Hasil untuk "Radioactivity and radioactive substances"

Maria Eduarda santos, Tatiane Sabriela Camozzato, Lucas Faconi Camargo

Nuclear Medicine in Brazil has shown significant growth, with approximately 2 million procedures performed annually across 436 facilities. Ensuring that radiation exposure remains within safe limits is critical to protect patients and staff, making radiometric surveys an essential part of safety protocols. This study investigated the distribution of radiation in a nuclear medicine service in Florianópolis, Santa Catarina, using biweekly measurements collected between 2021 and 2023. A total of 2,000 samples were gathered at 40 points using a Geiger-Müller detector. The data were analyzed and mapped onto the facility’s floor plan using Paint and Excel software to generate a radiometric map. The results identified areas with elevated radiation levels and notable regional differences. The highest exposure rates were found primarily in the radiopharmacy—where radioactive materials are handled, stored, and prepared—and in radiopharmaceutical administration rooms. This radiometric map proved effective in guiding radiological protection measures and highlights the importance of continuous radiation monitoring in clinical nuclear medicine environments.

Juarez de Jesus Rocha Pinto, Miguel Mattar Neto

There is much discussion today about the possibility of extending the lifetime of industrial plant components due to economic factors. Pressure vessels are among the most expensive components, and their replacement can significantly impact the operation of an entire plant. In this context, several Fitness-for-Service (FFS) methodologies can be applied to assess structural integrity, addressing not only economic aspects but also enhancing safety. Failure Assessment Diagrams (FADs) are widely used in FFS methodologies to prevent future failures by analyzing crack-type defects. These diagrams establish acceptability criteria based on the material toughness ratio and loading ratio. Recommended practices utilizing the BS-7910, API-579, and R6 methodologies are addressed in this work, alongside principles from fracture mechanics, material properties, and solid mechanics. The main objective was to develop computer programs in Matlab to analyze a case study involving a pressure vessel manufactured from SA-516 Gr 70 steel, determining the critical dimensions of semi-elliptical cracks in longitudinal and circumferential orientations of a cylindrical section. Level 2 evaluation, the most commonly used in FFS methodologies, was applied to develop the programs. This study enabled the creation of tools to automate calculations and generate FAD graphs, considering the critical depth and length of cracks. These tools support decision-making in structural design requirements and provide a means of evaluating equipment in service with crack-type defects, extending its operational lifetime. The FFS methodologies studied are based on ASME Codes for pressure vessels and piping, particularly Sections III and XI. Based on the analysis of API-579, BS-7910, and R6 methodologies under the operating conditions of the case study, it is possible to conclude that, for normal evaluations, critical length (2c) = 40.64 mm and critical depth (a) = 10.16 mm are acceptable values. However, for evaluations requiring safety considerations under the R6 procedure, applicable to Class A service equipment in the nuclear sector, only critical length (l) = 5 mm and depth (a) = 2.5 mm are permissible values.

Hirys Sales, Ester Andrade, Bruno Mendes

In vivo internal dosimetry can use a whole-body counter (WBC) to estimate radionuclides' incorporated activity (Bq) in internally contaminated individuals. The WBC must be calibrated to convert the count rate from the detector into activity incorporated in the person. Active physical phantoms could be used for the calibration procedure. Additive manufacturing allows the physical reproduction of ICRP computational models with good geometric fidelity. This study aims to develop imaging manipulation techniques to generate stereolithography (STL) parts for the 3D printing a male physical phantom based on the Adult Male Reference Computational Phantom (RCP_AM) model provided in the ICRP 110 publication. The Reference Male Phantom for Internal Dosimetry (RMPID) was developed based on the model provided by the ICRP in text file format containing the RCP_AM segmentation information. It was processed with an in-house C++ program that generated images in RAW format (Unprocessed images). The images were manipulated using freeware: ImageJ, MeshLab, FreeCAD, and Meshmixer. A set of 22 hollow portions, 44 pieces including the lids, which fit together, were obtained. The RMPID was printed in PLA (Polylactic Acid) on the Creality Ender 5 Plus 3D printer. The 3D-printed phantom parts passed leak tests, proving that imaging manipulation techniques resulted in well-sealed parts. That will allow the phantom to be safely filled with tissue-equivalent material containing a calibrated activity of the selected radionuclide. The design also makes the simulator easier to handle and to assemble during calibration routines. 

Zeyuan Feng, Zhaoyuan Peng, Haojie Dong et al.

This study systematically investigates the impact of natural radioactive background on the dark count rate (DCR) of 20-inch microchannel plate photomultiplier tubes (MCP-PMTs). Variations in PMT DCR under different radiation conditions were examined via underground tests, lead shielding experiments, and irradiation with \(^{55}\mathrm{Fe}\), \(^{60}\mathrm{Co}\), and \(^{90}\mathrm{Sr}\) sources. The experimental results indicate that natural radioactivity from surrounding air and rock in the underground environment results in a significantly higher DCR compared to laboratory conditions. Further, lead shielding experiments confirmed that effective shielding can markedly reduce the interference from environmental background radiation. Notably, $β$ particles from the \(^{90}\mathrm{Sr}\) source increased the DCR by approximately 14 kHz, whereas the effects of $\mathrm{X}$-rays from \(^{55}\mathrm{Fe}\) and $γ$-rays from \(^{60}\mathrm{Co}\) were comparatively minor. In addition, Geant4 simulations provided quantitative analysis of Cherenkov radiation induced by $β$ particles, with the simulation results closely matching the experimental data and confirming $β$ particles as the primary contributor to the DCR increase. These findings offer both theoretical and experimental evidence for a deeper understanding of the influence of radioactive background on 20-inch MCP-PMTs' performance in underground experiments and hold significant implications for improving the energy resolution of large-scale neutrino detection systems

Álvaro R. Barros, Ranulfo S. Dias, Gustavo Gama Souza et al.

Em maio de 2024, severas inundações afetaram diversas cidades no estado do Rio Grande do Sul, Brasil, incluindo a capital, Porto Alegre. Este estudo avalia os possíveis riscos radiológicos e nucleares decorrentes dessas inundações. Foram identificadas 106 instalações que utilizam materiais radioativos em regiões próximas, das quais 30 estão localizadas nas regiões de interesse, classificadas de acordo com os padrões de risco da IAEA. As inundações comprometeram sistemas de contenção e monitoramento, aumentando o risco de exposição a materiais perigosos em geral, incluindo materiais radioativos e nucleares. Locais de alto risco em São Leopoldo e Canoas, e locais de risco moderado em Porto Alegre e São Leopoldo foram afetados pelas inundações. O estudo ressalta a necessidade de aprimorar os sistemas de segurança e resposta a desastres para proteger a saúde pública e o meio ambiente.

Alexandre Soares Leal, João Gabriel Oliveira Marques, Amir Zacarias Mesquita et al.

The IPR-R1 Triga nuclear research reactor of the Nuclear Technology Development Center (CDTN) is one of the oldest reactors in operation in the world. It is a compact and inherently safe reactor that operates at a continuous power level of 100 kW with a solid homogeneous General Atomic (GA) fuel element of zirconium hydride moderator homogeneously combined with 20% enriched uranium. The reactor core is at the bottom of a tank under approximately 6.0 meters of shielding water. The long operation time of the reactor, 63 years, and the contact of the water with the core, can induce corrosive processes in the IPR-R1 reactor and affect its safe operation. To keep the water quality according to the chemical-physical recommended standards, a quality management program, as recommended by the International Atomic Energy Agency (IAEA), was implemented. The water quality management program is a guideline of good practices applied to nuclear reactors, targeting to keep their water coolants at specified physical-chemical standard. The main aim of the present work is to introduce IPR-R1 Triga’s water chemistry program results from the second half of 2022 till the first half of 2023, when the installation returned to its regular activities after the Covid-19 pandemic. The physical-chemical parameters evaluated (e.g.: pH, alpha and beta radiation, electrical conductivity and gamma emitters) shows that the IPR-R1 reactor operates within recommended safety standards.

S. S. Sarycheva

Interventional procedures are accompanied with high levels of patient exposure and even with the possibility of radiation skin damage. That’s why any actions leading to reduction of patients’ exposure levels are of utmost importance. Implementation of diagnostic reference levels is considered to be one of the most successful actions to reduce patient exposure levels. However the basic concept of diagnostic reference levels cannot be used for interventional radiology due to fact that procedures are not standardized. The article studies the main difficulties in applying the standard concept of diagnostic reference levels for interventional radiology procedures and proposes a new concept, taking into account the specifics of these procedures; the domestic and international documents are analyzed. The list of interventional procedures for diagnostic reference levels establishment is suggested based on the statistical data on performed procedures in the Russian Federation. The results of this study were used for the new Russian guidelines “Optimization of radiation protection of patients undergoing medical radiation diagnostic examinations through the use of diagnostic reference levels”.

P. S. Kuptsova, L. N. Komarova, E. R. Vypova

In the modern world, such a situation has developed that the development of nuclear energy and the use of sources of ionizing radiation in various fields of activity have created a potential threat of radiation hazard to humans. In this connection, the actual direction is the study of ways to increase the radioresistance of human cells and tissues to the action of ionizing radiation. In addition, radioprotective compounds are also important in radiotherapy, since normal tissues of patients must be protected from radiation damage when using high doses of radiation in the treatment of malignant neoplasms. However, the radioprotectors currently used have some disadvantages. The aim of this work is to study the radioprotective properties of fumaric acid and 3-hydroxypyridine fumarate under the action of gamma radiation and radiation of 12C ions on tumor (SK-N-BE neuroblastoma) and normal (hTERT fibroblasts) human cells. The effect of radiation was evaluated according to the criteria of cell survival in culture, doubling time and clonogenic activity. It has been shown that the use of fumaric acid and 3-hydroxypyridine fumarate has a radioprotective effect on normal and tumor cells when they are irradiated with gamma radiation at doses of 1, 4, 6 and 10 Gy. The use of fumaric acid and 3-hydroxypyridine fumarate does not have a radioprotective effect on tumor cells when they are irradiated with 12C ions. A comparative analysis of the results of the action of the preparations with gamma rays and 12C ions showed a significant dependence of the manifestation of modifying properties on the quality of radiation. The study of cell doubling time showed that the presence of drugs in the control did not increase this indicator. On the contrary, under the action of gamma radiation at a dose of 10 Gy, the preparations reduced the doubling time of fibroblasts by more than two times and the doubling time of neuroblastoma cells by almost 1.5 times. The data obtained indicate that the antioxidant properties of the studied preparations open up new possibilities for modifying the action of ionizing radiation in the treatment of oncological diseases. The use of fumaric acid and 3-hydroxypyridine fumarate will reduce the radiation load on healthy cells, including reducing the effect of secondary products on healthy cells beyond the Bragg peak under the action of carbon ion therapy.

Radhika Batra, Sneha Harish C, Swati Gupta et al.

The severe acute respiratory syndrome coronavirus 2 pandemic started in the December of 2019 at China. The second wave of the pandemic in India peaked between April-May 2021. In order to reduce the transmission and infectivity of the virus several vaccines were approved for emergent use. Studies have shown the effectiveness of vaccination in reducing the clinical severity of infection by the corona virus. In this study we aim to assess the effect of vaccination on the computed tomography severity score (CTSS). The study included 140 patients who tested positive for COVID 19 on RT PCR or rapid antigen test. Seventy of these patients had received at least one dose of vaccination and 70 patients were unvaccinated.  CT scan of the chest was done for all patients and a CTSS ranging from 0 to 25 was assigned depending on the extent of lobar involvement. We found that a higher percentage (72.86%) of unvaccinated patients had severe disease compared to the vaccinated group (38.57%), 5.71% of unvaccinated patients had mild disease compared to 30% of vaccinated patients. The difference between the two groups was found to be statistically significant. On comparing the CTSS of patients with and without vaccination in our study, we found a significant reduction in the severity scores in the vaccinated group. Through this study the vaccine’s efficacy could be validated objectively. This article aims to emphasize the role of vaccination in our fight against the pandemic caused by the corona virus.

Isaac J. Arnquist, Maria Laura di Vacri, Nicole Rocco et al.

Flexible printed cables and circuitry based on copper-polyimide materials are widely used in experiments looking for rare events due to their unique electrical and mechanical characteristics. However, past studies have found copper-polyimide flexible cables to contain 400-4700 pg $^{238}$U/g, 16-3700 pg $^{232}$Th/g, and 170-2100 ng $^{nat}$K/g, which can be a significant source of radioactive background for many current and next-generation ultralow background detectors. This study presents a comprehensive investigation into the fabrication process of copper-polyimide flexible cables and the development of custom low radioactivity cables for use in rare-event physics applications. A methodical step-by-step approach was developed and informed by ultrasensitive assay to determine the radiopurity in the starting materials and identify the contaminating production steps in the cable fabrication process. Radiopure material alternatives were identified, and cleaner production processes and treatments were developed to significantly reduce the imparted contamination. Through the newly developed radiopure fabrication process, fully-functioning cables were produced with radiocontaminant concentrations of 20-31 pg $^{238}$U/g, 12-13 pg $^{232}$Th/g, and 40-550 ng $^{nat}$K/g, which is significantly cleaner than cables from previous work and sufficiently radiopure for current and next-generation detectors. This approach, employing witness samples to investigate each step of the fabrication process, can hopefully serve as a template for investigating radiocontaminants in other material production processes.

Yu Zhang, Zhimin Wang, Min Li et al.

The primary objective of the JUNO experiment is to determine the ordering of neutrino masses using a 20-kton liquid-scintillator detector. The 20-inch photomultiplier tube (PMT) plays a crucial role in achieving excellent energy resolution of at least 3% at 1 MeV. Understanding the characteristics and features of the PMT is vital for comprehending the detector's performance, particularly regarding the occurrence of large pulses in PMT dark counts. This research paper aims to further investigate the origin of these large pulses in the 20-inch PMT dark count rate through measurements and simulations. The findings confirm that the main sources of the large pulses are natural radioactivity and muons striking the PMT glass. By analyzing the PMT dark count rate spectrum, it becomes possible to roughly estimate the radioactivity levels in the surrounding environment.

Seung Hun Shin, Hyeonmin Lee, H. Kim

Lucas Mateus Ferreira de Amorim, Viviane Khoury Asfora, Raquel Aline Pessoa et al.

The aim of this work was to investigate the Thermoluminescence (TL) and the Optically Stimulated Luminescence (OSL) responses of Li2B4O7: Cu, Ag synthesized using two method: a) solid-state and b) liquid combustion methods. In both procedures 0.4% mol of CuN2O6.3H2O and 0.1%mol of AgNO3 were used as dopants. The techniques of X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for structural and morphological characterization. The results showed that the samples synthesized using the combustion method are mostly formed by Li2B4O7:Cu,Ag, while those produced by the solid-state method showed the presence of LiBO2. This fact affects the luminescence response of the samples, Those produced by combustion have higher TL and OSL sensitivities. The IRSL response was not observed for both sample’s batch. Future studies will be carried out to evaluate the use of Li2B4O7:Cu,Ag synthesized by solid-state for high dose dosimetry.

Ryan Sheatsley, Matthew Durbin, Azaree Lintereur et al.

One of the principal uses of physical-space sensors in public safety applications is the detection of unsafe conditions (e.g., release of poisonous gases, weapons in airports, tainted food). However, current detection methods in these applications are often costly, slow to use, and can be inaccurate in complex, changing, or new environments. In this paper, we explore how machine learning methods used successfully in cyber domains, such as malware detection, can be leveraged to substantially enhance physical space detection. We focus on one important exemplar application--the detection and localization of radioactive materials. We show that the ML-based approaches can significantly exceed traditional table-based approaches in predicting angular direction. Moreover, the developed models can be expanded to include approximations of the distance to radioactive material (a critical dimension that reference tables used in practice do not capture). With four and eight detector arrays, we collect counts of gamma-rays as features for a suite of machine learning models to localize radioactive material. We explore seven unique scenarios via simulation frameworks frequently used for radiation detection and with physical experiments using radioactive material in laboratory environments. We observe that our approach can outperform the standard table-based method, reducing the angular error by 37% and reliably predicting distance within 2.4%. In this way, we show that advances in cyber-detection provide substantial opportunities for enhancing detection in public safety applications and beyond.

Marco Kaltofen, Maggie Gundersen, Arnie Gundersen

Т. A. Kormanovskaya, O. A. Istorik, I. K. Romanovich et al.

The paper presents data on indoor radon concentrations in the buildings of children institutions in a number of regions of the Russian Federation. The results of detailed radon surveys in 132 buildings of children institutions in 85 settlements of six districts of the Leningrad Region conducted in 2018-2020 were analyzed. In 14 buildings of children institutions in the Leningrad region (10.5% of all surveyed buildings) the hygienic limit on the indoor radon EEC was exceeded, the maximum measured value of radon concentration in the premises of children institutions reached 2200 Bq/m3. It seems appropriate to extend the experience of cooperation between the Directorate of the Rospotrebnadzor for the Leningrad Region and the Saint-Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev in conducting detailed radon surveys in children institutions on other regions of the Russian Federation that face problems with indoor radon.

Matheus Rebello do Nascimento, Jose Guilherme Pereira Peixoto, Leonardo de Castro Pacífico et al.

The X-ray spectrometry is subject to a diversity of problems that distort the measured beam. To observe them, spectra from N20, N25, N30, N60, N80, and N100 radiation qualities were obtained and evaluated their non-correction impact in the values of mean energy when compared with the requirements on ISO 4037-1 standard. The error percentages calculated were 2%, 2%, 2%, 11%, 9%, and 6%, respectively, related to partial energy deposition, efficiency loss, and charge trapping. These results suggest the need for correction of measured spectra, mainly for voltages higher than 30 kV.

Marcelo Vilela da Silva, Domingos D'Oliveira Cardoso, Sergio de Oliveira Vellozo

Particle accelerator technology has a deep impact on society. Its applications are well established mainly in the treatment of cancer and other diseases. This work aims to develop an experimental apparatus with 3He detectors for 16 MeV photoneutron measurements. The apparatus allows us to obtain multienergetic neutrons with the use of a 22 cm diameter spherical attenuator associated with different shield thicknesses. The microscopic processes of the fast and thermal neutrons in the detector were described by the two energy-group diffusion equation. The Detector Response  Dose Rate results show a directly proportional relationship between these two variables with a degree of reliability attested by the linear correlation coefficient .Particle accelerator technology has a deep impact on society. Its applications are well established mainly in the treatment of cancer and other diseases. This work aims to develop an experimental apparatus with 3He detectors for 16 MeV photoneutron measurements. The apparatus allows us to obtain multienergetic neutrons with the use of a 22 cm diameter spherical attenuator associated with different shield thicknesses. The microscopic processes of the fast and thermal neutrons in the detector were described by the two energy-group diffusion equation. The Detector Response  Dose Rate results show a directly proportional relationship between these two variables with a degree of reliability attested by the linear correlation coefficient .

V. Yu. Golikov, A. V. Vodovatov

This paper demonstrates the shortcomings of the existing method of radiation control in the X-ray rooms and the interpretation of the results of the measurements to assess the compliance of the working conditions of various groups of exposed individuals with radiation safety requirements. A new method of interpretation of the measurement results is proposed, considering the relative time spent by certain categories of exposed persons in the corresponding rooms during the use of the X-ray units, as well as the use of personal protective equipment (lead aprons). The interpretation of the measurement results in the treatment room according to the new approach has demonstrated the compliance of the working conditions to the Norms and Rules of radiation safety, provided that the worker is wearing a protective apron. The proposed approach to the interpretation of the results of the measurements in adjacent rooms leads to both reduced and stricter requirements for the stationary shielding. The paper includes a special focus on the incorrect calculation of stationary shielding for the installation of several X-ray units in one X-ray room within the framework of the current approach.

Anne Aguiar Araujo

This work aims to present a methodology that guides the operating organization to carry out periodic inspections in the nuclear PWR reactor pressure vessels. At first, fundamental concepts of nuclear energy and their application were discussed. This discussion allowed the presentation of: functions and characteristics of PWR reactor pressure vessels and the understanding of damage and effects of irradiation in the materials used in the manufacture of these vessels. From the recommendations of codes and publications related to pressure vessel integrity and inspections, for nuclear applications, the minimum requirements that should be considered in the inspection program preparation for this equipment were established. Furthermore, this paper shows the advantages of using computational tools to manage inspection results allowing the operators to plan and monitor the activities for the maintenance so as to avoid financial loss and environmental damage.