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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Métodos de estudo de variáveis e processos de dinâmica sedimentar marinha com radionuclídeos naturais e artificiais / Methods of study of variables and processes of marine sedimentary dynamics with natural and artificial radionuclides

Paulo Alves de Lima Ferreira 31 August 2018 (has links)
A onipresença dos radionuclídeos naturais e artificiais nas diversas matrizes ambientais é passível de ser aproveitada como ferramenta em estudos de dinâmica sedimentar marinha, pois estes nuclídeos registram processos em escalas espaciais e temporais de acordo com seus níveis e distribuição espacial e vertical em sedimentos. Dentro deste contexto, este trabalho demonstrou o uso de radionuclídeos naturais (210Pb, 226Ra, 230,232Th, 234,238U) e artificiais (137Cs) em estudos de dinâmica sedimentar marinha com a espectrometria gama como única técnica analítica, através da apresentação de um conjunto de métodos de aplicação de radionuclídeos, modelos matemáticos e de interpretação de seus resultados. A primeira aplicação descrita foi uma avaliação quantitativa da sedimentação no Sistema Santos-São Vicente, que permitiu um estudo das variações espaciais e ao longo do tempo na sedimentação deste sistema costeiro. Outra aplicação foi o uso da ocorrência e distribuição espacial de 137Cs como uma ferramenta estratigráfica em sistemas costeiros do Oceano Atlântico Sul, com um modelo matemático cujos resultados indicaram um padrão latitudinal nos níveis de atividade deste nuclídeo consistente com observações de sua deposição atmosférica reportadas pela literatura internacional. Finalmente, um modelo de sedimentação e idade baseado nas relações entre isótopos de Th e U (validado com resultados de isótopos estáveis de oxigênio e bio/magnetoestratigrafia) foi empregado para estimar taxas de sedimentação e idades em testemunhos quaternários de duas margens continentais passivas (oeste do Oceano Atlântico Sul e Mar do Sul da China). Com os resultados deste modelo, observou-se períodos de aumento nos níveis de 230Th que podem sugerir a influência de fatores como variações na taxa de deposição de 230Th e ciclos orbitais de Milankovitch. / The occurrence of natural and artificial radionuclides in the environment can be used as a tool for studies of marine sedimentary dynamics, as these nuclides record environmental processes at both spatial and temporal scales. Within this context, this work aimed at demonstrating the use of natural (210Pb, 226Ra, 230,232Th, 234,238U) and artificial (137Cs) radionuclides in studies of sedimentary dynamics with gamma spectrometry as sole analytical technique. This was done through the application of several mathematical models and methods of radionuclides\' data interpretation. The first application was a quantitative assessment of sedimentation in the Santos-São Vicente coastal system, studying its spatial variations during the last century. Another application was the use of the occurrence and spatial distribution of 137Cs as a stratigraphical tool for age studies in coastal systems of the South Atlantic Ocean. With the results of a mathematical model it was possible to infer values of radionuclide deposition that showed a latitudinal pattern in the levels of this element, consistent with international reports of fallout atmospheric deposition. Finally, a model of sedimentation and age determination based on the relationships between Th and U isotopes was used to estimate sedimentation rates in Quaternary cores from two passive continental margins (South Atlantic western margin and South China Sea margin). The model was validated by statistical comparison with data of stable oxygen isotopes and bio/magnetostratigraphy. The results of this model showed periods with an increase on the 230Th excess activity that could be related to variations on Th deposition rate and the influence of Milankovitch orbital cycles on Th and U deposition.
12

Migration and gamma ray assessment of uranium on a gold tailings disposal facility / Jaco Koch

Koch, Jaco January 2014 (has links)
This project aims to quantify natural gamma radiation in gold tailings disposal facilities (TDFs) relative to uranium concentration data in order to use natural gamma detection methods as alternative methods for uranium resource estimation modelling in gold tailings. Uranium migration within the New Machavie TDF was also investigated as migration affects both the grade of the TDF as a uranium resource and poses a threat to the environment. In order to determine the most appropriate radiometric testing procedure, various methods were employed for natural gamma detection, including surface natural gamma spectrometry, borehole natural gamma spectrometry and scintillometry, as well as incremental sampling. These measurements were then statistically compared to ICP-MS analyses to find the best method, and then modelled to apply volumetric resource estimation procedures. The oxidation reduction potential was also tested as uranium geochemistry is dependent on oxidation for mobilisation. Furthermore, leaching tests were employed to relate specific anions as a mode of transportation in solution. Results indicated that down-hole natural gamma spectrometry performed the best and that 2376.87 kg of uranium is present in the TDF. Migration modelling indicated that uranium is mobilised away from the oxidized top area of the TDF and that accumulation occurs in the saturated zone of the TDF under a reducing environment. Sulphate anions as the result of pyrite oxidation are primarily responsible for the mobilisation as radionuclides in New Machavie. The results of this project can be applied to the resource estimation of all uranium bearing tailings facilities prior to re-mining as a means to decrease exploration costs and to accurately model the distribution of uranium. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
13

Radioelementos naturais na área do Projeto Rio Preto (GO)

Duarte, Cynthia Romariz [UNESP] 08 November 2002 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:32:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-11-08Bitstream added on 2014-06-13T19:02:55Z : No. of bitstreams: 1 duarte_cr_dr_rcla.pdf: 8348425 bytes, checksum: 2de5f5ce715dc0484f953288876f320c (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os radioelementos naturais U, Th e K foram caracterizados na área do Projeto Rio Preto (GO), executado pela extinta Nuclebrás, após a realização de etapa de campo para reconhecimento da área e amostragem de corpos litológicos das formações aflorantes na área. Sua determinação foi efetuada por espectrometria gama que possibilitou a mensuração dos nuclídeos 40K, 214Bi e 208Tl. Para o universo total de amostras (n = 288) também foram efetuadas análises químicas dos óxidos SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, K2O, Na2O, CaO e P2O5 com o intuito de se proceder a caracterização química das rochas da região. Os valores de concentração de óxidos e de nuclídeos permitiram a confecção de mapas de sua distribuição pela área de estudo. Para amostras selecionadas foram realizadas leituras de espectrometria alfa para a determinação dos isótopos de U presentes. As razões 234U/238U e eU/U, relativas às leituras por espectrometria alfa e gama, respectivamente, foram determinadas para avaliar a situação de equilíbrio radioativo na cadeia natural de decaimento do urânio. Foi utilizada também a autorradiografia para identificar a presença de minerais radioativos em lâminas de xistos e gnaisses da Formação Ticunzal. / The natural radioelements U, Th and K were characterized in the area of the Rio Preto project held by Nuclebrás, after recognizing the area and sampling the rocks occurring there. The determination was performed by gamma spectrometry that allowed to quantify the nuclides 40K, 214Bi and 208Tl. All rock samples (n = 288) were chemically analyzed in terms of the oxides SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, K2O, Na2O, CaO and P2O5. The values of concentration of oxides and nuclides were used to generate distribution maps in the studied area. Alpha spectrometry was utilized for selected samples in order to determine the U-isotopes. The 234U/238U and eU/U ratios relative to the alpha and gamma spectrometry readings, respectively, were determined to evaluate the radioactive equilibrium condition in the natural uranium series decay. Autorradiography was also used to identify the presence of radioactive minerals in shales and gneisses from Ticunzal Formation.
14

Estudo dos processos sedimentológicos na Margem Continental Sudeste do Brasil pelo uso de radionuclídeos naturais / Study of thesedimentological process in the Shelf and Upper Slope off Southeast Brazil throught the use of natural radionuclides

Luisa Mariutti Cordero 09 November 2010 (has links)
A Oceanografia, recentemente, vem fazendo uso dos mais diferentes radionuclídeos os quais funcionam como traçadores e auxiliam em uma maior compreensão dos processos de dinâmica oceânica, movimentação e deposição do fundo marinho. No Brasil, porém, há pouca informação a respeito dos teores de radionuclídeos naturais para a região costeira e oceânica e poucos são os estudos que utilizam esses radionuclídeos como ferramentas de compreensão de processos oceânicos. Neste contexto, este trabalho determinou atividades de 238U, 232Th e 40K por espectrometria gama e realizou análises granulométricas em amostras de sedimentos marinhos da Margem Continental Sudeste do Brasil. Os níveis variaram de 1,48 a 52,76 Bq kg-1 para o 238U, 10,63 a 49,45 Bq kg-1 para o 232Th e 65,45 a 873,28 Bq kg-1 para o 40K. Os resultados mostraram afinidade entre as frações finas do sedimento com 40K e 232Th. A razão 238U/232Th mostrou ser bom indicador de condições redox dos sedimentos. Verificou-se uma diferença nos níveis dos três radionuclídeos entre os setores ao norte e ao sul da Ilha de São Sebastião, com valores mais elevados ao sul. Estas diferenças foram relacionadas aos processos sedimentares dominantes em cada setor e aos agentes hidrodinâmicos responsáveis por tais processos. / Recently, Oceanography has been using a variety of radionuclides as tracers to understand ocean dynamic processes, handling and disposal of sediments in seabed. In Brazil, there is little information about the contents of natural radionuclides on the coast and deep ocean and few studies using radionuclides as tools to comprehend oceanic processes. In this context, this work determined grain size and activities of 238U, 232Th and 40K using gamma spectrometry in marine sediments from shelf and upper slope off Southeast Brazil. The levels ranged from 1,48 to 52,76 Bq kg-1 for 238U, from 10,63 to 49,45 Bq kg-1 for 232Th and, from 65,45 to 873,28 Bq kg-1 for 40K. 40K and 232Th showed good correlation with grain size (mud and clay content) and 238U/232Th ratios appeared to be good indicators of sediment redox conditions. There was a difference in levels of radionuclides between sectors northward and southward of São Sebastião Island, with higher values in south sector. These differences were related to differences in sedimentary processes in each sector and to the hydrodynamic agents responsible for these processes.
15

Determinação de 238U e 232Th em amostras ambientais por espectrometrias alfa e gama

FARIAS, Emerson Emiliano Gualberto de 10 May 2011 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-02-06T15:57:59Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) dissertação_Emerson_Farias_corrigida_sem_assinatura.pdf: 1653100 bytes, checksum: f58076ed14de44a96ed097b6dd697195 (MD5) / Made available in DSpace on 2017-02-06T15:57:59Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) dissertação_Emerson_Farias_corrigida_sem_assinatura.pdf: 1653100 bytes, checksum: f58076ed14de44a96ed097b6dd697195 (MD5) Previous issue date: 2011-05-10 / Nos últimos anos tem-se observado uma preocupação crescente da população em relação à presença de radionuclídeos no meio ambiente. As principais atividades que podem contribuir para o incremento da concentração desses contaminantes envolvem tanto processos industriais como aplicações médicas. Não menos importantes, no entanto, são os radionuclídeos naturais encontrados no ambiente, os quais podem ter suas concentrações aumentadas como resultado de beneficiamento de matéria prima para a extração de metais, como é o caso das areias minerais, ricas em cianita, ilmenita rutilo e zirconita, as quais podem apresentar elevadas concentrações de urânio e tório. A quantificação de radionuclídeos envolve, de maneira geral, técnicas de Instrumentação Nuclear. Dentre essas, as espectrometrias alfa e gama estão entre as mais utilizadas nas medições de radionuclídeos naturais em matrizes ambientais. Portanto, tornam-se cada vez mais importantes o estudo e o aperfeiçoamento das metodologias utilizadas em cada uma dessas técnicas, proporcionando maior precisão e exatidão nas determinações. Nesse contexto, o presente trabalho visou a comparação entre as diversas metodologias utilizadas nas técnicas de espectrometria alfa e espectrometria gama para a determinação de 238U e 232Th em amostras ambientais, especificamente em areias minerais. A validação das metodologias utilizadas foi feita utilizando-se materiais de referência fornecidos pela Agência Internacional de Energia Atômica. Para a técnica de Espectrometria Alfa as amostras foram previamente digeridas por fusão alcalina e receberam traçadores de 232U e 229Th. Após a purificação em resina de troca iônica e eletrodeposição em disco de aço inoxidável, as amostras foram contadas por um período de 80.000 segundos em um espectrômetro alfa.Para a espectrometria gama, alíquotas de 50 g de cada amostra foram acondicionadas em potes cilíndricos de plástico e contadas. As aquisições de dados foram feitas por um período de 80.000 segundos e as linhas gama utilizadas para a determinação do 238U foram as de 63 keV, 93 keV e 1001 keV. Para o 232Th, por outro lado, foram utilizadas as linhas de 338 keV, 911 keV e 969 keV. As quatro metodologias de determinação de 232Th (338 keV, 911 keV, 969 keV e espectrometria alfa) geraram valores de concentrações próximos daqueles constantes dos certificados em materiais de referência, indicando a viabilidade da utilização de qualquer das metodologias. Dentre as metodologias estudadas para a determinação de 238U, a espectrometria alfa e a espectrometria gama, pela linha de 1001 keV, foram as mais indicadas para amostras do tipo das analisadas no presente trabalho, pois apresentaram valores em concordância com os constantes dos certificados dos materiais de referência. Os resultados das análises das areias minerais mostraram concentrações de urânio-238 variando de 60 a 12.256 Bq.kg-1, com um valor médio de 3.634 Bq.kg-1. A concentração de atividade média observada nas amostras de zirconita foi de 6.723 Bq.kg-1, enquanto que a atividade média encontrada para as outras areias minerais associadas foi de 545 Bq.kg-1, ou seja, dentre as areias minerais presentes no depósito analisadas, as que merecem maior atenção, do ponto de vista da proteção radiológica, são as de zirconita. Por outro lado, as determinações de tório-232 mostraram concentrações de atividade variando de 40 a 7.205 Bq.kg-1 e um valor médio de 1.465 Bq.kg-1. Apenas duas amostras tiveram concentrações acima desse valor (ambas eram de areias minerais de zircão), o que reforça a necessidade de maior atenção, do ponto de vista da proteção radiológica, para as amostras de zirconita. / There has been a great concern in recent years related to the presence of radionuclides in the environment. The main activities which may contribute for the increase in the concentration of those contaminants in the environment involve industrial processes, as well as, medical applications. Not less important, however, are the natural radionuclides found in the environment, which can be concentrated as a result of raw material transformation. This is the case of mineral sands processing for the extraction of kyanite, ilmenite, rutile and zircon, which can have higher than normal concentrations of uranium and thorium. For the measurement of radionuclides as contaminants, the main forms of determination involve techniques of Nuclear Instrumentation. For this reason, it is very important to study and improve these techniques in order to obtain reliable results, as far as precision and accuracy are concerned. Thus, the present study aimed to compare the techniques of alpha spectrometry and gamma spectrometry for the determination of 238U and 232Th in environmental samples, specifically in mineral sands. The validation of the methodologies was carried out by using reference materials provided by the International Atomic Energy Agency. For the determination of 238U and 232Th by alpha spectrometry, samples were digested by alkaline fusion, spiked with 229Th and 232U tracers, purified by passing through an ion exchange resin, electrodeposited on stainless steel disks and counted for 80,000s. For the determination by gamma spectrometry, 50 g of each of the samples were placed in plastic cylindrical containers and counted for 80,000s. The main gamma lines used for determining 238U were 63 keV, 93 keV and 1001 keV. For 232Th, on the other hand, the 338 keV, 911 keV and 969 keV gamma lines were used. The four methodologies for the determination of 232Th, namely 338 keV, 911 keV, 969 keV and alpha spectrometry, led to concentration values in agreement with the certified values for the reference materials. Among the methods studied for the determination of 238U, alpha spectrometry and gamma spectrometry using the 1001 keV line, were the most suitable for the type of samples analyzed in this study. The results of the analyses performed for mineral sands showed concentrations of uranium-238 ranging from 60 to 12,256 Bq.kg-1, with an average of 3,634 Bq.kg-1. The average activity concentration observed in samples of zircon was 6, 723 Bq.kg-1, while the average activity found for other mineral sands was of 545 Bq.kg-1, showing that zircon sands deserve greater attention, from the standpoint of radiological protection, among the mineral sands analyzed. Moreover, the determinations of thorium-232 showed activity concentrations ranging from 40 to 7,205 Bq.kg-1 with an average of 1,465 Bq.kg-1. Only two samples showed 232Th concentrations above this value (both were of zircon sands), which reinforces the need for greater attention, from the point of view of radiological protection, for samples of zircon.
16

Studium vlivu jaderných elektráren na životní prostředí pomocí radioanalytických metod / Investigation of NPPs’ environmental impacts using radioanalytical methods

Brunčiaková, Miriama January 2015 (has links)
This thesis' objective is to analyse local environmental impact of NPP. For impact determination, it is necessary to monitor the locality for a long period. For biomonitoring method, gamma-spectrometers might be used. It should be calibrated before the measurement. Within the thesis investigation, spectrometer of the faculty was calibrated in the laboratory of ionizing radiation and three samples of Czech nuclear facilities outlet were analysed.
17

DEVELOPMENT OF A TECHNIQUE TO LOCALIZE AND QUANTIFY VOLUMETRIC LOW-LEVEL WASTE FROM CANDU PLANTS

Zhou, Peixiao January 2023 (has links)
With the complex composition of the radioisotopes and waste materials, the characterization of the volumetric low-level wastes from CANDU plants is challenging. This study presents a technique to localize and quantify the contaminations presented in the CANDU waste containers. MCNP-based models are developed for an N-type coaxial HPGe detector and a LaBr3 detector to simulate the photon peak information. The simulated efficiency and the experimental count rates are combined to estimate the activity of unknown waste samples. During the spectrum collection of a 4L Marinelli beaker source and 1-quart waste samples, the MCNP algorithm showed better accuracy in activity estimation than the Mirion ISOCS/LabSOCS software. With further development, this method has the potential to outperform the popular commercial software in estimating activity for volume sources with complex geometry and uneven distribution. The multi-detector array models with hotspot designs are also studied in this work to provide real-time information about the location and activity of the contamination inside the 2.2 m3 industrial low-level waste containers. The on-site measurements show promising results as the position of the contamination was able to be located within a volume of 61×40×34 cm. Overall, this technique has good potential to be utilized in the nuclear industry for large-volume low-level waste analysis. / Thesis / Master of Science (MSc)
18

In Vivo Measurement of Aluminum in Alzheimer's Disease and Related Studies

K. Mohseni, Hedi January 2016 (has links)
Alzheimer’s disease accounts for up to 80% of the cases of dementia making it the most common type of dementia. As of 2015, 46.8 million people are suffering from Alzheimer’s disease worldwide with an alarming rate of increase in the onset of the disease. Despite the ongoing research, the true cause of Alzheimer’s disease remains unknown. Aluminum is one of the major environmental toxins linked to the etiology of Alzheimer’s disease. A pilot clinical study for non-invasive measurement of bone aluminum was performed at the in vivo neutron activation analysis facility at McMaster University including 15 Alzheimer’s and 15 control subjects. A significant difference in bone aluminum, relative to calcium, was found between the two groups. Multiple methods of analysis were investigated to determine the method with the lowest minimum detection limit. The method of in vivo neutron activation analysis allows for the simultaneous activation of multiple elements. As such, it was possible to measure the magnesium levels, which has been shown to be involved in Alzheimer’s disease, in the study subjects. The results of bone measurements did not show a significant association between bone magnesium levels and Alzheimer’s disease. Moreover, the short-term kinetic behaviours of sodium and chlorine, both essential for the human body, were studied. The outcome of this study revealed an increase in the biological half-lives of sodium and chlorine with age and a higher variability in Alzheimer’s patients compared to control subjects. Finally, bone samples from parenteral nutrition patients were analyzed to determine their aluminum content for comparison and benchmarking purposes. The present results suggest a possible association between bone aluminum and the presence of Alzheimer’s disease. No such association was found for magnesium or the biological half-lives of sodium and chlorine. The technique of in vivo neutron activation analysis was shown to be a promising tool for measuring bone aluminum and magnesium; however, a better detection limit is required to strengthen the current results. / Dissertation / Doctor of Philosophy (PhD) / Alzheimer’s disease is the most common form of dementia. The cause of Alzheimer’s disease is unknown, but both genetic and environmental factors are known to be involved. Different elements have been studied for their possible role in this disease. Aluminum and to a lesser extent magnesium have been linked to the etiology of Alzheimer’s disease. The current thesis presents the results of a clinical study that utilizes the method of in vivo neutron activation analysis to measure aluminum and magnesium in the hand bone of Alzheimer’s disease and control subjects. In vivo neutron activation analysis is a non-invasive method that uses neutrons to activate elements in the human body and measures the radiation emitted. Different methods of analyzing the resulting data were investigated to find the most suitable analysis approach. The biological half-lives of sodium and chlorine were also measured to investigate their short-term kinetic behaviour and pattern with age.
19

Istraživanje gasovitih radioaktivnih produkata uranijuma i torijuma / Research of the gaseous radioactive products of uranium and thorium

Forkapić Sofija 17 January 2014 (has links)
<p>U okviru ove doktorske disertacije autor već duže vreme radi&nbsp;na razvijanju i primeni niskofonske gama-spektrometrije na&nbsp;određivanju sadržaja uranijuma i ostalih radionuklida gama&nbsp;emitera u uzorcima zemlji&scaron;ta i sedimenta, kao i na praćenju&nbsp;<br />njihove distribucije i korelacije &scaron;to je od značaja za mapiranje&nbsp;radioaktivnosti poljoprivrednog zemlji&scaron;ta. Pored toga&nbsp;doktorant se bavi proučavanjem ravnoteže u radioaktivnim&nbsp;nizovima uranijuma i torijuma, čiji gasoviti produkti radon&nbsp;<sup>222</sup>Rn i toron&nbsp;<sup>220</sup>Rn kao inertni gasovi difuzijom napu&scaron;taju&nbsp;mesto generisanja i na taj način obrazuju značajne&nbsp;koncentracije u zatvorenim prostorima, &scaron;to predstavlja veliki&nbsp;<br />problem za niskofonske podzemne laboratorije i radijacioni&nbsp;rizik izloženog stanovni&scaron;tva. U sklopu ovih istraživanja&nbsp;razvijen je i egzaktan matematički model za određivanje&nbsp;<br />faktora ravnoteže između radona i torona i njihovih&nbsp;kratkoživećih produkata. Dobijeni rezultati će se koristiti za&nbsp;testiranje postojećih metoda merenja radona razvijenih u&nbsp;<br />laboratoriji i primenu za merenje koncentracije aktivnosti&nbsp;radona u urbanim sredinama. Ujedno proučavanje ovih pojava&nbsp;i iznalaženje korekcija na raspad može imati primenu i u&nbsp;drugim nuklearnim analitičkim tehnikama kod kojih je period&nbsp;poluraspada mete uporediv sa vremenom merenja.</p> / <p>In this dissertation the author has been working on the&nbsp;development and application of low-level gamma spectrometry&nbsp;method to determine the content of uranium and other&nbsp;radionuclides gamma emitters in soil and sediment, as well as&nbsp;monitoring their distribution and correlation which is important&nbsp;to map the radioactivity of agricultural soil. In addition, author&nbsp;studies the equilibrium in the radioactive series of &nbsp;uranium and&nbsp;thorium, which gaseous products radon&nbsp;<sup>222</sup>Rn and thoron&nbsp;<sup>220</sup>Rn as inert gases leave the place of origin by diffusion and&nbsp;thus forming significant concentrations indoors, which is a&nbsp;significant problem for the low-level underground laboratories&nbsp;and population radiation risk. As part of this research an exact&nbsp;model for the determination of radon and thoron equilibrium&nbsp;was developed. The results will be used to test existing&nbsp;methods of measuring radon developed in the laboratory and&nbsp;the application of the measurement of radon activity&nbsp;concentration in urban areas. At the same time the study of&nbsp;these phenomena and decay corrections may have application&nbsp;in other nuclear analytical techniques in which the half-life of&nbsp;the target is comparable with the time of measurement.</p>
20

Dosimetria de Rn-222 no ar em ambientes localizados acima e abaixo do nível do solo / Dosimetry of Rn-222 in the air in environments located above and below ground level

Cazula, Camila Dias 23 March 2015 (has links)
A exposição da população em geral à radiação ionizante surge principalmente a partir de fontes naturais. A principal contribuição é decorrente da inalação do radônio (Rn-222), um gás que ocorre naturalmente (UNSCEAR, 2000). A concentração de Rn-222 num ambiente é controlada por fatores como a permeabilidade do solo e teor de água, a variabilidade meteorológica, características de construção da fundação e da pressão diferencial positivo habitual entre o solo e o ambiente interno. Estudos indicam que a concentração de radônio, apresenta uma variação significativa no subsolo, térreo e andares superiores das edificações. O objetivo deste estudo é determinar os níveis de radônio, nos subsolos, térreos e andares acima do nível do solo, em uma universidade na cidade de São Paulo e um edifício residencial na cidade de Peruíbe. As medidas de Rn-222 foram realizadas através do método passivo com detectores de traços nucleares de estado sólido (CR-39). Os ambientes estudados apresentam concentrações de Rn-222 bastante inferiores aos valores recomendados pela Comissão Internacional de Proteção Radiológica, publicados no documento de 2009, de 300 Bq/m3 para residências e 1000 Bq/m3 para locais de trabalho. No edifício residencial na cidade de Peruíbe, analisaram-se ainda, as concentrações de Ra-266, Th-232 e K-40 em materiais de construção utilizados na construção do edifício, por meio de espectrometria gama. A dose efetiva total para o morador devido à exposição externa foi de 0,8 mSv a-1, inferior ao limite de dose anual para público em geral de 1 mSv a-1. / Exposure of the general population to ionizing radiation comes mainly from natural sources. The main contribution is due to inhalation of radon (Rn-222), a gas that occurs naturally (UNSCEAR, 2000). The Rn-222 concentration in the environment is controlled by factors such as soil permeability and water content, the weather variability, materials used in the foundation and the usual positive pressure differential between the soil and the internal environment. Studies indicate that the concentration of radon shows a wide variation in the basement, ground floor and upper floors of buildings. The objective of this study is to determine radon levels in basements, ground floor and floors above ground level, at a university in the city of São Paulo and in one residential building in the city of Peruíbe. Rn-222 measurements were performed using the method with nuclear track of solid state detectors (CR-39). The studied environments present Rn-222 concentration well below the values recommended by the International Commission on Radiological Protection, published in the 2009 document, of 300 Bq/m3 for homes and 1000 Bq/m3 for the workplace. In the residential building, the concentration of Ra-266, Th-232 and K-40 in the materials used in the building construction was also analyzed, by gamma spectrometry. The effective total dose for the resident due to external exposure was 0.8 mSv y-1, lower than the annual dose limit for the general public of 1 mSv y-1.

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