Hasil untuk "Radioactivity and radioactive substances"

Jiaxiang Wang, T. W. Penny, Yu-Han Tseng et al.

We measure event-by-event discrete changes in the net electric charge of an optically levitated silica microsphere arising from individual radioactive decays within the sphere, in coincidence with energy depositions in a nearby scintillation detector. The net charge of the levitated sphere is continuously monitored by measuring its driven response to an oscillating electric field, allowing individual charge-change events to be resolved on millisecond timescales with precision below an elementary charge. Simultaneously, $α$ and $β$ particles emitted during decays of implanted $^{212}$Pb and its daughters are detected using a scintillator read out with an array of silicon photomultipliers. By correlating reconstructed charge-change times with the scintillator response, we can directly attribute abrupt changes in the sphere's net charge to individual nuclear decays, and identify differences in the distribution of charges ejected for $α$ and $β$ decays. These results establish a new approach for studying low energy charged particles emitted by radioactive decays at the single-decay level, and identify showers of radiogenically produced low-energy electrons emitted by $α$-decaying radon daughters implanted near solid surfaces.

Soraia Azeredo, Renan Oliveira, Elaine Gusmão et al.

The X-ray radiography technique is highly efficient in investigating the manufacturing techniques employed by an artisan when creating a sculpture, as well as assessing the state of conservation and restoration processes. For instance, it allows the determination of whether the artist carved the sculpture from a single piece of massive wood or if it was sculpted in multiple parts, subsequently assembled using nails, hooks, or metal spikes. It also provides insights into whether the artwork underwent certain restoration processes and reveals its current state of preservation or degradation. This information can offer insights into the artist preferred creation technique, potentially the most popular technique of the time. It can also help estimate the period when the artwork underwent restoration and aid in choosing the appropriate restoration technique. In this study, we present the results of an investigative analysis of the internal structure, using digital X-ray radiography, of two wooden sacred sculptures representing biblical characters King David and his wife Bathsheba, dating back to the 18th century and housed in the Church of Our Lady of Pilar in Duque de Caxias, RJ, Brazil. Both sculptures are covered with layers of stain, with a prevailing golden hue on the garments. The obtained radiographic images show that the artist carved various parts of the sculptures and later assembled them using metal pegs. Additionally, recent nails were visible, indicating that the sculptures underwent a restoration process. All digital radiographic images were captured in high resolution using a flat-panel detector.

E. A. Kosarlukova, L. V. Repin, A. M. Biblin et al.

The primary quantity used for monitoring exposure levels of the general population and personnel at radiation facilities is the individual effective dose. This metric accounts for variations in the radiosensitivity of specific organs and tissues by employing corresponding tissue weighting factors recommended by the ICRP. These factors were derived based on medico-demographic data from two artificially constructed populations: "Euro-American" and "Asian." Estimates of relative harm, calculated from risk assessments, served as the basis for establishing the recommended values of tissue weighting factors for organs and tissues. However, the use of effective dose as a risk measure in cases of non-uniform exposure within specific populations raises questions about the appropriateness of applying alternative tissue weighting factors in its calculation to more rigorously account for differences in relative radiosensitivity. The study aims to assess whether the recommended values of nominal risk coefficients and weighting factors for organs and tissues provide a comparable level of safety for the Russian population compared to that provided for the ICRP nominal population. Materials and Methods: The assessment of radiation-induced cancer risk was conducted using Russian medico-demographic data from 1993 to 2022, applying the interpopulation radiation risk transfer model from ICRP Publication 152. Results and Discussion: The calculations indicate that risk estimates for most organs and tissues in the Russian population have gradually increased for males over the 30- year period. However, with the exception of thyroid cancer risk in females, these estimates do not exceed the corresponding values used to establish the tissue weighting factors. Conclusion: The current system of risk indicators and dose limits provides an adequate level of protection for the Russian population and does not require revision until international approaches to radiation protection are updated.

Hanzhen Lin, Yukun Lu, Wolfgang Ketterle

This paper lays out the principles of how Bose-Einstein condensates can modify radioactive decay. We highlight the challenges of many modes and short coherence times due to the $\approx$ MeV energies of the emitted radiation. Recent proposals for gamma ray and neutrino lasers claim that using a Bose-Einstein condensate as a source would solve these issues. We show that this is not the case, and the proposed experiments would have a gain of only $10^{-20}$ or smaller. We also analyze proposals for gamma ray lasers based on stimulated annihilation of positronium Bose-Einstein condensates.

A. I. Radin, T. A. Marchenko, A. N. Razdaivodin

The purpose of the study is to analyze the forest fire dangers of the Bryansk region forests, taking into account their radioactive contamination and potential risks for forestry workers involved in forest fires extinguishing. Significant areas of radioactive contamination of forests with a predominance of sites belonging to the classes of high and very high natural fire danger, restrictions on economic activity and a long fire-hazardous period contribute to the occurrence of radioactive forest fires. The analysis of the combined data on forest fires and radioactive contamination of forest areas showed that most forest fires occur outside the zones of radioactive contamination and are not radioactive. The largest number of fires occurs at the beginning of the fire season. Radioactive forest fires in most cases arise from the burning of dry grassy vegetation, as a result of the transition from lands of other categories and through the fault of the population. The average effective dose of additional radiation per a workday can be estimated at 1.96 μSv, and the maximum at ~ 15.4 μSv. Most fires are extinguished in the early stages and do not have time to cover large areas. It indicates the effective work of the forest fire service

Constantin Ulrich, Tassilo Wald, Emily Tempus et al.

Effortless and precise segmentation with minimal clinician effort could greatly streamline clinical workflows. Recent interactive segmentation models, inspired by METAs Segment Anything, have made significant progress but face critical limitations in 3D radiology. These include impractical human interaction requirements such as slice-by-slice operations for 2D models on 3D data and a lack of iterative refinement. Prior studies have been hindered by inadequate evaluation protocols, resulting in unreliable performance assessments and inconsistent findings across studies. The RadioActive benchmark addresses these challenges by providing a rigorous and reproducible evaluation framework for interactive segmentation methods in clinically relevant scenarios. It features diverse datasets, a wide range of target structures, and the most impactful 2D and 3D interactive segmentation methods, all within a flexible and extensible codebase. We also introduce advanced prompting techniques that reduce interaction steps, enabling fair comparisons between 2D and 3D models. Surprisingly, SAM2 outperforms all specialized medical 2D and 3D models in a setting requiring only a few interactions to generate prompts for a 3D volume. This challenges prevailing assumptions and demonstrates that general-purpose models surpass specialized medical approaches. By open-sourcing RadioActive, we invite researchers to integrate their models and prompting techniques, ensuring continuous and transparent evaluation of 3D medical interactive models.

H. Ogawa, Y. Takeuchi, H. Sekiya et al.

This paper investigates the removal of radon from purified and ambient airs by Ag-zeolite. Ag-zeolite is known to have very high performance for airborne radon removal. The dependence of zeolite type and silver content on the performance of radon removal was evaluated. The performance of radon removal by single pass and radon emanation were also evaluated. In addition, the adsorption performance due to zeolite solidification and the change in adsorption performance due to moisture in the gas were evaluated in order to investigate properties that should be considered for future practical use. These properties will be adaptable to the development of air purification systems for the large volume ultra-low radioactivity experiments.

P. A. P. Celestino, G. M. A. A. Sordi

Most radiation exposure to personnel comes from inspection, maintenance, and repair within the reactor compartment. The objective of this paper was to discover the garment that, at the same time, presents the best result for the attenuation of ionizing radiation, as well as good ergonomics for the maintenance professional of mobile nuclear plants. For this, market research was carried out and, as a result, nine Radiation Protection Vestments (VPRs) were found, from five different manufacturers and from three countries, the United States, Japan and China; and which are feasible to be acquired. To choose the VPR, the optimization techniques of CIPR 55 were used: Multi-Attribute Utility Analysis and Multi-Criteria Outranking Analysis. Based on the information provided by the manufacturers, five attributes were chosen for comparison: protection cost, percentage of ionizing radiation attenuation, weight, discomfort, and surface decontamination of the vestment. To verify the robustness of the analytical solution, the values of the scaling constants were re-calculated, where it was observed that the analytical solution found is strongly influenced when the protection cost is changed, as it is the highest cost VPR among all those surveyed. The VPR chosen by both optimization techniques was the STEMRAD 360, which has the highest attenuation of ionizing radiation, as well as being the VPR with greater emphasis on ergonomics.

А. Yu. Popova, A. V. Vodovatov, I. K. Romanovich et al.

Computed tomography has become the main method of early diagnostics of COVID-19 during the pandemic of the novel coronavirus infection. Based on results of computed tomography of the chest it is possible to diagnose viral pneumonia associated with COVIS-19, to quickly assess the lung damage volume and severity of changes, to perform quick routing of patients and to start antiviral treatment. Hence, 2020 was associated with a rapid increase in the number of computed tomography examinations with corresponding changes in the structure of X-ray diagnostics. The aim of the current study was to evaluate the impact of the pandemic of the novel coronavirus infection on the structure of X-ray diagnostics and collective doses from medical exposure in the Russian Federation in 2019-2020. The study was based on the results of analysis of the federal state statistical surveillance forms №3-DOZ and №30 as well as on the data on Covid-19 morbidity in the regions of the Russian Federation. The results of the study indicate that there were no significant changes in the structure of X-ray diagnostics in 2020 compared to 2019 except for the increase in the number of computed tomography examinations. Their contribution to the total number of X-ray examinations has increased to 8,2% in 2020 compared to 4,6% in 2019. Contribution of other imaging modalities to the total number of X-ray examinations has not changed significantly. In 2020 the number of X-ray examinations decreased by 20% in average, varying from 6% for diagnostic nuclear medicine to 42% for interventional examinations. At the same time, the number of computed tomography examinations has rapidly increased by 60%. The structure of collective dose from medical exposure has significantly changed in 2020. Contribution of computed tomography to the collective dose in 2020 accounted for to 74% compared to 57% in 2019. Contribution of other imaging modalities has decreased by the factor of 1,5-2. Contribution of radiography examinations has decreased to 10,5% compared to 19% in 2019. Collective doses have correspondingly decreased by 20-30% for all imaging modalities except for computed tomography. Collective dose from computed tomography has increased by 71% compared to 2019. The number of all X-ray examinations in the Russian Federation has decreased by 12%: from 294 million in 2019 to 258 million in 2020. Collective dose from medical exposure has rapidly increased in 2020 by 30% to 115 thousand man. -Sv compared to 88 thousand man. -Sv in 2019. In average, in regions of the Russian Federation in 2020 each second computed tomography examination has been performed as a part of COVID-19 diagnostics with 2,3 computed tomography examinations per person infected with COVID.

Claudio Henrique dos Santos Grecco, Jaqueline Tavares Viana de Souza, Paulo Victor Rodrigues Carvalho et al.

The knowledge of workers constitute as valuable resources, as they enable organizations to perform their functions successfully. However, there are conditions that favor the loss of this knowledge in organizations, as for example, the natural aging of workers and consequently the retirement and staff turnover. Then, it becomes important for organization to seek the preservation these knowledge. For a successful implementation of Knowledge Management (KM), it is important to identify the barriers or critical factors that affect the success of the KM process. From the perspective of the nuclear organizations, no systematic framework exists on characterizing a set of critical success factors (CSFs) for implementing KM. Furthermore, the CSFs assessment deals with uncertainty and imprecision of human judgments. In this context, this paper presents a decision support method using CSFs and logic fuzzy to assess the KM in nuclear organizations.  Fuzzy theory is essentially used in mapping quantitative models for decision support and representation methods in imprecise and uncertain environments. The decision support method was applied at the Laboratory of Human-Systems Interfaces of the Nuclear Engineering Institute. The results showed that the method is a good assessment tool for the elaboration of nuclear knowledge management strategies.

Henning O. Back, Walter Bonivento, Mark Boulay et al.

The DarkSide-50 experiment demonstrated the ability to extract and purify argon from deep underground sources and showed that the concentration of $^{39}$Ar in that argon was greatly reduced from the level found in argon derived from the atmosphere. That discovery broadened the physics reach of argon-based detector and created a demand for low-radioactivity underground argon (UAr) in high-energy physics, nuclear physics, and in environmental and allied sciences. The Global Argon Dark Matter Collaboration (GADMC) is preparing to produce UAr for DarkSide-20k, but a general UAr supply for the community does not exist. With the proper resources, those plants could be operated as a facility to supply UAr for most of the experiments after the DarkSide 20k production. However, if the current source becomes unavailable, or UAr masses greater than what is available from the current source is needed, then a new source must be found. To find a new source will require understanding the production of the radioactive argon isotopes underground in a gas field, and the ability to measure $^{37}$Ar, $^{39}$Ar, and $^{42}$Ar to ultra-low levels. The operation of a facility creates a need for ancillary systems to monitor for $^{37}$Ar, $^{39}$Ar, or $^{42}$Ar infiltration either directly or indirectly, which can also be used to vet the $^{37}$Ar, $^{39}$Ar, and $^{42}$Ar levels in a new UAr source, but requires the ability to separate UAr from the matrix well gas. Finding methods to work with industry to find gas streams enriched in UAr, or to commercialize a UAr facility, are highly desirable.

Dirk Eidemüller

Catarine Santos Lopes Alencar, Ana Rita Noborikawa Paiva, Elizabeth S. Ribeiro Somessari et al.

The major part of the world production of hydrogen (H2) is originated from a combination of methane steam reforming and water-gas shift reaction resulting in an H2-rich mixture known as reformate gas, which contains about 1% vol (10,000 ppm) of carbon monoxide (CO). The preferential oxidation reaction of CO in H2-rich mixtures (CO-PROX) has been considered a very promising process for H2 purification, reducing CO for values below 50 ppm allowing its use in PEMFC Fuel Cells. Au nanoparticles supported on TiO2 (Au/TiO2) catalysts have been shown good activity and selectivity for CO-PROX reaction in the temperature range between 20-80 ºC; however, the catalytic activity strongly depends on the preparation method. Also, the addition of Cu to the Au/TiO2 catalyst could increase the activity and selectivity for CO-PROX reaction. In this work, AuCu/TiO2 catalysts with composition 0.5%Au0.5%Cu/TiO2 were prepared in a single step using electron beam irradiation, where the Au3+ and Cu2+ ions were dissolved in water/2-propanol solution, the TiO2 support was dispersed and the obtained mixture was irradiated under stirring at room temperature using different dose rates (8 – 64 kGy s-1) and total doses (144 – 576 kGy). The catalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction transmission electron microscopy, temperature-programmed reduction and tested for CO-PROX reaction.  The best result was obtained with a catalyst prepared with a dose rate of 64 kGy s-1 and a total dose of 576 kGy showed a CO conversion of 45% and a CO2 selectivity of 30% at 150 oC.

Marco Antonio Costa Cardoso, Victor Gabriel Leandro Alves, Simone Coutinho Cardoso

Evaluation of the dose distribution delivered in a radiosurgery treatment of an acoustic neuroma using an adapted Alderson phantom and radiochromic film to assess absolute dose. A system was developed to perform the dose measurements, using the Alderson Rando phantom´s head carrying a modified slice, where a material reproducing the tumor was inserted. The phantom’s head with the modified slice was irradiated in a medical linear accelerator, using a procedure similar to that adopted in real cases, and radiochromic films were used to assess dose values. The suitability of the dose distribution delivered in the treatment was evaluated by comparing the Dose Volume Histograms, obtained from the Treatment Planning System (TPS) and by radiochromic film measurements. An agreement around 3% between experimental data and TPS´s calculations, showing an acceptable concordance with the planning results. The established approach of transforming 2D arrays of dose in a 3D one is satisfactory, validating it. The developed method shows to be an excellent alternative to quality control in radiosurgery using the radiochromic film to assess absolute dose.

Diego Vergaças de Sousa Carvalho, Carlos Henrique de Mesquita, Gustavo Martinez Gregianin

Computed tomography technology uses an electromagnetic radiation source or particulate radiation source, to analyze / study different samples that can range from living organisms to the most diverse objects (rocks, phantoms, etc.). The use of the radioactive materials may cause harm to the operator if he is exposed to the source of radiation, so aiming at the safety of the operator, the objective of this work is to develop an Internet of Things automation system for the opening of the Industrial Process Tomography source port for industrial tomography applications. Thus, this system can drive the stepper motors through this platform can be opened at a safe distance to the operator, avoiding the operator to take radiation dose to perform this operation. For the IPT project, five source ports were made so that each was positioned diametrically opposite each array of detectors. In this project we used 192Ir sources that have activity of 18,500 MBq and that were produced in the reactor IEA-R1, from the neutron bombardment of the pellet containing stable isotope 191Ir. The main characteristics of 192Ir are: half-life of 74.2 days; radiation energy from 0.13 to 0.65 MeV. For the safety of the operator during the opening of the sources, an automated opening system with IoT that can be activated with software installed on the tomography or by a smartphone application  by the MQTT protocol, which makes it possible to be monitored in real time at long distance showing the opening and closing status of each source port.

Thiago Lynyker da Silva Bernardes, Rafael Aquino Amadeu, Rodrigo Sousa Santos et al.

In the present work, the characteristics of the shale rock, collected in the surrounds of Limeira, in the interior of São Paulo, were studied. Shales are mostly fine granules, susceptible to the mineralogical rearrangement, and their chemical composition is quite varied due to the geomorphology and the tectonism undergone by the sedimentary basins. They are impermeable structures, formed by the consolidation of layered clay with thin laminations. Because of these characteristics presented, together with the decline of petroleum production, a growing interest in a better understanding and knowledge of the physical-chemical properties of the shale rocks inner is observed.  In this work, the gamma-ray computed industrial tomography technique was established to be used in the characterization of the shale samples. The results were validated using those obtained by conventional methodologies, such as scanning electron microscopy (SEM), x-ray fluorescence and x-ray diffraction. Several characteristics have been studied, such as the analysis of the particle morphology, the contrasts and distributions of these particles in the internal structure of the rock, identification of the types of elements present (quantitative analysis), as well as establishing the proportion of each element present in the mineral through its crystalline structure, with images of the rock internal structure.

Higor Fabiano Pereira de Castro, Guilherme Augusto Moura Vidal, Tiago Augusto Santiago Vieira et al.

Spacer grids are one of main components of a Pressurized Water Reactor (PWR) fuel assembly. They are able to improve heat transfer from rod bundles to the water flow by increasing turbulence and mixture of this flow. On the other hand the pressure drop increases because spacer grids. Experimental and Computational Fluid Dynamics (CFD) analysis have been used to understand how spacer grids affect the water flow. This analysis is important to improve spacer grids thermal-hydraulic performance. This paper aims to investigate numerically and experimentally the water flow through PWR spacer grids. The numerical and experimental procedures have been developed for a 5x5 rod bundle with spacer grids at the Nuclear Technology Development Center (CDTN) in Belo Horizonte, Brazil. At CDTN, measurements of the velocity components are acquired with a 2D LDV (Laser Doppler Velocimetry) system and the numerical results are obtained using ANSYS CFX code. The measurements are obtained at one height downstream from a spacer grid and compared to CFD simulations for a flow rate at Reynolds number of 5.4x104 . Results show good agreement between both methodologies. The great repeatability and low experimental uncertainty evaluated (< 1.24%) in this work can be used to validate other CFD codes.

Paolo Finocchiaro

Nuclear physics experiments are always in need of more and more advanced detection systems. During the last years relevant technological developments have come out with many improvements in terms of performance and compactness of detector materials, transducers, electronics, computing and data transmission. In light of these achievements some applications previously prohibitive, mainly because of size and cost, have become feasible. A few applications of nuclear detection techniques are discussed, starting from the neighboring field of particle beam diagnostics, moving to the medical diagnostics and ending up into the radioactive waste handling. New radiation sensors are shown and explained, as exploited in the DMNR project for the radioactive waste online monitoring which merged into the MICADO Euratom project.

Oleg K. Vlasov, Pavel Krajewski, Irina A. Zvonova et al.

The analysis of instrumental data of “Prague” and “Warsaw” scenarios on the dynamics of 131I specific activities in the grass is carried out. Reconstruction of the 131I the specific activities dynamics in the grass in the Mazovia and Bohemia localities is performed in three models: direct calculation the input data of the “Prague” and “Warsaw” scenarios, homogeneous cloud, heterogeneous rain and heterogeneous cloudhomogeneousrain. The actual 137Cs fallout densities in the grass sampling sites in average more than 2.9 times for Prague and 2 times for Warsaw. Effective rain during the main fallout at the grass sampling sites, reconstructed on the model of a homogeneous cloud is 3–4 times more than at the nearest weather stations during this time. A realistic scenario of the input data leading to the optimal agreement of the calculated and instrumental data is revealed. It is shown that direct calculations and the homogeneous cloud model give almost identical results and lead to a significantly better agreement with the instrumental data than the an inhomogeneous cloud model. The calculated and instrumental data show a significant decrease in the 131I specific activity in the grass after the end of the main fallout due to its flushing from the grass surface by strong prolonged rain 13 and 19 days after the accident in Mazovia and 30 and 35 days in Bohemia. Uncertainties in the results of reconstruction of the dynamics of 131I and 137Cs activities in vegetation are estimated. The meangeometric values and standard mean-geometric deviations of the calculation/ 8instrumental data ratios are: 0.8–1.1 and 1.8–1.9 for grass.

Thiago Altair, Larissa M. Sartori, Fabio Rodrigues et al.

Certain subterranean environments of Earth have naturally accumulated long-lived radionuclides, such as 238U, 232Th and 40K, near the presence of liquid water. In these natural radioactive environments (NRE), water radiolysis can produce chemical species of biological importance, such as H2. Although the proposal of radioactive decay as an alternative source of energy for living systems has existed for more than thirty years, this hypothesis gained strength after the recent discovery of a peculiar ecosystem in a gold mine in South Africa, whose existence is dependent on chemical species produced by water radiolysis. In this work, we calculate the chemical disequilibrium generated locally by water radiolysis due gamma radiation and analyse the possible contribution of this disequilibrium for the emergence of life, considering conditions of early Earth and having as reference the alkaline hydrothermal vent (AHV) theory. Results from our kinetic model points out the similarities between the conditions caused by water radiolysis and those found on alkaline hydrothermal systems. Our model produces a steady increase of pH with time, which favours the precipitation of minerals with catalytic activity for protometabolism, as well as a natural electrochemical gradient in this aqueous environment. In conclusion, we described a possible free-energy conversion mechanism that could be a requisite for emergence of life in Hadean Earth.