Ce travail porte sur la réalisation d'un microspectromètre SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) incluant des compteurs de photons SNSPD (Superconducting Nanowire Single Photon Detector). Il met en œuvre un interféromètre intégré à guide d'onde en arête bouclé, en SiN, sous lequel sont disposés 24 nanofils supraconducteurs SNSPD en NbN échantillonnant les interférences au pas de 160nm, à une longueur d'onde centrée sur 1.55µm. La conception, l'étude des composantes optique et électronique, la fabrication et la caractérisation à 4.2K sont décrites, jusqu'à la mise en évidence d'une modulation de puissance lumineuse dans le guide conformément à la formation attendue d'interférences. Le SWIFTS-SNSPD constitue le premier dispositif optoélectronique supraconducteur à part entière, doublement intégré. Sa capacité unique d'échantillonnage direct de franges d'interférences ouvre de nombreuses perspectives, pour des applications allant de l'astrophysique aux télécoms. / This work presents the realization of a SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) micro-spectrometer with SNSPD (Superconducting Nanowire Single Photon Detector) photon counters. The device features an integrated interferometer made of a SiN loop ridge-waveguide, with an array of 24 NbN-nanowire SNSPD underneath that samples at a 160nm period the interferogram of a laser light, at a wavelength centred on 1.55µm. The conception, preliminary studies of integrated optics and electronics, fabrication and characterization at 4.2K of the final device are described, in particular the observation of the detected signal modulation in the waveguide in agreement with the expected interference formation. The SWIFTS-SNSPD constitutes the first stand-alone, fully integrated superconducting optoelectronic device. Its unique capability of direct sampling of light interferogram opens numerous perspectives, with possible applications ranging from astrophysics to telecommunications.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-07-23T11:04:17Z No. of bitstreams: 0 / Made available in DSpace on 2015-07-23T11:04:17Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-07-23T11:04:17Z No. of bitstreams: 0 / Made available in DSpace on 2015-07-23T11:04:17Z (GMT). No. of bitstreams: 0 / Os experimentos realizados e apresentados nesta dissertação resultaram na caracterização neutrônica de núcleos na configuração cilíndrica com 30 varetas combustíveis de diâmetro com um espaço, criado pela retirada de 16 varetas centrais, preenchido com água leve (H2O) ou água pesada (D2O) no reator nuclear de pesquisa IPEN/MB-01. Nestes núcleos, efetuou-se experimentos de correlação de canais nucleares, calibração de barras de controle e irradiação de detectores de ativação de diversos materiais em forma de folhas, cujas faixas energéticas de atuação abrangem grande parte do espectro de nêutrons do núcleo do reator, para a obtenção de parâmetros nucleares, como excessos de reatividade, reatividades totais, atividades saturadas por núcleo alvo, razões espectrais, razões de cádmio e fluxo de nêutrons multigrupo. Com a irradiação de fios de ativação de ouro na parte radial foram obtidas as formas espaciais dos fluxos de nêutrons térmicos e epitérmicos. Os resultados mostraram as características espectrais dessa nova configuração com o espaço das 16 varetas combustíveis preenchido com os dois materiais moderadores. No espaço com a água leve houve um aumento significativo de 294% do fluxo de nêutrons térmicos em comparação com a configuração padrão retangular de 28×26 varetas combustíveis. Com a água pesada aumentou-se a reatividade do sistema com ρ = (783 ± 54) pcm a mais de excesso de reatividade que na configuração com água leve. Os resultados calculados foram simulados nos códigos computacionais MCNP5, SANDBP e CITATION, onde se obtiveram resultados acurados e precisos para as atividades saturadas por núcleo alvo, as distribuições energéticas e espaciais dos fluxos de nêutrons da parte ativa e de parte do refletor e as comparações diretas das seções de choque entre as razões espectrais experimentais e calculadas. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Empresa Brasileira de Pesquisa AgropecuÃria / FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O objetivo do trabalho foi avaliar o efeito da aplicaÃÃo pÃs-colheita de 1-MCP e filme de PVC na conservaÃÃo de pinha, fruta-do-conde ou ata (Annona squamosa L.), durante o armazenamento refrigerado. Os frutos foram colhidos na maturidade fisiolÃgica, em plantio comercial localizado no municÃpio de Limoeiro do Norte, CE, oriundos de produtores da AssociaÃÃo dos Fruticultores do Apodi â ASFRUTA, em seguida, transportadas para o LaboratÃrio de Frutas e HortaliÃas do Departamento de Tecnologia de Alimentos/Centro de CiÃncias AgrÃrias/Universidade Federal do Cearà (DTA/CCA/UFC) e LaboratÃrio de Fisiologia Tecnologia PÃs-Colheita da Embrapa AgroindÃstria Tropical, em Fortaleza, CE. Foram testados tratamentos pÃs-colheita e o tempo de armazenamento (15,0  2ÂC e 90  5% UR) de 0, 0,5, 2, 4, 6, 8 e 10 dias. Os tratamentos aplicados foram: controle, 200 ppb de 1-MCP, filme de PVC e 200 ppb de 1-MCP + filme de PVC. Foram avaliados quanto a: perda de massa fresca (PMF); firmeza da polpa (FP); aparÃncia externa (APE); pH; acidez total titulÃvel (ATT), sÃlidos solÃveis (SS); aÃÃcares solÃveis totais (AST); aÃÃcares redutores (AR), amido; compostos fenÃlicos, atividade das enzimas polifenoloxidase e peroxidase e relaÃÃo SS/ATT. O experimento foi realizado em delineamento inteiramente casualizado em esquema fatorial (tratamentos pÃs-colheita x tempo de armazenamento), com 3 repetiÃÃes (bandejas com 2 frutos). A perda de massa fresca e queda na firmeza foi mais lenta nos frutos tratados com 1-MCP + filme e filme de PVC, obtendo ao oitavo dia notas mÃdias de 111,8 e 71,6 (N). O teor de sÃlidos solÃveis (SS) foi temporariamente atrasado pelo tratamento 1-MCP + filme, que no oitavo dia de armazenamento apresentou reduÃÃo de 4 Brix comparado com os demais tratamentos. A relaÃÃo SS/ATT aumentou durante o armazenamento para os quatro tratamentos possivelmente devido ao aumento do SS e à reduÃÃo na acidez a partir do segundo dia. Em relaÃÃo aos compostos fenÃlicos, apenas os compostos fenÃlicos oligomÃricos apresentaram significÃncia para os frutos tratados com filme de PVC. Os demais compostos fenÃlicos dÃmeros e polimÃricos nos quatro tratamentos nÃo apresentaram diferenÃa significativa. NÃo houve diferenÃa significativa entre os tratamentos para as enzimas polifenoloxidase (PPO) e peroxidase (POD), logo os tratamentos filme de PVC e 1-MCP nÃo promoveram efeito sobre as enzimas. / The aim of the study was to evaluate the effect of postharvest application of 1- methylcyclopropene (1-MCP) and film of PVC in the conservation of pinha (Annona squamosa L.), during refrigerated storage. The fruits were harversted at the physiological maturity stage in a planting of a commercial area localized in Limoeiro do Norte, Ceara â Brazil, producers arising from The Fruit Farmers Association of Apodi â ASFRUTA, and carried to the Laboratory of Fruits and Vegetables of Department of Food Science â Center of Agricultural Science â Federal University of Cearà and the Laboratory of Physiology and Technology Postharvest of Embrapa Agribusiness Tropical, Fortaleza, CE. Postharvest treatments and the storage time (15,0  2ÂC and 90  5% UR) were tested in fruits that were stored for 0, 5, 2, 4, 6, 8 and 10 days. The applied treatments were as follow: control, 200 ppb of 1-MCP, film of PVC and 200 ppb of 1-MCP + PVC film. The following variables were evaluated: fresh mass loss (LMS); firmness of the pulp (PF); external appearance (AE); pH; total titratable acidity (TA); soluble solids (SS); total soluble sugars (TSS); reducing sugars (RS), starch, phenolics compounds, polifenoloxidase and peroxidase activities and SS/ATT ratio. Experimental design was completely randomized in factorial (treatments postharvest x storage time), with three replication (trays with 2 fruits). The fresh mass loss and the decrease in firmness was slower in the fruits treated with 1-MCP + film and PVC film, obtaining in the eighth day, the value of 111,8 and 71,6 (N). The soluble solids (SS) tenor was temporarily delayed by the treatment 1-MCP + film which at the eighth day of storage, decreased of 4 Brix, compared with the others treatments. The SS/AT ratio increased during the storage, in four treatments, possibly because the increase of the SS and the reduction in acidity from the second day. Regarding to the phenolic compounds, only the oligomeric phenolic compounds, showed significance for the fruits treated with PVC film. Others phenolic dimers and polymers, in four treatments, didnât show significance difference. There was no significance difference between the treatments for polifenoloxidase (PPO) and peroxidase (POD). Thus the PVC film and 1-MCP didnât promote effect on the Enzymes.

Ce travail se place dans le cadre des réacteurs nucléaires de 4ème génération tels que les réacteurs à neutrons rapides et caloporteur gaz (RNR-G), pour lesquels des matériaux réfractaires comme le nitrure de titane (TiN) enroberont le combustible afin de permettre la rétention des produits de fission. Cette étude a porté sur le comportement thermique intragranulaire du xénon dans des échantillons de TiN obtenus par frittage à chaud sous charge. Le rôle de la microstructure sur le comportement thermique du xénon a été étudié. Plusieurs lots ont ainsi été synthétisés sous différentes conditions de température et de composition de la poudre initiale. Le xénon a été introduit par implantation ionique. Les échantillons ont ensuite subi des traitements thermiques entre 1300°C et 1600°C, soient les températures accidentelles envisagées. Un transport majoritaire du xénon vers la surface a été mis en évidence. Ce dernier est ralenti lorsque la température de frittage augmente. Des différences de comportement ont été observées selon les poudres mises en oeuvre dans la synthèse et selon l'orientation cristalline du grain considéré. Le relâchement du xénon a également été corrélé à l’oxydation de TiN. Des bulles de Xe dès 0,38 % atomique ont été observées. Leur taille est proportionnelle à la concentration en Xe et augmente avec la température de recuit, d’où une certaine mobilité du Xe au sein de TiN. Plusieurs mécanismes pouvant expliquer cette mobilité sont proposés. En complément, des calculs ab initio ont confirmé le caractère fortement insoluble du Xe dans TiN et révélé que les bilacunes sont les plus favorables à l'incorporation du xénon au sein de ce matériau. / This work concerns the generation IV future nuclear reactors such as gas-cooled fast reactor (GFR) for which refractory materials as titanium nitride (TiN) are needed to surround fuel and act as a fission product diffusion barrier. This study is about Xe thermal behavior in sintered titanium nitride. Microstructure effects on Xe behavior have been studied. In this purpose, several syntheses have been performed using differents sintering temperatures and initial powder compositions. Xenon species have been introduced into samples by ionic implantation. Then, samples were annealed in temperature range from 1300°C to 1600°C, these temperatures being the accidental awaited temperature. A transport of xenon towards sample surface has been observed. Transport rate seems to be slow down when increasing sintering temperature. The composition of initial powder and the crystallographic orientation of each considered grain also influence xenon thermal behavior. Xenon release has been correlated with material oxidation during annealing. Xenon bubbles were observed. Their size is proportional with xenon concentration and increases with annealing temperature. Several mechanisms which could explain Xe intragranular mobility in TiN are proposed. In addition with experiments, very low Xe solubility in TiN has been confirmed by ab initio calculations. So, bivacancies were found to be the most favoured Xe incorporation sites in this material.

Les réacteurs GEN IV (GFR) nécessitent l’emploi de matériaux d’enrobage ayant une bonne transparence aux neutrons, une conductivité thermique élevée et agissant comme barrière de diffusion pour les produits de fission. Le but de cette étude est de déterminer le rôle de la température et de l’irradiation sur le comportement du xénon implanté dans l’oxycarbure de zirconium (ZrCxOy). A cet effet, des poudres de deux stoechiométries ZrC0,95O0,05 et ZrC0,8O0,2 ont été synthétisées puis frittées par frittage flash, ou sous charge. Pour étudier le rôle de la fluence d’implantation sur la migration thermique du xénon dans le ZrC0.95O0.05, des ions 136Xe2+ ont été implantés à une énergie de 800 keV à trois fluences : 1015, 1016 et 1017 at/cm². Les échantillons ont ensuite été recuits sous vide secondaire dans une gamme de températures de 1500 à 1800°C. Les profils de distribution du xénon ont été mesurés par RBS ou par SIMS. Des analyses par MET, MEB, NBS et PAS-DBS ont été réalisées à chaque étape. Cette étude a montré qu’à 1015 et 1016 at/cm2 le xénon est piégé dans des bulles nanométriques dans les murs de dislocations. A 1017 at/cm2, la coalescence des bulles de plus grandes tailles conduit au relâchement du xénon aux joints de grains. Pour les échantillons de ZrC0,8O0,2, les recuits conduisent à une oxydation de surface corrélée à un important relâchement du xénon. Parallèlement, des expériences d’irradiation ont été effectuées sur la plateforme JANNUS et auprès du Tandem afin de déterminer le rôle respectif des dégâts balistiques et électroniques sur la migration du xénon. Nous avons observé que ces conditions d’irradiation n’entrainaient pas de migration du xénon / Refractory ceramics are considered for the GEN IV reactors (GFR). Transition metal carbides, like ZrC, are candidates as components for fuel elements owing to their good thermal stability and their neutronic performance. An extensive study was carried out to elucidate the role of temperature on the diffusion of xenon, an abundant and volatile radionuclide, in zirconium oxycarbide. For that purpose, dense zirconium carbide samples ZrC0.8O0.2 and ZrC0.95O0.05 were synthesized using Spark Plasma Sintering and Hot Pressing. 136Xe2+ ions were implanted at three fluencies: 1015, 1016 and 1017 at/cm2, at an energy of 800 keV. Thermal annealing were carried out under vacuum in a temperature range of 1500°C to 1800°C. The Xe distribution profiles were measured either by Rutherford Backscattering Spectrometry or by Secondary Ion Mass Spectrometry before and after the different treatments. Our results show that the ZrC0.8O0.2 stoichiometry is not stable at high temperature and for the ZrC0.95O0.05 stoichiometry, the Xe migration behaviour depends on the implantation fluence. The role of the implantation defects, their evolution during annealing and the trapping of Xe into bubbles was evidenced using Positron Annihilation Lifetime Spectroscopy and Transmission Electron Microscopy. In order to simulate the effects due to neutron irradiation, irradiation experiments were carried out at the JANNUS irradiation platform at CEA Saclay and the Alto Tandem accelerator at Orsay taking into account the respective roles of the ballistic and electronic processes. We observed that no xenon migration occurred after irradiation

This master´s thesis deals with an air cooled condenser. The specific attention is focused on the condenser in the Brno´s waste-to-energy plant SAKO. The general process of calculation of the heat transfer coefficient is introduced, which is the base for the calculation of the condenser´s output. This process is later used for the calculation of a specific condenser. A considerable part of the thesis is concentrated on the analysis of behavior of the condenser of SAKO in various conditions from the theoretical point of view and then also in terms of real operation using provided operational data.

Thesis is focused on calculation of the condenser of flue gas, which is created by burning of natural gas. In the first part is theoretical overview of equations describing film condensation and physical properties of the flue gas. The second part deals with practical thermal calculation of the specified condenser. In third part parametric study is done in which a tempature of cooling water at inlet and the coefficient of excess air are changed. The last part of the thesis is dedicated to geometric design of the flue gas condenser whose required power is 8 MW.

The thesis focuses on comparison of the original and the new solutions of cooling water circuit of the York cooling units for the purpose of cooling water flow increase for the absorption units in the Dukovany Nuclear Power Plant. The individual parts of the cooling units that were changed and modified within a reconstruction are described here. The aim of the work is also to process and compare the original and the new solutions of the cooling units and the cold source station from the available measured data. The data are processed into illustrative graphs and tables. Based on the obtained data we can observe the changes achieved by the reconstruction that have affected the effectiveness of the cooling units.

Dans les réacteurs à neutrons rapides refroidis au sodium (RNR-Na), une défaillance dans le système de refroidissement du coeur ou de protection du réacteur peut conduire à un accident grave. Dans un tel scenario, les matériaux du coeur (combustible et acier) fondent pour former un mélange appelé corium susceptible d'interagir avec le réfrigérant (sodium). Une telle interaction (Fuel Coolant Interaction, FCI) peut générer des évènements énergétiques aptes à mettre en danger les structures du réacteur. La violence de l'explosion dépend essentiellement de l'état du mélange corium-sodium. Connaître les caractéristiques des trois phases en présence dans la zone d'interaction (corium, sodium liquide, vapeur de sodium) est donc crucial. Le manque de connaissances de la phénoménologie de l'interaction conduit à l'étudier au moyen de dispositifs expérimentaux. PLINIUS-2, la future plateforme expérimentale du CEA Cadarache consacrée aux grandes masses, sera dédiée à l'étude de la phénoménologie de l'interaction corium-réfrigérant (eau et sodium). L'objectif du présent travail est de développer, pour cette installation, un système d'imagerie basée sur des radiographies X afin de visualiser et de mieux comprendre l'interaction corium-sodium. Un algorithme de post-traitement de ces images a aussi été écrit afin de les analyser, d'en déduire la répartition des trois phases dans le système et de contribuer ainsi à l'amélioration de la modélisation numérique. Ce travail de thèse a été conduit en trois étapes. La première était consacrée à une étude bibliographique des expériences passées d'interaction corium-sodium et des mécanismes de fragmentation mis en jeu. Cette étude, complétée d'une analyse statistique des distributions de particules obtenue alors, a montré que les particules générées lors de ces expériences sont extrêmement fines avec des diamètres caractéristiques inférieurs au mm. Ces très petites tailles de particules combinées aux limites de détection de notre système d'imagerie nous ont amenés à travailler plutôt sur la détection de nuages de particules que de particules individuelles. Dans une deuxième étape, la simulation du nuage de particules de corium suivie de la conception de fantômes (maquettes 3D) représentant les trois phases du milieu ont été réalisées. Les simulations de nuages de fragments dans le sodium liquide et la vapeur ont été réalisées avec le logiciel CEA MODHERATO. Sur la base des résultats de ces calculs, certains fantômes ont été fabriqués afin de générer des images "réelles" à l'aide d'une chaîne d'imagerie existant au CEA. Ces fantômes représentatifs de la zone d'interaction corium-sodium ont été fabriqués pour faciliter le développement et la calibration du logiciel de traitement d'images. La troisième étape de cette thèse était dédiée à la conduite des expériences avec les fantômes 3D et au développement du logiciel de traitement des images ainsi obtenues. Les radiographies X des fantômes ont été générées à l'aide du système d'imagerie de l'installation KROTOS du CEA Cadarache. Les images ont ensuite été traitées avec le logiciel appelé PICSEL que nous avons développé afin de localiser les trois phases en présence dans la zone d'interaction. PICSEL a ensuite été appliqué à une expérience d'interaction corium-eau réalisée dans l'installation KROTOS dans le cadre du projet ALISA de collaboration Europe-Chine; ceci a permis une première validation du logiciel. Ainsi, lors de cette thèse, un système de radioscopie X a été défini pour visualiser l'interaction corium-sodium dans les expériences de la future installation PLINIUS-2 du CEA Cadarache. Une analyse qualitative des images produites par ce système (expériences menées avec des fantômes) est aussi réalisée avec le logiciel PICSEL développé lors de cette thèse afin de mieux caractériser le mélange, de mieux comprendre les mécanismes de l'interaction et de contribuer ainsi à l'amélioration de la sûreté des réacteurs à neutrons rapides. / In Sodium-cooled Fast Reactors (SFR), hypothetical failure of the core cooling system or the plant protection system may lead to a severe accident scenario. In such a scenario, core materials (fuel and cladding) melt down generating a hot molten mixture called corium. This corium may interact with the coolant (liquid sodium) leading to Fuel Coolant Interaction (FCI) which can generate energetic events and hence jeopardize the reactor structures. The yield of these energetic events strongly depends on the state of the corium-sodium mixture prior to the energetic event. Therefore, the knowledge of the features of the mixture composed of three-phases (i.e., corium, liquid sodium, and sodium vapor) is crucial. The lack of knowledge on the phenomenology of the interaction emphasizes the need to study it with the help of experiments. PLINIUS-2, the future large-mass experimental platform of CEA Cadarache, will be dedicated to experiments aiming at understanding the interaction phenomenology of prototypic corium with coolant (sodium and water). The present research aims to develop a high-energy X-Ray imaging system for this facility, to visualize and better understand the corium-sodium interaction. An image-processing algorithm to analyze the three-phase repartition is also developed to contribute to the improvement of numerical modeling. This Ph.D. research has been executed in three steps. In the first step, a bibliographic study of the past experiments was carried out to better understand the physics of the interaction and the mechanism of fragmentation during corium-sodium interaction. This bibliographic study, along with a statistical analysis of the particle size distribution data of various experiments conducted in the past, revealed that the particles formed in these tests are extremely fine fragments with characteristic diameters smaller than 1 mm. Due to the small particle size and the detection limitations of corium fragments in sodium with our X-Ray system, clouds of particles were detected instead of individual particles. In the second phase, the simulation of clouds of corium particles followed by the designing of phantoms (3D mock-ups) representing the 3-phase medium was carried out. Simulations of clouds of corium fragments in liquid sodium and vapor were performed using the CEA Cadarache in-house tool MODHERATO. Based on the results obtained from the simulations, certain phantoms were designed to conduct some physical experiments. These phantoms representative of the FCI interaction zone were manufactured to experimentally evaluate the performance of the radioscopy system and to facilitate the development and calibration of the image processing software. The third step of this work was dedicated to performing experiments with the phantoms and analyzing the radiographic images by developing an image processing algorithm. Experiments were carried out with phantoms in several configurations with the X-Ray radiography system at the CEA Cadarache KROTOS facility. The radioscopic images obtained were treated by developing a new comprehensive image processing and analysis code called PICSEL to identify the three phases composing the medium. Further verification and validation of the PICSEL software were carried out on a test conducted between corium and water at the KROTOS facility under the Euro-Chinese project “ALISA”. Thus, in this Ph.D. research, an X-Ray imaging system was qualified to visualize the corium-sodium interaction in the future PLINIUS-2-FR facility. A qualitative analysis of the images produced by this system was also performed using the PICSEL software to better characterize the evolution of the three-phase mixture and understand the FCI phenomenon, knowledge of which is deemed essential to improve the safety and designs of future sodium-cooled fast reactors.