Development of a radiochemical method for extraction chromatographic separation of Pb and Bi radioisotopes of forensic and environmental interest

This work describes the purification and separation of some radionuclides of 210Pb and/or 210Bi that might be used in calibration of nuclear spectroscopic instruments for forensic purposes and environmental studies. The retention and desorption investigations have been done by Dowex HCR-S/S resin as the cationic exchanger by batch mode. Full retention of metal ions was achieved in 0.1 M HNO3 solution after an equilibration period of 2 h at room temperature. The uptake of Pb and Bi is reached to more than 95 and 85%, respectively. Desorption studies by several reagents indicated that 1 M citric acid and ammonium acetate are efficient to elute and separate Bi and Pb. Taking into consideration all the above obtained results, column applications packed by the Dowex HCR-S/S resin were carried out to separate 214,210Pb and 214Bi radionuclides either in TENORM-concentrate or old certified reference of 226Ra solution. The column application results revealed that the recovery of Pb and Bi radionuclides was ∼93%. In the radiochemical part, the eluted Bi was impure due to presence of 23% Pb. In contrast, 70% of pure Pb was obtained. Thus, the radionuclides 210Pb can be recovered from several waste resources by this method. It can be concluded that the Dowex HCR resin can be an alternative economic material that could be used to produce 210Pb from the TENORM wastes generated from some strategic industries.

Assessment of the current levels of 241Am and 137Сs in soils and foodstuff, as well as of public internal exposure to ionizing radiation in populated areas adjacent to the Chernobyl NPP exclusion zone (case study: the Bragin district of the Gomel region, Belarus)

This paper is part of a research cycle focusing on studying the current levels of 241Am and 137Cs in soils and local foodstuffs of populated areas neighboring the Chernobyl exclusion zone. Our objective was to estimate the maximum annual committed internal doses to individuals of the Bragin-area settlements from inhalation and consumption of locally produced foods. We updated the data on the levels of 241Am and 137Сs in soils of 28 settlements of the district. Specific activity of 241Am in soils in two of the settlements were the highest of all; we took and analyzed samples of local-grown foodstuff. 241Am in food samples was measured via a radiochemical method with the use of selective chromatographic resins and alpha-spectrometry measurement. A gammaspectrometry technique was used to measure 241Am in soil and 137Сs in soil and food samples. The most contaminated by 241Am and 137Cs appeared the soils in the town of Bragin, the administrative center of the district where the respective levels were as high as 2.8 and 560 kBq/m2. Among the analyzed samples, the specific activities of 241Am in root and tuber crops were one-digit values, while the samples of leafy vegetables contained a few tens of mBq/kg of the same radionuclide. That said, however, 241Am concentrations in food samples were lower than those of 137Сs by three orders of magnitude. The results showed an apparent difference between estimated annual committed internal doses to the Bragin residents due to 241Am intake and that resulting from 137Сs with the respective 0.03 and 1.7 mSv/year. The maximum doses to population of the Bragin-district villages from inhalation of 241Am varied from 0.006 to 0.033 mSv/year exceeding the doses from inhaled 137Сs – 0.0002-0.002 mSv/year – by one order of magnitude. The major contribution to the public internal exposure today is 137Сs intake through consumption of contaminated food that produced locally; its contribution is about 93-99% of the total internal dose received by the Bragin-district residents.

An Automated SeaFAST ICP-DRC-MS Method for the Determination of 90Sr in Spent Nuclear Fuel Leachates

To reduce uncertainties in determining the source term and evolving condition of spent nuclear fuel is fundamental to the safety assessment. ß-emitting nuclides pose a challenging task for reliable, quantitative determination because both radiometric and mass spectrometric methodologies require prior chemical purification for the removal of interfering activity and isobars, respectively. A method for the determination of 90Sr at trace levels in nuclear spent fuel leachate samples without sophisticated and time-consuming procedures has been established. The analytical approach uses a commercially available automated pre-concentration device (SeaFAST) coupled to an ICP-DRC-MS. The method shows good performances with regard to reproducibility, precision, and LOD reducing the total time of analysis for each sample to 12.5 min. The comparison between the developed method and the classical radiochemical method shows a good agreement when taking into account the associated uncertainties.

Development of methods for the preparation of radiopure 82Se sources for the SuperNEMO neutrinoless double-beta decay experiment

A radiochemical method for producing82Se sources with an ultra-low level of contamination of natural radionuclides (40K, decay products of232Th and238U) has been developed based on cation-exchange chromatographic purification with reverse removal of impurities. It includes chromatographic separation (purification), reduction, conditioning (which includes decantation, centrifugation, washing, grinding, and drying), and82Se foil production. The conditioning stage, during which highly dispersed elemental selenium is obtained by the reduction of purified selenious acid (H2SeO3) with sulfur dioxide (SO2) represents the crucial step in the preparation of radiopure82Se samples. The natural selenium (600 g) was first produced in this procedure in order to refine the method. The technique developed was then used to produce 2.5 kg of radiopure enriched selenium (82Se). The produced82Se samples were wrapped in polyethylene (12 μm thick) and radionuclides present in the sample were analyzed with the BiPo-3 detector. The radiopurity of the plastic materials (chromatographic column material and polypropylene chemical vessels), which were used at all stages, was determined by instrumental neutron activation analysis. The radiopurity of the82Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for208Tl was 8–54 μBq/kg, and for214Bi the detection limit of 600 μBq/kg has been reached.

An Efficient Radiochemical Method for Extraction of 226Ra From the Soil Samples

Background: Radium-226 is a radioactive element, with a very long half-life of 1600 years, producing radon gas. According to the United States Environmental Protection Agency, radon gas is the second most important factor causing lung cancer. Objectives: The purpose of this study was to separate 226Ra from the soil of high background radiation area by a radiochemical method for using in radon calibration chamber. Methods: 226Ra can be used in standard calibration chambers for calibration of radon detection systems. For this purpose, radiochemical method was used to extract radium from the soil with a high concentration of 226Ra. Four soil samples used in this study were selected from high background radiation areas of Ramsar, north of Iran. Equal amounts of samples were gathered from each region and ground. The specific activity of radium-226 was measured with HPGe detector. The highest specific activity of radium-226 (44.8 Bq/g) belonged to Talesh-Mahaleh. After radiochemical separation of 226Ra, the specific activity of extracted radium crystals was measured with the HPGe detector. Results: According to the results, the specific activity of 226Ra was found to be 94.97 Bq/g. Therefore, the specific activity of 226Ra was 2.12 times greater in the extracted crystals than in the original soil samples. Conclusion: The results indicate that using the radiochemical method proposed in this study, 226Ra can be extracted with an efficiency of 42%

241Am on the territories adjacent to the Belarusian sector of the Chernobyl NPP resettlement zone: soil contamination, foodstuffs and population internal dose assessment

241Am is the only radionuclide of Chernobyl radioactive fallout the content of which until 2058 continues to increase. The purpose of this work is to assess the 241Am internal exposure doses of residents of settlements on the territory adjacent to the resettlement lands of the Chernobyl nuclear power plant. To achieve this goal the current levels of 241Am and accompanying 137Cs content in the soil and foodstuffs were determined at the private settlements of the Bragin district of Gomel region of Belarus. 241Am (Eγ 59.6 keV) content in soil samples and 137Сs (Eγ 661 keV) content in soil/food samples were determined by gamma spectrometry. Determination of 241Am specific activity in food samples was performed by the radiochemical method using selective extraction-chromatographic resins. With an average level of 1.3 kBq/m2 , the maximum soil contamination density of 241Am can reach 3.6 kBq/m2 , and for 137Cs it is one or two orders of magnitude higher and ranges from 50 kBq/m2 to 350 kBq/m2 . The maximum specific activity of 241Am in products is determined in samples of leafy parsley – 33 mBq/kg, and in samples of potatoes, beets, onions per feather – not exceed 5 mBq/kg. The content of accompanying 137Cs in samples of plant products is in the range of 3-12 Bq/kg. In estimation of the internal dose of exposure by the food chain it is conservatively assumed that the population receives all the main components of the diet in their own farmstead. Calculation of the dose of internal exposure during inhalation is made under the assumption that the population performs work in the garden 4 hours a day for 7 months. The total expected dose of internal exposure from 241Am residents of settlements is dominated by the inhalation component, while the oral route is dominant in the formation of the total dose of internal exposure from concomitant 137Сs, which is 20 or more times higher than 241Am.

Technology Development on Reactor Dismantling and Investigation of Contamination in FUGEN

Advanced Thermal Reactor (ATR) FUGEN is the heavy water-moderated, boiling light water-cooled, pressure tube-type reactor. The commercial operation of FUGEN started on Mar. 1978 and terminated on Mar. 2003 and the decommissioning of FUGEN has been carried out since the decommissioning plan was approved in 2008. In order to perform the decommissioning work such as dismantling and decontamination safely and reasonably, technology development for the decommissioning has been promoted actively. This paper describes a part of technology development as follows. (1) Technology development on reactor dismantling The reactor of FUGEN is made of various materials such as stainless steel, carbon steel, zirconium alloy and aluminum which have relatively high activity concentration by operation for 25 years. With consideration of these characteristics, the reactor will be dismantled under water remotely in order to shield the radiation and prevent dust from migrating from water to air generated by the cutting considering the usage of zirconium alloy which is likely to be oxidized. In addition, laser cutting method whose features are fast cutting speed and less secondary waste in cutting will be applied for reactor dismantling. However, laser cutting method has no experiences to be applied to dismantlement of reactor facilities. Therefore, laser cutting for actual dismantled objects in air was demonstrated in controlled area in FUGEN using laser cutting system composed of articulated robot and laser cutting head. As a result, safety and applicability of laser cutting system was confirmed. From now on, primary cutting work in air, cutting demonstration with a relatively high dose rate and mock-up test in water for dismantling the actual reactor will be carried out. (2) Technology development on investigation of contamination It is necessary to evaluate radioactive inventory in the facilities accurately in order to reflect the evaluated data to dismantling plan appropriately. Therefore, the investigation of the contamination for the facilities has been carried out for safe and reasonable decommissioning work. The in-situ simple investigation method for the contamination of inner pipes which is mostly dominated by Co-60 is started to develop using the portable NaI(Tl) spectrometer. This method complements conventional investigation method to take samples from the pipes and to analyze them by radiochemical method to figure out the contamination of the whole facility.

Some Structural and Chemical Changes in Endocardial Endothelium of Rats in Emotional and Pain Stress Complicated by Hypercholesterolemia

The objective of the research was to study the content of some neutral lipids of endocardial endothelium in rats in relation to structural changes occurring in it, in the co-existence of emotional and pain stress, as well as alimentary hypercholesterolemia. Materials and methods. The electric-impulse model was used for stress modeling. Alimentary hypercholesterolemia was modeled feeding animals an atherogenic diet. The concentration of triacylglycerols, free and esterified cholesterol were examined using the method of thin-layer chromatography performed on silica gel. The concentration of free fatty acids was determined using the radiochemical method. The state of endocardial endothelium was studied with the help of light microscopy; the impression smears obtained from macro preparations of ventricle were analyzed.Results. In co-existence of stress and hypercholesterolemia, significant increase in free cholesterol as well as free fatty acid concentration was noticed. This essentially exceeded the analogical indices under the action of stress only. Structural changes in the endocardium followed by desquamation of separate endotheliocytes were the result of stress reaction. In the action of both pathogenic factors, this process was intensified; layer-by-layer exfoliation of endotheliocytes was observed. Conclusions. In acute emotional and pain stress, changes in lipid spectrum of membrane structures of endocardial endotheliocytes the main manifestation of which is the accumulation of free cholesterol in cells and increase in the levels of free fatty acids take place. The increase in the number of desquamated endothelial cells is the result of stress action as well. Alimentary hypercholesterolemia significantly increases such pathological changes.