L’extraction réductrice liquide-liquide est une des voies pyrochimiques les plusprometteuses pour assurer le retraitement des déchets nucléaires. Cette techniqueconsiste à extraire à haute température des éléments initialement en solution dansun sel fondu sur une nappe métallique. Afin d’améliorer les transferts de masse,l’utilisation de forces électromagnétiques permettant de brasser sans contact matérielle coeur des bains et l’interface elle-même a été envisagée.Les cinétiques d’extraction de trois lanthanides (cérium, néodyme et samarium)ont été étudiées expérimentalement. Une étude préalable nous a conduit à travaillersur le couple fluorure de lithium/antimoine et à utiliser le lithium comme agentréducteur. Les investigations réalisées ont démontré que le mécanisme contrôlant lacinétique rapide des transferts est la diffusion des espèces réactives à l’interface.La simulation numérique du réacteur expérimental faisant intervenir de multiplescouplages a également été réalisée. Elle a permis de déterminer les écoulementsturbulents dans chacune des phases. Les transferts de masse simulés ont ensuiteété comparés aux mesures expérimentales. / Reductive extraction is one of the most promising pyroprocess for processing spentnuclear fuel. The extraction of elements from a molten salt to a liquid metal occurs athigh temperature. At the interface between the two immiscible flows mass transfersare ensured via a redox reaction. To increase these transfers, electromagnetic forcescan be used to stir the bulk of both phases and of the interface itself without materialcontact.The kinetic of extraction of three lanthanides (cerium, neodymium and samarium)has been experimentally studied. We worked on lithium fluoride/antimony system,the reducing agent being lithium. Theses experiments show that mass transfers arefast for all studied lanthanides and are controlled by diffusion of reactive species atthe interface.The numerical simulation of experimental reactor which involves many stronglycoupled phenomenon has been performed. Turbulent flows have been computed inboth phases. Mass transfers have then been deduced and compared to experimentalresults.

No description available.

One of the key challenges the world will need to face during the 21st century is global warming and the consequent climate change. Its presence is indisputable, and decarbonizing the gird emerges as one of the required pathways to achieve global sustainable objectives. Solar energy power plants have the potential to revert this situation and solve the problem. One way to harness this energy is through Concentrated Solar Power plants. The major advantage and potential of this technology is its ability to integrate cost-effective Thermal Energy Storage (TES), which is key with such an inherently intermittent resource. On the other hand, the drawback is the high current Levelized Cost of Energy (LCOE). The other main way to harness that highlighted solar energy is the use of Photovoltaic panels, which have recently achieved very competitive LCOE values. On the other hand, the storage integration is still a very pricey option, normally done with Battery Energy Storage Systems (BESS). As a conclusion, a hybrid power plant combining the LCOE of the PV and the TES of the CSP emerges as the key way of achieving a very competitive solution with a big potential. This master thesis aims at exploring the possibilities of a hybrid CSP and PV power plant with a sCO2 power cycle, integrated in the primary, secondary and tertiary electricity markets. To achieve this purpose, firstly, a Python-based Energy Dispatcher was developed to control the hybrid power plant. Indeed, the Dispatcher is the tool that decides when to produce, when to store… following an optimization problem. This can be formulated mathematically, and that was done and integrated into the Python code using Pyomo, a software for optimization problems. As a result, the Dispatcher achieved an effective control of the plant, showing intelligent decisions in detailed hourly analyses. The results were very promising and included optimization functions as maximizing the profitability of the plant or the total production, among others. To proceed with the Techno-economic assessment of the hybrid plant, the electricity markets were studied. The main source of income of any power plant is normally the revenue from selling electricity to the grid, but since there are several markets, there are also other possibilities. In this thesis, it was assessed from a Techno-Economic perspective how the performance and optimal design of the plants vary when providing different services extra to selling electricity to the grid. The conclusion was that even though the Net Present Value (NPV) achieved working on the spot market was already very high, the extra value added from participating in the secondary or tertiary markets was indisputable. Indeed, the profits attained in those markets were between two and four times higher than the ones of the spot market. This is a specific case, but a trend was identified: these hybrid power plants have a huge possibility and a bright future on the service markets. As a consequence, this thesis shows the huge potential of hybrid power plants integrated in the grid participating in several markets. It also lays the foundation for future studies in other locations, under different conditions and with different technologies, among others.

Στα πλαίσια της παρούσας διδακτορικής διατριβής έγινε προσπάθεια να μελετηθούν μέσω φασματοσκοπίας Raman τα δομικά και τα δυναμικά χαρακτηριστικά διαφόρων ανόργανων υγρών και γυαλιών σε μεγάλο θερμοκρασιακό εύρος. Αναπτύχθηκαν μέθοδοι, με τις οποίες επιτεύχθηκε η φασματοσκοπική μελέτη υλικών υψηλής καθαρότητας σε θερμοκρασίες έως και 2000oC. Τα φασματοσκοπικά δεδομένα Raman διαφόρων γυαλιών και υγρών περιορίζονται σε θερμοκρασίες έως 1000oC λόγω διαφόρων πειραματικών δυσκολιών που παρουσιάζονται σε μετρήσεις δονητικής φασματοσκοπίας σε υψηλές θερμοκρασίες. Η κυριότερη δυσκολία είναι η πολύ ισχυρή ακτινοβολία μέλανος σώματος, η οποία υπερκαλύπτει το ασθενές σήμα Raman μην επιτρέποντας από κάποιο σημείο και πέρα τη λήψη των φασμάτων. Προκειμένου να ξεπεραστούν οι πειραματικές δυσκολίες αναπτύχθηκε στα πλαίσια της παρούσας διδακτορικής διατριβής ένα σύστημα Raman που συνδυάζει τις «τεχνικές ελλείψεως δοχείου» (“containerless techniques”) και τη χρήση ενός laser υπερύθρου (CO2-laser) ως θερμαντική πηγή, επιτρέποντας τη λήψη φασμάτων για πρώτη φορά σε θερμοκρασίες έως και 2000oC. Οι «τεχνικές ελλείψεως δοχείου» χωρίζονται σε δύο κατηγορίες, την «τεχνική αιώρησης» του δείγματος (“levitation technique”) όπου το υλικό αιωρείται υπό μορφή υγρής σταγόνας σε κατάλληλης γεωμετρίας ακροφύσιο με χρήση προωθητικού αερίου και την «τεχνική αυτοϋποστήριξης» του δείγματος (“self-support technique”) όπου το υγρό υποστηρίζεται από τη στερεά φάση του ίδιου υλικού. Το βασικότερο πλεονεκτήμα του συνδυασμού της φασματοσκοπίας Raman, των «τεχνικών ελλείψεως δοχείου» και της θέρμανσης με χρήση ενός laser υπερύθρου είναι ο σημαντικός περιορισμός της θερμικής εκπομπής, αφού απουσιάζει η ισχυρή θερμική εκπομπή του φούρνου, δίνοντας τη δυνατότητα μελέτης υψηλότηκτων υλικών αποφεύγοντας μολύνσεις, ετερογενή πυρηνοποίηση, αντιδράσεις μεταξύ υλικών και δοχείων σε υψηλές θερμοκρασίες επιτρέποντας την εφαρμογή της επιθυμητής ατμόσφαιρας στο υπό εξέταση υλικό. Μελετήθηκαν με δονητική φασματοσκοπία Raman μη-οξυγονούχες (ZnCl2, ZnBr2, xZnCl2-(1-x)AlCl3) και οξυγονούχες (SiO2, K2Si4O9, xCaO-(1-x)SiO2, xCaO-(1-x)Al2O3) ενώσεις με ενδογενείς πειραματικές δυσκολίες, όπως πολύ υψηλά σημεία τήξης (~2000oC για την περίπτωση των οξειδίων), υψηλή υγροσκοπικότητα, μεγάλες τάσεις ατμών κ.α. ξεπερνώντας τους διαφόρους πειραματικούς περιορισμούς και πραγματοποιήθηκε προσπάθεια σύνδεσης ανάμεσα στο δομικό και δυναμικό χαρακτήρα τους λαμβάνοντας φάσματα Raman σε θερμοκρασιακό εύρος που περιλαμβάνει την κρυσταλλική, υαλώδη, υπέρψυκτη και υγρή κατάσταση. Από τις πληροφορίες που λαμβάνονται για τα τοπικά πολύεδρα συναρμογής σε μικρής κλίμακας τάξη μέσω φασματοσκοπίας Raman γίνεται προσπάθεια να διασαφηνιστεί ο ρόλος των «τροποποιητών του δικτύου» (“network modifiers”) κατά την εισαγωγή τους σε υλικά με πλήρως πολυμερισμένες, τρισδιάστατες, δικτυακές τετραεδρικές δομές (“network formers”). Η δομή σε ενδιάμεσης κλίμακας τάξη (φάσμα Raman χαμηλών συχνοτήτων), η κορυφή Boson, η ημιελαστική κορυφή και χαρακτηριστικά όπως ο εύθραυστος/ισχυρός χαρακτήρας και η μη-εκθετική/εκθετική συμπεριφορά των υπό μελέτη υλικών προσδιορίστηκαν συναρτήσει της θερμοκρασίας και τα αποτελέσματα αναλύονται στα πλαίσια θεωρητικών και φαινομενολογικών μοντέλων που αφορούν την υαλώδη μετάβαση. / e present the Raman spectroscopic results concerning the structure and the dynamics of several inorganic melts and glasses in a broad temperature range. The development of pioneering methods appropriate for high temperature material research and their combination with Raman spectroscopy provided spectroscopic results of high-purity materials at temperatures up to 2000oC. High-temperature Raman data are limited at temperatures below 1000oC due to several experimental difficulties concerning high-temperature vibrational measurements. The main difficulty is the intensive black body radiation, which overwhelms the weak Raman signal and consequently no spectrum can be recorded. In order to overcome the experimental difficulties, we developed a Raman setup, which combines the “containerless techniques” with the use of an infrared laser (CO2-laser) as a heating source permitting the recording of Raman spectra at temperatures up to 2000oC. The “containerless techniques” are divided in two main categories. The “levitation technique”, where the liquid sample is levitated using a nozzle with the appropriate geometry and a supporting gas and the “self-support technique”, where the liquid sample is supported from the solid part of the same material. The main advantage of the Raman spectroscopy-containerlees techniques-laser heating combination is the effective limitation of the black body radiation giving the opportunity to use the desirable atmosphere on the sample and study high-melting materials preventing contamination, heterogeneous nucleation, reactions between materials and containers at high temperatures. We studied several non-oxide (ZnCl2, ZnBr2, xZnCl2-(1-x)AlCl3) and oxide (SiO2, K2Si4O9, xCaO-(1-x)SiO2, xCaO-(1-x)Al2O3) systems with intrinsic experimental difficulties, such as high melting points (~2000oC), hygroscopic nature, high vapor pressures etc. We recorded Raman spectra in extensive temperature range covering the crystalline, the glassy, the supercooled and the molten state in order to elucidate the structure and the involved dynamics of these materials. Information concerning the local coordination polyhedra in short range order have been used for clarifying the role of “network modifiers” inside the fully polymerized threedimensional tetrahedral networks (“network formers”). The structure in medium range order (low-frequency Raman spectrum), the Boson peak, the Quasi-Elastic line and characteristics such as the fragile/strong character and the non-exponential/exponential behavior of these materials have been put under focus and the results are discussed in the framework of the current phenomenological status of the field.

La corrosion des échangeurs de chaleur est un problème économique et technique majeur des Unités de Valorisation Energétique de Ordures Ménagères (UVEOM). Elle est causée par l’action combinée (i) des gaz de combustion contenant notamment HCl et SO2 et (ii) des cendres riches en chlorures et sulfates alcalins, et sels de métaux lourds. Les travaux présentés dans ce mémoire s’inscrivent dans le projet ANR SCAPAC (n°11-RMNP-0016) et portent sur l’influence des paramètres expérimentaux (température, teneur en chlorures dans les cendres, présence de gaz corrosifs et présence de chlorures de métaux lourds dans les cendres) sur la tenue à la corrosion de deux alliages utilisés en milieu UVEOM : l’acier 16Mo3 et l’alliage base nickel Inconel 625. Ces travaux ont permis de mettre en évidence que la présence de phases fondues, l’augmentation de la teneur en chlorures, la présence de 10% en masse de ZnCl2 dans les mélanges de cendres et la présence de gaz corrosifs (HCl, SO2) dans l’atmosphère sont trois facteurs qui ont induit une corrosion plus importante sur les matériaux, de manière plus prononcée sur l’alliage base fer. Une autre partie du travail s’est focalisée sur l’influence des éléments d’alliage Fe, Cr et Mo. Des alliages « modèles » dont les compositions oscillent autour de la composition de l’alliage Inconel 625 commercial ont été synthétisés par fusion haute fréquence et leur tenue à la corrosion a été évaluée sous air et sous atmosphère corrosive. La bonne optimisation de l’alliage commercial a ainsi été démontrée sous air. Sous atmosphère gaz corrosifs, une teneur en chrome supérieure à 22% massique s’est montrée indispensable à la bonne tenue de l’alliage / Corrosion of heat exchangers is an economic and technical issue in Waste-to-energy plants. It is caused by the combined action of (i) flue gas containing HCl and SO2 and (ii) chlorides and alkali sulfates rich ash. This work is part of the ANR project SCAPAC (supported by the ANR-11-RMNP 0016) and focused on the influence of experimental parameters on the corrosion behavior of two commercial alloys used in Waste-to-Energy plants: the 16Mo3 steel and the nickel-based alloy Inconel 625. This study allowed to highlight that the presence of molten phase, the increase in the chloride content, the presence of 10% by weight of ZnCl2 in the ash mixtures and the presence of corrosive gases (HCl, SO2) in the atmosphere are three factors that have induced an higher corrosion of materials, more pronounced on the iron alloy base. Another part of the work has been focused on the influence of alloying elements Fe, Cr and Mo. Thus, model alloys with compositions oscillating around the composition of Inconel 625 commercial alloy were synthesized by high frequency induction and their corrosion resistance was evaluated in air and in corrosive atmosphere. Good optimization of the commercial alloy has been demonstrated in air. In corrosive atmosphere, a minimum chromium content was required to obtain a good corrosion resistance

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2017-05-25T17:33:34Z No. of bitstreams: 0 / Made available in DSpace on 2017-05-25T17:33:34Z (GMT). No. of bitstreams: 0 / Fósforos a base de silicatos de Ca e Mg foram preparados pelo método sol-gel combinado com o processo de sais fundidos. O gel de sílica foi obtido a partir da solução de Na2SiO3 usando soluções de cloretos de európio, disprósio, cálcio e magnésio. Assim, estes cloretos foram homogeneamente distribuídos no gel. O gel obtido foi seco e tratado termicamente a 900°C por 1h para permitir a fusão dos sais presentes. Em seguida o material foi lavado com água até teste negativo para íons Cl- e seco em estufa a 80°C. A redução do európio para Eu2+ foi realizada em um forno sob atmosfera de 5% de H2 e 95% de Ar a 900°C por 3h para obter os fósforos de CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+. Nos difratogramas de DRX das amostras, a diopsita foi identificada como fase cristalina principal e quartzo, como a secundária. Micrografias obtidas por MEV (microscopia eletrônica de varredura), das amostras, mostraram morfologia acicular, esférica, folhas e bastonetes das partículas e dos aglomerados . Curva de análise térmica (TGA-DTGA) revelou que a temperatura de cristalização do CaMgSi2O6:Eu2+ é próxima de 765°C. Estudos de espectroscopia de fotoluminescência foram baseados nas transições interconfiguracionais 4fN → 4fN-1 5d do íon Eu2+. O espectro de excitação apresentou banda larga relativa à transição de transferência de carga ligante metal (LMCT) O2- (2p) → Eu3+ na região de 250 nm e bandas finas oriundas das transições 4f → 4f do íon Eu3+ , mostrando a transição 7F0 → 5L6 em 393 nm quando a emissão é monitorada em 583,5 nm. E o espectro de emissão com excitação monitorada em 393 nm apresentou picos finos entre 570 e 750 nm característicos das transições 5D0 → 7 FJ (J = 0 - 5) do íon Eu3+ , indicando que o íon Eu3+ se encontra em um sítio com centro de inversão. Os resultados obtidos indicam que o método desenvolvido é viável na síntese de fóforos, CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+ como foi proposto. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Selon le taux de sodium, par exemple de bonnes caractéristiques thermoélectriques pour les phases riches en sodium, ainsi que la supraconductivité pour certaines compositions (x ~ 0.3) hydratées, en font un exemple de choix pour étudier les corrélations entre la structure et les propriétés. La première partie de ce travail utilise l’électrochimie et la technique de batteries au sodium pour explorer en détail et de manière continue le diagramme de phase de ce système (pour x ≥ 0.5), en particulier avec un suivi in situ par diffraction des rayons X de l’intercalation d’ions sodium. Les compositions monophasées sont caractérisées par un potentiel électrochimique propre, et leur stabilité thermique relative est étudiée lors de cyclages à différentes températures.Dérivant de P2-NaxCoO2, le système ordonné OP4-(Li/Na)CoO2 se caractérise également par des propriétés thermoélectriques remarquables. La seconde partie de ce travail approfondit la connaissance de ce système caractérisé par une intercalation alternée des ions lithium et sodium. A partir de cet empilement, par des échanges ioniques topotactiques, trois nouveaux empilements théoriquement simulés sont expérimentalement mis en évidence et caractérisés. Il s’agit des polytypes inédits O4-LiCoO2 et D4-AgCoO2, ainsi que de l’empilement OD4-(Li/Ag)CoO2, premier exemple d’une intercroissance NaCl / delafossite au sein d’une même structure lamellaire. / The P2-NaxCoO system exhibits various outstanding physical phenomena such as promising thermoelectric properties (for x ~ 0.7) and superconductivity for hydrated compositions. The first part of the present study uses electrochemistry through sodium batteries to deeply explore the P2-NaxCoO2 phase diagram (for x ≥ 0.5) in a continuous way, with especially an in situ XRD experiment that follows sodium ions intercalation. Peculiar single-phase compositions are characterized by a specific electrochemical voltage, and their relative thermal stability is studied through electrochemical cycling at various temperatures.The second part of this project deals with the ordered OP4-(Li/Na)CoO2 system which also exhibits promising thermoelectric features. Its structure is characterized by an alternate intercalation of lithium and sodium ions. Using this system, topotactic ionic exchanges enable to obtain three new stackings, O4-LiCoO2, D4-AgCoO2, and the OD4-(Li/Ag)CoO2 which are first simulated, experimentally evidenced and then characterized. The OD4 stacking is thefirst example of a NaCl / delafossite intergrowth in the same layered structure.

Les préoccupations actuelles concernant l'exploitation sécuritaire des centrales nucléaires existantes et la conception d’architectures spéciales envisagées pour la quatrième génération de réacteurs nucléaires se combinent avec l’intérêt plus prononcé pour l'efficacité et la fiabilité de l'équipement d'un système énergétique. Cela fait que dans un souci de meilleure compréhension et optimisation basée sur des moyens modernes de conception assistée par l’ordinateur, l'étude de différentes parties de ces systèmes fait de plus en plus l’objet de recherches approfondies. . Parmi les types proposés pour la quatrième génération de réacteurs nucléaires font partie ceux ayant comme agent de refroidissement les sels fondus, respectivement le sodium fondu. En raison de leurs propriétés physiques, les sels fondus et le sodium liquide ont le potentiel d'être déplacés par les pompes électromagnétiques. Cet ouvrage est à la fois une étude approfondie des phénomènes qui se produisent en raison de l'écoulement du fluide dans le champ électromagnétique d’une pompe électromagnétique - interaction magnétohydrodynamique - et un rapport sur les capacités et les avantages des outils informatiques modernes pour faciliter la conception et l'optimisation des pompes électromagnétiques. Afin d’atteindre l'objectif principal de la thèse, notamment une meilleure compréhension des phénomènes interdépendants spécifique à l’opération des pompes électromagnétiques, deux objectifs secondaires ont été considérés. Le premier objectif concerne la pleine exploitation des modèles électromagnétiques numériques en éléments finis afin d'obtenir autant d'informations que possible sur le comportement des pompes électromagnétiques, dans l’hypothèse où on ne tient pas compte de l'écoulement des fluides. Le deuxième objectif était la construction des modèles numériques qui réunissent l’électromagnétisme et la dynamique des fluides, respectivement des modèles numériques qui regroupent les deux phénomènes caractérisant l’écoulement magnétohydrodynamique dans les canaux des pompes électromagnétiques. Dans l'étude dédiée au pompage électromagnétique de sels fondus, la thèse met en évidence des problèmes spécifiques liés à la génération de forces électromagnétiques dans les fluides faibles conducteurs d'électricité et fournit des résultats sur les applications où le pompage électromagnétique de sels fondus peut être efficace. À l’aide des modèles électromagnétiques nous avons obtenu des informations importantes sur l'influence du nombre de pôles électromagnétiques et de la fréquence d’alimentation sur la caractéristique Pression - Vitesse des pompes annulaires à induction. Ils ont été analysés le phénomène de blindage créé par les parois métalliques - avec des répercussions négatives sur les performances de la pompe, les effets de freinage exercés à l'entrée et à la sortie du canal de la pompe et la relation entre la capacité de surcharge hydrodynamique et la caractéristique Pression - Vitesse des pompes à induction. Une section spéciale a été consacrée à l'analyse de la dépendance de la force électromagnétique du temps et de l’espace et à l’étude de non-uniformitées des quantités de nature électromagnétique en direction azimutale dans les pompes annulaires à induction.Dans le chapitre qui traite de l'interaction magnétohydrodynamique à base de modèles couplés, ils sont proposés deux modèles qui couplent l'électromagnétisme et l’écoulement. Ils sont présentés les avantages des modèles couplés, en matière de la précision des résultats, par rapport aux modèles électromagnétiques. Il est également présenté l'évolution des profils de vitesse, de densité de force et de courant sous l'influence du champ électromagnétique et de l’écoulement de sodium à vitesses différentes. Les contributions de la thèse sont complétées par des observations importantes sur les méthodes de travail et les logiciels utilisés tout au long de l'étude. / The actual concerns with respect to safe operation of existing nuclear plants and to designing special architectures envisaged for the fourth generation of nuclear reactors, corroborated with the increasing interest for efficiency and reliability of any equipment belonging to an energetic system, make that more and more research endeavors to be devoted to the study of various parts of these systems for a better understanding and optimization based on modern techniques of computer aided design. Among the types proposed for the fourth generation of nuclear reactors belong those that have as cooling agent molten salts, respectively liquid sodium. Many reactors of previous generations use mechanical pumps of special design for driving the coolants. Molten salts and liquid sodium, thanks to their physical properties, have the potential to be driven using electromagnetic pumps. Although the technology of electromagnetic pumping of electroconductive fluids was developed since the first half of the last century, currently it undergoes a revival due to the reconsideration of its multiple technological and security advantages. This work is both an intimate study of the phenomena that occur as a result of the electroconductive fluids flow in the electromagnetic field of an electromagnetic pump – magnetohydrodynamic interaction - and a report on the capabilities and advantages of modern computational tools to facilitate design and optimization of electromagnetic pumps.To achieve the principal goal of deeper understanding of the interdependent phenomena specific to electromagnetic pumps operation, two auxiliary objectives were considered. The first is related to the full exploitation of electromagnetic finite element models in order to retrieve as much information as possible about electromagnetic pumps behavior in a simplifying hypothesis that does not take into account the fluid dynamics. The second auxiliary objective is to build numerical models that couple the electromagnetism and the fluid dynamics, namely the two interdependent physics that govern the magnetohydrodynamic flow through channels of electromagnetic pumps.In the section dealing with the study of electromagnetic pumping of molten salts, the thesis highlights specific problems related the generation of electromagnetic forces in fluids with low electrical conductivity and provides results with respect to applications where electromagnetic pumping of molten salts can be effective. With the electromagnetic numerical models were obtained important data about the influence of the number of electromagnetic poles and supply frequency on the Pressure – Velocity characteristic of annular linear induction pumps. Were analyzed the shielding effect generated by the metallic walls - with negative repercussions on pumps performances, braking effects exerted at pump inlet and pump outlet and the connection between the overload capacity and Pressure – Velocity characteristic of induction pumps. A special portion was devoted to the analysis of the time and space dependence of the electromagnetic force and to the study of the non-uniformities of electromagnetic quantities in azimuth direction of annular linear induction pumps.In the chapter devoted to the magnetohydrodynamic interaction through coupled models, the thesis proposes two models that couple the electromagnetism and the fluid flow, one realized using multiphysic software and the second by coupling two different softwares. There are presented the advantages of the coupled models with respect to the results accuracy in comparison with electromagnetic models. It is presented the evolution of velocity, force and current densities profiles under the influence of the electromagnetic field and of different sodium mean velocities.The contributions of the thesis are completed with significant observations related to the study methods and software tools used along the study process. / Preocupările actuale în legătură cu exploatarea în siguranță a centralelor nucleare existente și în legătură cu proiectarea arhitecturilor speciale de reactoare nucleare pentru generația a patra,coroborate cu interesul tot mai pronunțat pentru eficiența și fiabilitatea oricărui echipament dintr-un sistem energetic, fac ca tot mai multe demersuri de cercetare să se îndrepte spre studiul diverselor subansamble ale acestor sisteme pentru o mai buna înțelegere și optimizare pe baza mijloacelor moderne de proiectare asistată de calculator. Din rândul tipurilor propuse pentru generația a patra de reactoare nucleare fac parte și cele care au ca agent de răcire săruri topite, respectiv sodiu topit. Multe reactoare nucleare de generație anterioară folosesc ca mijloc de antrenare a fluidelor de răcire pompe mecanice de construcție specială. Sărurile topite ăi sodiul lichid, datorită proprietăților fizice,au potențialul de a fi recirculate cu ajutorul pompelor electromagnetice. Deși tehnologia pompării electromagnetice a fluidelor electroconductoare a fost dezvoltată încă din prima parte a secolului trecut, în prezent cunoaște o renaștere datorită reconsiderării multiplelor avantaje tehnologice și de securitate în exploatare. Lucrarea de față este atât un studiu al fenomenelor intime ce au loc ca urmare a curgerii fluidelor electroconductoare în câmpul electromagnetic al pompelor electromagnetice – interacțiune magnetohidrodinamică - cât și un raport despre capabilitățile și avantajele uneltelor moderne de calcul de a înlesni proiectarea și optimizarea pompelor electromagnetice. Pentru a atinge scopul principal al tezei, și anume o înțelegere mai adâncă a fenomenelor interdependente specifice funcționării pompelor electromagnetice, au fost considerate două obiective secundare. Primul obiectiv se referă la exploatarea la maximum a modelelor electromagnetice numerice în element finit cu scopul de a obține cât mai multe informații cu putință despre comportamentul pompelor electromagnetice în ipoteza care nu ia în considerare curgerea fluidelor. Al doilea obiectiv a fost construirea unor modele numerice care cuplează electromagnetismul și curgerea, respectiv, cuplează modelele numerice ale celor două fenomene ce caracterizează curgerea magnetohidrodinamică din canalele pompelor electromagnetice. În partea dedicată studiului pompării electromagnetice a sărurilor topite, teza evidențiază problemele specifice legate de generarea forțelor electromagnetice în fluide slab conductoare electric și oferă rezultate cu privire la aplicațiile unde pomparea electromagnetică a sărurilor topite poate fi eficientă. Cu ajutorul modelelor electromagnetice s-au obținut date importante despre influența numărului de poli electromagnetici și frecvența de alimentare asupra caracteristicii Presiune – Viteză a pompelor electromagnetice inelare de inducție. Au fost analizate fenomenul de ecranare creat de peretii metalici – cu repercursiuni negative asupra performanțelor pompelor, efectele de frânare exercitate la intrarea și la ieșirea din canalul de pompare și legătura dintre capacitatea de suprasarcină hidrodinamică și caracteristica Presiune – Viteză a pompelor de inducție. O secțiune specială a fost consacrată analizei dependenței de timp și a variației de la punct la punct a forței electromagnetice, precum și studiului neuniformităților mărimilor de natură electromagnetic în direcție azimutală în pompele inelare de inducție. În capitolul despre interacțiunea magnetohidrodinamică pe baza modelelor cuplate, se propun două modele ce cuplează electromagnetismul și curgerea fluidelor, unul realizat cu ajutorul unui singur software și al doilea realizat prin cuplarea a două software-uri diferite. Sunt prezentate avantajele modelelor cuplate din punctul de vedere al acurateței rezultatelor în comparație cu modelele electromagnetice …