Hasil untuk "Radioactivity and radioactive substances"

Theodor Adam, Petr Otáhal, Michael Komárek

Tiago Augusto Santiago Vieira, Geovana Loren Cruz, Yasmim Martins Carvalho et al.

The Molten Salt Fast Reactor (MSFR) represents a significant innovation within the Generation IV nuclear reactor systems, distinguished by its use of molten salt as both fuel and coolant. This study presents a methodology for performing steady-state coupled neutronics and thermal-hydraulics (TH) calculations for the Molten Salt Fast Reactor (MSFR) using Monte Carlo (MC) and Computational Fluid Dynamics (CFD) techniques. The reactor was fed with fuel salt using LiF as base salt, thorium (232Th) as a fertile material and 233U as fissile material. Uncertainty quantification was performed using an extended Grid Convergence Index (GCI) method. The extended Grid Convergence Index (GCI) method was applied to quantify uncertainties in temperature, velocity, and power density profiles. The results highlight the significance of coupled convergence, particularly for the power density field, and reveal lateral recirculation and hot spot formation in the reactor core. The noise reduction techniques applied to the MC simulations effectively smoothed power density profiles, reducing statistical uncertainty.

Patrícia de Lara Antonio, Linda Viola Ehlin Caldas

Thermoluminescence (TL) and optically stimulated luminescence (OSL) are two techniques based in the luminescence phenomenon. They can be applied to study the response of materials which present the property of emitting light after the steps of irradiation and subsequent stimulus, that can be thermal (in the case of TL) or optical (OSL). These materials may also be capable of exhibiting phototransfer effect in their response, and this characteristic can be observed through the TL photo-transfer (PTTL) and OSL photo-transfer (PTOSL). The purpose of this work was to verify the presence of the PTTL and PTOSL responses on the Spectrolite material, after irradiation with gamma source (60Co) and illumination with LEDs (wavelengths in the UV region), for application in gamma radiation dosimetry. For this, the signal of Spectrolite samples was studied in relation to their TL/PTTL and OSL/PTOSL responses by means of three steps: 1) irradiation and measurement of TL and OSL responses; 2) irradiation, post-irradiation thermal treatment (PITT) and measurement of TL and OSL signals; and 3) irradiation, PITT, illumination with LEDs and measurement of PTTL and PTOSL signals. The results obtained showed the presence of photo-transfer effect in the PTTL response, but not in the PTOSL response; this fact demonstrates the need for further studies to verify the PTTL and PTOSL responses, with variations in the wavelength of light and the illumination time. For application of this material in gamma radiation dosimetry, these other studies are needed. 1) irradiation and measurement of TL and OSL responses; 2) irradiation, post-irradiation thermal treatment (PITT) and measurement of TL and OSL signals; and 3) irradiation, PITT, illumination with LEDs and measurement of PTTL and PTOSL signals. The results obtained showed the presence of photo-transfer effect in the PTTL response, but not in the PTOSL response; this fact demonstrates the need for further studies to verify the PTTL and PTOSL responses, with variations in the wavelength of light and the illumination time. For application of this material for gamma radiation dosimetry, these other studies are needed.

Ana Luísa da Costa Vieira, Fernanda do Nacimento Moura

This work is about radiation protection training at Sirius, a unique radiation facility in Brazil for being a synchrotron-type particle accelerator. Research in several areas takes place at the facility, attracting researchers from all over the world. The radiological protection group at Sirius works continuously to ensure everyone's safety, in addition to shielding and monitoring, there are several security elements and one of them is the application of radiological safety training, where the researcher is presented the “Search” procedure. At the end of the training, the researcher answers a feedback form, which is used as a satisfaction survey. In the first semester for 2022, 46 people were trained of which 43.47% responded to the feedback form. Of the total responses, 95% were satisfied. Due to the large number of people attending Sirius, the radiation safety training is in the process of moving to an online format, which brings new challenges.

Fiorela Merma Velasco, Mariela Bellotti, Pablo Andres

Mammography is a radiation medical exam, which makes detection of mammary microcalcifications possible at an early stage. The dose received by the patient’s breast is known as the average glandular dose, which is considered a quality control indicator. Estimation of this parameter implies knowing the effective energy of the x-ray beam delivered. This is the case when thermoluminescent dosimetry is the method of choice. The algorithm developed to discriminate the x-ray energy the mammography patient has been exposed to while undergoing routine procedures, applies two thermoluminescent dosimeters, one of them filtered by a 1 mm thick aluminum layer. The effective energy of the x-ray beam and the correction factor are obtained by knowing the relation between the filtered and non-filtered dosemeters readout. This algorithm was then used to estimate the average glandular dose following the IAEA TRS 457 protocol. The dose values computed were compared with the international diagnostic reference levels suggested by the technical literature.

Ken'yo Uh, Masanori Kameyama, Gaku Nishiyama et al.

We develop a 2-D numerical model of magmatism and mantle convection to understand the volcanism on the Procellarum KREEP terrane (PKT) of the Moon, which continued for billions of years with two peaks of activities at 3.5-4 Gyr ago and around 2 Gyr ago. In our model, the effects of the PKT on lunar evolution are considered by initially imposing a region of localized radioactive enrichment. The calculated volcanism has two peaks induced by different mechanisms. The first peak occurs at 3.5-4 Gyr ago when magma generated in the deep mantle by internal heating ascends to the surface as partially molten plumes. The basaltic blocks in the uppermost mantle formed by this magmatism, then, sink to the deep mantle, triggering further plumes that cause the resurgence of volcanism at $\sim$2 Gyr ago. Our model shows that localized radioactive enrichment is important for the long-lasting volcanism with a couple of peaks.

A. J. González, L. R. Sánchez, A. Torres et al.

Image-guided interventional procedures have become one of the medical applications that produces the highest doses of radiation for both the patient and the personnel involved in it. Safety assessment was applied to a generic service where image-guided interventional procedures was carried, using the semi-quantitative method of risk matrix, implemented in the Cuban SECURE-MR-FMEA code. The process map was prepared, identifying 6 stages with 76 accidental sequences. Values showed that the first screening for the developed model reports 45 % of high risks, 42% and 13 % of moderate and low risks, and once the number of controllers increased, high risks decrease to 11 % and there is an increase in moderate and low risks of 54 % and 35 % respectively. These results stress the importance of using all necessary measures for the protection of the public, patients and occupationally exposed workers.

Cibele Bugno Zamboni, Dalton Nogueira da Silva Giovanni, Mateus Ramos de Almeida et al.

In this investigation, the elements Ca and S were evaluated in a single nail clipping using compact and portable X-ray spectrometer model X-123 SDD with Ag target. Experimental conditions for current, voltage and excitation time were investigated. These analyses can be useful for a variety of applications, including nutritional and medical diagnosis, such as, the evaluation of bone dysfunctions by measurement of Ca (bone decalcification) and S for nutrition evaluations (collagen production). This analysis offers some benefits comparatively to blood and serum analyses, such as, non-invasive collection, fast analyses (minutes) and low cost. In addition, nail clippings are simple to obtain, easy to store, and easy to transport. This pilot study show a positive expectation for clinical application using in-vitro nail test.

Rodrigo Modesto Gadelha Gontijo

In Brazil, currently there are six preclinical molecular imaging centers and seven different small animal PET systems in use. However, there is still no national specific legislation for research laboratories focused on preclinical molecular images, unlike clinical nuclear medicine centers. A standardization of quality control protocols is needed to harmonize the use of small animal PET scanners in the research field. Thus, the aim of this work was to propose a National Program for Quality Control (NPQC) for the preclinical PET imaging systems in Brazil. This work was based on the quality control tests performed in Molecular Image Laboratory LIM/CDTN based on NEMA NU 4-2008 as described and presented in doctoral thesis of GONTIJO, 2019. The proposal of the NQCP was based on the CNEN NN 3.05 Publication (2013) and includes fundamental tests to be adopted, if possible, in laboratory practice to corroborate the experimental data. The Quality Control Program implemented in LIM/CDTN is an innovative and unprecedented proposal in the scope of preclinical molecular imaging services in Brazil. Therefore, the LIM/CDTN Program was carried out as a pilot to evidence the applicability and viability of the NQCP using small animal PET scanners. Summarizing, this work presents a viable set of Quality Control tests and their periodicities like a proposal for standardization to harmonize the use of this imaging technology in the field of research. Therefore, a National Quality Control Program (NQCP) applied to small animal PET scanners.

Fania Caicedo, Pedro Luiz Guzzo, Viviane Khoury Asfora

This study investigates the effect of the dose-rate in the thermoluminescent glow curves of a single crystal of quartz. The samples were sensitized by the γ radiation combined with the heat-treatments. The glow curves were registered in zeroed (unsensitized) and sensitized conditions using an optical filter centered in violet spectral region. Tens mGy test doses were administered with one β (90Sr/90Y) source and two γ radiation sources (60Co and 137Cs). The TL curves were deconvoluted using a first-order kinetic model. Differences in the glow curves and trapping parameters were observed between zeroed and sensitized samples. Differences were found in the TL curves comparing the three radiation sources. The principal variation is the remarkable increase in the TL signal above 350 °C, which is observed only in sensitized samples with the minor dose-rate source (137Cs). This signal seems to be associated with deep trapping states. The intensities of the components defining the first peak and the high temperature signal show a dependence on the dose-rate. The dose-rate dependence of the first-peak components is explained by the competing effects that may take place during the excitation stage. The components that fitted the sensitized peak (260 oC) do not exhibit a clear dependence on the dose-rate of radiation source.

H. Tagawa, J. Kawarabayashi, Taiki Yoshii et al.

Clearance is the removal of regulatory control by a regulatory body from radioactive material or radioactive objects. One method of evaluating the radioactivity for clearance is measuring the storage container containing the waste from the outside with a radiation detector. Due to the amendment of clearance regulations of Japan in 2020, plastic and metal mixtures (power cables, switchboards, etc.) can be released under the clearance. However, when the storage container containing these substances is measured as it is, the non-uniform distribution of the atomic number and the density of each substance in the storage container makes it difficult to consider the actual radiation shielding effect. In order to incorporate reliable radiation shielding into radionuclide concentration evaluation, we propose to introduce a non-destructive inspection method, such as CT scan that can give information on the inside of container. Assuming that the elements contained in the storage container were known as prior information, we experimentally verified whether it was possible to identify the elements by the CT scan. In this study, rods of PMMA, aluminum, copper and iron in small container were scanned by CT and images were reconstructed by FPB and ML-EM methods. The results showed that each element could be distinguished from each other successfully when the voltage of X-ray tube was over 100 kV.

S. Razanov, G. Ogorodnichuk, Мykola Komynar

Over the past few decades, the level of radiation has significantly increased due to artificial sources – radionuclides. In particular, the Chernobyl accident led to the release of about 50 million Кі of various types of radionuclides into the environment. As a result of the accident at the Chernobyl nuclear power plant in Ukraine, a large number of territories of the Zhytomyr region are polluted – 50%, Kiev – 26%. About 26% of the contaminated area falls on the Chernigov, Rivne, Sumy and Volyn regions. The radioactive substances that were part of the nuclear fuel were concentrated in the environment, from where they partially migrate along the soil-plant-living organisms chain, causing a number of negative changes in them. Immediately after the Chernobyl accident, iodine-131 posed a great danger to living organisms; its radioactivity in the contaminated area was 7.3 MКi. Iodine-131 is a beta and gamma emitter with a half-life of 8.04 days. This element is characterized by high activity in the soil-plant-production-organism system. It enters the body by the oral route and accumulates mainly in the thyroid gland. At the same time, cesium-134, cesium-137 and strontium-90 are also dangerous for living organisms, the share of which is about 3% of the total radioactivity. All other radionuclides that were released into the environment during the Chernobyl accident are less dangerous due to the low rate of entry into living organisms. Cesium-137 has a half-life of 30.2 years and is absorbed into the body in three ways: percutaneous, aerial and oral. The largest proportion of cesium-137 is ingested orally. It is a chemical analogue of potassium and is actively involved in the metabolic process. Therefore, it can accumulate in high amounts in body tissues. About 10% of cesium-137 is excreted from the body with indigestible food residues, and the vast majority - with urine. Cesium-137, penetrating into the body, is concentrated mainly in muscle tissue, and comparatively less in bone tissue. It is excreted from bone tissue much more slowly than from muscle tissue. Now in the environment there is still about 50% of cesium-137, which got into the environment as a result of the Chernobyl accident. Radionuclides in the soil are in a moving state, therefore they move to certain layers of it. The speed of such movement of radionuclides in the soil depends on its properties, the content of mineral and organic substances. In particular, it was revealed that the migration of cesium-137 on mineral sod-podzolic soils is ten times lower than on peat and peat-bog soils. This is typical of the soil of the ecological zone of Polesie. The composition of the soils of this zone includes no more than 1.0% of clay, 0.8-1.2% of humus, 3-5% of the silty fraction, causing a high migration of radionuclides. Cesium-137 in these soils is in the sod in a fast-moving form and rather intensively migrates into the vegetation. It has been proven that the mineral part and humus firmly fix cesium-137. The accident resulted in about 1,500,000 pollution in Ukraine. Hectares of forests, most of which have lost their practical value and are withdrawn from use. It has been established that the main amount of radionuclides is concentrated in the upper five-centimeter soil layer and in the forest litter, which is characteristic of pine forests. In pine forest stands, 30-60% strontium-90 and 40-80% cesium-137 are concentrated in the litter, and about a third of radionuclides are concentrated in deciduous forests. Most radionuclides enter plants by the root route. Some authors report that sometimes plants accumulate significantly more radionuclides, even with a lower content of them in the soil. This trend is observed in the Polesie of Ukraine. Over the past 15 years, the strontium-90 content in plant products has not changed significantly. Researchers have studied the peculiarities of the accumulation of radioactive substances by melliferous plants, which can actively accumulate cesium-137. Plants of the family Rosaceae, buckwheat, buttercups are classified as active accumulators of radiocesium. A high content of strontium-90 is characterized by silver cinquefoil, caustic buttercup, and such honey plants as red and white clover, alfalfa, horned lily, sainfoin and mouse peas, common heather, blueberries intensively accumulate both cesium-137 and strontium-90. The intensity of accumulation of cesium-137 in bee pollen, perge and homogenate of drone larvae produced by bees from pollen of winter rape, sunflower and buckwheat in different ways was studied.

T. Ross, S. Ametamey

E. I. Tolstykh, M. O. Degteva, A. V. Akleyev

Assessment of the lymphocyte doses is relevant for solving a number of radiobiological problems, including the risk assessment of hemoblastosis (leukemia, multiple myeloma, lymphoma etc.), as well as the use of circulating lymphocytes as “natural biodosimeters”. The latter is because the frequency of chromosomal aberrations occurring in lymphocytes following radiation exposure is proportional to the accumulated dose. Assessment of doses to the circulating lymphocytes requires due account of: first, the dose accumulated by the lymphocyte progenitors in the red bone marrow; and second, the dose accumulated during lymphocyte circulation through lymphoid organs. The models presented by International Commission on Radiological Protection (ICRP-67, ICRP-100) allow calculating the dose for specific lymphoid organs based on known level of radionuclide intakes. A recently developed model of circulating T-lymphocyte irradiation takes into account all sources of exposure and age-related dynamics of T-lymphocytes: (1) exposure of lymphocyte progenitors in red bone marrow: (2) exposure of T-lymphocytes in the lymphoid organs, taking into account the proportion of resident lymphocytes and the residence time of circulating lymphocytes in the specific lymphoid organs. The objective of the study is to assess the dose coefficients allowing for the transition from the ingestion of 141,144Ce, 95Zr, 103,106Ru, 95Nb to the doses accumulated in circulating T-lymphocytes. For calculations, we used the dose coefficients from ICRP publications for specific lymphoid organs, as well as published data on the residence time of circulating lymphocytes in lymphoid organs and tissues. As a result, it was shown that the doses in circulating T-lymphocytes are higher than those in the red bone marrow, but lower than the doses to the colon wall. The dose coefficients were age dependent; the maximum values were typical for newborns. The obtained dose coefficients for 141,144Ce, 95Zr, 95Nb and 103,106Ru can be used to estimate the tissue and organ doses based on data on the frequency of chromosomal aberrations in peripheral blood lymphocytes.

E. K. Nilova, V. N. Bortnovsky, S. A. Tagai et al.

The results covered in this paper relate to the “Khoiniki” research sub-unit of a larger-scale sequence of studies focused on the local assessments of the present-day 241Am and 137Cs concentrations in the soils and locally produced foods, with the estimation of the public internal radiation doses in the residential areas of the Gomel region of the Republic of Belarus most closely adjacent to the ChNPP resettlement zone. The objective was to make a conservative estimate of a committed annual dose of internal exposure from 241Am and 137Сs received by the villagers of 96 farmsteads in 30 settlements of the private sector of Khoiniki countryside through both, inhalation and consumption of local foodstuffs. The results obtained in this study include an update of the existing contamination levels of 241Am and 137Сs present in the local soils and foods grown or produced in private backyards and households. 241Am in food samples was determined by alpha-spectroscopy radiochemical analysis with the use of selective extraction-chromatographic resins. Gamma-spectrometry techniques were used to measure 241Am in soil samples and 137Сs in soil and food samples. Based on our findings, the present-day deposition density of 241Am in the soils does not exceed 4 kBq/m2 , while the values of 137Cs contamination are by one to two orders of magnitude higher than that of 241Am and vary between 30 and 500 kBq/m2 . Generally, the values of activity concentration of 241Am detected in local soils are well within 10 Bq/kg in the majority of inspected villages, with the exception of three sites where higher levels of 241Am contamination is soils were detected ranging from 14 to 16 Bq/kg. The ambient dose rates in the countryside range from 0.05 to 0.38 μSv/hour, with the average of 0.15 μSv/hour. No cases of 137Сs contamination above the established reference levels of 80, 100 and 90 Bq/ kg have been found in the local food samples of, respectively, potatoes, vegetables (incl. roots and tubers) and grains. The content of 241Am in the staple foods produced in the area varies from single digits to tenths of mBq/ kg, which is less by three orders of magnitude than 137Сs activities concentrationd found in the same staples. Of the two pathways contributing to the local committed internal exposure from 241Am, the dominant one is through inhalation (0.006–0.038 mSv/year) prevailing over the consumption pathway of this same radioisotope by at least one order of magnitude. At the time of gardening and other household field works, the existing levels of 241Am contamination in soils are estimated to produce from 85 to 98% of the internal radiation dose received by individuals from inhaling the total of 241Am and 137Сs. The maximum committed annual doses of internal exposure from 137Сs are estimated to be above 1 mSv/year in 6 out of 30 villages engaged in our study. At the same time, the estimated internal radiation dose due to 241Am does not surpass 0.04 mSv/year. The 137Сs major contribution to the internal exposure of villages in the Khoiniki countryside is through food consumption.

André Luiz Candido da Silva, Antonio Teixeira e Silva

The aim of this work is to present a comparative analysis in terms of the irradiation performance of cylindrical uranium dioxide fuel rods and monolithic uranium molybdenum fuel plates in pressurized light water reactors. To analyze the irradiation performance of monolithic uranium molybdenum fuel plates when subjected to steady state operating conditions in light water pressurized reactors, the computer program PADPLAC-UMo was used, which performs thermal and mechanical analysis of the fuel taking into account the physical , chemicals and irradiation effects to which this fuel is subjected. For the analysis of the uranium dioxide fuel rods, the code FRAPCON was used, which is an analytical tool that verifies the irradiation performance of fuel rods of pressurized light water reactor, when the power variations and the boundary conditions are slow enough for the term permanent regime to be applied. The analysis for a small nuclear power reactor, despite the higher power density applied to the fuel plate in relation to the fuel rod, showed that the fuel plates have lower temperatures and lower fission gas releases throughout the analyzed power history, allowing the use of a more compact reactor core without exceeding the design limits imposed on nuclear fuel.

S. S. Sarycheva

This survey is devoted to the staff radiation protection in X-ray operating rooms. For self-safety staff must regularly and correctly use the protective equipment, which is ensured by their availability, convenience and manoeuvrability during procedures performing. The rapid development of interventional radiology led to the fact that the staff work in this area have one of the highest levels of occupational exposure. Unfortunately, domestic radiation protection system does not keep pace with such a rapid development of this branch of medicine. The article shows the basic principles of the distribution of scattered radiation in the X-ray operating room during the procedures performing. The distribution of scattered radiation around the patient for various modes of C-arm angiographic systems is shown. Graphical examples of scattered radiation distribution in X-ray operating rooms are given. Collective and individual protective equipment specifically designed for staff radiation protection in X-ray operating room are considered in detail. The common data on the protection features of the recommended staff protection equipment are presented. Most of the considered protection equipment is mandatory in many European countries, but not mentioned in domestic regulatory documents yet. The proposals for the modernization of the domestic radiation protection system for staff of X-ray operating rooms have been made. These recommendations focused on providing X-ray operating rooms with relevant radiation protection equipment, including eye protection, following the accumulated world experience and international regulations.

Jakkapon Phanthuwongpakdee, S. Babel, T. Kaneko

Han Guo, Xinshui Huang, Ning Zhang et al.

: As the main force of new energy, nuclear energy is widely used in the world because of its high energy density, high efficiency and cleanness. However, a large number of radioactive substances produced from mining, processing of uranium (as main raw material of nuclear energy) and reprocessing of spent fuel will be released into environment through leaks and other ways. Owing to the high chemical toxicity and strong radioactivity, the releases of radioactive substances pose a potential threat to the environment and human health. Therefore, the efficient enrichment and separation of radioactive substances play a key role in the sustainable development of nuclear energy. As a main separation method, adsorption is widely used in the removal of radionuclides. Covalent organic frameworks (COFs) materials have good application towards adsorption of radioactive substances due to their high chemical stability, controllable structure and high specific surface area. In this review, the adsorption behavior and interaction mechanism of UO 22+ , TcO 4− , I − and other radionuclides from aqueous solution on COFs and their composites under different environmental conditions are reviewed in details. At last, the challenges and prospective in adsorption of radionuclides by COF materials in environmental remediation are put forward.