Letteratura scientifica selezionata sul tema "Réacteurs refroidis par métal liquide"
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Tesi sul tema "Réacteurs refroidis par métal liquide":
Jourdy, Benjamin. "Analyse des effets d'échelle sur le comportement thermo-hydraulique de jets impactants". Electronic Thesis or Diss., Université de Lorraine, 2023. http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2023_0063_JOURDY.pdf.
Safety studies and numerical modelling implemented within the framework of studies on fast neutron reactors imply a need for validation of calculation codes using representative mock-ups. A safety issue identified in this type of reactor is the rise of the radial jet resulting from the impact of hot jets from the core to the Upper Core Structure (UCS). This rise induces thermal fluctuations and thermal stratification in the upper plenum causing thermal fatigue on the components. Understanding the various mechanisms at work in the phenomenon of radial jet raising is necessary in order to be predictive about the operating conditions for which this phenomenon occurs. For this purpose, the MICAS mock-up is used, which geometrically reproduces the upper plenum of the ASTRID reactor on a 1/6 scale, using water as a simulating fluid instead of sodium. In order to validate the ASTRID simulation codes, the representativeness of the MICAS mock-up must be validated with respect to its reduced scale but also to its simulating fluid. In order to study the transposition of the jet behaviour between different scales, a method of scale effects analysis is introduced, based on three mock-ups at different scales but representative of the reactor. A phenomenological study is carried out on a simplified model, PIGNIA, allowing to verify experimentally the theoretical dependence of the trajectory of the jet on the densimetric Froude number of the radial jet, justifying its conservation as a similarity parameter for the transposition of the jet behaviour. A transfer function to relate the radial jet conditions to the nozzle outlet conditions is established theoretically and validated experimentally. To obtain a critical value of the densimetric Froude number in representative geometry, tests are performed on the MICAS model. Based on the experimental conditions of MICAS leading to the rise of the jet, two representative mock-ups are sized: MOJIT-Eau and MOJI/4, respectively at scales 1/2,5 and 1/4 relative to MICAS. A study of the flow under isothermal conditions on the MOJIT-Eau and MOJI/4 mock-ups shows an attachment of the radial jet to the surface of the core, due to Coanda effect. This effect depends only on the geometrical quantities of the system. A thermal-hydraulic study is finally carried out to verify the conditions of extrapolation of the recovery phenomenon. A binary behaviour is observed on the rise of the jet, which is either attached and runs along the core or detached and rises in the plenum. The Coanda effect plays a major role on the stability of the jet. The densimetric Froude number alone is not sufficient to characterize this phenomenon, which occurs on MICAS. A new dimensionless number L, representing the competition between inertia, buoyancy and Coanda effects, is then defined. This number allows for the correct transposition of the detachment and thus the rise of the jet between MICAS, MOJIT-Eau and MOJI/4. The conditions expected on ASTRID by the conservation of this number allow to study the distortion of the water-sodium similarity on the heat exchanges. Water is then verified as a relevant choice for the representativeness of small-scale mock-ups with respect to ASTRID by estimating the Péclet number (representing the heat exchange modes) of the reactor: the change of fluid corrects the change of scale on these aspects
Mouly, Aude. "Modélisation de la formation et de la détente rapide d'une bulle polyphasique pour l'évaluation des conséquences d'un accident grave de RNR_Na". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0362.
A new generation of nuclear reactor is nowadays developed in order to take into account the economic, environmental and societal stakes of the 21th century. Among the different concepts taking part of the fourth generation, the sodium fast reactors (SFR) are studied in this PhD thesis. These reactors are the only ones of the fourth generation already having a considerable operating feedback in France.To achieve the safety objective of this new generation, the safety approach has to be adapted as soon as the reactor preconceptual and conceptual phases in order to integrate severe accidents, identify and define limitation ways as well as their consequences. This work, dedicated to the study and to the modelling of the expansion phase of a severe accident in SFR, is positioned in the CEA's work dynamic by contributing to the development of the safety approach. The goal of this PhD is to create a tool modelling the important physical phenomena induced by a power excursion in a molten material pool. This involves the formation of a vaporized sodium and molten material bubble and its subsequent expansion.After conducting detailed state of art of the different phenomena involved in the expansion phase, dimensional analysis of the physical processes is performed in order to identify the important ones. Based on this analysis, a model is developed and integrated into a tool, aiming at determining and prioritising the total phenomenon contributions to mechanical loadings on SFR vessel depending on the studied severe accident scenario. A validation step of the tool is then realised in two parts; Separate effect tests and global tests, using experimental results and calculation results obtained with other validated tools. Finally, preconceptual parametrical studies are performed to quantify the results variability due to modelling, scenarios and physical data uncertainties
Maury, Cécile. "Spectroscopies analytiques innovantes pour l'amélioration de la sûreté des réacteurs nucléaire à neutrons rapides refroidis au sodium". Paris 6, 2012. http://www.theses.fr/2012PA066428.
Finne, Jörgen. "Chimie des mélanges de sels fondus : application à l'extraction réductrice d' actinides et de lanthanides par un métal liquide". Paris 6, 2005. http://www.theses.fr/2005PA066296.
Paumel, Kevin. "Contribution à l'étude de la transmission des ultrasons à une interface solide - gaz - liquide : application au contrôle non destructif des réacteurs de quatrième génération refroidis par du sodium liquide". Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22054.pdf.
Under the ultrasonic inspection of the fourth generation of sodium cooled reactors, the goal is to study the conditions for the appearance of a very bad acoustic coupling of the transducer with liquid sodium. Under certain conditions, the non wetting of the surface of the transducer by sodium causes trapping gas pockets in the roughness. A first quasi-static analysis based on the crevice model allows to study the dependence of the stability of these gas pockets on the temperature, the hydrostatic pressure, and the level of dissolved gas saturation of the liquid. In order to develop a parametric study based on the size and gas surface fraction, several samples are made. An ultrasonic experiment using various frequencies can measure the transmission through these samples. Meanwhile, three different models describing the experimental setup are proposed, the latter being based on a description of the dynamic behaviour of a simple gas pocket geometry. The comparison of experimental and analytical results (of the last model) show a similar pattern of the dependence of the transmission on the various parameters
Paumel, Kevin. "CONTRIBUTION A L'ETUDE DE LA TRANSMISSION DES ULTRASONS A UNE INTERFACE SOLIDE - GAZ - LIQUIDE. Application au contrôle non destructif des réacteurs de quatrième génération refroidis par du sodium liquide". Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2008. http://tel.archives-ouvertes.fr/tel-01053699.