Hasil untuk "Radioactivity and radioactive substances"

Qing Wang, Kezheng Lei, Zhiyang Zhu et al.

Phillip Imgram, Dinko Atanasov, Michail Athanasakis-Kaklamanakis et al.

We present two newly constructed experimental setups - REBEL (Resonant Excitation of Beams with Electromagnetic fields and Lasers) and STRIPE (Stopping and Trapping of Radioactive Isotopes for Precision Experiments) - integrated into a single offline beamline at KU Leuven. REBEL is designed for collinear laser spectroscopy of ion bunches following isobaric separation with a multireflection time-of-flight mass spectrometer, enabling high-sensitivity measurements of mass-selected fast-ion beams. In contrast, STRIPE focuses on the deceleration, trapping, and laser cooling of ions in a segmented linear Paul trap, optimized for long interrogation times and precision spectroscopy. The shared infrastructure features stable high-voltage operation ($<10$ ppm), modular vacuum sections, and a fast-beam switchyard to route ions to either experiment. Initial results include a mass-resolving power of $R \approx 12900$ in REBEL and successful ion trapping and laser cooling of ions with a kinetic energy of 10 keV in STRIPE, with improved performance achieved using a frequency-modulated cooling laser. This dual-system platform enables the development and benchmarking of advanced spectroscopy and trapping techniques and is compatible with future operation at radioactive ion beam facilities.

Carlo Broggini, Giuseppe Di Carlo, Luca Di Luzio et al.

We propose to investigate the time modulation of radioisotope decays deep underground as a method to explore axion dark matter. In this work, we focus on the $α$-decay of heavy isotopes and develop a theoretical description for the $θ$-dependence of $α$-decay half-lives, which enables us to predict the time variation of $α$-radioactivity in response to an oscillating axion dark matter background. To probe this scenario, we have recently constructed and installed a setup deep underground at the Gran Sasso Laboratory, based on the $α$-decay of Americium-241. This prototype experiment, named RadioAxion-$α$, will allow us to explore a broad range of oscillation's periods, from a micro-second up to one year, thus providing competitive limits on the axion decay constant across 13 orders of magnitude in the axion mass, ranging from $10^{-9}$ eV to $10^{-20}$ eV after one month of data collection, and down to $10^{-22}$ eV after three years.

Vanderlei Vilaça Moura, Talita Santos, Claubia Pereira

This study presented the recovery of uranium oxide and thorium oxide from aluminothermic slag from the metallurgical processing of columbite – a niobium/tantalum mineral with the presence of U3O8 and ThO2 – from a mining-industrial facility. The methodology consisted of sampling, comminution, and leaching using sulfuric acid. The head sample showed contents of (1.78 + 0.14) % for U3O8 and (3.66 + 0.04) % for ThO2. The metallurgical recovery reached values above 80% for the uranium oxide and above 70% for the thorium oxide for pH < 1.5 and process time greater than eight hours.

D. B. Monteiro, J. R. Maiorino

The suitable cooling of fuel elements in a nuclear reactor is an important requirement that must be met to avoid that the fuel temperature rises above the safety limits according to the reactor design. During the reactor operation, there are transients that could lead to a temperature that overcomes these limits, such as those related to the cooling system. The CFD codes are tools that could aid in the understand of the phenomenon during such transients, allowing to access details of the flow that are not possible, or are possible only with limitations, by using other kind of codes or experiments. In the present work, the results obtained using ANSYS-CFXÒ code for the IEA-R1 reactor during a steady state and transient of slow loss of cooling accident event are presented. The results obtained shown a good agreement with experimental data reported and works that used this reactor as case of study. These results are part of a research in which the main objective is to simulate the flow of the coolant in the fuel element channels during transients. These results would support an initial analysis of the flow during the transition from forced to natural convection that occurs when the coolant flow falls below a settled value and the valve on the bottom of the core opens by gravity, aiming to understand better phenomena involved and the limitations of the models available in the ANSYS-CFXÒ code.

Haiyan Du, Chengbo Du, Ke Han et al.

Low radioactive material screening is becoming essential for rare event search experiments, such as neutrinoless double beta decay and dark matter searches in underground laboratories. A gaseous time projection chamber (TPC) can be used for such purposes with large active areas and high efficiency. A gaseous TPC with a Micromegas readout plane of approximately 20$\times$20 cm$^2$ is successfully constructed for surface alpha contamination measurements. We have characterized the energy resolution, gain stability, and tracking capability with calibration sources. With the unique track-related background suppression cuts of the gaseous TPC, we have established that the alpha background rate of the TPC is 0.13$\pm$0.03 $μ$Bq/cm$^2$, comparable to the leading commercial solutions.

Thomas Ferreira da Costa Campos, Kenji Freire Motoki, Valéria Fonsêca da Silva Pastura et al.

This research had the objective of studying the absorbed dose of the street corner intersections from the South zone of Natal city, Brazil. This city grew up on dune lands, on siliciclastic rocks from Barreiras Formation, these dunes are quartz-sand and have heavy mineral layers bearing uranium and thorium (monazite, xenothymeo, thorianite, ilmenite, rutile, zircon, magnetite and columbite-tantalite). Not all streets in Natal city have paving, in the part with more movement they have asphalt covering over cobblestone, in the less busy have cobblestone covering, and in the quiet streets are in natural dune sand. In situ Gamma radiation measurements were performed with three portable spectrometers model RS-230 with BGO crystal, about 1 meter above the ground. The absorbed dose ranged from 11 to 150 ƞGy/h (MG: 40; Median: 39; SD: 18). In gamma spectrometry measure, Uranium varied between 0.1 to 6.2 Eq.A. ppm (MG: 1.6; Median: 1.4; SD: 1), Thorium between 0.7 to 32 Eq.A. ppm (MG: 6; Median: 5; SD: 3.3), Potassium ranged between 0.1 to 3.9 Eq.A. % (MG: 1.2; Median: 1.2; SD: 0.7). The values ​​of the absorbed dose of external radiation measured in the studied street corners show values lower than the world average of 59 ƞGy/h, and annual effective dose is also lower than the global average value of 0.48 mSv/a. Areas with higher U-K contents correspond to areas with asphalt/cobblestone capping, while areas with higher Th contents correspond to sandy streets and dunes in protected areas. This fact denote a lower radiometric risk to the population.

Mariana Yuamoto, Rochelle Lykawka, Iana Quintanilha de Borba et al.

Fluoroscopy-guided cardiac electrophysiology procedures are among the most critical x-ray exposures. However, occupational doses are still little-known. In this study, an alternative methodology was developed to estimate the occupational dose and evaluated its optimization in cardiac electro-physiology procedures. The procedures were reproduced by simulation and the dose rates of the staff were measured at chest and eyes height through electronic dosimeters. The dose rate for different modes of operation and FOV were evaluated. The occupational dose was estimated through the product of the dose rate in the staff's position in the room, the median time of exposure and the mean of these procedures performed by the HCPA in 2019. As a result, it was observed that the decreasing order of the estimated occupational dose was Physician A - Physician R - Nursing Staff and Radiographer - Physician B and Supplier, with the following values in mSv/year of 6.16 - 3.98 - 2.54 - 2.17, respectively. A 37.04% reduction in the occupational dose was observed with the change in FOV, up to 59.26% with different modes of acquisition and 31.82% distancing 50 cm from the most exposed position. The dose of staff is significant. However, due to the optimization of protocols already implemented in HCPA, the estimated doses are in accordance with the recommended dose limits. As optimization actions verified in this study, it is suggested the proper selection of FOV, the adoption of acquisition modes with dose reduction and the distance from the x-ray source.

Haiyan Du, Chengbo Du, Karl Giboni et al.

In experiments searching for rare signals, background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential. We propose to develop a gaseous time projection chamber (TPC) with a Micromegas readout for radio screening. The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector. The detector can distinguish the origin of an event and identify the particle types with information from trajectories, which significantly increases the screening sensitivity. For $α$ particles from the sample surface, we observe that our proposed detector can reach a sensitivity higher than 100 $μ$Bq$\cdot$m$^{-2}$ within two days.

Leonardo Santiago Melgaço Silva

Brachytherapy is the use of radiotherapy with insertion of radiation sources close to the site that needs treatment. It has become an extremely sought-after option by research fields for its impressive efficiency and practicality. In addition to being a fast-paced procedure, it allows patients to leave hospital care very soon after it is done, without pain or with minor discomfort, which can be considered an advantage. The brachytherapy procedure is divided into two stages, obtaining images of the region where seed implantation will take place and the application itself.  The images are obtained by ultrasonography, which will guide the insertion of the needle into the patient's body.  During the injection, the patient is anesthetized and immobilized, so that movements that compromise the accuracy of the needle, which, by the current manual method, are already subject to oscillations are avoided. Currently the application of radioactive seeds is done manually by a clinician who uses needles and monitors their positions through the images generated by ultrasound equipment. Thus, the main objective of this project was to improve the prototype of the Prostate Seed Implantation System (SISP), developed by the Nuclear Engineering Department of the UFMG (Nuclear Engineering Department).  Thus, the device allows automated scanning on x, y and z axes, facilitating the application of radioactive seeds in prostate brachytherapy treatments, which in current treatments are done manually by the clinician. And the possibility of controlling this movement via BLUETOOTH technology.

V. P. Ramzaev, A. N. Barkovsky, A. A. Bratilova

The collection of representative soil samples in the territory of settlements and subsequent measurements of the content of radionuclides in these samples under laboratory conditions (the so-called “ex situ method”) is a generally accepted technology for determining the density of soil contamination with 137Cs in the populated areas contaminated due to the Chernobyl accident. Recently, as a supplement or alternative to the ex situ method, researchers are developing field (in situ) gamma-spectrometry methods. These methods allow determining the density of soil contamination with 137Cs directly on site, without soil sampling and laboratory analysis. At the same time, the in situ methodology has several limitations, the most important of which is a lack of generally recognized metrological basis for measurements and interpretation of results. Hence, before using a particular technique and measuring device for carrying out large-scale in situ measurements, it is necessary to validate (to assess the suitability) of the selected in situ method using an established ex situ method. The aim of this study was to validate the method for determining the density of 137Cs soil contamination in kitchen gardens using the MKS AT6101D spectrometer-dosimeter in situ. The method was recently presented by a Russian-Swedish-Belarusian group of researchers in an article published in the Journal of Environmental Radioactivity (https://doi.org/10.1016/j.jenvrad.2021.106562). To validate this method, we selected 10 representative kitchen garden plots. The plots were located in six settlements of the Bryansk region in Russia. The territory of the settlements had been heavily contaminated with 137Cs as a result of the Chernobyl accident: the officially established levels of the density of soil contamination by 137Cs ranged from 111 to 511 kBq/m2 in 2017. Field gamma-ray spectra were recorded at a height of 1 m above the ground in the center of kitchen garden plots using the MKS AT6101D device. The measurement duration was in the range of 1207–1801 s (the mean value = 1383 s). Samples of soil in the kitchen gardens were taken layer by layer (with a step of 5 cm) to a depth of 20 cm using a demountable cylindrical sampler. The 137Cs content in each soil layer was determined in the laboratory using a stationary semiconductor gamma spectrometer. The values of the 137Cs contamination density of the sampled soils ranged from 77 to 548 kBq/m2. It was found that the results of the ex situ analyzes of soil samples were in a good agreement with the contamination density values obtained with the in situ method. On average, the difference between two methodologies was 7% (a maximum of 20%). The results of the study confirm that the method proposed by the international group is suitable for determining the density of soil contamination by 137Cs in kitchen gardens in remote period after the Chernobyl accident.

Luiza Mascarenhas Balieiro, Henrique Barcellos de Oliveira, Luiz Felipe Teixeira Silva et al.

Approximately 75% of breast cancer cells express estrogen receptor positive, being the second leading cause of cancer death among women worldwide with an incidence of 25% per year. 16α-[18F]-fluoro-17β-estradiol, FES-18F, is a radiopharmaceutical that binds to estrogen receptors enabling the acquisition of molecular images for non-invasive diagnosis of primary and metastatic breast cancer using PET-CT. The objective of this work was to study the synthesis of FES-18F in the GE TRACERlab® MXFDG module, using the chemical kit and the ABX® disposable cassette, and to determine the process yield and the analytical parameters to be used in the routine production of this radiopharmaceutical. Automated synthesis occurs in 75 minutes and includes percolation of [18F-] fluoride into an anion exchange cartridge, cartridge elution, 3-step azeotropic drying, labeling using precursor 3-methoxymethyl-16β,17β-epiestriol-O-cyclic sulfone (MMSE) and a hydrolysis step. Product purification is done in the module using solid phase extraction (SPE) cartridges. The radiochemical yield was reproductive, regardless of fluor-18 activity at entry into the module, and the results of quality control tests suggest that the radiopharmaceutical meets the criteria established for other fluor-18-labelled radiopharmaceuticals that have monographs in official compendiums. In vivo biodistribution studies in healthy animals and with a tumor model developed with MCF-7 cells, demonstrated radiopharmaceutical uptake in excretory organs and specificity for breast tumor cells.

Paola Andrea Bustamante, Maria Carolina Anessi

All tissue banking activities are depending on tissue donors. The donor rate is still low in Argentina, and the tissue demanding is still not fulfilled. For this reason, tissue engineering has become a necessary discipline to be investigated. Our project is conducted to obtain a 3D resorbable printed scaffold seeded with mesenchymal stem cell (MSC), to conduct real bone. We produced three polylactic acid (PLA) filaments with different loads of hydroxyapatite (HA): 3%, 5% and 10%. The mixtures were homogenous and the three filaments were suitable for 3D printing and were used to print 3D scaffolds samples. The scaffolds were irradiated with range doses of 15 kGy to 25 kGy for sterilization purposes and to evaluate if the degradation polymer rate is regulated with the irradiation dose. The elaborated filaments were optimally printable. In addition they turned out to be not cytotoxic (cell viability greater than 70%) and whit good cellular adherence. In this way, our biomaterial seems to be good for scaffolds for bone replacement.

Claudio Domingues Almeida, João Emílio Peixoto

Em mamografia, a otimização das doses é importante devido ao grande número de mulheres que realizam exames para a detecção precoce do câncer de mama. Além disso, nas duas últimas décadas foram introduzidas tecnologias digitais. Diversos estudos mostram que a dose na mamografia computadorizada CR pode ser superior à da mamografia convencional, indicando a necessidade de sua otimização. O objetivo deste trabalho é apresentar um procedimento usando a razão contraste-ruído (CNR) na otimização da dose e da qualidade da imagem em mamografia digital. O processo de otimização em mamografia digital tem início com a determinação da CNR alvo (CNRalvo). Ela é definida como o valor de CNR que permite atingir o limiar de contraste mínimo de 23% para os discos de 0,1 mm de diâmetro no simulador CDMAM. A CNRalvo é estimada a partir da análise, do limiar de contraste em função da CNR medidos com várias técnicas radiográfica e variadas espessuras de PMMA. A seguir, o sistema do mamógrafo de controle automático das técnicas radiográficas para as diversas espessuras de mama deve ser ajustado de modo a se obter sempre a CNRalvo e doses glandulares médias (DGM) que não ultrapassem os níveis aceitáveis. A aplicação deste procedimento de otimização mostrou que, em uma amostra de 162 pacientes, foram observadas diferenças estatisticamente significativas entre as médias da DGM e da CNR (p < 0,05) quando comparadas com uma amostra de 152 pacientes antes da otimização. Houve uma redução de 14,5% da DGM e a qualidade das imagens clínicas foi mantida.

E. N. Shleenkova, S. Yu. Bazhin, G. N. Kaidanovsky et al.

In 2011 the International Commission on Radiation Protection established the threshold value of the absorbed dose in the lens of the eye for the development of cataract equal to 0.5 Gy for acute and chronic exposure. A dose limit for exposure of the lens of the eye was established equal to 20 mSv per year, averaged over five consecutive years (100 mSv over 5 years), and 50 mSv for any single year. The Russian regulatory documents specify the dose limit for the exposure of the eye lens equal to 150 mSv per year and there are noclear criteria determining the conditions under which it is necessary to carry out individual monitoring of exposure of the eye lens, but it should be expected that in Russia the dose limit will also be reduced in the coming years. Objectives of the study: assessment of the absorbed doses in the eye lenses of the staff of medical facilities working with radiopharmaceuticals; identification of the relationship between the absorbed dose in the eye lens and the type and range of activities of the radionuclides; justification of the feasibility and identification of categories of staff for regular individual monitoring of the eye lens doses in nuclear medicine departments. Within the framework of the study, the absorbed dose in the eye lens for staff members working with the radiopharmaceuticals in nuclear medicine departments of two medical facilities in St. Petersburg were measured, the possibility of detection of  high eye lens doses for these workers was analyzed. The monitoring period was set to 1 month. The workers were divided into two groups depending on the type of radionuclides in the radiopharmaceuticals they commonly work with: 1) the staff of the PET departments and the radiochemistry units working the with radiopharmaceuticals labeled with positron emitting radionuclides (11C, 18F, 68Ga) 2) the staff of the departments of nuclear medicine working with radiopharmaceuticals labeled with 89Sr, 99mTc. Measurements of the operational quantity Н (3 ) were carried out by the method o f thermoluminescent dosimetry. We used individual dosimeters that met the conditions for determining the operating values. Dosimeters designed to measure Н (3) were located on the collar of a dressing gown without an attenuator. The results of measurements of Н (3 ) indicated that the collected dose depends on the type of the work, the equipment of the nuclear medicine unit, the radionuclide and its activity both at the workplaces and for the entire period of data collection. High dose values were obtained for procedural nurses, radiochemists and technologists who worked with positron-emitting radionuclides (18F, 68Ga and 11C), which, when extrapolated to a year, can exceed 20 mSv. For this category of workers, it is advisable to carry out individual monitoring of external irradiation of the eye lenses after a preliminary assessment of the level of exposure of workers and an assessment of the risks of high doses of the eye lens.

Håvard Thørring, Frøydis Meen Wærsted, Agnes Raaness et al.

Wynn V. Jacobson-Galán, Raffaella Margutti, Charles D. Kilpatrick et al.

We present $\textit{Hubble Space Telescope}$ imaging of the Calcium-rich supernova (SN) 2019ehk at 276 - 389 days after explosion. These observations represent the latest photometric measurements of a Calcium-rich transient to date and allows for the first opportunity to analyze the late-time evolution of an object in this observational SN class. We find that the late-time bolometric light curve of SN 2019ehk can be described predominantly through the radioactive decay of ${}^{56}\textrm{Co}$ for which we derive a mass of $M({}^{56}\textrm{Co}) = (2.8 \pm 0.1) \times 10^{-2}$$\rm{M}_\odot$. Furthermore, the rate of decline in bolometric luminosity requires the leakage of $γ$-rays on timescale $t_γ = 53.9 \pm 1.30$ days, but we find no statistical evidence for incomplete positron trapping in the SN ejecta. While our observations cannot constrain the exact masses of other radioactive isotopes synthesized in SN 2019ehk, we estimate a mass ratio limit of $M({}^{57}\textrm{Co}) / M({}^{56}\textrm{Co}) \leq 0.030$. This limit is consistent with the explosive nucleosynthesis produced in the merger of low-mass white dwarfs, which is one of the favored progenitor scenarios in early-time studies of SN 2019ehk.

Neilo M. Trindade, Stephanie L. Dardengo, Matheus C.S. Nunes et al.

A alexandrita natural (BeAl2O4:Cr3+) é um mineral amplamente encontrado no Brasil e tem sido investigada para atuar como um detector de radiação ionizante (dosímetro) com o uso da técnica da termoluminescência (TL). A utilização de materiais naturais na área, é interessante pelo seu menor custo comparado aos sintéticos, além da possibilidade de atuarem na dosimetria retrospectiva. Diferentes características das curvas TL de sete amostras foram investigadas, como a linearidade, homogeneidade, repetibilidade e fading. As amostras foram irradiadas com doses entre 0,5 – 5 Gy, utilizando uma fonte beta de 90Sr/90Y. Os resultados demonstram que a curva TL segue o mecanismo cinético de primeira ordem, além de possuir uma dose-resposta linear, boa repetibilidade e estabilidade do sinal em temperatura ambiente para até 33 dias de armazenamento após a dose. O ajuste também revelou cinco picos nas temperaturas 355, 405, 445, 530 e 585 K (taxa de aquecimento de 1 K/s). A caracterização química constatou que as amostras utilizadas são predominantemente formadas por alexandrita com uma porção significativa de fases apatita. Em geral, os resultados trazem características desejáveis dos materiais dosimétricos, sugerindo que a alexandrita tem potencial de aplicação na área.

PROSPECT Collaboration, J. Ashenfelter, A. B. Balantekin et al.

The Precision Reactor Oscillation and Spectrum (PROSPECT) Experiment is a reactor neutrino experiment designed to search for sterile neutrinos with a mass on the order of 1 eV/c$^2$ and to measure the spectrum of electron antineutrinos from a highly-enriched $^{235}$U nuclear reactor. The PROSPECT detector consists of an 11 by 14 array of optical segments in $^{6}$Li-loaded liquid scintillator at the High Flux Isotope Reactor in Oak Ridge National Laboratory. Antineutrino events are identified via inverse beta decay and read out by photomultiplier tubes located at the ends of each segment. The detector response is characterized using a radioactive source calibration system. This paper describes the design, operation, and performance of the PROSPECT source calibration system.

G. G. Onischenko, I. A. Zvonova, M. I. Balonov et al.

The article describes the main areas of scientific and administrative activities of professor P.V. Ramzaev during his work in the Research Institute of Radiation Hygiene. In particular, the results of a study of global radioactive fallout in the Far North of the USSR, as well as a study of the radiation situation and an assessment of the doses to the public after the accident at the Chernobyl NPP, are presented in a systematic way. The leading role of P.V. Ramzaev in the development of hygienic regulation and in the development of the theory of health is shown. The activities of P.V. Ramzaev in the International Commission on Radiological Protection are discussed in detail. The role of P.V. Ramzaev in the development of the law «On Radiation Safety of the Population» is shown.