Les alliages de zirconium sont utilisés comme matériaux de gainage des combustibles nucléaires dans les réacteurs à eau pressurisée. Ces gaines sont utilisées dans un milieu extrêmement radiatif et corrosif, elles peuvent dans certains cas être le siège de fortes variations de température et doivent répondre à des sollicitations mécaniques importantes, que ce soit en conditions de service ou accidentelles. Dans un tel contexte, il est intéressant de pouvoir prédire les transformations de phases ayant lieu au sein de la gaine en fonction des variations de température et de composition chimique, la précipitation de phases fragiles induites par la présence des éléments d’alliages, mais aussi de tester de nouvelles compositions d’alliages afin de l’optimiser.La méthode la plus adaptée pour la modélisation thermodynamique de systèmes multiconstitués est la méthode Calphad (CALculation of PHAse Diagrams). Il s’agit d’une méthode semi-empirique, consistant à modéliser les enthalpies libres des différentes phases constitutives d’un système par ajustement de certains paramètres, dans le but de reproduire les données expérimentales.Ce mémoire détaille la construction d’une base de données thermodynamiques du système quinaire Cr-Fe-Nb-Sn-Zr selon la méthode Calphad. L’originalité de notre démarche est liée à l’utilisation des calculs DFT de manière systématique et massive. Il s’agit en particulier de calculer par DFT les enthalpies de formation de tous les end-members des phases intermétalliques constitutives du système quinaire. De plus, des calculs sur des mailles « quasi aléatoires » (SQS) sont également effectués de manière systématique afin de déterminer les enthalpies de mélange des solutions solides binaires en structure fcc, bcc et hcp. En outre, une étape importante de ce travail consiste à compléter les données expérimentales de la littérature par de nouvelles mesures sur des systèmes choisis. En particulier, nous nous sommes employés à décrire quelques équilibres de phases des systèmes ternaires Cr-Nb-Sn, Cr-Fe-Sn, Cr-Sn-Zr et Fe-Nb-Sn qui n’avaient jamais été déterminés expérimentalement. Nous avons ensuite utilisé ces calculs et ces nouvelles données expérimentales en complément de données de la littérature comme données d’entrée pour la modélisation thermodynamique des vingt sous-systèmes binaires et ternaires du système quinaire considéré. Enfin, le pouvoir prédictif de notre base de données a pu être vérifié en confrontant ces prédictions à des données expérimentales relatives à des alliages quinaires industriels ou à de nouveaux concepts de gaines / Currently, zirconium alloys are used as fuel cladding materials in PWR (Pressurized Water Reactors). The claddings stand in a very corrosive and radiative environnement, and can be submitted to temperature variations. In addition, the claddings will be subjected to mechanical stresses in reactor or accidental conditions. Thus, it appears useful to have a better understanding of phase transformations occurring in these alloys, as a function of temperature and chemical composition variations, but also to forecast the precipitation of fragile phases induced by the addition of alloying elements. At last, the ability to test new alloy compositions may allow to optimize it.The most suitable method for the thermodynamic modeling of multicomponent systems is the Calphad method (CALculation of PHAse Diagrams). The Calphad method is a widely used technique of semi-empirical modelling of phase diagrams. It consists in the description of the Gibbs energies of the different phases by fitting parameters allowing to describe the experimental data.This report details the design of a thermodynamic database considering the five following elements Zr, Cr, Fe, Nb, and Sn. The originality of this database lies in a systematic use of DFT calculations. Indeed, DFT calculations are performed to predict the formation enthalpy of the intermetallic phases appearing in these systems. Moreover, the SQS method (Special Quasirandom Structure) is used to predict the mixing enthalpy of the fcc, bcc and hcp binary solid solutions. Besides, experimental investigations are an important step of this thesis. Since no experimental data were available for the Cr-Fe-Sn, Cr-Nb-Sn, Cr-Sn-Zr and Fe-Nb-Sn ternary systems, new experimental data are provided, within this study, on the isothermal sections of these systems at different temperatures. All these calculated data in addition to the experimental data and the data from literature are used as input data for the Calphad modelling of the twenty binary and ternary systems which are then combined in the new database. A last part is dedicated to comparisons between predictions obtained with our new database and experimental results on industrial quinary alloys and a new concept of claddings

abstract: The United States Department of Energy (DOE) has always held the safety and reliability of the nation's nuclear reactor fleet as a top priority. Continual improvements and advancements in nuclear fuels have been instrumental in maximizing energy generation from nuclear power plants and minimizing waste. One aspect of the DOE Fuel Cycle Research and Development Advanced Fuels Campaign is to improve the mechanical properties of uranium dioxide (UO2) for nuclear fuel applications. In an effort to improve the performance of UO2, by increasing the fracture toughness and ductility, small quantities of oxide materials have been added to samples to act as dopants. The different dopants used in this study are: titanium dioxide, yttrium oxide, aluminum oxide, silicon dioxide, and chromium oxide. The effects of the individual dopants and some dopant combinations on the microstructure and mechanical properties are determined using indentation fracture experiments in tandem with scanning electron microscopy. Indentation fracture experiments are carried out at room temperature and at temperatures between 450 °C and 1160 °C. The results of this work find that doping with aluminosilicate produces the largest favorable change in the mechanical properties of UO2. This sample exhibits an increase in fracture toughness at room temperature without showing a change in yield strength at elevated temperatures. The results also show that doping with Al2O3 and TiO2 produce stronger samples and it is hypothesized that this is a result of the sample containing dopant-rich secondary phase particles. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2014

Made available in DSpace on 2014-10-09T12:27:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:15Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Business Administration in Project Management in the Faculty of Business at the Cape Peninsula University of Technology 2013 / The nuclear industry has established stringent controls to ensure that electricity is produced in a safe and reliable manner. It is expected that a nuclear power plant should be operated safely, adheres to processes and procedures that govern those safe operations, and implements projects or modifications that are of a high quality; and this would be considered as ‘business as usual’. This is crucial for an industry that is under constant scrutiny, since every project or modification, which is implemented, is critically judged. One important contributing factor to the successful operation of any nuclear power plant is the implementation of projects and modifications in accordance with respective nuclear codes and standards, specifications, processes and procedures. The industry demands that this should be a norm, as quality is synonymous with safety and reliability; factors that cannot be compromised or divorced from each other on a nuclear power plant. Recently, however, there has been great concern relating to non-conformances experienced throughout the project lifecycle, which ultimately affects the quality of modifications and projects, which are implemented at the plant. The research project investigates factors that affect project quality at a nuclear power plant in South Africa. Against the above backdrop, the research problem was “the delivery of poor quality projects have an adverse effect on modifications and projects, which are implemented at the nuclear power plant in South Africa”. The primary research objectives of this study are the following: · To investigate the root cause and impact of inconsistent project quality practices on the project lifecycle; and · To recommend measures that should be established to improve the way in which project quality is conducted throughout the project lifecycle.

Submitted in partial fulfilment of the requirements for the degree of Master of Technology (M Tech) Cape Peninsula University of Technology 2014 / The increased demand for electricity has persuaded a number of countries world-wide to re-evaluate their strategies on energy production. These strategies largely focus on expanding the power generation capacity and adjustment of the amount of energy generated from various sources, in the light of global climate change, security of energy supply and fossil fuel price volatility (OECD report, 2010). In the United States of America (USA), for example, according to Ansolabehere & Konisky (2009), a projection of 40% rise in electricity demand is forecast over the next three decades presenting a need for diversifying the energy mix and expanding power generation capacity. The need for expanding energy supply is increasingly becoming more pronounced in a number of developing countries as well. The demand for energy warrants generation of energy from a variety of sources: coal-fired power plants, gas turbines, wind farms and nuclear power facilities. In order to transmit electricity efficiently these facilities need to be located near residential centres. The challenges associated with the construction of such centres are multi-fold. The option of nuclear power generation is a very divisive issue with as many opponents as supporters, and it has certainly been put back on the agenda in many countries including China, India and Russia, with over 250 nuclear projects in the pipeline globally. The construction of nuclear power plants is often masked with opposition from the public resulting in huge delays in completing the projects yet, nuclear energy is considered as one of the most comprehensive and cost-effective generating options which has the potential to reduce carbon dioxide emissions, meet the ever-increasing demand for electricity as well as making a crucial contribution to energy independence and security of supply.

Por considerar que o uso das tecnologias de informação e comunicação às práticas pedagógicas, aliadas à abordagem dos assuntos nucleares é tema relevante, desafiador e ainda pouco explorado, o presente projeto visou criar um espaço de reflexões acerca das relações de aprendizagem e o papel do professor em sala de aula no contexto escolar de nível médio. Para o desenvolvimento dessa pesquisa, utilizou-se metodologia qualitativa. Como instrumentos de coleta de dados utilizaram-se gravações de áudio e vídeo, anotações em diários de aula, produções textuais dos sujeitos investigados e arquivos de registro da navegação realizada no ambiente do software educativo. A utilização de recursos digitais e, principalmente, do software educativo Cidade do Átomo, possibilitou a realização do exercício de representações de papéis, cujo objetivo é abordar assuntos científicos e tecnológicos polêmicos, tal como os relacionados à produção de energia elétrica a partir da energia nuclear. Nessa atividade, os estudantes interpretam diversos papéis de um mesmo contexto, defendendo e debatendo os pontos de vista convergentes de seus personagens. Foi possível evidenciar na participação dos estudantes por meio de questionamentos e relações estabelecidas entre seus pares e com os recursos tecnológicos a formação de um ambiente de interação proveitoso. Esta constatação evidencia a potencialidade do espaço educativo formado, que resultou em reforço do processo ensino-aprendizagem. / By considering that the use of information technology and pedagogical practices communication allied with an approach of nuclear subject it’s a relevant, challenging and yet not well developed theme, the present project aimed to create speculative space about the learning relationship and the role of the educator in a middle school context. To the development of this research were used a qualitative methodology. As data collecting instrument were used audio and video recordings, diary class annotations, textual productions of the analyzed subjects and navigation record files of the educational software ambient. Use of digital resources, mainly the educative software “Cidade do Átomo”, enabled the roleplaying game, whose objective is the approach of scientific and technologic polemic subjects, such as the nuclear energy production. In this exercise, the students played various roles on the same context, defending and debating their characters point of view. By the use of questions and discussion of the peer relationship with the technological resource, was possible to bespeak a beneficial interactive environment. This statement endorses the potentiality of the educative space, which resulted in a reinforcement of the teaching-learning process.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2017-07-05T12:43:39Z No. of bitstreams: 1 PDF - Ewerton Moraes Luna.pdf: 61662990 bytes, checksum: 58168b08280c9278fe76deb2dbe5ad59 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2017-07-20T12:12:28Z (GMT) No. of bitstreams: 1 PDF - Ewerton Moraes Luna.pdf: 61662990 bytes, checksum: 58168b08280c9278fe76deb2dbe5ad59 (MD5) / Made available in DSpace on 2017-07-20T12:12:28Z (GMT). No. of bitstreams: 1 PDF - Ewerton Moraes Luna.pdf: 61662990 bytes, checksum: 58168b08280c9278fe76deb2dbe5ad59 (MD5) Previous issue date: 2017-03-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The purpose of this work is to analyze the conceptual and historical quality of on-line materials from some websites belonging to scientific dissemination magazines, in which the criteria is that created from the review literature relevant to the topic of nuclear energy. To do this, we needed initially, a large literary revision regarding the topic and its nuances, looking for informations about scientists and journalists, providing us an accurate guide on the quality, of the didactic potential and deficiency in disclosure considered scientific research. We also made an investigation about fundamental historical aspects necessary to fomentation that would give us a consolidation on this subject, delimiting between events that led to the discovery of nuclear fission and the production of the first atomic bombs. We delimit our methodology within a qualitative approach, seeking to explore and describe all topics related to this topic, which are published in four magazine websites, Galileu, Superinteressante, Ciência Hoje and Scientific American Brasil. After analyzing strictly the subject of the cited journals, our results point to conceptual and historical errors and corrections, deficiencies in relation to sources from the used research, the need for cooperation between academic and journalistic professionals, fanciful disclosures on the subject, without a total concern about the reader's profile. / Este trabalho tem por objetivo analisar a qualidade conceitual e histórica das matérias on-line de alguns sites pertencentes a revistas de divulgação científica, segundo os critérios criados a partir da revisão da literatura pertinente ao tema de energia nuclear. Para isso, fez-se necessário, inicialmente, uma ampla revisão literária a respeito desse tema e suas nuances, onde buscamos informações pertinentes entre cientistas e jornalistas, proporcionando-nos um norteamento mais acurado a respeito da qualidade, do potencial didático e deficiência na divulgação de matérias consideradas científicas. Além disso, uma investigação sobre os aspectos históricos necessários a uma fomentação que nos proporcionasse uma consolidação a respeito desse tema, delimitando-se entre os eventos que levaram à descoberta da fissão nuclear e à produção das primeiras bombas atômicas. Delimitamos nossa metodologia dentro de uma abordagem qualitativa, procurando explorar e descrever todos os aspectos pertinentes ao tema, veiculadas em quatro sites de revistas, Galileu, Superinteressante, Ciência Hoje e Scientific American Brasil. Após uma análise criteriosa do assunto nas revistas citadas, nossos resultados apontam para acertos e desacertos conceituais e históricos, deficiências em relação às fontes das pesquisas utilizadas, necessidade de cooperação entre profissionais do meio acadêmico e do jornalismo, divulgações fantasiosas sobre o assunto, sem uma total preocupação com o perfil do leitor.

Por considerar que o uso das tecnologias de informação e comunicação às práticas pedagógicas, aliadas à abordagem dos assuntos nucleares é tema relevante, desafiador e ainda pouco explorado, o presente projeto visou criar um espaço de reflexões acerca das relações de aprendizagem e o papel do professor em sala de aula no contexto escolar de nível médio. Para o desenvolvimento dessa pesquisa, utilizou-se metodologia qualitativa. Como instrumentos de coleta de dados utilizaram-se gravações de áudio e vídeo, anotações em diários de aula, produções textuais dos sujeitos investigados e arquivos de registro da navegação realizada no ambiente do software educativo. A utilização de recursos digitais e, principalmente, do software educativo Cidade do Átomo, possibilitou a realização do exercício de representações de papéis, cujo objetivo é abordar assuntos científicos e tecnológicos polêmicos, tal como os relacionados à produção de energia elétrica a partir da energia nuclear. Nessa atividade, os estudantes interpretam diversos papéis de um mesmo contexto, defendendo e debatendo os pontos de vista convergentes de seus personagens. Foi possível evidenciar na participação dos estudantes por meio de questionamentos e relações estabelecidas entre seus pares e com os recursos tecnológicos a formação de um ambiente de interação proveitoso. Esta constatação evidencia a potencialidade do espaço educativo formado, que resultou em reforço do processo ensino-aprendizagem. / By considering that the use of information technology and pedagogical practices communication allied with an approach of nuclear subject it’s a relevant, challenging and yet not well developed theme, the present project aimed to create speculative space about the learning relationship and the role of the educator in a middle school context. To the development of this research were used a qualitative methodology. As data collecting instrument were used audio and video recordings, diary class annotations, textual productions of the analyzed subjects and navigation record files of the educational software ambient. Use of digital resources, mainly the educative software “Cidade do Átomo”, enabled the roleplaying game, whose objective is the approach of scientific and technologic polemic subjects, such as the nuclear energy production. In this exercise, the students played various roles on the same context, defending and debating their characters point of view. By the use of questions and discussion of the peer relationship with the technological resource, was possible to bespeak a beneficial interactive environment. This statement endorses the potentiality of the educative space, which resulted in a reinforcement of the teaching-learning process.