L’élaboration de combustible nucléaire UO2-30%PuO2 pour les nouveaux réacteurs nucléaires de Génération IV repose sur l’utilisation de plutonium issu du recyclage des combustibles MOX (Mélange d’OXydes UO2-PuO2) des réacteurs actuels. Par rapport au Pu initial, ce plutonium présente une proportion d’isotopes fissiles beaucoup plus faible et une quantité plus importante (x30) en 238Pu dont l’activité spécifique alpha et la puissance thermique sont importantes. Le procédé d’élaboration du combustible qui consiste à mettre en forme les poudres d’oxydes par pressage met en jeu un lubrifiant organique, le stéarate de zinc. L’objectif de la thèse est d’étudier le comportement en température et sous irradiation de ce composé. Un effet de la montée en température et du vieillissement en température a été observé sur les propriétés cristallographiques du stéarate de zinc, avec une amorphisation partielle du matériau qui engendre une détérioration de ses propriétés de lubrification dès 110°C. La dégradation radiolytique du stéarate de zinc a été étudiée à travers l’analyse des gaz produits par irradiation alpha au contact de poudres de PuO2 ou par irradiation externe aux hélions, complétée par des analyses physico-chimiques du stéarate irradié. Les rendements de production de gaz sont calculés et permettent d’établir un mécanisme de radiolyse. Il a été montré que l’impact de la radiolyse sur les propriétés de lubrification est moindre que l’effet de la température. Le couplage des dégradations a un effet synergique, avec une détérioration des propriétés de lubrification observée à des températures plus faibles que sur le matériau non irradié. A partir de ces résultats, des recommandations d’utilisation du stéarate de zinc ont été proposées. / The manufacturing of nuclear fuels UO2-30%PuO2 for the Gen IV nuclear reactors is based on the use of plutonium coming from MOX (Mixed OXides) fuel recycling from actual reactor. This plutonium would contain a few quantities of fissionable isotopes and a significant amount (x30) of 238Pu compared to initial Pu. This isotope possesses a strong alpha activity and a great thermal power. The manufacturing process which consists in powders pressing will use zinc stearate, an additive used as lubricant. The aim of this PhD is to study the behaviour in temperature and under irradiation of this compound. An effect of temperature increasing and thermal ageing has been observed on crystallographic properties with a material amorphisation and a deterioration of lubricant properties from 110°C. Radiolytic degradation of zinc stearate has been studied through the analysis of gases produced by alpha radiation at the contact of PuO2 powders or by external radiation by helions, with the support of chemical analysis of irradiated solid. Gaz production yields are calculated and enable establishment of a radiolysis mechanism. It has been showed that impact of radiolysis on lubricant properties is less important than temperature effect. The coupling of degradations has a synergic effect, with a deterioration of lubricant properties observed at lower temperature compared to non-irradiated material. From these results, recommendations for use of zinc stearate have been proposed.

Foram preparados eletrocatalisadores PtRu/C (nanopartículas PtRu suportadas em carbono) utilizando processos radiolíticos (radiação gama) e testados na oxidação direta na oxidação direta de metanol. Neste procedimento submeteu-se à radiação gama, sob agitação, soluções de água/2-propanol e água/etileno glicol, ambas contendo íons dos metais precursores e o suporte de carbono. Foram variadas as razões volumétricas água/2-propanol e água/etileno glicol e a dose de radiação total recebida (kGy). A razão atômica nominal Pt:Ru utilizada em todos os experimentos foi de 50:50. Os eletrocatalisadores obtidos foram caracterizados por análise de raios X por energia dispersiva (EDX), por difração de raios X (DRX), por microscopia eletrônica de transmissão (MET) e por voltametria cíclica (VC). A eletro-oxidação do metanol foi estudada por voltametria cíclica (VC) utilizando a técnica do eletrodo de camada fina porosa. Os eletrocatalisadores preparados no meio reacional água/2-propanol apresentaram tamanho de cristalito na faixa de 3 - 5 nm e razão atômica Pt:Ru de 50:50. Os eletrocatalisadores preparados em água/etileno glicol apresentaram tamanho de cristalito na faixa de 2 - 3 nm, menores que os obtidos em água/2-propanol, no entanto, as razões atômicas Pt:Ru obtidas foram de aproximadamente 80:20, mostrando que nem todo o rutênio foi reduzido nas condições estudadas. Na eletro-oxidação do metanol, a atividade catalítica dos materiais obtidos mostrou-se bastante dependente do álcool utilizado e das razões volumétricas água/2-propanol e água/etileno glicol utilizadas nos meios reacionais. Os eletrocatalisadores preparados em água/2-propanol mostraram desempenho inferior aos preparados em água/etileno glicol, os quais mostraram desempenhos similares ou superiores (amperes por grama de platina) ao eletrocatalisador comercial PtRu/C da E-TEK, tido como referência na área. / PtRu/C (carbon-supported PtRu nanoparticles) anode electrocatalysts were prepared using radiolytic process (gamma radiation) and tested for methanol electro-oxidation. In this process, water/2-propanol and water/ethylene glycol solutions containing the metallic ions and the carbon support were submitted to gamma radiation under stirring. The water/alcohol ratio (v/v) and the total dose (kGy) were studied. A nominal Pt:Ru atomic ratio of 50:50 were used in all experiments. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry (CV). The electro-oxidation of methanol was studied by cyclic voltammetry using the thin porous coating technique. The electrocatalysts prepared in water/2-propanol showed crystallite size in the range of 3-5 nm and Pt:Ru atomic ratio of 50:50. The electrocatalysts prepared in water/ethylene glycol showed crystallite size (2-3 nm) smaller than the ones obtained in water/2-propanol, however, the Pt:Ru atomic ratios obtained were approximately 80:20, showing that only part of ruthenium ions were reduced. For methanol oxidation the electrocatalytic activity depends on the water/2-propanol and water/ethylene glycol ratio used in the reaction medium. The electrocatalysts prepared in water/2-propanol showed inferior performance to the ones prepared in water/ethylene glycol, which showed similar or superior performances (amperes per gram of platinum) to the commercial electrocatalyst from E-TEK.

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Os desafios energéticos que enfrentamos no presente, ou seja, a busca por novas fontes renováveis de energia tem recebido muita atenção nos últimos anos. Na tentativa de minimizar os problemas ambientais tem-se investido no tratamento de resíduos, pois gerenciar resíduos como o lodo de esgoto é difícil e caro. Entretanto, o lodo pode ser utilizado como matéria prima na produção de energia através da pirólise onde quatro frações são geradas: líquida aquosa, líquida orgânica, sólida e gasosa. A gama de substâncias agregadas ao lodo que podem ser convertidas com a pirólise por vários mecanismos reacionais durante as etapas do processo podem conferir características únicas às frações combustíveis formadas principalmente por hidrocarbonetos de cadeias longas. As formas de tratamento adequado para a matéria prima para maximizar o rendimento de combustível ajustado ao modelo de reator também devem ser considerados. Portanto, o conhecimento das características químicas e físico-químicas das biomassas, ou seja, o lodo de esgoto, bem como as formas de conversão desta para a produção de energia e as características dos combustíveis produzidos é fundamental. / As a way to encourage the treatment and use of sewage sludge and assist in the resolution of the challenges that have been faced today, with regard to the search for alternative energy sources, sewage sludge can be used as raw material for obtaining fuels and chemicals via pyrolysis whose products can be obtained into four fractions: aqueous, organic, solid and gaseous. The range of substances added to the sludge that can be converted to pyrolysis several reaction pathways during stages of the process may confer unique characteristics to fuel fractions formed mainly by long-chain hydrocarbons. Besides, the forms of treatment used in the sewage sludge have to be appropriate to the reactor model to improve the yield of fuel. Therefore, knowledge of the chemical and physico-chemical properties of that biomass, along with the ways for the conversion of that biomass into energy and the characteristics of the fuels produced have to be known to improve the use of sewage sludge in the pyrolysis process.

O objetivo do presente estudo foi avaliar o comportamento do fogo em queimas controladas, com o fim de estabelecer relações entre as variáveis do comportamento do fogo e fatores determinantes de propagação (material combustível e variáveis climáticas). Este trabalho foi desenvolvido em três áreas experimentais e em três períodos do dia de realização das queimas: no horário de 07:00 as 11:00 horas da manhã, no horário de 13:00 as 17:30 horas e de 18:00 as 21:00 horas, nos municípios de Gurupi-TO e Dueré-TO, no mês de junho de 2016. A primeira área, denominada Gurupi I, está distante 3 km do município de Gurupi-TO, com vegetação Andropogon gayanus (altura média de 1,80 cm); a segunda área, denominada Gurupi II, está distante 4 km do município de Gurupi-TO, com Andropogon gayanus (altura média entre 40-60 cm) e a terceira área, denominada Dueré, fica aproximadamente a 40 km do município de Gurupi-TO, com vegetação típica de Cerrado Stricto Sensu. Para a realização da coleta de material combustível, a metodologia empregada foi a de “amostragem destrutiva” que consiste na retirada de todo o material contido no quadrante (1x1 m). O material combustível foi separado em vivo e morto, e por classes diamétricas (< 0,7 cm; 0,7 – 2,5 cm; 2,5 – 7,6 cm; > 7,6 cm). De acordo com as análises estatísticas, Gurupi I foi a área que apresentou maior biomassa de material combustível vivo e morto com diâmetro < 0,7 cm (3,789 t.ha-1; 9,912 t.ha-1). Já na área Dueré, o material combustível vivo e morto com diâmetro <0,7 cm apresentou uma carga de 0,451 t.ha-1; 3,492 t.ha-1 respectivamente. O material combustível morto, com diâmetros > 0,7 cm, foi observado somente na área de Dueré com uma carga total de 0,879 t.ha-1. Com relação aos resultados obtidos em Dueré, a velocidade média do vento variou de 0,0 m.s-1 (período da tarde) a 0,02 m.s-1 (período da noite). Na intensidade do fogo, esta variação ficou entre 118,60 kcal.m-1 s-1 (manhã) e 361,45 kcal.m-1.s-1 (tarde) e a (noite) com a menor intensidade 53,21 kcal.m-1.s-1. Em Gurupi I, com relação à altura das chamas no período da manhã, foi observado o menor valor (1,12 m) e no período da tarde o maior valor (3,47 m). Em Gurupi II, a velocidade média de propagação foi maior nas queimas realizadas no período da manhã (0,02 m.s-1) e da tarde (0,04 m.s-1). A temperatura e a umidade relativa do ar foram, respectivamente, maiores e menores no período da tarde com os seguintes valores: 37,4º C e 17,0%, e apresentaram correlação com os parâmetros de comportamento do fogo e foram incluídas nos modelos matemáticos gerais ajustados para predição da velocidade de propagação (R2 = 0,44); da intensidade do fogo (R2 = 0,60) e da altura das chamas (R2 = 0,74). De forma geral as variáveis que mais exerceram influência no comportamento do fogo foram as variáveis meteorológicas como umidade relativa e temperatura do ar. / The objective of the present study was to evaluate the behavior of fire in controlled burning, in order to establish relationships between fire behavior variables and propagation determinants (combustible material and climatic variables). This work was developed in three experimental areas divided into three periods of the day for the firing of the burns, from 07:00 to 11:00 in the morning, from 13:00 to 17:30 and from 18:00 at 21:00 hours, in the municipalities of Gurupi-TO and Dueré-TO, in June 2016. The first area, called Gurupi I, is 3 km from the municipality of Gurupi-TO, with vegetation Andropogon gayanus (average height of 1.80 cm); The second area, called Gurupi II, is 4 km from the municipality of Gurupi-TO, with Andropogon gayanus (average height between 40-60 cm) and the third area, called Dueré, is approximately 40 km from the municipality of Gurupi-TO, With vegetation typical of Cerrado Stricto Sensu. For the collection of combustible material, the methodology used was the "destructive sampling" used by different authors, which consists of the removal of all the material contained in the quadrant. The combustible material was separated in vivo and dead, and by diametric grades (<0.7 cm, 0.7 - 2.5 cm, 2.5 - 7.6 cm, >7.6 cm). According to the statistical analysis, Gurupi I was the area that presented the largest biomass of living and dead combustible material with a diameter of <0.7 cm (3.789 t.ha-1; 9.912 t.ha-1). In the Dueré area, live and dead fuel with a diameter of <0.7 cm had a load of 0.451 t.ha-1; 3.492 t.ha-1 respectively. The dead fuel material, with diameters> 0.7 cm, was observed only in the Dueré area with a total load of 0.879 t.ha-1. Regarding the results obtained in Dueré, the average wind speed ranged from 0.0 m.s-1 (afternoon period) to 0.02 m.s-1 (night time). In the fire intensity, this variation was between 118.60 kcal.m-1.s-1 (morning) and 361.45 kcal.m-1.s-1 (late) and at (night) with the lowest intensity 53.21 kcal.m-1.s-1. In Gurupi I, the height of the flames in the morning was observed the lowest value (1.12 m) and in the afternoon showed the highest height (3.47 m). In Gurupi II, the average propagation velocity was higher in the morning (0.02 m.s-1) and in the afternoon (0.04 m.s-1). The temperature and relative humidity were respectively higher and lower in the afternoon with the following values: 37.4°C and 17.0%, and presented correlation with fire behavior parameters and were included in the mathematical models General adjusted for propagation velocity prediction (R2= 0.44); of the fire intensity (R2 = 0.60) and the height of the flames (R2 = 0.74). In general, the variables that exerted most influence on fire behavior were the meteorological variables, such as relative humidity and air temperature.

La presente tesis tuvo como objetivo diseñar un equipo de volumen constante para caracterizar los parámetros físicos en la inyección de combustibles líquidos en medios inertes (sin combustión). Para lograr este objetivo, primero se realizó una revisión de un consolidado de artículos relacionados con el trabajo de tesis desarrollado. Además, se relacionaron los conceptos de termo-fluidos y resistencia de los materiales para construcción del equipo de volumen constante. Mediante la norma VDI 2221 se evaluaron distintos diseños preliminares con el objetivo de encontrar el diseño óptimo de este equipo. Luego, se definieron los parámetros para el diseño del equipo: presión interna de 10 MPa y volumen interno de 4L. Con estos parámetros se procedió a dimensionar el equipo de volumen constante usando el código ASME para recipientes a presión. Debido a que el código ASME no está enfocado directamente al diseño de este tipo de equipos, se validó dicho diseño mediante un análisis por el método de elementos finitos, con el cual se verificó que el equipo cumplía con las exigencias mecánicas. Luego, se procedió a realizar los planos de ingeniería y de detalle del equipo. Finalmente, se realizó un metrado de los materiales y posterior proceso de fabricación con la finalidad de realizar un análisis de costos de fabricación del equipo, en el cual se obtuvo un valor de S/. 59 437.70 nuevos soles. / Tesis

An accumulated combustible dust layer on some hot process equipment such as dryers or hot bearings can be ignited and result in fires when the hot surface temperature is sufficiently high. The ASTM E 2021 test procedure is often used to determine the Hot Surface Minimum Ignition Temperature for a half inch deep layer of a particular dust material. This test procedure was used in this thesis to study possible effects of combustible liquid (such as lubricating oil) and powder additives in the dust layer as well as air flow effects. The following combustible dusts were used: paper dust from a printing press, Arabic gum powder, Pittsburgh seam coal, and brass powder. To develop an improved understanding of the heat transfer, and oxygen mass transfer phenomena occurring in the dust layer, additional instrumentation such as a second thermocouple in the dust layer, an oxygen analyzer and gas sampling line, and an air velocity probe were used in at least some tests. Hot Surface Minimum Ignition temperatures were 220oC for Pittsburgh seam coal, 360oC for paper dust, 270¡Ãƒâ€° for Arabic gum powder, and > 400oC for brass powder. The addition of 5-10 weight percent stearic acid powder resulted in significantly lower ignition temperature of brass powder. When combustible liquids were added to the dust layer, the ignition temperatures did not decrease regardless of the liquids¡¯ ignitibility because the liquids seemed to act as heat absorbents. Although air velocity on the order of 1 cm/s did not affect test results, much larger air velocities did affect the results. With 33 cm/s downward airflow at the elevation of the surface of the layer, Pittsburgh seam coal was not ignited at 230¡Ãƒâ€° which was 10¡Ãƒâ€° higher than the 220¡Ãƒâ€° hot surface ignition temperature without airflow. Based on the results and data from the additional instrumentations, modifications of the ASTM E2021 test procedure are recommended.

Les piles à combustible sont des systèmes qui permettent de convertir directement de l'énergie chimique en énergie électrique. La structure physique d'une pile à combustible est composée d'une cathode et d'une anode poreuses séparées par un électrolyte dense. Les piles à combustible à oxydes solides (Solid Oxide Fuel Cell (SOFC))offrent une alternative intéressante pour la production d'énergie et une certaine polyvalence dans leur utilisation. Les recherches actuelles se focalisent sur l'abaissement de la température de fonctionnement de ce type de pile (500-700°C) pour augmenter leur durée de vie, diminuer les coûts de fabrication et les dégradations aux interfaces. Afin de compenser ces problèmes, la recherche tend vers des matériaux présentant de meilleures propriétés électrochimiques ou en modifiant la microstructure de la cathode pour améliorer le transfert de masse et le transfert de charge. La cathode est une couche très importante dans la pile SOFC car elle présente une résistance de la polarisation dont la réduction constitue un défi important à traiter. Dans une première partie de ce travail de thèse nous avons développé une méthode pour permettre d'améliorer les propriétés électrochimiques de cathodes de manganite de lanthane dopée au strontium (LSM). La seconde partie a été consacrée à l'élaboration et la caractérisation par spectroscopie d'impédance de demi-cellules symétriques de SOFC avec un matériau composite à base de LSM permettant d'améliorer les propriétés électrochimiques des électrodes à des températures comprises entre 600 °C - 700 °C. / Fuel cells are systems that convert chemical energy directly into electrical energy. The physical structure of a fuel cell is composed of a porous cathode and anode separated by a dense electrolyte. Solid Oxide Fuel Cells (SOFC) offer an alternative for power generation and versability in their use. Current research focuses on lowering the operating temperature of this type of fuel cell (500-700°C) to increase their life, reduce manufacturing costs and damageto the interfaces. In order to compensate these problems, research tends towards materials with better electrochemical properties or by modifying the microstructure of the cathode to improve mass transfer and charge transfer. The cathode is a very important layer in the SOFC stack because it has a polarization resistance whose reduction is a major challenge to deal with. In a first part of this thesis work we have developed a method to improve the electochemical properties of strontium doped lanthanum manganite (LSM) cathodes. The second part was devoted to the elaboration and caracterization by impedance spectroscopy of SOFC symmetric half-cells with a LSM-based composite material allowing to improve the electochemical properties of electrodes at temperatures between 600-700 °C.

La croissance des unités de distribution des ressources énergétiques ainsi que l'intégration des nouvelles technologies dans la production et le stockage d'énergie, ont imposé un contrôle nouveau et de nouvelles stratégies opérationnelles. Grâce à sa capacité de stockage et étant considérée comme une énergie propre; la pile à combustible (Pac) est l'une des technologies les plus prometteuse en tant que source d'énergie stationnaire dans les réseaux micro et aussi dans les applications de transport. Par conséquent, deux sujets principaux sont abordés dans cet ouvrage, la conception et l'installation d'un banc d'essai complet instrumenté a membrane échangeuse de polymère (PEM) Pac et de conception et l'essai expérimental d'une nouvelle stratégie de contrôle dynamique d'échange de l'énergie pour les systèmes multi - source et multi - charge. Pour définir le test instruments banc exigences, un examen complet de modèle dynamique est donné dans la première partie. Dans la prochaine section seront inclues, les renseignements concernant la configuration de la conception et la mise en œuvre de banc d'essai de Pac, i.e., critères de spécification des instruments, acquisition, et affichage des données du système. Des résultats expérimentaux sont réalisés afin de démontrer les potentialités de l'installation. Dans le chapitre suivant, une nouvelle stratégie de contrôle dynamique de l'énergie d'échange (DSER) sera introduite et testée par simulation et expérimentalement dans un système à deux ports. Afin d'établir une comparaison et d'intégrer la DSER dans une application Pac, un système à trois ports - y compris un modèle statique de Pac - et deux différentes approches de contrôle, seront testés par simulation dans le cinquième chapitre. La thèse s’achèvera par quelques conclusions et quelques thèmes de recherche potentiels générés à partir de ce travail. / The growth of distributed energy resources together with the incorporation of new technologies in the generation and storage of energy are imposing new control and operational strategies. Due to its storage capability and that it is considered to be clean energy; fuel cell (FC) is one of the most promissory technologies as a stationary energy source in micro grids and also in transportation applications. Therefore, two main issues are addressed in this work; the conception, design, and setup of a fully instrumented test bench for proton exchange membrane (PEM) FC stacks and the design and experimental test of a new dynamic energy-exchange control strategy for multi source and multi load systems. To define the test bench instrument requirements, in the first part a complete dynamic model review is given. In the next section, relevant information regarding the setup of the FC test bench design and implementation is included, i.e., specification criteria of the instruments and acquisition and data display system. Some experimental results are performed in order to demonstrate the potentialities of the setup. In the following chapter, a new dynamic energy exchange control strategy (DSER) is introduced and tested in a two port system via simulation and experimentation. In order to establish a comparison and integrate the DSER in a FC application, in the fifth chapter a three port system – including a static model of FC – and two different control approaches, are tested via simulation. The thesis is closed with some concluding remarks and some potential research topics generated from this work.