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Este trabalho apresenta uma extensiva série de resultados experimentais da condutividade induzida por radiação X contínua, durante e após a irradiação, em amostras de PET e Kapton. As medidas foram realizadas variando-se uma série de parâmetros, tais como: o campo elétrico aplicado, a taxa de exposição, a espessura da amostra, o tipo de eletrodo, a energia da radiação e as condições ambientes. Foram feitas ainda medidas da corrente termo-estimulada em amostras irradiadas e não irradiadas, que permitiram verificar a presença de armadilhas nos materiais. Medidas da corrente fotônica com diferentes eletrodos e espessuras das amostras, constataram a influência do eletrodo no valor dessa corrente. Finalmente um modelo teórico foi desenvolvido, baseado na teoria de balanço dos portadores generalizada, com a inclusão do efeito do campo elétrico na taxa de geração de portadores (efeito Onsager). O ajuste teórico-experimental permitiu a determinação numérica dos principais parâmetros de condução, tais como, mobilidade dos portadores, coeficiente de recombinação e densidade de armadilhas, para os dois materiais estudados. / In this work we present extensive results of measurements of the prompt and delayed radiation-induced conductivity of samples of PET and Kapton. Experimental parameters, such as the effective energy of the radiation, the exposure rate, the total dose, the value of the applied electric field, the nature of the electrodes, and the ambienta1 conditions were changed within wide limits. We also report measurement of thermally stimulated currents for non-irradiated and for irradiated samples which allowed us to investigate the trap-structure of the materials. Measurements of photo-Compton currents with different electrode materials and sample thicknesses gave information about the relation between the nature of the electrodes and the amplitudes of the currents. Based on the generalized rate theory of radiation-induced conduction we developed a theoretical model which includes the effect of the applied electric field on the carrier generation yield (geminate recombination, Onsager effect). Comparison of experimental and theoretical curves allowed us to determine the values of the main conduction parameters, such as carrier mobility, recombination coefficient, trap densities, for the materials under investigation.

abstract: There has been a renewed interest to understand the degradation mechanism of concrete under radiation as many nuclear reactors are reaching their expiration date. Much of the information on the degradation mechanism of concrete under radiation comes from the experiments, which are carried out on very small specimens. With the advent of finite element analysis, a numerical predictive tool is desired that can predict the extent of damage in the nuclear concrete structure. A mesoscale micro-structural framework is proposed in Multiphysics Object-Oriented Simulation Environment (MOOSE) finite element framework which represents the first step in this direction. As part of the framework, a coupled creep damage algorithm was developed and implemented in MOOSE. The algorithm considers creep through rheological models, while damage evolves exponentially as a function of elastic strain and creep strain. A characteristic length is introduced in the formulation such that the energy release rate associated with each element remains the same to avoid vanishing energy dissipation with mesh refinement. A creep damage parameter quantifies the effect of creep strain on the damage that was calibrated using three-point bending experiments with varying rates of loading. The creep damage model was also validated with restrained ring shrinkage tests on cementitious materials containing compliant/stiff inclusions subjected to variable drying conditions. The simulation approach explicitly considers: (i) moisture diffusion driven differential shrinkage along the depth of the specimen (ii) viscoelastic response of aging cementitious materials (iii) isotropic damage model with Rankine′s failure initiation criterion, and (iv) random distribution of tensile strengths of individual finite elements. The model was finally validated with experimental results on neutron-irradiated concrete. The simulation approach considers: (i) coupled hygro-thermal model to predict the temperature and humidity profile inside the specimen (ii) radiation-induced volumetric expansion of aggregates (RIVE) (iii) thermal, shrinkage and creep effects based on the temperature and humidity profile and (iv) isotropic damage model with Rankine’s criterion to determine failure initiation. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

Dans le cadre de l’entreposage et du stockage des colis de déchets nucléaires et du transport de combustibles usés, nous nous sommes intéressés par l’étude de la production d’hydrogène de deux produits de corrosion de l’aluminium : l’hydroxyde d’aluminium (Al(OH)3) et l’oxyhydroxyde d’aluminium (AlO(OH)).La production du dihydrogène par irradiation de ces matériaux a été étudiée en fonction de la taille et de la structure que ce soit à température ambiante ou après. Afin d’avoir une meilleur compréhension des mécanismes de production de ce gaz, les défauts créés par irradiation ont été caractérisés en utilisant la Résonnance Paramagnétique Electronique (RPE). Différentes sources d’irradiation ont été utilisées comme le rayonnement Gamma, les électrons accélérés et les ions lourds. Dans un second temps, l’effet de l’hydratation de surface des matériaux a été également étudié. Enfin, l’effet de la présence d’impuretés sur la production de H2 a été brièvement étudié. / Dihydrogen production is a critical issue for the current management of nuclear wastes. One potential source of hydrogen generation is the radiolysis of hydrated mineral phases encountered in the nuclear waste transportation and storage casks. We chose to study aluminum hydroxide (Al(OH)3) (Bayerite) and oxyhydroxides (AlOOH) (Boehmite) as model compounds. The determination of molecular hydrogen production was evaluated with respect to structure and particle size at room temperature and after annealing. In order to have a better understanding of the mechanisms and to identify the precursors of molecular hydrogen, we studied the irradiation defects and their stabilities using Electron Paramagnetic Resonance (EPR). The effect of adsorbed water and structural water on the molecular hydrogen production was studied. Different radiation sources were used such as Gamma radiation, electron beam radiations and heavy ions. In the last part, preliminary results related to the impact of impurities on hydrogen production are presented.

<p>While radiation therapy is a standard treatment modality for managing primary and metastatic brain tumors, it causes irreversible and progressive long-term side effects that decrease the quality of life for pediatric brain tumor survivors. These side effects, known as radiation-induced brain injury (RIBI) and which occur at least 6 months post-treatment, create challenges in education, employment, and social relationships throughout the patients’ lifetime. With the prognosis for pediatric cancer patients constantly improving, long-term side effects such as RIBI pose a major clinical problem for post-treatment care. To create and evaluate treatments for this clinical injury, it is critical to understand how this condition forms and develops. However, this cannot be done in patients due to the invasive nature of cranial biopsies. The current scientific understanding behind the pathophysiology of these late-delayed forms of RIBI is therefore built upon studies of pre-clinical animal models. Such experimental models, typically of healthy rodents, are not currently capable of accurately replicating the radiological and histological changes seen in human patients. This inconsistency limits the efficacy of preclinical discoveries when translated to clinical trials. To address this issue, we chose to establish a mini-pig model for RIBI using a standard clinical approach of radiation delivery and follow-up imaging. Our hypothesis is that cranial irradiation of the mini-pig brain will elucidate the clinical magnetic resonance imaging (MRI) signatures of RIBI, which will then correspond to characteristic changes in diffusion properties, metabolite profiles, immune constituents, and glial and neuronal cell subpopulations as evidenced by advanced MRI techniques and histopathology. As such, results from Aim 1 have highlighted not only incongruencies between rodent models and clinical findings, but also various inconsistencies in current assessment techniques of late-delayed RIBI in patients. Additionally, results from Aim 2 have established the feasibility of a mini-pig model of RIBI based on the current clinical standard of diagnosis. Finally, results from Aim 3 describe characteristic changes in diffusion properties and histological appearances as well as novel changes in metabolite concentrations within our mini-pig model late-delayed RIBI. In conclusion, this intermediate animal model of RIBI can replicate the clinical condition and may ultimately provide valuable insight into the pathophysiology of RIBI. </p>

En France, les matériaux à base de ciment sont utilisés comme matrice de conditionnement des déchets nucléaires de faible et moyenne activité. La radiolyse de l'eau est due aux déchets nucléaires stockés dans les matériaux. La formation de ses produits radiolytiques tels que le gaz H₂ doit être évaluée pour des raisons de sécurité. Les silicates de calcium hydratés (C-S-H) représentent le principal produit (50%) d'hydratation du ciment Portland (CP). L’objectif de cette étude est de comprendre les mécanismes radiolytiques de la production d'hydrogène dans les C-S-H, d'étudier l'effet d'impuretés (telles que des ions alcalins, hydroxydes ou nitrates supplémentaires) sur la production de gaz H₂ dans les C-S-H et d'examiner l'existence d'interactions entre les phases principales (C-S-H et portlandite) du ciment Portland. Après avoir caractérisé les échantillons par diverses techniques, ils ont été soumis à différents types d'irradiation (faisceaux gamma et électrons et ions lourds (HI) pour déterminer leur rendement radiolytique en H₂, G(H₂). Dans les C-S-H, il a été démontré que, sous irradiation gamma, la production d’H₂ est indépendante de la teneur en eau et que les C-S-H produisaient autant d’H₂ que la même masse d’eau. Ainsi, le mécanisme de production d’hydrogène est très efficace dans les C-S-H. La comparaison entre les résultats obtenus sous rayons gamma et ceux obtenus sous HI implique qu’il n'y a pas ou peu d'effet de transfert d’énergie linéique (TEL) dans les C-S-H. Ainsi, les réactions de recombinaison semblent limitées. L’introduction d’ions nitrates dans la structure des C-S-H induit une diminution importante du G(H₂). L’irradiation des hydrates de C2S et C3S constitués majoritairement de C-S-H et de portlandite indique qu’il n’y a pas de phénomènes de transfert d’énergie entre ces phases. Enfin, les expériences de spectroscopie par résonance paramagnétique électronique (RPE) ont permis de proposer des mécanismes radiolytiques dans les C-S-H. L’ensemble de ces résultats nous permettent de mieux comprendre les effets d’irradiation dans les ciments. / In France, cementitious materials are used as conditioning matrix of low level and intermediate level nuclear wastes. Water radiolysis occurs due to the nuclear wastes stored in the materials. The formation of its radiolytic products such as H₂ gas must be evaluated for safety reasons. Calcium silicate hydrate (C-S-H) is the main product (50%) of hydration of Portland Cement (PC). The aim of this study is to understand the radiolytic mechanisms of the hydrogen production in C-S-H, to investigate the effect of impurities (such as alkali ions, additional hydroxides or nitrates ions) on H₂ gas production in C-S-H and to examine if interactions exist between different main phases (C-S-H and portlandite) in cement matrix. After using various characterization techniques, samples were submitted to different types of irradiation (gamma rays and electrons and heavy ions (HI) beams) to determine their H₂ radiolytic yield, G(H₂). In C-S-H system, it has been shown, under gamma irradiation, that G(H₂) does not depend on water content, moreover, C-S-H system itself produce efficiently H₂ gas. The comparison between the results obtained under gamma rays and that obtained under HI implies: there is no/ low LET effect in C-S-H. While with nitrate ions in C-S-H, a large decrease of G(H₂) is observed. Irradiation of C2S and C3S hydrates mainly composed of C-S-H and portlandite shows that here is no energy transfer phenomena between these two phases. Finally, the electron paramagnetic resonance (EPR) spectroscopy experiments have enabled proposing radiolytic mechanisms. All these results help us to understand the radiation effects in cements.

Immobilization of proteins by covalent coupling to polymeric materials offers numerous excellent advantages for various applications, however, it is usually limited by coupling strategies, which are often too expensive or complex. In this study, an electron-beambased process for covalent coupling of the model protein bovine serum albumin (BSA) onto polyvinylidene fluoride (PVDF) flat sheet membranes was investigated. Immobilization can be performed in a clean, fast, and continuous mode of operation without any additional chemicals involved. Using the Design of Experiments (DoE) approach, nine process factors were investigated for their influence on graft yield and homogeneity. The parameters could be reduced to only four highly significant factors: BSA concentration, impregnation method, impregnation time, and electron beam irradiation dose. Subsequently, optimization of the process was performed using the Response Surface Methodology (RSM). A one-step method was developed, resulting in a high BSA grafting yield of 955 mgm−2 and a relative standard deviation of 3.6%. High efficiency was demonstrated by reusing the impregnation solution five times consecutively without reducing the final BSA grafting yield. Comprehensive characterization was conducted by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and measurements of zeta potential, contact angle and surface free energy, as well as filtration performance. In addition, mechanical properties and morphology were examined using mercury porosimetry, tensile testing, and scanning electron microscopy (SEM).

No description available.

Made available in DSpace on 2014-07-29T15:25:19Z (GMT). No. of bitstreams: 1 Tese Rosangela da S Correa.pdf: 1513256 bytes, checksum: a25a4559d449be027efcb11728fce7c2 (MD5) Previous issue date: 2012-04-10 / Among the available methods for the diagnosis and early detection of breast cancer, the most indicated for mass screening is the mammography. To guarantee its effectiveness, this exam needs to be performed using high quality standards and the lowest radiation dose possible. Therefore, the present research aimed to assess the infrastructure and performance of the equipments available at the mammography services in the state of Goiás, regarding coverage, quality, and radiological protection (dose) of patients, in order to provide early detection of breast cancer by an opportunistic screening. A prospective study was carried out, from 2007 to 2010, to observe the diagnostic imaging services which perform mammography, initially for the Brazilian Unified National Health System (SUS) and, in 2010, the services of the private system were included. Data collection was divided into two phases: the first, to collect information on infrastructure and the second, to apply tests in order to evaluate the performance characteristics of equipment and materials used. We calculated the conformity of the assessed items in terms of quality of image and equipment performance and estimated the average dose in glandular tissue and the risk of radioinduced carcinogenesis, as well as the risk of mortality by radioinduced tumors. The results were presented in four articles. In the first, we showed that mammography coverage in the state of Goiás in 2008 was 66% among women in the 50 69-year age group, considering biennial mammography. In the second article, we concluded that the implementation of the Mammography Quality Control Program was effective to achieve better quality mammography in SUS services. In the beginning of our research, only 2.9% of SUS services were within the desired range of quality and, after two interventions (2008 and 2009), 20% of them reached it. The results of the third article, in which we verified the infrastructure and quality of services performing mammography, both for SUS and private systems, showed no difference in quality of exams between them. However, the evaluation between types of technology used showed difference between radiation doses (p < 0.001) applied during mammography. In the fourth article, we estimated the benefit risk balance of screening mammography carried out in the state of Goiás in 2010. The excess absolute risk of radioinduced cancer and the lifetime risk presented significant difference for types of technology (p < 0.001) and types of health system (p < 0.019) according to the age group of screening. The ratio lives saved/lives lost was 75.5/1 for screening at the 40 70-year age group and 166.5/1 at the 50 70-year age group. The results showed that coverage of the 50 69-year age group in the state of Goiás is near the recommended standards for the beginning of organized screenings. However, when assessed per regional health unit, coverage was non-uniform, presenting high concentration of equipments and exames at the Central Regional. The initial evaluation of equipment performance indicated the need to implant actions for controlling mammography quality and risk. The actions of the Mammography Quality Control Program proved to be effective to enhance the quality of mammography, although the same does not remain true for the radiation dose used in mammography. These doses are lower in conventional mammography equipments than in those coupled to image digitization systems. Regarding radiological protection, screening women who are 50 70 years old, when performed biennially using conventional mammography equipments, presented more benefit. / Entre os métodos disponíveis para diagnóstico e detecção precoce de câncer de mama, o mais indicado para o rastreamento em massa é a mamografia. Para garantir sua efetividade, é preciso que esse exame seja realizado com padrão de qualidade ótimo e a menor dose possível. Nesse contexto, a presente pesquisa teve como proposta avaliar a infraestrutura e o desempenho dos equipamentos instalados nos serviços de mamografia no estado de Goiás, no que se refere à cobertura, qualidade da mamografia e proteção radiológica (dose de exposição) das pacientes, tendo em vista a proposta de detecção precoce do câncer de mama por meio de rastreamento oportunístico. Realizouse um estudo prospectivo, que compreendeu o período de 2007 a 2010, durante o qual foram observados os serviços de diagnóstico por imagem que realizavam mamografia, inicialmente para o Sistema Único de Saúde (SUS) e, em 2010, incluíram-se os serviços do sistema privado. Dividiu-se a coleta de dados em duas etapas: a primeira, para levantamento de informações sobre infraestrutura e a segunda, para aplicação de testes com o objetivo de avaliar os parâmetros de desempenho dos equipamentos e materiais utilizados. Foram calculados: o percentual de conformidade nos itens avaliados referentes a qualidade da imagem e desempenho dos equipamentos, e estimada a dose média no tecido glandular mamário e os riscos de carcinogênese radioinduzida, bem como, o risco de mortalidade por tumores radioinduzidos. Os resultados foram apresentados em quatro artigos científicos. No primeiro, mostrou-se que a cobertura da mamografia no estado de Goiás em 2008 foi de 66% entre as mulheres na faixa etária de 50 a 69 anos, considerando-se a realização de mamografia bienal. No segundo artigo, concluiu-se que a implantação do Programa de Controle de Qualidade em Mamografia foi efetiva para a melhoria da qualidade da mamografia nos serviços do SUS. No início da pesquisa, somente 2,9% dos serviços do SUS estavam na faixa desejável de qualidade e, após duas intervenções (2008 e 2009), 20% deles a atingiram. Os resultados do terceiro artigo, em que se verificou a infraestrutura e a qualidade dos serviços que realizavam mamografia, tanto para o sistema SUS, como para o sistema privado, mostraram não haver diferença na qualidade do exame entre eles. Porém, a avaliação entre os tipos de tecnologia empregados mostrou diferença entre as doses (p < 0,001) de radiação aplicadas durante a mamografia. No quarto artigo, estimou-se a relação benefício risco do rastreamento mamográfico realizado no estado de Goiás em 2010. O risco absoluto de excesso de câncer radioinduzido e o risco ao longo da vida apresentaram diferença significativa para os tipos de tecnologia (p < 0,001) e o tipo de atendimento dos serviços (p < 0,019) segundo a faixa etária de rastreamento. A razão de vidas salvas/vidas perdidas foi de 75,5/1 para o rastreamento na faixa de 40 a 70 anos e de 166,5/1 na faixa de 50 a 70 anos. Os resultados apontaram que a cobertura para a faixa de 50 a 69 anos no estado de Goiás está próxima do recomendado para o início de rastreamento organizado. Entretanto, quando avaliada por regional de saúde, a cobertura mostrou-se desigual e com grande concentração de equipamentos e exames na Regional Central. A avaliação inicial do desempenho dos equipamentos indicou a necessidade de implantação de ações para controle da qualidade da mamografia e do risco. As ações do Programa de Controle de Qualidade em Mamografia mostraram-se efetivas para a melhoria da qualidade da mamografia, embora o mesmo não tenha ocorrido com a dose de radiação empregada na mamografia. As doses nos mamógrafos convencionais são mais baixas do que nos mamógrafos acoplados aos digitalizadores de imagem. Em termos de proteção radiológica, o rastreamento na faixa etária de 50 a 70 anos, quando realizado bienalmente em mamógrafos com tecnologia convencional, apresentou maior benefício.