Made available in DSpace on 2014-10-09T12:41:13Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:33Z (GMT). No. of bitstreams: 0 / Visando contribuir com o desenvolvimento de uma metodologia adequada ao Brasil para deposição de fontes seladas fora de uso, o presente estudo avaliou cenários de migração de radionuclídeos para fora de um repositório profundo tipo poço tubular. Considerou-se uma fratura anelar como caminho preferencial de fluxo da água subterrânea, que futuramente adentrará os poços, entrando em contato direto com as fontes. No futuro, fenômenos naturais e ação antrópica poderiam levar à degradação dos materiais que formam as barreiras artificiais do repositório e formar uma via preferencial de transporte e migração dos radioisótopos depositados. Haveria intrusão de água subterrânea e contato com as fontes seladas, corrosão e transporte dos radioisótopos para o ambiente acessível ao homem. A modelagem de transporte considerou percolação de água subterrânea numa fratura causada pelo descolamento entre o tubo de aço e a pasta de cimento, que separa o repositório do meio geológico. Foram simulados cenários de migração e o estudo poderá ser aproveitado na escolha de sítio e de novas técnicas para selagem. Diferentes gradientes hidráulicos e espessuras de fratura, entre outros parâmetros, influirão diretamente no fluxo pela fratura postulada que resultarão em diferentes tempos de trânsito até a biosfera. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:49:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:52Z (GMT). No. of bitstreams: 1 09668.pdf: 6341914 bytes, checksum: 8514c212809df88b758a80f7ad2d2fd8 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T12:35:45Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T12:35:45Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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O tratamento do câncer de próstata com o implante permanente das sementes de iodo-125 cresceu expressivamente nos Estados Unidos da América nos últimos anos. A técnica também vem sendo utilizada por hospitais e clínicas particulares no Brasil. As sementes utilizadas são importadas a custos elevados, o que as tornam proibitivas para uso em hospitais públicos, pois um implante requer, pelos menos, 80 sementes. Para minimizar custos financeiros e possibilitar a distribuição para entidades de saúde pública, iniciou-se o desenvolvimento da técnica de produção das sementes no País. A soldagem a laser é uma das técnicas de selagem da semente de iodo-125, que é feita nas duas extremidades do tubo de titânio, de modo a permitir a classificação da semente como fonte selada, atendendo aos rigorosos testes estabelecidos nas normas ISO 2919 e ISO 9978. O objetivo deste trabalho foi estudar e desenvolver um sistema alternativo de soldagem a laser Nd:YAG para sementes de iodo-125, com o propósito de fornecer dados de projeto e parâmetros operacionais para implantação de uma produção rotineira automatizada no IPEN-CNEN/SP. O desenvolvimento do trabalho apresentou as seguintes fases: corte e limpeza do material (tubo de titânio), projeto, fabricação e montagem de um sistema completo automatizado para a soldagem dos tubos de titânio, determinação dos parâmetros de soldagem (feixe de laser, gás de assistência e focalização), ensaios dos corpos de prova soldados e avaliação da repetitibilidade e eficiência do sistema. O sistema de soldagem a laser desenvolvido mostrou-se eficaz em virtude do eficiente processo de automação utilizado, capaz de produzir sementes de iodo-125 com soldas de qualidade que atendem aos critérios dos severos ensaios determinados nas normas ISO 2919 e ISO 9978. / The treatment for prostate cancer by permanent implant of iodine-125 seeds has increased significantly in the United States of America in recent years. This technique has also been used by hospitals and private clinics in Brazil. The seeds used are imported at a high cost, which makes them prohibitive for use in public hospitals, since an implant requires, at least, 80 seeds. In order to reduce the financial costs and enable the distribution to public health institutions, the technique for the seeds production in the country has been developed. The laser welding is one of the possible procedures to seal the iodine-125 seeds and it will be performed in both ends of the titanium tube: this will allow the seed classification as a sealed source, meeting the rigorous assays established by the ISO 2919 and the ISO 9978 standards. The objective of this research was to study and develop an alternative Nd:YAG laser welding system for iodine-125 seeds, with the purpose of providing project data and operational parameters for the implementation of an automated routine production at IPEN-CNEN/SP. The development of this work presented the following phases: the material (titanium tube) cutting and cleaning, the project, manufacture and assembly of a complete automated system to weld the titanium tubes. The determination of the welding parameters (laser beam, shield gas and focus), the assays of the welded specimens and the evaluation of repeatability and system efficiency have, also, been carried out. The laser welding system developed showed to be efficient for the automation process used and capable of producing seeds of iodine-125 with high quality weldings, meeting the criteria for the severe assays determined by the ISO 2919 and the ISO 9978.

Fontes radioativas seladas são largamente empregadas no mundo. A Agência Internacional de Energia Atômica AIEA estima em dezenas de milhões de fontes radioativas no mundo. No Brasil, este número é próximo de 500 mil unidades, considerando-se as fontes de pára-raios e detectores de fumaça. Uma fonte selada pode tornar-se desnecessária, seja devido ao seu decaimento ou outro motivo, sendo classificada como fontes radioativas seladas fora de uso (FRS). No Brasil, a maioria das FRS é considerada rejeito radioativo e são encaminhadas a um dos institutos da CNEN. Sem uma estratégia definida para a deposição das FRS, estas são armazenadas aguardando uma solução. A Gerência de Rejeitos Radioativos - GRR do IPEN-CNEN/SP é o principal centro de recepção desse material e até meados de 2010 havia recebido cerca de 14.000 fontes. O processo proposto para a gestão dessas FRS consiste em retirá-las de suas blindagens originais e transferi-las a outra blindagem, projetada para esse fim. As operações de transferência são realizadas em uma cela quente, garantindo a segurança radiológica. Uma das exigências da CNEN é que todas as fontes seladas sejam caracterizadas. No processo estudado, a avaliação da atividade de cada fonte será feita utilizando-se um detector, do tipo câmara de ionização tipo poço. O presente trabalho tem por objetivo desenvolver uma metodologia para aferir ou determinar a atividade de FRS armazenadas na GRR de acordo com sua geometria e determinar suas incertezas. / Sealed radioactive sources are widely used in many applications of nuclear technology in industry, medicine, research and others. The International Atomic Energy Agency (IAEA) estimates tens of millions sources in the world. In Brazil, the number is about 500 thousand sources, if the Americium-241 sources present in radioactive lightning rods and smoke detectors are included in the inventory. At the end of the useful life, most sources become disused, constitute a radioactive waste, and are then termed spent sealed radioactive sources (SSRS). In Brazil, this waste is collected by the research institutes of the Nuclear Commission of Nuclear Energy and kept under centralized storage, awaiting definition of the final disposal route. The Waste Management Laboratory (WML) at the Nuclear and Energy Research Institute is the main storage center, having received until July 2010 about 14.000 disused sources, not including the tens of thousands of lightning rod and smoke detector sources. A program is underway in the WML to replacing the original shielding by a standard disposal package and to determining the radioisotope content and activity of each one. The identification of the radionuclides and the measurement of activities will be carried out with a well type ionization chamber. This work aims to develop a methodology for measuring or to determine the activity SSRS stored in the WML accordance with its geometry and determine their uncertainties.

Fontes radioativas seladas são largamente empregadas no mundo. A Agência Internacional de Energia Atômica AIEA estima em dezenas de milhões de fontes radioativas no mundo. No Brasil, este número é próximo de 500 mil unidades, considerando-se as fontes de pára-raios e detectores de fumaça. Uma fonte selada pode tornar-se desnecessária, seja devido ao seu decaimento ou outro motivo, sendo classificada como fontes radioativas seladas fora de uso (FRS). No Brasil, a maioria das FRS é considerada rejeito radioativo e são encaminhadas a um dos institutos da CNEN. Sem uma estratégia definida para a deposição das FRS, estas são armazenadas aguardando uma solução. A Gerência de Rejeitos Radioativos - GRR do IPEN-CNEN/SP é o principal centro de recepção desse material e até meados de 2010 havia recebido cerca de 14.000 fontes. O processo proposto para a gestão dessas FRS consiste em retirá-las de suas blindagens originais e transferi-las a outra blindagem, projetada para esse fim. As operações de transferência são realizadas em uma cela quente, garantindo a segurança radiológica. Uma das exigências da CNEN é que todas as fontes seladas sejam caracterizadas. No processo estudado, a avaliação da atividade de cada fonte será feita utilizando-se um detector, do tipo câmara de ionização tipo poço. O presente trabalho tem por objetivo desenvolver uma metodologia para aferir ou determinar a atividade de FRS armazenadas na GRR de acordo com sua geometria e determinar suas incertezas. / Sealed radioactive sources are widely used in many applications of nuclear technology in industry, medicine, research and others. The International Atomic Energy Agency (IAEA) estimates tens of millions sources in the world. In Brazil, the number is about 500 thousand sources, if the Americium-241 sources present in radioactive lightning rods and smoke detectors are included in the inventory. At the end of the useful life, most sources become disused, constitute a radioactive waste, and are then termed spent sealed radioactive sources (SSRS). In Brazil, this waste is collected by the research institutes of the Nuclear Commission of Nuclear Energy and kept under centralized storage, awaiting definition of the final disposal route. The Waste Management Laboratory (WML) at the Nuclear and Energy Research Institute is the main storage center, having received until July 2010 about 14.000 disused sources, not including the tens of thousands of lightning rod and smoke detector sources. A program is underway in the WML to replacing the original shielding by a standard disposal package and to determining the radioisotope content and activity of each one. The identification of the radionuclides and the measurement of activities will be carried out with a well type ionization chamber. This work aims to develop a methodology for measuring or to determine the activity SSRS stored in the WML accordance with its geometry and determine their uncertainties.

Auctions have a long history and are an effective method to distributed resources. In the era of Internet and e-commerce, electronic sealed-bid auction play an important role in business. However, it is a risk to run a sealed-bid auction through the Internet, which is an open and unreliable environment. There are many security concerns about correctness and fairness of the auction and privacy of the bidders in electronic sealed-bid auctions. Cryptology seems to be the only security solution for electronic sealed-bid auction. On the other hand, a practical electronic sealed-bid auction scheme must be efficient. So efficient application of cryptographic tools to electronic sealed-bid auction is the focus of this thesis. Firstly, security requirements of sealed-bid auctions are surveyed. The auction result must be determined correctly according to the submitted bids and the pre-defined auction rule. The bidders must compete with each other in a fair play and none of them can take advantage of others. The auction must be publicly verifiable, so that the auction result is acceptable by everyone. Usually, a losing bidder hopes to keep his bid secret, so the losing bids should be kept secret. In different applications, different auction rules may be applied. So, to avoid a tie, a large number of biddable prices must be accepted in some applications. Secondly, the currently known sealed-bid auction schemes are classified. In recent years, many sealed-bid auction schemes based on various cryptographic primitives have been proposed. Nearly all of them can be classified into five models. In the Model 1, each bid is known to the auctioneers, who can find the winning bid and winner very efficiently. Bid privacy is not implemented in Model 1. In Model 2 homomorphic bid opening is employed, so that the winning bid and winner can be found while the losing bids are kept secret. In Model 3 very strong bid privacy is achieved through a Dutch-style bid opening, which is highly inefficient. In Model 4, the link between the bids and bidders instead of confidentiality of the bids is kept secret. This kind of confidentiality is weaker than normal bid privacy and called relative bid privacy in this thesis. (Complete confidentiality of the bids in the end of the auction is called absolute bid privacy.) Implementation of relative bid privacy can be very efficient if an efficient anonymous channel can be constructed. Model 5 uses secure evaluation to open the bids and find the auction result and makes it possible to achieve absolute bid privacy efficiently. Three main cryptographic primitives are explored and employed to design new auction schemes in four auction models. The first tool is batch verification, which can improve computational efficiency in auction schemes. The second is mix network, which can be used to implement anonymous channels in Model 4 and Model 5. Two new efficient mix networks are designed and used in Model 2, Model 4 and Model 5. The third is secure evaluation, which is employed in two new auction schemes in Model 5 to achieve strong bid privacy efficiently. Other cryptographic primitives employed in the auction schemes include efficient 1-out-of-w oblivious transfer in Model 2 and key chain in Model 3. Five new auction schemes are proposed. The first scheme in Model 2 batch verifies bid validity to improve efficiency. The second scheme optimises the key chain used in Model 3 to obtain a more advanced auction scheme. The third scheme implements a concrete anonymous channel in Model 4 for the first time and achieves relative bid privacy and high efficiency convincingly. The last two employ new secure evaluation techniques to achieve absolute bid privacy and high efficiency. With these five new auction schemes, better solutions are achieved in various auction applications.

L'objectif de cette thèse est d’étudier l'influence du fluage sur les propriétés mécaniques résiduelle du béton. En effet, les sections des éléments d’une structure précontrainte sont majoritairement soumise à une contrainte de compression. En raison de la relaxation des contraintes (due au fluage du béton notamment) et de la charge appliquée, des contraintes de traction peuvent apparaitre au cours de la vie de l’ouvrage. Ainsi, il est nécessaire de connaître la valeur des propriétés mécaniques résiduelles après l'effet de fluage.Le travail se concentre sur le fluage propre (sans échange hydrique avec le milieu environnant) et il comprend une partie expérimentale et une partie numérique. Dans la partie expérimentale, des essais de fluage en compression et en traction indirect (essai Brésilien) ont été effectués sur le béton en utilisant différents niveaux de chargement appliqué à différents âges du béton. A la fin de chaque essai de fluage, un essai quasi statique a été réalisé sur le même béton pour déterminer l'effet du fluage sur les propriétés mécaniques résiduelles. Afin de vérifier l'effet d’une précharge en compression sur la résistance en traction, comme dans le cas d’une structure précontrainte vieillissante ou soumise à un chargement accidentelle, une campagne d’essai Bresilien avec un préchargement quasi statique en compression a également été réalisée. Les résultats montrent que le comportement après fluage dépend fortement de l’âge de chargement et du sens de sollicitation. Numériquement, un modèle mésoscopiques a été utilisé pour simuler le fluage et les propriétés mécaniques après fluage. En effet, sous un chargement constant seule la pâte de ciment flue tandis que les agrégats agissent comme un obstacle à ce fluage. Par conséquent, les contraintes de traction se produisent à l'interface pâte de ciment/agrégats conduisant à microfissures dans cette zone Les déformations viscoélastique sont correctement reproduite à différents niveaux de chargement mais la modification du comportement résiduel du béton ne peut pas être uniquement expliqué par la micro-fissuration / The aim of this study is to evaluate the effect of creep on the concrete mechanical properties evolution. In prestress structures, in the first concrete is completely subjected to compressive stresses. With time, due to relaxation of the prestressed cables and applied load, some tensile stresses may take place in the concrete. So, it is necessary to know the value of the residual mechanical properties after creep effect.The work which concerns only with basic creep (where there is no drying), includes an experimental part and a numerical part. In the experimental part, compressive and tensile (Brazilian) creep tests were carried out on the concrete using different loading levels that applied at different ages of concrete.At the end of each creep test a strength test was carried out on the same concrete for determining the creep effect on the residual mechanical properties. To evaluate the effect of quasi-instantaneous loading in compression and then in tension, some preloading compressive tests were carried out. These tests were accomplished especially to distinguish the effect of quasi-instantaneous effect from that of creep. A quasi-instantaneous compressive test was achieved until a given level and then a Brazilian strength test was carried out to evaluate the effect of compressive preloading on the tensile strength.Numerically, a mesoscopic model was developed for simulating creep and mechanical properties after creep had taken place. The reason for which this mesoscopic technique was used is related to the fact that under the considered loading level of concrete, only the cement paste creeps while the aggregate act as an obstacle to this creep. As a result, tensile stresses arise at cement past-aggregate interface leading to micro cracks at this zone. With this technique, creep strain can generate some damage at mesoscale without any coupling between creep and damage as in sence phenomenological models.

A análise de qualidade de vinhos é altamente requisitada no setor da enologia. No entanto, o simples ato de abrir a garrafa desvaloriza o produto, sendo necessário o desenvolvimento de métodos alternativos não-invasivos. Atualmente, dois métodos não-invasivos têm sido propostos para análise da qualidade de vinhos em garrafas lacradas: análise do perfil diamagnético e espectroscopia de ressonância magnética (RMN) em alta resolução, usando um ímã de tomógrafo de RMN. No entanto, esses métodos têm baixa seletividade e/ou usam aparelhos que custam milhares de dólares, o que limita seu uso rotineiro. Neste trabalho de mestrado avaliou-se o uso de métodos rápidos de medidas relaxométricas (T1 e T2) para estudar vinhos diretamente nas embalagens lacradas. Neste tipo de medida utilizou-se um equipamento de RMN 1H no domínio do tempo, de baixo custo, baseado em um ímã permanente tipo Halbach de 0,23 T e 10 cm de bore livre utilizando as sequências de pulso CPMG e CP-CWFPx-x. Os dados obtidos foram comparados com medidas realizadas em um equipamento de RMN-DT padrão, mais homogêneo, porém que requer a abertura da garrafa. Todos os decaimentos obtidos foram tratados com ferramentas quimiométricas, correlacionando os dados multivariados com medidas dos metais paramagnéticos ferro, manganês e cobre de cada vinho. Os resultados mostraram que a variação de relaxação dos vinhos ocorreu devido à concentração de Mn2+, que tem uma relaxatividade maior do que o Fe3+ e o Cu2+. Portanto, os resultados mostram que os vinhos de diferentes origens geográficas têm diferentes perfis de relaxação conforme a concentração de metais absorvidos durante o crescimento das uvas, inerente às propriedades edafoambientais de seu local de origem (terroir). / The quality control of wines is highly requested in the enology sector. However, opening the bottle devalues the product, therefore it\'s necessary to develop alternative and non-invasive ways of analysis. Nowadays two non-invasive methods have been proposed to analyze wine in sealed bottles: diamagnetic profile of the bottle and high resolution nuclear magnetic spectroscopy (NMR) using an NMR imaging magnet (MRI). These methods, though, have low selectivity and/or use expensive hardware, making it\'s usage limited. In this study, rapid methods to measure the relaxometric constants (T1 and T2) were evaluated to study wines directly in sealed bottles. To do that it was used a 1H TD-NMR equipment of low cost, based on a permanent Halbach magnet with 0,23T and a 10cm bore. CPMG and CP-CWFPx-x pulse sequences were used and the results were compared to the ones obtained by standard TD-NMR equipment, which is more homogeneous but requires the bottle to be opened. The NMR decays obtained with these two sequences were treated using chemometric tools and correlated to paramagnetic ions content in the samples (Fe3+, Mn2+ and Cu2+). The results show that variation of wine relaxation time is related to the the Mn2+ content, that has higher relaxivity than Fe3+ and Cu2+. As consequence, wine from different geographic origins have different relaxation profiles due to the presence of metals absorbed by the grapes whilst their growth. The metal concentrations in grapes are inherent to soil and environmental properties of the wines origin site (terroir).