Radiochemical Method Research Articles

Targetry for the in-beam activation of tracer particles for positron emission particle tracking

Positron emission particle tracking measures the trajectory of a single radioactively labelled tracer particle by coincident detection of emitted annihilation photons. The technique enables the non-invasive study of dense opaque flows, with the tracer acting as a small neutrally buoyant flow-follower. The University of Cape Town has established a PEPT facility at iThemba LABS, utilising tracer particles produced through radiochemical methods, and measured using adapted positron tomographs. An activation approach producing the positron emitter 18F inside glass target spheres of diameter between 5.0 and 10 mm using accelerated beams of alpha-particles has been explored. The reaction 16O(O, x)18F is used, exploiting the high concentration of natural oxygen and the correspondingly high cross-sections for 18F formation. A standard target holder for the batch production of radionuclides at iThemba LABS was modified, reducing the entrance window thickness, allowing ingress of circulating cooling water, and adapted for a primary tparticle beam of 100 MeV energy delivered by the separated sector cyclotron (SSC) of iThemba LABS. Two-hour bombardment at nominal beam current 0.8 eµA produced activities up to ~ 110 MBq (3 mCi), with over 95% of the activity being 18F.

Preliminary development of a radiochemical separation method to determine 135Cs and 135Cs/137Cs isotopic ratio by a non-radiometric technique

Preliminary development of a radiochemical separation method to determine 135Cs and 135Cs/137Cs isotopic ratio by a non-radiometric technique

The Role of Adrenoreceptors and Calcium Ions in the Pathogenesis of Endocardium Endothelium Damage of Rats Under Stress Action on the Background of Hypercholesterolemia

Abstract. Topicality. Endothelial dysfunction is a key link in the pathogenesis, formation and progression of clinical manifestations of a significant number of cardiovascular system diseases. Some pathogenetic links and structures associated with morphofunctional disorders of cardiac endothelial cells under the stress conditions and its combination with hypercholesterolemia need further examination.
 The aim of the study was to investigate the role of adrenoreceptors and calcium ions (by using of adrenoreceptors and Ca2+-channels blockers) in the pathogenesis of endocardium endothelium damage (by the content of free fatty acids in it and the number of exfoliated cells) as a result of emotional and pain stress action and its influence on the background of hypercholesterolemia.
 Materials and methods of research. An electro-pulse model was used for stress reproduction. The alimentary hypercholesterolemia was simulated by keeping animals on an atherogenic diet during 2 months. To establish the role of the above-mentioned cellular structures in the mechanisms of endothelial cell damage, the following pharmacological drugs were administered to animals: β-adrenoblocker, α-adrenoblocker and Ca2+-channel blocker. The endocardium endothelium state was studied by using light microscopy, by analyzing the smears-imprints from macropreparations of ventricles by counting the number of endothelial cells in them. The content of free fatty acids was determined by radiochemical method.
 Research results. It has been shown that β-adrenoblocker and Ca2+-channel blocker significantly limit the damage of endocardium endothelium of left ventricle under the action of emotional and pain stress, and to a much lesser extent, the same effect has α-adrenoblocker. The protective effect of mentioned preparations under the action of stressor factor against the background of alimentary hypercholesterolemia significantly decreases.
 Conclusions. The obtained data, their analysis and comparison with the results of other experimental and clinical studies allow to make certain conclusions about the pathogenesis of endothelial dysfunction under emotional stress, as well as under conditions of its combination with hypercholesterolemia. In particular, an important link in the development of structural and some biochemical changes of endocardial endothelial cells is the toxic effect of catecholamines, which affect the organism’s functional systems mainly by β-adrenoreceptors (involving Ca2+ ions), to a lesser extent – by α-adrenoreceptors.
 Key words: endocardium, stress, hypercholesterolemia, adrenoreceptors, calcium.

Stages of radiation monitoring on the territory of the Tula region affected in consequence of the Chernobyl NPP accident

More than half of the Tula oblast territory was contaminated following the accident at the Chernobyl nuclear power plant. This article describes the stages of radiation hygiene monitoring of objects in the habitat in the Tula region impacted by radioactive contamination. Information is given on changes in radioactively contaminated areas at different periods after the accident. An assessment is made of the radiological situation at the initial “iodic” period of the accident, the subsequent “cesium” period, and at the current stage. A description is given of work done by the oblast’s state sanitary and epidemiological service based on radiation monitoring results for reducing the radiation exposure of the population at different stages of supervision. Information is supplied on high levels of gamma background up to 35 mkSv/h during the “iodic” period. Tabulated data are supplied on exceeding the tentative maximum permissible level of iodine-131 content in dairy products produced in Plavski district, the most contaminated area in the region. Data are given on laboratory tests on food products for total beta activity in 1986-87 and the frequency of exceeding the permissible level of cesium-137 content during 1986. The above permissible content of radionuclides in food products was registered only in 1986 due to surface contamination of plants, while in wild mushrooms this took place as late as 2004. Currently, the proved content of cesium-137 and strontium-90 in food products is determined only by the radio-chemical method. A table is supplied showing results of radio-chemical research on major dose contributing food products from 2010 to 2021. The article supplies a table with numeric values of annual average effective doses of radiation sustained by the population of settlements located in the Chernobyl radioactively contaminated zone during 1986 through 2021. The dose of the population’s exposure to the Chernobyl radiation since 1994 does not exceed 1 mSv/year. In 2021, the population’s annual effective dose in 98.3% of settlements amounted to less than 0.2 mSv/year.

Вариация поглощенной дозы облучения дикого кабана, обитающего на территории радиоактивного загрязнения

The article presents the results of the assessment of the absorbed dose rate from incorporated radionuclides of 137Cs and 90Sr in the body of wild boar living in an area with different levels of radioactive contamination. The internal irradiation dose was evaluated for incorporated 137Cs in muscle and 90Sr in bone tissue of wild boar. During the assessment, it was assumed that radionuclides 137Cs uniformly distributed in the tissue and are in equilibrium conditions, and radionuclides are 90Sr concentrated in the bone tissue of the animal, during the year the concentration of radionuclides is assumed to be constant. In total, samples were obtained from 117 wild boar individuals, among which 87 animals were seized in the exclusion zone and 30 in the resettlement zone. From the animal carcass, spot samples of muscle tissue were taken according to 500 ± 50 g, the 137Cs content in the samples was determined for raw, natural mass. The activity of 90Sr in bone tissue was determined by radiochemical method. As a result of the studies, it was found that the average total exposure dose of wild boar seized in the exclusion zone is twice that of animals seized in the resettlement zone (p < 0,05) and amounted to 653,6 ± 73,5 mGy/day for animals harvested in the exclusion zone and 328,8 ± 31,4 mGy/day for wild boar living in the zone resettlement. Analysis of the coefficients of variation showed that the maximum variation is observed among the values of the absorbed dose of radiation from the incorporated 137Cs in animals that were seized in the exclusion zone. The minimum variation rate occurs with respect to the external exposure dose in animals harvested in the resettlement zone. There is no significant difference (p < 0,05) between the median absorbed dose of exposure of wild boars living in the exclusion zone and the resettlement zone. The result of our studies suggests that the density of contamination is not the main factor determining the formation of an animal’s radiation dose.

Визначення активності 63Ni в конструкційних матеріалах АЕС

The γ-spectra were measured of the structural materials of the 2nd unit of the Chornobyl NPP which were irradiated by bremsstrahlung with end-point energy 37 MeV. Using the ratio of the 57Co and 58Co activities, the nickel and cobalt masses ratio was determined. Using the obtained data and the measured 60Co activity in the studied samples, a method for determining of the 63Ni activity was developed. Radiochemical validation of the created method was performed and good quantitative agreement of 63Ni activities obtained by spectroscopic and radiochemical methods was obtained.

129I in sediment cores from the Celtic Sea by AMS through a microwave digestion process

Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH2-NH2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH2OH·HCl) and sodium bisulfite (Na2S2O5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in solution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine-129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores.

Determination, Separation and Application of 137Cs: A Review.

In the context of the rapid development of the world’s nuclear power industry, it is necessary to establish background data on radionuclides of different samples from different regions, and the premise of obtaining such basic data is to have a series of good sample processing and detection methods. The radiochemical analysis methods of low-level radionuclides 137Cs (Cesium) in environmental and biological samples are introduced and reviewed in detail. The latest research progress is reviewed from the five aspects of sample pretreatment, determination, separation, calculation, application of radioactive cesium and the future is proposed.

Investigation of the chemical and radiation stability of titanium dioxide with surface arsenate groups during 90Sr adsorption

The chemical and radiation stability of titanium dioxide with surface arsenate groups during 90Sr adsorption has been studied. The oxalate technique has been used to obtain a solution containing 90Sr from the objects of the aquatic environment of the Chornobyl Exclusion Zone. The dependence of the strontium adsorption on the acidity of the solution and the initial activity of the solution (Bq per mL) has been shown. SEM, XRF, and EDS spectroscopy confirm the chemical resistance of 4As–TiO2 during regeneration. According to the study with 90Sr, the decrease in the adsorption capacity of 4As–TiO2 during regeneration is associated with incomplete leaching of strontium from 4As–TiO2 micropores.Using an electron accelerator, the radiation resistance of titanium dioxide with surface arsenate groups to β- -particles with an energy of 1 MeV has been studied. The invariability of the elemental composition and adsorption properties of 4As–TiO2 at irradiation doses of 5·107Sv testifies to the high radiation resistance of 4As–TiO2. The result obtained indicates the promise of 4As–TiO2 for improving radiochemical methods.

Description of strontium precipitation in highly concentrated nitric acid

The precipitation of strontium in highly concentrated nitric acid is often used in standard radiochemical methods for 90Sr separation. In this work, the description of Sr behavior in such conditions was studied in the point of speciation simulation. Standard speciation method based on Phreeqc software was considered but two problems underlined the limits of this approach to study this process: inappropriate ionic strength correction model (for I > 10 M) and the particular dissociation of nitric acid. To overcome these issues, a multipurpose-fitting routine, Minuit, was used to fit chemical model parameters. A polynomial expression was also added to the model in order to take into account nitric acid dissociation. This alternative was proved successful to calculate the Sr precipitate in highly concentrated nitric acid. Comparison was made with the results obtained with Design of Experiment methodology.

Radiochemical Procedure for Measurement Specific Activities of Uranium Isotopes in Asphaltite Bioleaching Liquor by Alpha-Particle Spectrometry

An analytical procedure for the alpha-source preparation is investigated in the study to determine uranium radioisotopes specific activities in the bioleaching liquor leach from asphaltite samples taken from the Silopi region in Türkiye. The purpose is to develop a new radiochemical method that can provide the alpha-particle spectrometry requirements. The proposed analytical procedure includes sample preparation, radiochemical purification of uranium from bioleaching liquor, alpha-source preparation on a substrate and alpha-particle spectrometric analysis of isolated uranium. The method is valid for availability using the z-test, relative bias, and relative uncertainty outlier tests. The results show that the proposed analytical procedure is successfully implemented for measuring the activity concentration of uranium with high accuracy and precision in the bioleaching liquor.

Improvements in the radiochemical method for separating 226Ra in solid samples through coprecipitation with BaSO4

The aim of this work was to improve the commonly used method for 226Ra determination in water and to establish its application in solid samples. This method is based on the coprecipitation of Ra with BaSO4 and gross alpha counting of the precipitate. An exhaustive study of the coprecipitation behaviour of the most abundant cations present in solid samples was performed to avoid incorrect radiochemical yields. As a result, it was considered necessary to introduce two new purification steps into the conventional method. Likewise, two nuclides, 241Am and 226Ra, were compared to obtain the mass efficiency curve given their different behaviour in the coprecipitation process. While Ra behaves similarly to Ba, Am coprecipitates, forming mixed crystals that may behave differently in the self-absorption process. The influence of the cations on the chemical yield with no precipitate purification was: Sr2+≫Fe3+>Mg2+≈Ca2+>K+≈Na+. The method was successfully applied to soil, sediment, and plant ash samples.

Development of a rapid technique for sequential separation of plutonium/americium in nasal swab using solvent extraction and liquid scintillation spectrometry

A rapid radiochemical method has been developed for estimation of plutonium and americium in nasal swab using extractive liquid scintillation spectrometry. The method involves solvent extraction of plutonium and americium from pre-treated nasal swab using 0.2 M Di-(2-ethylhexyl)phosphoricacid prepared in toluene scintillator & back extraction of americium in aqueous phase using 0.35 M HNO3. Activity assessment was carried out using liquid scintillation spectrometry. Overall recovery obtained was 96% for plutonium and 76% for americium with a sample turnaround time of 3 h.

The role of chemistry in accelerator-based production and separation of radionuclides as basis for radiolabelled compounds for medical applications

Abstract Radiochemical separations used in large scale routine production of diagnostic and therapeutic radionuclides at a particle accelerator for patient care are briefly outlined. The role of chemistry at various stages of development of a production route of a novel radionuclide, namely nuclear data measurement, high-current targetry, chemical processing and quality control of the product, is discussed in detail. Special attention is paid to production of non-standard positron emitters (e.g. 44gSc, 64Cu, 68Ga, etc.) at a cyclotron and novel therapeutic radionuclides (e.g. 67Cu, 225Ac, etc.) at an accelerator. Some typical examples of radiochemical methods involved are presented.

Determination of strontium radioisotopes in routine and emergency samples

We present the radioanalytical strategies used for the determination of strontium radioisotopes in routine and emergency samples. While in routine monitoring, the main goal is to achieve limits of detection as low as possible. In emergency, priority is given to the rapid procurement of data about a contamination. The parameters accuracy, precision and detection limit of the radiochemical methods are shown. We present the results obtained over the past 22 years in proficiency tests and in the analysis of reference materials.

DISTRIBUTION OF TRITIUM IN SURFACE WATER AND PRECIPITATION IN RILA MOUNTAIN, BULGARIA

A study of the tritium content of surface water from three Rila lakes – Moussala lake, Aleko lake and Ice lake, and precipitation at Moussala mount has been performed by means of high precision nuclear and radiochemical methods. The measurements are part of a long-term environmental monitoring program developed and maintained by the Institute for Nuclear Research and Nuclear Energy, Bulgaria Academy of Science. The results for lake water and precipitation samples collected at Moussala part of Rila over the period 2012–2017 were found to range from ˂ 1.20 to 2.77 Bq.L-1 and from 2.14 to 4.12 Bq.L-1 respectively. The content of 3H in all samples is below the recommended level of 100 Bq.L-1. The obtained new results are used to assess the radiation status of the investigated water sources and can be used for evaluation of possible future changes and trends.

Selectivity analysis of 99Tc determination by LSC in the field of nuclear decommissioning

In this work, two Tc radiochemical isolation methods—a conventional method by Triskem TEVA® resin and a rapid method by Empore™ Tc Rad Disk—are compared in the field of nuclear decommissioning and 99Tc assessment. The conventional method results more selective than the rapid one, being able to remove almost 100% of the main radiological interferers with the exception of the 90Y; however, the rapid method obtains higher chemical yields (97% vs. 80%) and slightly lower detection limits (0.025 Bq vs. 0.030 Bq) than the conventional. Both methods are similar with regards to equipment and reagent costs.

URANIUM AND 210PO RADIONUCLIDES IN DRINKING WATER IN SOUTHERN BULGARIA AND EXPECTED RADIATION DOSES.

The activity concentrations of the naturally occurring radionuclides 238U, 234U and 210Po have been determined for the first time in drinking water from certain sources in Southern Bulgaria using nuclear and radiochemical methods. The results obtained for the water samples vary in the intervals 0.6-678 mBq l-1 for 238U, 1.4-1484 mBq l-1 for 234U, <0.3-13.6 mBq l-1 for 210Po and 1.04-10.6 for the 234U/238U ratio. The annual effective dose from 238U, 234U and 210Po ranges from 1.09 to 44.1μSv y-1, 0.78 to 46.8μSv y-1 and 0.77 to 62.8μSv y-1 for infants, children and adults, respectively. The annual effective dose due to consumption of drinking water is below the individual dose criterion of 100μSv y-1 recommended by the World Health Organization. The natural radioactivity of the water sources investigated is below the national and international limits.

Multi-patient dose synthesis of [18F]Flumazenil via a copper-mediated 18F-fluorination

BackgroundFlumazenil (FMZ) is a functionally silent imidazobenzodiazepine which binds to the benzodiazepine binding site of approximately 75% of the brain γ-aminobutyric acid-A receptors (GABAARs). Positron Emission Tomography (PET) imaging of the GABAARs with [11C]FMZ has been used to evidence alterations in neuronal density, to assess target engagement of novel pharmacological agents, and to study disorders such as epilepsy and Huntington’s disease. Despite the potential of FMZ PET imaging the short half-life (t1/2) of carbon-11 (20 min) has limited the more widespread clinical use of [11C]FMZ. The fluorine-18 (18F) isotopologue with a longer t1/2 (110 min) is ideally suited to address this drawback. However, the majority of current radiochemical methods for the synthesis of [18F]FMZ are non-trivial and low yielding. We report a robust, automated protocol that is good manufacturing practice (GMP) compatible, and yields multi-patient doses of [18F]FMZ.ResultsThe fully automated synthesis was developed on the Trasis AllinOne (AIO) platform using a single-use cassette. [18F]FMZ was synthesized in a one-step procedure from [18F]fluoride, via a copper-mediated 18F-fluorination of a boronate ester precursor. Purification was performed by semi-preparative radio-HPLC and the collected fraction formulated directly into the final product vial. The overall process from start of synthesis to delivery of product is approximately 55 min. Starting with an initial activity of 23.6 ± 5.8 GBq (n = 3) activity yields of [18F]FMZ were 8.0 ± 1 GBq (n = 3). The synthesis was successfully reproduced at two independent sites, where the product passed quality control release criteria in line with the European Pharmacopoeia standards and ICH Q3D(R1) guidelines to be suitable for human use.ConclusionReported is a fully automated cassette-based synthesis of [18F]FMZ that is Good Manufacturing Practice (GMP) compatible and produces multi-patient doses of [18F]FMZ.

Synthetic diversity in the preparation of metallic uranium.

Uranium metal is associated with several aspects of nuclear technology; it is used as fuel for research and power reactors, targets for medical isotope productions, explosive for nuclear weapons and precursors in synthetic chemistry. The study of uranium metal at the laboratory scale presents the opportunity to evaluate metallic nuclear fuels, develop new methods for metallic spent fuel reprocessing and advance the science relevant to nuclear forensics and medical isotope production. Since its first isolation in 1841, from the reaction of uranium chloride and potassium metal, uranium metal has been prepared by solid-state reactions and in solution by electrochemical, chemical and radiochemical methods. The present review summarizes the methods outlined above and describes the chemistry associated with each preparation.