Hasil untuk "Radioactivity and radioactive substances"

Raquel Cordeiro de Oliveira, Evelin Mirelle Lima Araújo, Osana Diniz Ferreira et al.

Currently, ionizing radiation has been used on a large scale in different areas of knowledge. However, despite the existence of several radioprotection regulations for workers, patients and members of the public, these are not sufficient to completely limit the possible harmful effects of ionizing radiation. For this reason, there is currently an interest in finding radiomodifying substances with radioprotective or radiomitigating activity. It is reported that approximately half of all cancer patients will require radiotherapy. Therefore, as a means of radioprotection, the use of radioprotective compounds is essential to preserve healthy cells from radiation-induced damage. Among these agents, the literature highlights natural compounds and extracts, one of which is Allium cepa, commonly known as "onion"—a plant with medicinal potential, as well as antitumoral and antioxidant properties. However, no studies have reported the application of onion extract as an antioxidant and radioprotective agent in mammalian cells. Thus, it is necessary to confirm the antioxidant and radioprotective capabilities of A. cepa extract in human lymphocytes, particularly for planned exposures to ionizing radiation. Accordingly, the aqueous extract of A. cepa bulbs was subjected to cell viability testing (MTT assay) and antioxidant capacity evaluation (ABTS and DPPH assays). Subsequently, in the presence of the extract, the micronucleus assay was performed in lymphocytes exposed to three absorbed radiation doses (ranging from 0.5 to 4 Gy). The results demonstrated that, depending on the radiation dose and extract concentration, A. cepa extract influences the formation of micronuclei. At the dose of 0.5 Gy, no statistically significant difference was observed between irradiated groups treated or not treated with the extract. At 2 Gy, an increase in micronucleus frequency was observed in the presence of the extract, whereas at 4 Gy, the opposite effect was noted. Our findings suggest that A. cepa extract is a compound with potential applications in the field of health-related radiation exposure, exhibiting dual behavior depending on its concentration and the radiation dose. These results pave the way for further investigations, involving new extract concentrations, different absorbed radiation doses, and individual variability.

Pedro Preza, Gustavo Fortins, Gabriel Jabarra

The accumulation of Naturally Occurring Radioactive Material (NORM) during oil and gas production is a well-known phenomenon in mature markets with established legislation and disposal methods. In Brazil, MTE Regulatory Standard No. 37, issued in 2018, established the first labor regulation addressing NORM as an occupational hazard. Since then, oil companies have focused on managing waste disposal, with particular emphasis on NORM management. As Brazil anticipates an increase in decommissioning and dismantling activities, advancing methods, regulatory limits, and solutions for NORM management is critical. This article presents the specific regulations and the practical experience for radiological protection of workers and proper radioactive waste management within oil and gas installations. Through technical visits, dose rate monitoring, and legislative analysis, the study contextualizes the operational environment of exploration and production units, detailing health risks, waste characteristics, and storage requirements. The article also underscores the sector's complexity, emphasizing the variability in NORM accumulation across different installations and the necessity for targeted protective measures due to the potential exposure of employees during cleaning and inspection activities.

Tiago Augusto Santiago Vieira, Yasmim Martins Carvalho, Higor Fabiano Pereira de Castro et al.

Abstract: This study presents a numerical investigation into the impact of various mesh element types on water flow results through a representative spacer grid, utilizing Computational Fluid Dynamics (CFD). The study evaluates the variations of the k−ϵ turbulence model available in Simcenter STAR-CCM+ across different mesh types. Three predominant cell types were employed: cartesian, polyhedral, and tetrahedral, alongside three k−ϵ models: Standard Two-layer (STL), Realizable Two-layer (RTL), and Elliptic Blending (EB). The analysis was conducted using a PWR vane-type spacer grid arranged in a 2x2 configuration. The findings demonstrated a strong correlation with experimental data available in the literature. However, the cartesian and tetrahedral meshes attenuated the velocity profiles post-spacer grid. The polyhedral mesh, in conjunction with the RTL and EB k−ϵ models, yielded results more closely aligned with the experimental data. Regarding Secondary Flow (SF), the results indicated a consistent trend of decreasing intensity downstream of the spacer grid. The Polyhedral EB and RTL models exhibited behavior most consistent with the experimental results.

Axel Gross, Samuel Cupp, Matthew R. Mumpower

The radioactive $β$-decay of nuclei synthesized in the rapid neutron capture process ($r$-process) releases a variety of particles, including electrons, $γ$-rays, neutrinos, and neutrons. These particles provide a rich set of multi-messenger signals that carry information about the astrophysical environments where neutron-rich nucleosynthesis occurs. In this work, we calculate from first principles the emission spectra resulting from the $β$-decay of $r$-process nuclei. Our approach incorporates detailed nuclear structure and decay data to model the energy distributions of each particle species. We couple the spectra with a nuclear reaction network simulation to obtain the temporal evolution of these distributions. We find that the emission distributions vary significantly in time and are non-thermal, with substantial average energies. We investigate these nuclear signals as a direct probe of heavy element formation and show that they are complementary observables to kilonova.

Renato Gomes, Thiago Carmo, Kelmo Braga et al.

This work aims to develop a robotic platform coupled to radiation detectors for application in radiological accident simulation experiments. To this end, a robot was assembled on a platform on six wheels with Arduino programming, seeking movement in different degrees of freedom. The robot was controlled by remote control and viewed by a camera so the operator could follow the path taken by the robotic platform. The radiation values were seen instantly from the display of the radiation monitor/detector (RadEye). This platform model used non-destructive tests with radioactive sources in the laboratory for an environmental radiometric survey simulating a radiological accident. The results showed the command synchronization between the controller and the platform in an environment with only the presence of the background and the visualization of the instantaneous dose rate in Sv/h. However, when faced with the radiation field, there was interference in the signals and communication controlling the robot's movements. However, due to the short exposure time to gamma rays, the electronic components did not show any damage. It can be concluded from this experience that the prototype should be improved by adding shielding to the electronic boards, which are sensitive to radioactivity. The relevance of this investigation lies in developing robotic platforms for exposure in environments that pose health risks and for the radiological protection of emergency teams in actions during radiological and nuclear accidents.

A. N. Barkovsky, S. A. Ogorodnikov

In  the  Russian  Federation,  there  is  a  constant  increase  in  the  number  of  radiation  medical  installations  with electron accelerators. Over the past 4 years, their number has increased 2.5 times. These installations contain pulsed electron accelerators that generate pulsed bremsstrahlung radiation with a maximum energy from 6 to 21 MeV. Currently, there are no devices designed for dosimetry of the pulsed photon radiation with energy of more than 10 MeV in the state register of measuring instruments of the Russian Federation. The most widely used radiation monitoring device for pulsed electron accelerators is the DKS-AT1123 X-ray and gamma radiation dosimeter designed for dosimetry of pulsed bremsstrahlung radiation with an energy of up to 10 MeV. The purpose of this work is to evaluate the possibility of using this device for dosimetry of pulsed bremsstrahlung radiation with a maximum energy of up to 20 MeV. The authors calculated the energy spectra of bremsstrahlung radiation for a point source with a maximum energy of 20 MeV behind flat concrete screens with a thickness of 1 m, 2 m and 3 m by the Monte Carlo method using the GEANT4 calculation program. The energy dependence of the registration efficiency of the DKS-AT1123 dosimeter was extrapolated to the energy range of 10–50 MeV in the kerma-approximation without taking into account the energy transfer by secondary electrons. It was assumed that it corresponds to the energy dependence of the total mass attenuation coefficient for the absorbed energy of gamma quanta in water. Using conversion coefficients for converting the fluence of monoenergetic photons into the effective dose rate at an anterior-posterior radiation incidence on the human body, real dose rates were calculated, and using the energy dependence of the dosimeter readings, the predicted results of measuring the unit dose rate with the DKS-AT1123 dosimeter behind a concrete protection with a thickness of 1, 2 and 3 m were obtained. It is shown that the maximum expected underestimation of the measurement results will not exceed 40% and practically does not depend on the thickness of the concrete shield in the thickness range from 1 to 3 m. To account for this underestimation, it is necessary to use the value of additional measurement error due to the energy dependence of the sensitivity of this device for the photon radiation energy of more than 10 MeV, equal to 70%. This makes it possible to use the measurement results obtained using this dosimeter to adequately characterize the state of radiation safety during operation of pulsed electron accelerators with a maximum energy of up to 20 MeV. It is possible to use a correction factor to the measurement results equal to 1.63 ±0.04 to compensate for this underestimation. The proposed approach can be used to create a methodology for using this dosimeter for radiation monitoring of medical electron accelerators with the energy of up to 20 MeV, if there are correction factors for radiation protection configurations and radiation energies encountered in practice.

Sanjeet S. Kaintura, Swati Thakur, Sarabjot Kaur et al.

In this work, radioactivity investigations of soil samples from neutral and agricultural sites in Punjab/India have been carried out to study the impact of land use patterns. The analysis of radiological, mineralogical, physicochemical, and morphological attributes of soil samples has been performed employing state-of-the-art techniques. The mean activity concentration of 238U, 232Th, 40K, 235U, and 137Cs, measured using a carbon-loaded p-type HPGe detector, in neutral land was observed as 58.03, 83.95, 445.18, 2.83, and 1.16Bq kg-1, respectively. However, in vegetation land, it was found to be 40.07, 64.68, 596.74, 2.26 and 2.11Bq kg-1, respectively. In the detailed activity analysis, radium equivalent (Raeq) radioactivity is found to be in the safe prescribed limit of 370Bq kg-1 for all investigated soil samples. However, the dosimetric investigations revealed that the outdoor absorbed gamma dose rate (96.08nGy h-1) and consequent annual effective dose rate (0.12mSv y-1) for neutral land, and the gamma dose rate (82.46nGy h-1) and subsequent annual effective dose rate (0.10mSv y-1) for vegetation land marginally exceeded the global average. The surface morphology of neutral land favored more compactness, while agricultural land favored high porosity. Various heavy metals of health concern, namely As, Cd, Co, Cr, Cu, Hg, Pb, Se, and Zn, were also evaluated in all soil samples using Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Pollution Load Index (PLI) and Ecological Risk Index (RI) revealed that vegetation land was more anthropogenically contaminated than neutral land, with maximum contamination from Hg and As.

Meng-Hua Chen, Li-Xin Li, En-Wei Liang

The observation of a kilonova AT2017gfo associated with the gravitational wave event GW170817 provides the first strong evidence that neutron star mergers are dominant contributors to the production of heavy $r$-process elements. Radioactive gamma-ray lines emitted from neutron star merger remnants provide a unique probe for investigating the nuclide composition and tracking its evolution. In this work, we studied the gamma-ray line features arising from the radioactive decay of heavy nuclei in the merger remnants based on the $r$-process nuclear reaction network and the astrophysical inputs derived from numerical relativity simulations. The decay chain of $^{126}_{50}$Sn ($T_{1/2}=230$ kyr) $\to$ $^{126}_{51}$Sb ($T_{1/2}=12.35$ days) $\to$ $^{126}_{52}$Te (stable) produces several bright gamma-ray lines with energies of $415$, $667$, and $695$ keV, making it the most promising decay chain during the remnant phase. The photon fluxes of these bright gamma-ray lines reach $\sim10^{-5}$ $γ$ cm$^{-2}$ s$^{-1}$ for Galactic merger remnants with ages less than $100$~kyr, which can be detected by the high energy resolution MeV gamma-ray detectors like the MASS mission.

Gonzalo Herrera, Patrick Huber

We show that placing a radioactive source such as ${}^{51}$Cr near a liquid xenon detector may allow to detect the contribution induced by the anapole moment to neutrino-electron scattering in the Standard Model at the 1-2 $σ$ level. Although the anapole moment of neutrinos induces a scattering rate with the same spectral shape as the neutral and charged current contributions, exposures of $\sim$ 60 tonne $\times$ source run at XENONnT or XLZD may be enough to accumulate sufficient statistics for a detection. We also discuss a simple model where the anapole moment of neutrinos is enhanced or decreased with respect to the SM expectation, further demonstrating how a potential measurement of the anapole moment of neutrinos would allow to constrain new physics.

L. A. Chipiga, I. A. Zvonova, A. V. Vodovatov et al.

Current patient release criteria established in NRB-99/2009 relate to four radionuclides used in Russia that period of the document preparation. These criteria were calculated only considering the radionuclide decay. Thus, these criteria give conservative assessments which require the patient to stay in dedicated protected room (“hot” room) of the radiotherapy department for several days and do not allow to radionuclide therapy to be given in the outpatient hospital which certainly reduces the availability of this type of treatment. Consideration of the biological excretion of the radiopharmaceutical will be able to make the patient release criteria after radionuclide therapy significantly softer. Recently, new promising radionuclides and radiopharmaceuticals for therapy have appeared, the introduction of which into medical practice is obstructed by the lack of the patient release criteria. Current study is devoted to justification of improvement the approach to definition of patient release criteria after radionuclide therapy with promising and applied radiopharmaceuticals considering biological excretion of radiopharmaceutical. As examples, calculations of patient release criteria were performed for 177Lu-PSMA, 177Lu-DOTA-TATE, 131I-mIBG и Na131I. The dosimetric model used for calculation is based on the model which was used for definition of the current patient release criteria in NRB-99/2009. Additionally, the biological excretion of the radionuclide in radiopharmaceutical, which was assessed according to the published data, was considered. Two phases of biological excretion were evaluated for considered radiopharmaceuticals (fast and slow fractions). The main contribution of the radionuclide decrease in the patient’s body during the first hours after the injection is made by the fast-eliminated fraction. During 4-6 hours after the administration about 50% of these radiopharmaceuticals eliminated via urine. The calculation of patient release criteria were performed for slow-elimination fractions which characterize the decrease of radionuclide activity in the body after the patient release. The following effective half-lives were used: 177Lu-PSMA – 60 hours, 177Lu-DOTA-TATE – 100 hours, 131I-mIBG – 45 hours, Na131I – 7.5 days. The calculations demonstrate when planning a course of radionuclide therapy with four administrations of 177Lu-PSMA, the release of a patient is allowed at the dose rate of 20 μSv/h from the patient at the distance of 1 m; in case of radionuclide therapy with 177Lu-DOTA-TATE, release of a patient is allowed at the dose rate of 12 μSv/h. Considering the fast-eliminated fraction in the first hours after the administration, it can be assumed that more patients with normal renal function can undergo radionuclide therapy with 177Lu-PSMA in the outpatient hospital. Some patients after the 177Lu-PSMA administration and patients in the therapy with 177Lu-DOTA-TATE may be held in the department in the “hot” rooms for 1-2 days until the dose rate decrease to the acceptable levels. The consideration of biological excretion of radiopharmaceutical makes it possible to soften patient release criterion for 131I-mIBG by four times and for Na131I – by 10%. It will allow to release patients after radionuclide therapy earlier without reduce of radiation safety of people around the patient and will increase the capacity of radionuclide therapy department.

Amy Bonsor, Mark C. Wyatt, Sebastian Marino et al.

Kuiper-like belts of planetesimals orbiting stars other than the Sun are most commonly detected from the thermal emission of small dust produced in collisions. Emission from gas, most notably CO, highlights the cometary nature of these planetesimals. Here we present models for the release of gas from comet-like bodies in these belts, both due to their thermophysical evolution, most notably the decay of long-lived radioactive nuclides and collisional evolution, including catastrophic and gentler resurfacing collisions. We show that the rate of gas release is not proportional to the rate of dust release, if non-catastrophic collisions or thermal evolution dominate the release of CO gas. In this case, care must be taken when inferring the composition of comets. Non-catastrophic collisions dominate the gas production at earlier times than catastrophic collisions, depending on the properties of the planetesimal belt. We highlight the importance of the thermal evolution of comets, including crucially the decay of long-lived radioactive nuclides, as a source of CO gas around young (<50Myr) planetary systems, if large (10-100s kms) planetesimals are present.

Carla Gomes Tinoco Andrade, Maria de Lourdes Moreira, Pedro Luiz da Cruz Saldanha

The advantages of Long-Term Operation (LTO) in dealing with the end-of-life-cycle issue of Nuclear Power Plants (NPPs) in operation today, when compared to the creation of new NPPs, have major social and economic implications. The Life Extension process of the Brazilian NPP Angra 1 has already started, and its methodology is well defined in the technical notes NT-CGRC-007/18, (CNEN, 2018a) [1] and NT-CGRC-08/18, (CNEN, 2018b) [2]. This work aims to present a critical analysis of the two technical notes. The technical notes are in an initial version, therefore, the results of their verifications and validations are presented, which were carried out through a qualitative analysis, the factors that can be modified to be adjusted and/or modified to generate improvements for the notes or documents that may replace them.

Wataru Fujiya, Hisato Higashi, Yuki Hibiya et al.

C-complex asteroids, rich in carbonaceous materials, are potential sources of Earth's volatile inventories. They are spectrally dark resembling primitive carbonaceous meteorites, and thus, C-complex asteroids are thought to be potential parent bodies of carbonaceous meteorites. However, the substantial number of C-complex asteroids exhibits surface spectra with weaker hydroxyl absorption than water-rich carbonaceous meteorites. Rather, they best correspond to meteorites showing evidence for dehydration, commonly attributed to impact heating. Here, we report an old radiometric age of 4564.7 million years ago for Ca-carbonates from the Jbilet Winselwan meteorite analogous to dehydrated C-complex asteroids. The carbonates are enclosed by a high-temperature polymorph of Ca-sulfates, suggesting thermal metamorphism at >300°C subsequently after aqueous alteration. This old age indicates the early onset of aqueous alteration and subsequent thermal metamorphism driven by the decay of short-lived radionuclides rather than impact heating. The breakup of original asteroids internally heated by radioactivity should result in asteroid families predominantly consisting of thermally metamorphosed materials. This explains the common occurrence of dehydrated C-complex asteroids.

Alexandre Melo Oliveira, Amir Zacarias Mesquita, Enio Pedone Bandarra et al.

To evaluate the synthesis and characterization of MWCNT (Multi-walled Carbon Nanotubes) with different degrees of functionalization in distilled water. The thermophysical properties (thermal conductivity and viscosity) of these nanofluids were measured at a temperature range (20-60°C) and concentrations (0.005-0.05%) by volume. Increases in thermal conductivity and viscosity were found 9.3% and 4.7%, respectively, at a volumetric concentration of 0.01% at a temperature of 30°C. The study of new fluids that improve the rate of removal of heat is fundamental to obtain greater efficiency of energy systems. Among the several factors that compromise the efficiency of the energy systems, we can highlight the thermophysical limitations of the conventional fluids, inhibiting in a very significant way some industrial applications. In this work we intend to improve the heat transfer characteristics of fluids commonly used by the addition of nanoparticles, made up of carbon nanotubes, in water which is the most used fluid for the cooling of nuclear reactors in operation today. It is intended to improve the heat transfer characteristics of fluids commonly used by the addition of nanoparticles, made of carbon nanotubes, through the addition of nanoparticles, made up of carbon nanotubes, in water which is the most used fluid for refrigeration of nuclear reactors currently in operation. In order to assess its benefits for the applicability and nuclear systems, ie primary coolant, safety systems, major accident mitigation strategies.

Carla Daruich de Souza, Carla Daruich de Souza, Carlos Alberto Zeituni et al.

Gold nanoparticles (NPs) have been intriguing scientists for over 100 years. Recently, they have been studied for new applications such as cancer treatment. Although the synthesis of gold nanoparticles is extensively reported, in the majority of cases the methodology is confused and/or not clear. We describe a new synthesis methodology for radioactive gold‐198 NPs. Gold-198 was activated in IPEN IEA-01 nuclear reactor. After that, chloroauric acid (HAuCl4) was formed by dissolving the radioactive gold with aqua regia and performing repeated heating cycles. 0.1 mM HAuCl4 containing 100 μL of 1 M NaOH was prepared in a flask equipped with a reflux condenser. The solution was brought to boil and stirred with a PTFE‐coated magnetic stir‐bar. Then 5 mL of sodium citrate was rapidly added. The reaction turns from light yellow to clear, black, dark purple until the solution attained a wine‐red color (2–3 min). Dynamic light scattering (DLS) confirmed 8 nm particles. The presence of gold‐198 (197.968 g/mol; half‐life: 2.69517; decay mode: β‐; average energy: 1.3723 MeV) was confirmed by an ORTEC HPGe detector. DLS was performed after complete decay confirming the 8 nm diameter maintenance. We were able to achieve radioactive gold‐198 NPs and are performing further studies such as: coating reactions, in‐vitro and in‐vivo studies.

Gleiser Rodrigues de Melo, Guilherme Soares Zahn, Frederico Antonio Genezini et al.

Neutron Activation Analysis (NAA) is a well-established nondestructive analytic technique where the gamma radiation emitted by an irradiated sample is analyzed using an HPGe detector. The Neutron Activation Laboratory (LAN) of IPEN-CNEN/SP has been performing NAA analyses for over 30 years, and has plans of implementing quality control protocols to their analyses. In this sense, the environmental monitoring of the laboratories where the detectors are used has been performed for many years, in a manual way with no more than 2 measurements per day. In this work, an automated monitoring station based on a microcontroller Arduino UNO board has been developed which comprises four thermo hygrometer sensors for monitoring different parts of the environment, plus a thermocouple for monitoring the inside of the liquid nitrogen dewar. The results obtained allow for a discussion on the performance and adequacy of the sensors.

Luana Lazzari, Esequia Sauter, Fábio Souto De Azevedo

In this work we solve numerically the one-dimensional transport equation with semi-reflective boundary conditions and non-homogeneous domain. The proposed methodology consists of applying the Nyström method in order to discretize the integral formulation of this problem which is an equation involving weakly singular integral operators. For this purpose, analytical and computational techniques were applied to deal with the singularities. The Nyström method is an integral method which approximates the integral operator by a numerical quadrature and turns the integral equation into a finite dimensional linear system. This formulation allows us to use any function to describe both scattering cross section and total cross section. The algorithm is implemented in C language with the use of routines of GNU scientific library and computational techniques for code optimization. The scalar flux was calculated for two numerical quadrature, namely Gauss-Legendre quadrature and Boole's rule. The numerical results were determined for transport problem with homogeneous and non-homogeneous domains. In order to validate the proposed method-ology, our numerical results were compared with those from the literature and presented with several correct significant digits.

Santeri Larnimaa, Markku Vainio, Ville Ulvila

We present the first report of optical absorption spectroscopy of H$^{36}\!$Cl, a radioactive isotopologue of hydrogen chloride. We used Fourier-transform infrared spectroscopy to determine the line center wavenumbers of the fundamental rovibrational band lines P(10)-R(10) and the first overtone band lines P(1)-R(7) with total uncertainty of less than 0.0018 cm$^{-1}$ (60 MHz) and 0.007 cm$^{-1}$ (0.2 GHz), respectively, at 68 % confidence level. We also performed a rotational analysis on the bands to determine the related molecular constants. We further compared the linewidths and relative intensities of the lines to those of the stable isotopologues H$^{35}\!$Cl and H$^{37}\!$Cl. The new spectroscopic information assists in developing optical instrumentation for the detection of H$^{36}\!$Cl.

Luigi Cosentino, Martina Giuffrida, Sergio Lo Meo et al.

One of the goals of the MICADO Euratom project is to monitor the gamma rays coming out of radioactive waste drums in storage sites on a medium/long term basis. For this purpose 36 low-cost gamma ray counters were designed and built to act as a demonstrator. These counters, named SciFi, are based on a scintillating fiber readout at each end by a silicon photomultiplier, as-sembled in a robust arrangement in form of 80 cm long pipes. Several counters will be placed around radwaste packages in order to monitor the gamma dose-rate by collecting a continuous data stream. The 36 sensors were thoroughly tested with a 22Na, a 137Cs and an AmBe sources, the results are quite satisfactory and the next step will be the test in a real environment

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