Radiochemistry最新文献

Samples of magnesium potassium phosphate compound containing boron-containing evaporator bottom simulant after concentrating liquid radioactive waste from nuclear power plants were synthesized. The possibility of solidifying up to 14 wt % evaporator bottom simulant components into a compound containing 15–20 wt % wollastonite was demonstrated. The phase composition of the samples obtained, their compressive strength, resistance to thermal cycles, water resistance, and hydrolytic durability were determined. The integral ¹³⁷Cs leaching rate is 5.7 × 10⁻⁴ g/(cm² day), and the leaching index is 10.7. The quality indicators of the compound obtained meet the regulatory requirements for a compound for solidifying radioactive waste.

The paper deals with the history of the high-level waste accumulation at the Mayak Production Association and the experience of the operation of the storage tanks. The procedures for the sampling of the precipitates from storage tanks and subsequent analysis of the samples are described. Experiments on the dissolution and washing of the precipitates were performed. Data on the activity of the precipitates are presented.

In the course of prolonged interaction in the system consisting of [⁹⁹Tc(hfa)(CO)₄] (hfa is the anion of 1,1,1,5,5,5-hexafluoroacetylacetone), triphenylphosphine (PPh₃) or pyridine (py), and CCl₄, the hfa anion is gradually displaced by the chloride ion with the formation of the complexes fac- and mer-[⁹⁹TcCl(CO)₃(PPh₃)₂] and fac-[⁹⁹TcCl(CO)₃(py)₂]. The crystal and molecular structures of the complexes were determined. The complex fac-[⁹⁹TcCl(CO)₃(PPh₃)₂] is the first structurally confirmed example of technetium(I) tricarbonyl bis(triphenylphosphine) complexes of facial structure.

The geochemical composition and radiogenic heat production (RHP) of granitoids from fourteen plutons in Egypt’s Eastern and Western Deserts was studied using inductively coupled plasma mass spectrometry (ICP-MS). The results show that light rare earth elements (LREEs) dominate over heavy rare earth elements (HREEs), and the Th/U ratios range from 1.75 to 6.81. RHP values vary significantly, from 1.31 to 9.17 µW/m³, with El Dib pegmatitic syenite showing the highest value and Abu Dabbab, the lowest. El Dib and Qattar granites are classified as high heat-producing rocks (HHP), while El Dokhan, El Sibai, Missikat, and Bir Safsaf granites fall into the moderate category (MHP). The remaining plutons are considered as low heat-producing (LHP), though their average RHP still exceeds the global upper continental crust average. No clear relationship was found between RHP and Th/U ratios or SiO₂ content. γ-Ray spectrometry (GRS) proved to be a reliable complementary method for assessing RHP. Overall, the findings highlight the geothermal potential of these granitic intrusions as promising heat sources in Egypt’s desert regions.

This study evaluates the specific activity and radiological hazards of primordial radionuclides (²²⁶Ra, ²³²Th, ⁴⁰K) in soils from five regions in Qena Governorate, Upper Egypt, and in chemical fertilizers using NaI(Tl) gamma-ray spectrometry. The soil activity concentrations (Bq/kg) spanned (4 ± 0.2)–(47 ± 2.3) for ²²⁶Ra, (6 ± 0.3)–(58 ± 3) for ²³²Th, and (14 ± 0.7)–(284 ± 14) for ⁴⁰K, with ⁴⁰K dominating in all samples except one from Qift. Fertilizers exhibited higher variability (Bq/kg): ²²⁶Ra (42 ± 2)–(169 ± 8), ²³²Th (32 ± 4)–(99 ± 4.9), and ⁴⁰K (30 ± 1.5)–(638 ± 32). Phosphate rocks from Umm al-Huwaitat showed moderate activity: (25 ± 4)–(203 ± 10 )Bq/kg. The average radiological indices for soils were 70.7 Bq/kg (Ra_eq) and 0.19 (H_ex), being well below global thresholds (370 Bq/kg; H_ex < 1). The annual effective dose equivalents (AEDE) for Qena soils were 0.039 µSv/year (outdoor) and 0.156 mSv/year (indoor), representing 3.9% and 15.6% of the ICRP (1990) public limit (1 mSv/year). Fertilizer Ra_eq values (168.6–251.9 Bq/kg) exceeded those of soils but remained within safe limits. The average excess lifetime cancer risk (ELCR) for soils was 0.69 × 10^–3, i.e., 47% of the global average (1.45 × 10^–3), and that for fertilizers reached 2.13 × 10^–3, being within negligible risk thresholds. The results align with global benchmarks, confirming minimal public and environmental radiological risks. The study establishes critical baseline data for monitoring population exposure and guiding agricultural practices in regions utilizing phosphate-based fertilizers. These findings underscore the importance of continued radiological surveillance in areas with intensive fertilizer use to ensure long-term safety.

The possibility of using new “heavy” diluents, carbonates of fluorinated alcohols, for extractive recovery and purification of uranium was examined. The physicochemical characteristics and extraction properties of the diluents were determined. Extraction mixtures based on tributyl phosphate and carbonates of fluorinated alcohols show promise for the uranium recovery from nitric acid process solutions owing to the following features: high distribution ratios of the target component, no third phase formation upon solvent loading, and insignificant extraction of nitric acid.

The main parameters of the sources of natural (cosmogenic) and anthropogenic carbon-14 at the reactor, radiochemical, and isotope plants of the Mayak Production Association are considered. The results of monitoring the specific activity of ¹⁴С in the air and vegetation in 1965 and 1982–1986 in Metlino settlement by specialists of the Research Experimental Station (ONIS) of the Mayak Production Association are analyzed. The results of monitoring the content of ¹⁴С in organs and tissues of adult inhabitants of the three towns nearest to the enterprise (Ozyorsk, Kasli, Kyshtym), obtained in the 1980s by staff members of Branch no. 1 of the Institute of Biophysics (Biophysics Institute) independently of the ONIS specialists, are discussed. From the results of measuring the specific activity of ¹⁴С in the air in Metlino settlement, the intake of anthropogenic ¹⁴С by adult inhabitants with the food was estimated at 66 kBq/year, and the total content of ¹⁴C in the living body, at 10.4 kBq. These data agree well with the results obtained by Biophysics Institute for the population of Ozyorsk, Kasli, and Kyshtym. Carbon-14 was mainly taken up with the local foodstuffs (74% with cereals, 9% with meat products, and 9% with dairy products). The rate of the ¹⁴C production in the nuclear fuel and reactor core materials by reactions of reactor neutrons with nuclei of light elements (nitrogen, oxygen, carbon) and by ternary fission of ²³⁵U (²³⁹Pu) was calculated. In industrial uranium-graphite reactors (PUGR), the major part of ¹⁴C (about 90%) generated in unintended voids (cavities formed as a result of graphite distortion) during nitrogen purging of graphite blocks. The ¹⁴C activity accumulated in the spent nuclear fuel of the WWER-440 is determined by the content of nitrogen impurity in fuel assemblies and at the permissible limit (up to 0.012 wt %) can significantly exceed the ¹⁴C production from the main materials (²³⁵U and oxygen). The calculated estimates do not contradict the results of single measurements of intensity of ¹⁴C release from Mayak stacks. In the 1980s total intensity of ¹⁴C release (for all sources) into the atmosphere was 60−90 TBq/year.

The heat capacity, thermal conductivity, and linear thermal expansion coefficient of non-radioactive borosilicate glass samples of various chemical compositions, simulating the vitrified cesium–strontium fraction, were determined by differential scanning calorimetry and dilatometry to justify the safety of the radioactive waste storage. The developed steps of remote experimental determination of the thermal characteristics allow working with real vitrified high-level waste samples and creating a database containing the characteristics of borosilicate glasses.

High-quality radioecological monitoring requires component measurement laboratories. Interlaboratory comparative tests are one of the most effective tools for evaluating the qualification. The accredited provider of the Bochvar High-Tech Research Institute of Inorganic Materials performed interlaboratory comparative tests of the radiometric parameters of soils, namely, of the specific activities of α-, β-, and γ-emitting radionuclides.

The radiation resistance of the AM-4VP macroporous anion-exchange resin producted by Smoly Corporate Group was evaluated. The influence of the absorbed radiation dose on the physical properties of the AM-4VP resin and on its performance in thorium sorption was examined. Experiments were performed on the plutonium recovery from process solutions in the dynamic mode on nonirradiated and irradiated samples of the AM-4VP anion-exchange resin. The radiation resistance of the resin was compared to that of VP-1Ap anion-exchange resin used in the process previously. At the absorbed γ-radiation does not exceeding 2 MGy, the physical characteristics of the AM-4VP anion-exchange resin and its performance in the plutonium sorption remain acceptable and practically are not inferior to those of the VP-1Ap resin. At the absorbed γ-radiation dose of 5 MGy, the AM-4VP and VP-1Ap resins undergo substantial radiation-chemical transformations leading to the virtually complete loss of their sorption ability.