (ICRP), and for non-smokers they were far below the world standard limit. The average annual effective dose due to inhalation of ²²²Rn for cigarette, vape, and hookah smokers and non-smokers in powdered blood samples were 5.76, 6.93, 7.30, and 0.27 mSv/year, respectively, being within the recommended limit (3–10 mSv/year) for smokers. The results indicate that smokers have a higher risk of lung cancer because they inhale more radon.

The radon and thoron concentrations in sixteen types of rock samples collected from different areas in Sulaymaniyah Governorate, Kurdistan Region of Iraq, were determined using the tube technique with CR-39 solid-state detector. The radon and thoron concentrations in rock samples varied from 189 to 91 and from 112 to 54 Bq m⁻³, respectively. The average radon and thoron concentrations in the sampling areas were 132 and 78 Bq m⁻³, respectively. The radon concentrations were below the suggested range of 200 to 600 Bq m⁻³ as recommended by ICRP. In addition, parameters related to the potential radiological hazards were calculated for the rock samples. The mean values of the estimated equilibrium potential alpha energy concentrations and annual effective dose for inhaled radon and thoron in the rock samples were 21.47, 2.117 mWL, and 1.252, 0.549 mSv year^–1, respectively. These values were compared with international standards.

The heat generation by high-level waste raises the temperature in the near-surface zone of the repository, and the effect of this factor on the behavior of radionuclides in the host fractured rock environment upon deep disposal of radioactive waste (RW) should be considered in predictive modeling. The sorption behavior and spatial distribution of Cs, Sr, and Am on the surface of a fractured rock sample of the Nizhnekansky massif depending on temperature were studied. The distribution coefficients of Sr and Am on the sample surface increase with increasing temperature from 25 to 70°C, whereas the Cs distribution coefficient does not increase. This difference may be associated with different mechanisms of the sorption of these radionuclides. Cs, Sr, and Am are nonuniformly distributed on mineral phases of the fractured sample and are preferentially retained on Ca(Sr)-zeolite forming the mineral composition of the fractures. The coefficients of the phase distribution of radionuclides on separate mineral phases/associations were determined by quantitative analysis.

The existing technologies for the production, separation, and purification of ⁶³Ni, as well as methods for the deposition of nickel coatings to fabricate a betavoltaic nuclear battery have been reviewed. A new integrated closed loop flowsheet for the production of highly enriched ⁶³Ni and deposition of ⁶³Ni coatings using a single reagent, phosphorus trifluoride (PF₃), in all stages of the process is proposed. The use of tetrakis(trifluorophosphine)nickel [Ni(PF₃)₄] allows isotopic enrichment of ⁶²Ni and ⁶³Ni, purification of irradiated Ni from radioactive impurities, and deposition of highly enriched ⁶³Ni onto a semiconductor substrate. The proposed flowsheet allows the amount of the liquid radioactive waste generated during isotope purification and coating deposition to be reduced as compared to traditional “wet” chemistry methods.