Radiochemistry最新文献

Spent iodine-bearing sorbents accumulated at the Mayak Production Association were subjected to chemical and radiochemical analysis. The mass fractions of sorbent macrocomponents (Al, Ag, NO₃^–, and total I) and related impurities (F^–, Cl^–, and SO₄^2–) were measured. The total specific α- and β-activity, the specific activity of long-lived α- and β-emitting radionuclides whose identification was analytically possible (⁹⁹Tc, U and Pu isotopes, and ²⁴¹Am), and that of the main dose-producing radionuclides (¹²⁹I, ¹³⁷Cs and ⁹⁰Sr) were determined. The uniformity of the Al, Ag, NO₃^–, ¹²⁹I, ¹³⁷Cs and ⁹⁰Sr distribution in the columns was estimated.

The phase formation of the phosphates Tc_0.5Zr_0.5P₂O₇, Tc_0.25Zr_0.75P₂O₇, and Tc_0.25Np_0.25Zr_0.5P₂O₇ for the immobilization of technetium and technetium–neptunium fractions was studied. The powders were obtained by precipitation from solution. The target phase formation temperature was 600°C. The compounds obtained are single-phase products and crystallize in the cubic system, space group Pa–3. The solidification of the real technetium–zirconium fraction from VVER-1000 SNF processing was performed. The hydrolytic durability of the samples was studied by long-term static leaching. The degrees of leaching were as follows: Tc, no more than 0.03%; Np, 0.008%; Zr, less than 0.001%.

¹⁴⁷Pm is used in industry in sealed radioactive sources for measuring the thickness or density of materials and as a power source in radioisotope thermoelectric generators for space research. Traditionally, ¹⁴⁷Pm is isolated from a mixture of fission fragments of heavy nuclei. An alternative method for producing the radionuclide is irradiation of neodymium with neutrons from a nuclear reactor. At the Research Institute of Atomic Reactors, reactor irradiation of neodymium oxide of natural isotopic composition was carried out and a pilot batch of ¹⁴⁷Pm was obtained.

The article discusses the key milestones in the establishment of the Unified State System for Radioactive Waste Management in the Russian Federation. It summarizes the main achievements from the implementation of two Federal Target Programs for Nuclear and Radiation Safety in Russia. The article evaluates the role that the Russian Academy of Sciences and its organizations play in addressing some fundamental problems associated with nuclear and radiation safety at nuclear legacy facilities, as well as with the management of spent nuclear fuel and accumulated radioactive waste.

The natural radioactivity levels in vegetable samples and the radon concentrations in 18 different types of vegetables collected from Bazyan location in Kurdistan Iraqi region were determined. CR-39 detector with a PVC tube was used to record the tracks density of alpha particles emitted by radon from vegetable samples. The results showed that the concentration of radon released from vegetable samples ranged from highest value of 311 Bq m^–3 in sample A12 (green peppers) to lowest value 9.8 Bq.m^–3 in sample A10 (wild rocket) with the average concentration of 162 Bq m^–3. The concentrations of radon released from vegetable samples were lower than the global permissible limit of the exposure to radon according to International Commission on Radiological Protection (ICRP) and International Atomic Energy Agency (IAEA), 200–800 Bq m^–3, and lower than the limit in foods, 400 Bq m^–3, according to ICRP. Thus, the samples studied pose no health risks.

Nano silicotitanate (SiTi) gel was prepared to test its sorption capacity for Mo(VI) and W(VI) and its performance as a base material for ⁹⁹Mo/^99mTc and ¹⁸⁸W/¹⁸⁸Re chromatographic column generators. X-ray diffraction analysis showed that SiTi is a crystalline material with a crystallite size of 5.5 nm. High-resolution TEM studies showed that the average particle size was 60 nm. According to field emission SEM studies, SiTi has a cloudy morphology with the presence of many cavities. As indicated by TGA and EDX studies, SiTi gel has the chemical formula SiTi₆O₁₁·7H₂O. Nitrogen chromatographic studies showed that SiTi has a BET surface area of 285 m²/g, total pore volume of 0.31 cm³/g, and average pore diameter of 3.7 nm. DLS studies showed that the hydrodynamic diameter distribution of SiTi particles is bimodal, with 86.5% of particles corresponding to the peak at 126.5 nm and 13.5%, to the peak at 724.4 nm. Electrophoresis studies indicated that SiTi gel has a zeta potential of –45.1 mV. According to Langmuir sorption isotherms, SiTi gel showed molybdate(VI)-⁹⁹Mo and tungstate(VI)-¹⁸⁸W maximum capacities in the ranges 162.87–192.31 and 67.93–196.85 mg/g, respectively, in the temperature range 25–60°C. The breakthrough capacities for ⁹⁹Mo and ¹⁸⁸W were found to be 69.8 mg Mo/g and 60 mg W/g, respectively. ⁹⁹Mo/^99mTc and ¹⁸⁸W/¹⁸⁸Re chromatographic column generators were prepared and successfully eluted to obtain ^99mTc and ¹⁸⁸Re with the average elution yields of 89.1 and 97.9%, respectively, and radiochemical purity of >97 % (as pertechnetate and perrhenate, respectively).

The results of studying the interaction of An(III–VI) with 2,6- pyridinedicarboxylic acid (2,6-PDCA) are summarized. The stability constants are estimated for complexes An^IV(PDC)_n^4–2n (n = 1–3). The total stability constant exceeds 10²⁵ mol^–3 L^–3 and increases in the series from Th(IV) to Pu(IV) by 8 orders of magnitude. The difference in the stability of the An(III) and An(IV) complexes leads to rapid oxidation of Pu(III) to Pu(IV) with oxygen in the presence of 2,6-PDCA. An(V) and An(VI) ions form 1 : 1 and 1 : 2 complexes with PDC. The formation of An(IV,V,VI) complexes leads to a shift in the redox potential of the (V)/(IV) and (VI)/(V) couples. An(V) disproportionate in the presence of 2,6-PDCA anions. For An(VI) complexes of 1 : 2 composition, the f–f transition bands are weakened, which is associated with the centrosymmetrical structure of the coordination polyhedron of the An atom. The stability of the An(VI) complexes was evaluated. An(III) ions form compounds with PDC^2– in which the metal : ligand ratio is 1 : 3. Compounds An^IV(PDC)₂ and those with an anionic moiety in the form of An^IV(PDC)₃^2– were obtained. The cations were imidazole, Cs⁺, Ln²⁺, and Ln³⁺. An(V) forms compounds with one and two PDC^2– ions. Compounds of UO₂²⁺ with PDC^2–, as well as UO₂(PDC)₂^2– compounds with organic and inorganic outer-sphere cations have been studied. According to X-ray diffraction analysis, the AnO₂(PDC)₂^2– have the center of symmetry. In the isostructural series [Li₂AnO₂(PDC)₂]·2H₂O, actinide contraction is expressed in a decrease in the An=O distances in the “yl” groups from U to Pu. In all cases, PDC^2– is coordinated in the tridentate fashion through two oxygen atoms of carboxyl groups and a nitrogen atom.

Extraction of actinides and lanthanides from nitric acid media with 4-(di-n-alkylphosphoryl)-4-methylpentan-2-one derivatives with different lengths of alkyl substituents at the phosphorus atom [hexyl (C6), octyl (C8), and decyl (C10)] was studied. High selectivity was demonstrated in the extractive separation of uranium(VI), thorium(IV), and rare earth elements (REEs) with the separation factor for U(VI) and the sum of REEs SF_U(VI)/ΣREE > 4500 and for thorium(IV) and the sum of REEs SF_Th(IV)/ΣREE > 5000. The influence of alkyl radicals at the phosphorus atom on the extraction capacity for f-elements was shown. The extraction capacity increases in the series C6 < C8 < C10. Isotherms of uranium(VI) and thorium(IV) extraction with γ-(dialkylphosphoryl) ketones C6, C8 and C10 were obtained.

The ⁷Be activity in near-surface atmospheric aerosols and in atmospheric precipitations that fell out on the territory of the Aleksandrov Research Institute of Technology during the eight-year period covering the end of the 24th and the beginning of the 25th solar activity cycles (2016–2023) are reported. The many-year mean volume activity of ⁷Be in atmospheric aerosols was calculated from the monthly data of the radiation monitoring of the atmosphere at four posts of the automated radiation monitoring system; the value of 3.2 mBq/m³ was obtained. The seasonal trends in variation of the ⁷Be volume activity in air with a gradual increase from January to a maximum in June, followed by a decrease in the second half of the year, were determined. The inverse dependence of the annual mean volume activity of ⁷Be in the aerosols on the solar activity (Wolf numbers) was confirmed. The correlation coefficients of the ⁷Be activity in aerosols with the weather parameters (air temperature, relative humidity, wind speed, atmospheric pressure, and amount of precipitations) were calculated. The independence of the ⁷Be content in atmospheric aerosols from anthropogenic factors and trends in the variation of its volume activity during a year cycle allow ⁷Be to be used in the future as a natural tracer for evaluating the air pollution with manmade radionuclides.