Radiochemical Method Research Articles

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.

Methodological progress of 18F-labeled aromatic PET radiotracers

PET serves as one of the most advanced imaging modalities, and its development depends on the improvement of radiotracers. Among numerous positron isotopes, 18F appears to be the best radionuclide candidate for PET radiotracers by virtue of its favorable physical characteristics. 18F-labeled aromatic radiotracers have been widely investigated by researchers due to its special metabolic stability. However, the development and application of 18F-labeled aromatic radiotracers have been limited due to lacking of radiochemical methods to obtain products with high selectivity, high radioactivity and high purity. This review focuses on the new labeling methods of 18F-labeled aromatic radiotracers from the aspects of electrophilic and nucleophilic substitution reactions. Key words: Hydrocarbons, aromatic; Isotope labeling; Fluorine radioisotopes; Positron-emission, tomography; Trends

Radiohalogenation of Organic Compounds: Practical Considerations and Challenges for Molecular Imaging

In the last few decades, advances in molecular imaging technologies have had a major impact on many aspects of healthcare. In particular, radiohalogenated compounds have been used for non-invasive visualization of human anatomy, for the diagnosis of disease and in drug development programs. As a consequence of these advances, a range of novel synthetic radiochemical methods have been reported that allow more effective and efficient radiohalogenation from a broader range of precursors. In developing new radiochemical methods, special requirements are required to optimize the incorporation of highly radioactive, short-lived, isotopically labelled reagents. This article highlights the key practical considerations and challenges encountered when utilizing the most commonly used radiohalogens in nuclear medicine.1 Introduction2 Synthetic Challenges for Radiohalogenation2.1 Radiofluorination2.2 Radioiodination3 Conclusions and Future Outlook

Investigation on the impact of three different quaternary methyl ammonium cartridges on the radiosynthetic yields of [18 F]fluoromethyl tosylate.

Our recent investigations for the radiosynthesis of [18 F]fluoromethyl tosylate have highlighted that choice of quaternary methyl ammonium (QMA) cartridge used during the radiosynthesis can significantly impact the radiochemical yields. Often the details of the QMA cartridge used in fluourine-18 syntheses are not fully described. However, our studies demonstrate that the type, the size, and nature (method by which it has been conditioned) of the QMA cartridge used during the radiosynthesis can make a significant impact in the labelling efficiency. This paper investigates the use of three QMA cartridges and demonstrates that radiochemical yield (decay corrected) of [18 F]fluoromethyl tosylate can increase from 46% to 60% by simply changing the QMA cartridge (and leaving all other reagents and labelling conditions exactly the same). These learnings may be applied to improve the radiochemical yields of a number of [18 F]-fluorinated tracers (and synthons), where the labelling step is base-sensitive to increase the radiochemical yield, thereby significantly benefiting the radiochemistry and nuclear medicine community. This paper also highlights the necessity of the radiochemistry community to ensure the details of QMA cartridges used in fluorine-18 chemistry are fully and accurately described, since this will improve the translation of radiochemical methods from one laboratory to another.

PP#91 - Linking computational, spectroscopic, and radiochemical methods to design the next-generation of radiometal chelators

PP#91 - Linking computational, spectroscopic, and radiochemical methods to design the next-generation of radiometal chelators

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

Abstract A radiochemical method for producing 82Se sources with an ultra-low level of contamination of natural radionuclides (40K, decay products of 232Th and 238U) 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), and 82Se 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 radiopure 82Se 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 produced 82Se 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 the 82Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for 208Tl was 8–54 μBq/kg, and for 214Bi the detection limit of 600 μBq/kg has been reached.

An Overview of Analytical Methods for in Vitro Bioassay of Actinides.

The bioassay of urine and fecal samples has been used since the 1940s to determine an individual's uptake of uranium and actinide elements such as americium and plutonium. Over the years, several analytical separation methods and techniques have been employed for these types of analyses. Analytical separations, ranging from solvent extraction and anion exchange to chromatography, and analytical techniques, ranging from autoradiography to kinetic phosphorescence to fission-track analysis and high-resolution solid-state alpha spectroscopy, have been used at one time or another. Over the last few decades, there have been significant advances in radiochemical separations, as well as an increased use of mass spectroscopy, to determine trace and ultratrace levels of actinides in urine and fecal samples. This review summarizes and discusses developments in radiochemical separation methods and advancements in analytical techniques for actinide bioassay since the early 1940s to the present, followed by a recent development and trend in the bioassay of actinides-particularly in urine and fecal samples.

Comparison of two methods for the rapid radiochemical analysis of air dust samples in emergency situations

The reliable determination of airborne radionuclides in air is a key aspect in decision-making for the protection against public exposure in the event of a nuclear or radiological emergency. Nowadays, this needs to be done in real time and at the international level. These needs require the development of fast response protocols and the harmonisation of results.This work presents two fast radiochemical methods for the simultaneous separation of alpha and beta emitters in aerosols and their performance in a series of samples.

Radiochemical isolation method for the production of 52gMn from natCr for accelerator targets

We report a novel, precipitation-based method for the isolation of Mn from Cr targets for cyclotron production of 52gMn. The separation produces no-carrier-added 52gMn with a decay corrected radiochemical yield of 85 ± 3% and apparent molar activity for DOTA of 1.3 GBq/μmol. This method reduces stable metallic impurities in the purified 52gMn compared to previously reported chromatographic methods.

Chemistry for Positron Emission Tomography: Recent Advances in 11 C-, 18 F-, 13 N-, and 15 O-Labeling Reactions.

Positron emission tomography (PET) is a molecular imaging technology that provides quantitative information about function and metabolism in biological processes in vivo for disease diagnosis and therapy assessment. The broad application and rapid advances of PET has led to an increased demand for new radiochemical methods to synthesize highly specific molecules bearing positron-emitting radionuclides. This Review provides an overview of commonly used labeling reactions through examples of clinically relevant PET tracers and highlights the most recent developments and breakthroughs over the past decade, with a focus on 11 C, 18 F, 13 N, and 15 O.

An alternative methodology for the determination of the radiochemical purity of 11C-methionine

Background[11C]Methionine ([11C]MET) acts as an oncological radiopharmaceutical for measuring increased protein synthesis in brain tumours while having low uptake in normal brain an. In several Latin American countries, the official pharmacopoeias are the United States of America Pharmacopoeia (USP) and the European Pharmacopoeia (EP). For determination of the radiochemical purity, we used the monograph of L-methionine injection ([11C] methyl-methionine) of the EP (01/2002: 1617) because it is not available in the USP.We present herein an alternative methodology for the determination of the radiochemical purity, which allows the assessment of the [11C]CH3I and of the degradation radioactive products.ResultsThe proposed method enabled a greater number of impurities to be determined than could be identified using the EP method. Under the conditions proposed by EP, it is not possible to determine the presence of [11C]CH3I or other lipophilic radiochemical impurities in the final product.For the determination of enantiomeric purity according to EP a chiral thin-layer chromatography (TLC) allows the determination of D and L methionine between the established limits. This is a slow method and presents an inadequate detection due to the decay of the sample. An alternative HPLC method was optimized.ConclusionThe proposed radiochemical purity method allowed the identification of a greater number of radiochemical impurities compared to the method proposed by the EP monograph in 16 min.The proposed enantiomeric purity method enables to perform the determination in a reasonable amount of time.A discussion concerning the limit of 95% radiochemical purity proposed by the EP is necessary. If more radiochemical impurities can be detected, it is more reasonable to propose a limit of 90% for this parameter to perform clinical examinations.

Rapid procedure for actinides and 90Sr analysis in emergency urine spot samples applied in the GHSI-RNWG emergency intercomparison exercise

A rapid radiochemical separation method for quantification of 90Sr, plutonium, americium, curium, uranium and thorium isotopes in urine spot samples has been developed. The validation and suitability of the method has been tested in the emergency intercomparison exercise organised by the Global Health Security Initiative/Radio-Nuclear Threats Working Group. Excellent results were obtained with bias of −0.07 (239Pu) and −0.11 (90Sr). CIEMAT Laboratory also fulfilled the established reporting schedule and submitted the results within 72 hours, as required.

Chemiluminescence-based aptasensors for various target analytes.

Aptamers (DNA or RNA) have complex three-dimensional shapes that can bind to specific targets. Relative to antibodies, aptamers benefit from their low cost of production, easy chemical modification, high chemical stability, reproducibility, and low levels of immunogenicity and toxicity. However, the true value of aptamers lies in their simplicity by which these molecules can be engineered into sensors as bio-recognition elements in diagnostics, drug discovery and therapy, environmental monitoring and food quality testing, etc. Many different types of techniques, such as optical, electrochemical, radiochemical and piezoelectronic methods, have been applied for the design of aptamer-based methods, in which chemiluminescence (CL) detection techniques have become very popular in recent years. This review focuses on the recent advances in the development of aptamer-based CL sensors for different target detection. We highlight specific examples that showcase the use of aptamers in practical applications, and provide the challenges and opportunities in this promising field.

Radio-green chemistry and nature resourced radiochemistry

The birth of green chemistry in 1990 influenced every branch of sciences including radiochemistry. The development of new radiochemical methods is now dictated by the green chemistry mandates, especially in terms of choosing solvents and reagents. Though there are numbers of environmentally benign reagents and solvents, but sometime atom economy is not fully maintained in the manufacturing process. A newer trend is to use chemicals from natural resources. This new trend in radiochemistry may be termed as “Nature Resourced Radiochemistry”. The development in last two decades in “Radio-green Chemistry” and “Nature Resourced Radiochemistry” has been briefly discussed in the review.

FUKUSHIMA FALLOUT IN SAKHALIN REGION, RUSSIA, PART 3: 137CS AND 134CS IN COW’S MILK

The study was conducted on Kunashir, Shikotan and Iturup Islands (Sakhalin Region of Russia) in order to evaluate the impact of the Fukushima accident on the “soil–grass–cow’s milk” exposure pathway. A total of 22 samples of cow’s milk were collected in the May 2011 – September 2012 period. Radiocaesium was isolated from thermally treated specimens using the antimony–iodide radiochemical method. The activity concentrations of 134Cs and 137Cs were measured by γ-ray spectrometry using high purity germanium detectors. Caesium-134 was detected in 18 of the total 22 samples of milk. The activity concentration of 134Cs in the samples varied from 0.08 Bq kg–1 to 2.00 Bq kg–1. Caesium-137 was quantified in all 22 samples: range = 0.088–2.43 Bq kg–1. On average, more than a half of the total 137Cs in the milk samples from Sakhalin Region was of Fukushima origin (mean = 60%, median = 57%, range = 13–95%). The highest activity concentrations and values of the soil–to–milk aggregated transfer coefficient, Tag, for 134Cs (and Fukushimaderived 137Cs) were observed in milk samples collected in mid-May 2011. The mean Tag values decreased in the May–October period of 2011 from 12 × 10−3 m2 kg–1 to 2.3 × 10−3 m2 kg–1. In September 2012, the Tag values remained unchanged (mean = 2.8 × 10−3 m2 kg–1) compared to those in September–October 2011. In the autumns of 2011 and 2012, the calculated values of Tag for Fukushima-derived radiocaesium were on average 17 times larger than the ones for pre-Fukushima 137Cs. The higher transfer of Fukushima-derived 137Cs (compared to pre-Fukushima 137Cs) for milk reflected the difference between the “new” and “aged” radiocaesium in the intensity of the radionuclide transfer from soil to grassland plants which were the major component of the cow’s diet in the area of our study. The ratio between the 137Cs activity concentration in the milk (fresh weight) and that in the grassland plants (dry weight) ranged from 0.028 to 0.11. The effective dose from ingestion of Fukushima-derived radiocaesium in locally produced cow’s milk for critical group of adult residents of the southern Kuril in the first year after the accident is conservatively estimated as 0.0027 mSv. The Fukushima accident has had a negligible impact on radiocaesium contamination of cow’s milk and the corresponding human exposure on the southern Kuril Islands: Shikotan, Kunashir and Iturup .

Simplified and automatable radiochemical separation strategy for the production of radiopharmaceutical quality 86Y using single column extraction chromatography

We present a simplified, automatable single-column radiochemical separation method using the extraction chromatographic branched-DGA resin for the production of no-carrier-added 86Y with a radiochemical yield higher than 95%, an apparent molar activity of 1.4 ± 0.4 Ci/μmol (DOTA) and 2.3 ± 0.7 Ci/μmol (DTPA), and a run-to-run recycling efficiency of the isotopically-enriched target of 98 ± 1%. These results enable the preparation of 86Y radiopharmaceuticals for 86Y/90Y-based cancer theranostic applications.

Development of 231Pa AMS measurements to improve radiological dose assessment from uranium mining and milling

Limited information exists on the movement and partitioning of 235U series radionuclides following their release to the environment from activities associated with the nuclear fuel cycle. Only three isotopes in the series, 235U, 231Pa and 227Ac, have half-lives greater than a month. The extent to which the radiologically-significant isotopes of the 235U series differentiate and fractionate in the environment, and then accumulate in biota, is largely controlled by the chemical properties of these three elements and by their biological uptake. This is particularly the case for biota with life cycles in the order of years. There is therefore potential for changes in the radiation dose received by humans and the environment during, for example, the operational and post-remediation phases of uranium mining practices, particularly where mine sites revert to traditional land uses such as hunting, fishing and camping.Natural activity concentrations of 235U are ∼20 times lower than for 238U. In an environmental context, however, the radiation dose that arises from subsequent members of the 235U decay chain will be determined by their abundance distribution and can exceed that from the 238U series. The half-lives of the protactinium isotopes allow only 231Pa to accumulate independently of its parent radionuclide along the transport pathways and/or through preferential uptake by biota. In particular, 231Pa could make a disproportionately high contribution to the dose if it is preferentially transported and/or taken up.The AMS technique is capable of assessing accumulation of 231Pa in natural environmental samples. We report on a new, safer radiochemical extraction method to prepare the 233Pa isotopic tracer (one that does not use hydrofluoric acid), and on the development of 231Pa AMS measurements at the Australian National University.

Comparison of solvent extraction and extraction chromatography resin techniques for uranium isotopic characterization in high-level radioactive waste and barrier materials

The development of Deep Geological Repositories (DGP) to the storage of high-level radioactive waste (HLRW) is mainly focused in systems of multiple barriers based on the use of clays, and particularly bentonites, as natural and engineered barriers in nuclear waste isolation due to their remarkable properties.Due to the fact that uranium is the major component of HLRW, it is required to go in depth in the analysis of the chemistry of the reaction of this element within bentonites. The determination of uranium under the conditions of HLRW, including the analysis of silicate matrices before and after the uranium-bentonite reaction, was investigated. The performances of a state-of-the-art and widespread radiochemical method based on chromatographic UTEVA resins, and a well-known and traditional method based on solvent extraction with tri-n-butyl phosphate (TBP), for the analysis of uranium and thorium isotopes in solid matrices with high concentrations of uranium were analysed in detail.In the development of this comparison, both radiochemical approaches have an overall excellent performance in order to analyse uranium concentration in HLRW samples. However, due to the high uranium concentration in the samples, the chromatographic resin is not able to avoid completely the uranium contamination in the thorium fraction.

RESULTS OF COMPREHENSIVE RADIOLOGICAL - HYGIENIC MONITORING IN SOME SETTLEMENTS OF RADIOLOGICALLY CONTAMINATED AREAS IN RIVNE REGION IN 2017.

Identification of the main factors of radiation exposure formation in the residents of surveyed settle-ments of radiologically contaminated territories in Rivne region and estimation of radiation doses in population ata current stage of the accident. Comprehensive radiological and hygienic monitoring was conducted within 7 settlementsof the Rokytnivsky district of Rivne region, namely in the Stare Selo, Vezhytsya, Perehodychi, Drozdyn', Berezove,Zabolottya, and Hrabun' villages. Assay of the incorporated 137Cs was held using a whole-body counter in residentsof the villages twice a year, i.e. in May and October. Basic foodstuffs were sampled for the assay of 90Sr and 137Cs alongwith interview of residents about the foodstuff consumption. External radiation doses were estimated. Mathe-matical, dosimetric, and radiochemical methods were applied. The annual effective exposure doses of population in the surveyed settlements of Rivneregion in the year of study were formed at the expense of internal exposure doses ranging from 0.13 mSv · year-1 to0.32 mSv · year-1, which is below the criterion for radiologically contaminated territories. It has been establishedthat the incorporation of 137Cs by the inhabitants is a principal factor of the internal radiation dose formation. The 137Cs incorporation occurs through the consumption of such basic foodstuffs as milk and forest products, primarilymushrooms, which traditionally occupy a significant part of the diet in the Polissya area. The 137Cs content in thevast majority of milk and mushroom samples significantly exceeded the permissible levels (PL). The maximum con-tent of 137Cs in the collected milk samples was 384.7 Bq · L-1, which is 4 times higher than PL, and 36.9 kBq · kg-1 indried mushrooms being 15 times higher than PL. The existing radiation and ecological situation in the areas that were exposed to radioactive contam-ination as a result of the Chornobyl disaster requires the continuation of monitoring of levels of radioactive con-tamination of foodstuffs, especially collected in forests, and doses of radiation exposure of the population.

Radioactivity level and concentration of metals in waters around power plants application of potential method for pollution assessment

Human activities may lead to increased levels of naturally occurring radioactive material and heavy metals in waters relative to undisturbed natural environment, consequently to reduced safety of environment. Therefore, evaluation of water quality from coal-fired power plants is essential to both environmental protection and protection of the human health. In this paper the concentrations of metals (K, Sr, and Pb) and corresponding radionuclides (40K, 90Sr, and 210Pb) for 22 water samples in the vicinity of five coal-fired power plants in Serbia were determined. The total metal concentrations were measured using an atomic absorption spectrometer. The activities of radionuclides 40K and 210Pb were determined by gamma spectrometry using HPGe detector, while the activity of 90Sr was determined by radiochemical analytical method and measured using low-level gas proportional counter. The water pollution status was assessed by the prospective method that is defined in this study. The preliminary results indicated that operation of the coal-fired power plants has no significant impact on the surrounding environment with regard to the radiological characteristics and content of metals of the investigated waters that can be used for suitable in future applications.