Tesi sul tema "Dépôts de déchets radioactifs – Restauration"
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Sakael, Clément. "Modélisation de la microstructure des alliages de Zirconium irradiés : application à un transitoire Accident de Perte de Réfrigérant Primaire et à la restauration en aval du cycle". Electronic Thesis or Diss., Centrale Lille Institut, 2023. http://www.theses.fr/2023CLIL0010.
The subject of this thesis concerns zirconium alloys which are used to manufacture the fuel rod cladding and fuel assemblies of pressurized water nuclear reactors. This type of alloy is chosen in the nuclear field for its low thermal neutron capture cross section. However, under neutron irradiation, changes in shape and volume, an increase in hardness and a significant reduction in the ductility of the material are observed, which means an increase in its embrittlement. This work focuses on the irradiation-induced growth of the cladding that results from an elongation in the basal plane and a contraction along the c ⃗ axis of the hexagonal lattice of the alpha phase of zirconium. This phenomenon amplifies beyond a threshold dose that coincides with the nucleation of dislocation loops and the formation of loop alignments as layers parallel to the basal plane. Nevertheless, the mechanisms of nucleation of defect clusters such as dislocation loops are still to be clarified. In order to have a better understanding of these phenomena, a multi-scale approach was used to model the evolution of the microstructure of zirconium alloys (i) during irradiation, (ii) during the transient phase of a loss-of-coolant accident (LOCA) and (iii) during the downstream restoration of the cycle. First, atomic scale calculations based on density functional theory (DFT) and empirical potentials are performed to determine the properties and characteristics of point defect clusters (self-interstitial clusters, vacancy clusters and dislocation loops).In order to have a better characterization of self-interstitial, the migrationenergies and diffusion coefficients of di- and tri-self-interstitials are calculated in moleculardynamics using DFT. Some of the results obtained by atomistic calculations are used as inputdata for an object kinetic Monte Carlo (OKMC) code, which simulates the evolution of themicrostructure of zirconium under conditions (i) to (iii)
Petit, Jean-Claude. "Le stockage des déchets radioactifs : perspective historique et analyse sociotechnique". Paris, ENMP, 1993. http://www.theses.fr/1993ENMP0419.
Coulon, Hervé. "Propriétés physico-chimiques de sédiments argileux français : contribution au stockage de déchets radioactifs". Lille 1, 1987. http://www.theses.fr/1987LIL10153.
Vinkler, Fabrice. "Couplages hydromécaniques dans les massifs rocheux : du stockage de déchets radioactifs à la stabilité des mines abandonnées". Vandoeuvre-les-Nancy, INPL, 1999. http://www.theses.fr/1999INPL099N.
Mellak, Abderrahmane. "Faisabilité des coulis de ciment saumurés et microsilicés adaptés aux formations salifères : application au domaine pétrolier et au stochage des déchets radioactifs". Université Robert Schuman (Strasbourg) (1971-2008), 1994. http://www.theses.fr/1995STR30004.
Nava, Romain. "Étude du cadre juridique relatif à la gestion des déchets radioactifs". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM1034.
Radioactive waste appeared simultaneously with the discovery of artificial radioactivity and saw their output is significantly increased with the development of the civil nuclear industry in the 1960s. Notwithstanding, it is only very recently that’s law has seized the difficult issue of their management through texts devoted to it.In the same way that radioactive waste is managed separately according to their activity and half-life, the legal framework for the management of radioactive waste has naturally led to a temporal dichotomy. Then we distinguish two main corpus of standards. The first-one supervises the radioactive waste whose management modes to immediately ensure the safety of people and the environment while the second-one deals with radioactive waste for which security must be guaranteed on long term, insofar as it does not exist to date definitive management solution for waste.This work aims to show how the specific provisions of each of the two bodies involved in the safety of people and the environment and expose potential persistent difficulties
Lefebvre, Christophe. "Influence de la cristallisation des oxyhydroxydes de fer sur la rétention du radium, du zinc, de l'arsenic et de l'uranium". Paris 11, 2002. http://www.theses.fr/2002PA112298.
The extraction of uranium leads to the creation of mill tailings containing numerous elements such as radium, zinc, arsenic and residual uranium. Those residues are disposed at the surface and shall be a long-term efficient protection barrier against the pollution of the elements that they contain. It was demonstrated that those elements are mostly contained in amorphous iron oxy-hydroxydes that precipitate during the treatment of the residues. Those iron oxy-hydroxydes (OHF) naturally crystallise to goethite and hematite : their retention properties can thus change and may have consequences on the immobilization of the elements that are still unknown. The objective of this work is therefore to understand the behavior of radium, zinc, arsenic and uranium during the crystallization of the amorphous OHF to goethite and hematite. The first part of the work consisted in defining a method that allows to reproduce the long-term crystallization of the OHF but on a reduced period of time in laboratory. Geothite was the only ultimate phase created by this method. Some hematite was obtained in presence of calcium. During the first steps of the OHF precipitation, radium was completely sorbed but the analysis demonstrated that radium was leached in the solution while the OHF crystallized in goethite. This phenomena was also observed in presence of calcium, although it was slower due to the fact that the crystallisation into goethite was slower too. This behavior could not be reproduced on the OHF coming from the Ecarpière site : radium was still contained in the solid as the OHF were still amorphous. Zinc, arsenic and uranium were entirely contained in the OHF, as soon as it was precipitating. No leaching could be observed, suggested that zinc and arsenic were integrated in the OHF structure
Bertrand, Nathalie. "Prévision de la corrosion sèche des conteneurs de déchets radioactifs en condition d'entreposage : étude des mécanismes d'oxydation du fer à basse température et simulation numérique de la croissance d'une couche d'oxyde". Phd thesis, Toulouse, INPT, 2006. https://hal.science/tel-04576177.
In the framework of research on long term behaviour of radioactive waste containers, this work consists on the one hand in the study of low temperature oxidation of iron and on the other hand in the development of a numerical model of oxide scale growth. Isothermal oxidation experiments are performed on pure iron at 300 and 400°C in dry and humid air at atmospheric pressure. Oxide scales formed in these conditions are characterized. They are composed of a duplex magnetite scale under a thin hematite scale. The inner layer of the duplex scale is thinner than the outer one. Both are composed of columnar grains, that are smaller in the inner part. The outer hematite layer is made of very small equiaxed grains. Markers and tracers experiments show that a part of the scale grows at metal/oxide interface thanks to short-circuits diffusion of oxygen. A model for iron oxide scale growth at low temperature is then deduced. Besides this experimental study, the numerical model EKINOX (Estimation KINetics OXidation) is developed. It allows to simulate the growth of an oxide scale controlled by mixed mechanisms, such as anionic and cationic vacancies diffusion through the scale, as well as metal transfer at metal/oxide interface. It is based on the calculation of concentration profiles of chemical species and also point defects in the oxide scale and in the substrate. This numerical model does not use the classical quasi-steady-state approximation and calculates the future of cationic vacancies at metal/oxide interface. Indeed, these point defects can either be eliminated by interface motion or injected in the substrate, where they can be annihilated, considering sinks as the climb of dislocations. Hence, the influence of substrate cold-work can be investigated. The EKINOX model is validated in the conditions of Wagner's theory and is confronted with experimental results by its application to the case of high temperature oxidation of nickel
Nguyen, Minh Thu. "Modélisation hydromécanique des ouvrages de stockage des déchets radioactifs avec prise en compte de l'endommagement et du transfert de l'hydrogène". Rennes, INSA, 2008. http://www.theses.fr/2008ISAR0006.
The argilite of Callovo Oxfordien is a sedimentary rock formed in sea water which is made up mainly of quartz, carbonates, argillaceous minerals and various minerals. This heterogeneity of constitution associated with a very low porosity of about 12% confers on argillite a specific behaviour. Indeed this specific behaviour is induced by: (i) of the mechanisms on a microscopic scale of type forces contact with friction for solid minerals quartz and calcite, of repulsion and viscosity for argillaceous minerals and (ii) of the strong interactions between the solid and fluid phases. Thus the conceptual model of the short-term behaviour is proposed while being based on five hydraulic characteristics: (1) two surfaces of loads of the type Drescher & Mroz, associated a pressure of consolidation of 200MPa and a cohesion on healthy argillite, (2) the creation of an anisotropic damage induced by the strains in extension under states of stresses deviators, (3) a distribution of the stress between the solid phases and fluids which uses the coefficient of Biot depend on the maximum damage, (4) a concept of the effective stress for the partially saturated states by calling upon an equivalent pore pressure which depends on the capillary pressure and an average value of the damage and (5) the absence of volumic strains of swelling on healthy argillite. The plastic strain-rates are specified by the non_associative flow rule with the plastic loading surface F and the plastic potential G. On the other hand the behaviour differed from argillite utilizes many mechanisms, chemical, physicochemical and a slip on the scale of the argillaceous layers inducing of the phenomena of viscosity. In the absence of a consensus related mainly to the experimental difficulties and being the subject of current research of the geotechnical grouping of research, one thus proposed a simplified macroscopic model. The introduction of a phase gas into the computer code of finite elements CLEO allowing simulating the transfer of hydrogen. The dealt with problems relate to a standard work cell in direct contact with argillite (without bentonite barrier) with a production of H2 variable in time. These modelling are proposed without heating effect. Lastly, simulations of the saturation of an embanked gallery have the aim of studying the basic phenomena brought into play at the time of the resaturation of a gallery. One proposed a hierarchisation in the processes of simulation by adopting the development of the two conceptual models, one bearing on physics and the other on the numerical aspects. The numerical conceptual model milked space-time introduction of the constituent voluminal elements
Hoteit, Hussein. "Simulation d'écoulements et de transports de polluants en milieu poreux : application à la modélisation de la sûreté des dépôts de déchets radioactifs". Rennes 1, 2002. http://www.theses.fr/2002REN10060.
Nguyen, Than Son. "Influence de la nature du liant et de la température sur le transport des chlorures dans les matériaux cimentaires". Toulouse, INSA, 2006. http://www.theses.fr/2006ISAT0025.
The objective of this work is to document the effect of the temperature on the chloride diffusion through cement-based materials. The chloride diffusion coefficient, the penetration profiles and the chloride interactions with the solid phase were highlighted. The materials were CEM I and CEM V/A mortars and pastes. They were cured in wet room (21 ± 2 °C, 90% relative humidity) for 1 month in the case of CEM I and 3 months in the case of CEM V before the experiments started. The temperature levels were 5, 21, 35 and 80 ºC. In addition, microstructure analyses were carried on using X-rays diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The experimental results were then used to continue to develop the numerical code, MsDiff, developed in our research group. A good agreement between the numerical concentration profiles and the experimental ones was found
Huang, Yun. "Modélisation micromécanique du comportement différé des roches argileuses : application au stockage des déchets radioactifs". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10043/document.
Claystones are extensively investigated in France in the framework of feasibility studies for geological repository of nuclear waste. Under the coordination of the French Agency for radioactive waste management (ANDRA), laboratory tests and numerical modeling have been performed for the characterization of thermo-hydromechanical properties of claystones. Due to the very long life of radioactive waste, the characterization of long term hydromechanical behaviors of claystones is a crucial issue. For this purpose, laboratory creep tests associated with microstructural analysis have been performed on claystones with different degrees of saturation. It is found that two main mechanisms are at the origin of macroscopic time dependent deformation. The first one is related to viscoplastic flow of clay matrix and the second one is due to subcritical propagation of microcracks in clay matrix. In this thesis, two creep mechanisms are studied respectively. As micromechanical approaches can lead to a better description of behavior in relation to the microstructure of the rock, in this work, we implemented a multi-scale model based on the behaviors of each component and microstructure of claystones
Harmand, Béatrice. "Contribution a la compréhension des processus de transport de colloïdes en milieu naturel poreux ou fracturé : application à la rétention de particules de latex dans un sable". Vandoeuvre-les-Nancy, INPL, 1996. http://docnum.univ-lorraine.fr/public/INPL_T_1996_HARMAND_B.pdf.
Jia, Yun. "Contribution à la modélisation thermo-hydro-mécanique des roches partiellement saturées : application au stockage des déchets radioactifs". Lille 1, 2006. https://ori-nuxeo.univ-lille1.fr/nuxeo/site/esupversions/bf9141e8-50b7-4681-a346-3bfb1c214d7c.
Lecocq, Yannick. "Contribution à l'analyse et à la modélisation des écoulements turbulents en régime de convection mixte : application à l'entreposage des dechets radioactifs". Poitiers, 2008. http://theses.edel.univ-poitiers.fr/theses/2008/Lecocq-Yannick/2008-Lecoq-Yannick-These.pdf.
In the frame of radioactive waste management, this work aims to study the flow around a heating wall-mounted cylinder in cross flow in URANS approach. Well-known limitations of first order turbulence models lead us to consider second order turbulence modelling. In that frame, a heat transfer model is developed and validated on academic test cases. To begin with, when mixed convection regime is dominant, these simulations, completed by an isotherm one, all performed with low-Reynolds k–w SST model, give prominence to several eddy structures registered by the bibliography. One simulation is also performed with the high-Reynolds Rij–epsilon SSG model. With the k–w SST model, the heat transfer is correctly reproduced compared to the VALIDA experiment lead by the CEA, though with the Rij–epsilon SSG model, it is strongly under-estimated. It is supposed that it comes from the use of wall functions. Subsequently, when natural convection is predominant, flow topology becomes completely different and the heat transfer becomes less accurate to the VALIDA experiment. Following Durbin’s approach, the Elliptic Blending-Reynolds Stress Model EB–RSM, consists in accounting for wall effects, and in wall blockage in particular. Following this formalism, an Elliptic Blending-Algebraic Flux Model is developed, the EB-AFM. With this model, a priori tests in the three convection regimes and then simulations on the same test cases show major improvements in flow predictions. This leads to an interesting perspective to an intermediate model between SGDH and transport equations
Tran, Trung Duc. "Modélisation hydro-mécanique avec prise en compte de la production d’hydrogène dans les ouvrages de stockage des déchets radioactifs". Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10168.
The first part of this work is about the evaluation of a pressure of gaseous hydrogen produced by HA cells passing through the interfaces to the drift. Indeed, the calculations without consideration of interfaces show that the transfer of hydrogen takes place primarily by diffusion of hydrogen into the water through the foundation. However, in storage, the presence of many interfaces by construction (between bentonite core - Argillite etc.) or by fracturing of materials under the effect of hydrogen pressure, are the preferential pathways for transfer of gaseous hydrogen. The GTI (Gas Transfer in Interface) model was chosen to simulate the transfer of hydrogen produced by the HA cells to the backfilled drift. The maximum hydrogen pressure in the backfill is obtained in the case where the interface is always open. At 4500 years it goes from 5.2 MPa (always open interface) to 3.8 MPa by the valve effect due to the increase of hydrogen pressure. The comparisons between numerical simulations with and without taking into account the hydrogen pressures show that hydrogen pressures no or very little impact the pore pressure, the effective radial and orthoradial stresses. As a result, the simulations may be performed by considering a hydrogen pressure at atmospheric pressure, which is to work in a biphasic medium. The second part concerns the fractured zones induced by the excavation of volume. And the observations in the laboratory Meuse Haute Marne show the anisotropic fractured areas around drifts and HA cells consist of vertical and horizontal discontinuities. The weak anisotropies of stresses and Young modulus for the drifts oriented along σH (σv approximativement égal à σh) is not possible to reproduce the strong anisotropy of fractured areas in the plane σv - σh by a hypo-elasticity model with anisotropic initial diagenesis. For modelling these discontinuities, a rheological model was developed by EGC named SC2D combining two types of elastic-plastic behavior: one is associated with an anisotropic damage resulting behavior of the argillite enhanced by calcite and the other characterizing the phase of clay that means the argillite without reinforcement by calcite and plastic deformation when the stress state reaches the surface of diagenesis. Damage coefficients are evaluated from an extension relation of Weibull in considering the expansion deformations in the directions of diagenesis X(σH), Y(σh), Z(σv). The drifts around the fractured zones are characterized by areas where damage coefficients are unitary. Furthermore, the discontinuities are activated when damage reachesoefficient unit and these discontinuities are perpendicular to the directions of diagenesis and vertical or horizontal with them
Migliore, Thomas. "Estimation des paramètres de transport dans un milieu hydro-géologique et analyse d'incertitudes". Nice, 2009. https://tel.archives-ouvertes.fr/tel-00442635v3.
In this work, we are interested in estimating solute transport parameters in a porous medium with a low permeability, from a theorical and applied point of view in connection with the storage of long- lived nuclear waste in deep geological layer. In recent years, the problem of nuclear waste management has become a major concern of society. The mathematical models used for storing waste in deep level are based on the flow and transport equations in porous media? These models require the knowledge of the physical parameters of the different geological layers. Since those parameters (porosity and diffusion) are not directly accessible by measurements, we studied firstly the aspect of parameters identification and fixed areas. To solve this inverse problem, we used deterministic (or variational) methods based on the minimization of a quadratic criterion (or cost function) with the objective of finding all the parameters that minimize the criterion. We have broken down the media in homogeneous areas in which the coefficients have been identified (zonation technique), for this, we differentiated the convection-diffusion code traces with the automatic differentiation software Tapenade to get the adjoint code of traces. In a second step, we used this work to solve the zones identification problem, starting form a modified geological configuration, we searched for the actual geological configuration by identifying the parameters whose supports are these zones. Then, by grouping the identified coefficients by isovalues, we obtained the desired configuration
Rougeau, Patrick. "Apport de l'étude de matériaux analogues anciens à la modélisation du comportement des barrières ouvragées en ciment vis-à-vis de la migration des radioéléments". Poitiers, 1994. http://www.theses.fr/1994POIT2319.
Smidts, Olivier. "Analyse probabiliste du risque de stockage de déchets radioactifs par la méthode des arbres d'événements continus". Doctoral thesis, Universite Libre de Bruxelles, 1997. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212182.
Dans cette thèse, l'analyse d'incertitude liée à la composition du milieu géologique est partagée entre l'écoulement et le transport de la manière suivante: a) une solution moyenne de l'écoulement est tout d'abord déterminée à l'aide d'un code basé sur la méthode des différences finies. Cette solution est ensuite soumise à une analyse de sensibilité. Cette analyse débouche sur la résolution d'un problème inverse afin d'améliorer l'estimation initiale des paramètres moyens d'écoulement; b) l'effet de la variation aléatoire de la vitesse d'écoulement est envisagé lors du transport des radionucléides. Le transport est résolu à l'aide d'une méthode Monte Carlo non analogue.
L'analyse de sensibilité du problème d'écoulement est réalisée à l'aide d'une méthode variationnelle. La méthode proposée a comme avantage celui de pouvoir quantifier l'incertitude de structure; c'est-à-dire l'incertitude liée à la géométrie du milieu géologique.
Une méthodologie Monte Carlo non analogue est utilisée pour le transport de chaînes de radionucléides en milieu stochastique. Les apports de cette méthodologie pour le calcul du risque reposent sur trois points:
1) L'utilisation d'une solution de transport simple (sous la forme d'une solution adjointe) dans les mécanismes de la simulation Monte Carlo. Cette solution de transport permet de résumer, entre deux positions successives du marcheur aléatoire, les processus chimicophysiques (advection, diffusion-dispersion, adsorption, désorption,) apparaissant à l'échelle microscopique. Elle rend possible des simulations efficaces de transport en accélérant les mécanismes de transition des marcheurs aléatoires dans le domaine géologique et dans le temps.
2) L'application de la méthode des arbres d'événements continus au transport de chaînes de radionucléides. Cette méthode permet d'envisager les transitions radioactives entre éléments d'une chaîne selon un même formalisme que celui qui prévaut pour les simulations de transport d'un radionucléide unique. Elle permet donc de passer du transport d'un radionucléide au transport d'une chaîne de radionucléides sans coûts supplémentaires en temps de calcul et avec un coût supplémentaire en mémoire limité.
3) L'application de techniques dites de "double randomization" au problème de transport de radionucléides dans un milieu géologique stochastique. Ces techniques permettent de combiner efficacement une simulation Monte Carlo de paramètres avec une simulation Monte Carlo de transport et ainsi d'inclure l'incertitude associée à la composition du milieu géologique explicitement dans le calcul du risque.
Il ressort de ce travail des perspectives prometteuses de développements ultérieurs de la méthodologie Monte Carlo non analogue pour le calcul du risque.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Zhang, Yumeng. "Modélisation et simulation des dispositifs de ventilation dans les stockages de déchets radioactifs". Thesis, Nice, 2015. http://www.theses.fr/2015NICE4132/document.
The objective of this thesis is to develop models and algorithms to simulate efficiently the mass exchanges occurring at the interface between the nuclear waste deep geological repositories and the ventilation excavated galleries. To model such physical processes, one needs to account in the porous medium for the flow of the liquid and gas phases including the vaporization of the water component in the gas phase and the dissolution of the gaseous components in the liquid phase. In the free flow region, a single phase gas free flow is considered assuming that the liquid phase is instantaneously vaporized at the interface. This gas free flow has to be compositional to account for the change of the relative humidity in the free flow region which has a strong feedback on the liquid flow rate at the interface
Truche, Laurent. "Transformations minéralogiques et géochimiques induites par la présence d'hydrogène dans un site de stockage de déchets radioactifs". Phd thesis, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00439788.
Patinaux, Leny. "Enfouir des déchets nucléaires dans un monde conflictuel. Une histoire de la démonstration de sûreté de projets de stockage géologique, en France (1982-2013)". Thesis, Paris, EHESS, 2017. http://www.theses.fr/2017EHES0164.
It takes up to hundreds of thousands of years for the radioactivity contained in some nuclear waste to decrease under acceptable threshold. How engineers and scientists from the French agency for nuclear waste management (Andra) prove the safety of an underground disposal on such a temporality? Based on the study of the Andra's archives and on internal observation, this thesis intends to address and answer the above question.This thesis is first and foremost a social history of scientific practices used to study the evolution of storage (geology, materials science, numerical simulation...) between the 1980’s and 2013. It's also a study of the role of research in governing the back end of the nuclear fuel cycle, after the French law of 1991 provided nuclear waste management with legal framework. Burying nuclear waste is the only option to manage them. However, the distinction between the research undertaken in Bure underground laboratory and their purpose, has allowed Andra's siting. Engineers and scientists from this agency are faced with the epistemic inability to understand exhaustively the evolution of storage during hundreds of thousands years. The progress of the project and researches work jointly and the pursuit of science constantly disrupts the understanding of the storage evolution. When, in the 1990s, the public demonstration of storage safety became a condition of its acceptance, the Andra progressively gave up the idea that a formal demonstration, like a mathematical one, could be produced. Since the 2000s, the storage safety has been based on a “cluster of arguments” which ensures a degree of control over the deposit evolution. Finally, this thesis shows how the French nuclear waste management has been promoted as a prime example of technical democracy
Kastyuchik, Alexey. "Evaluation of alkaline electro-activated water and eggshell as acid mine drainage neutralization and mine tailing remediation agents". Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26072.
This study aimed to investigate the capacity of a calcite biowaste alone or mixed with alkaline chemical materials and the efficiency of the electro-activation process in neutralizing acidity and maintaining alkaline conditions in a sulfide mine tailing (SMT). In a first set of experiments, chicken eggshell residue (CES) alone (2, 4, 6, 8 and 10%) or mixed with cement concrete (1 – 2%), MgO (1 – 2%), calcitic limestone (1 – 2%) or dolomitic limestone (1 – 2%) was used to neutralize sulfide mine tailing (SMT) acidity and to precipitate trace metallic elements. The highest rate of CES (10%) increased the initial tailing pH value from 2.61 (without amendment) to 7.24, indicating that CES had sufficient lime value to increase the pH of acid SMT. However, the SMT samples mixed with either CES + cement (1 – 2%) or CES + MgO (1 – 2%) had a high pH (≥ 8). The results suggested that magnesium compounds and calcareous products rich in hydroxides, oxides and carbonates present in limed SMT would provide long-term protection against acid deposition or re-acidification of limed SMT. In a second set of experiments, several trials were carried out to assess the effectiveness of electro-activation process composed by two compartments, anode and cathode, under different electric, geometrical, quantitative and qualitative parameters, in neutralizing acidity and maintaining alkaline conditions in a SMT alone or mixed with CES introduced into the cathode compartment. All treatments significantly influenced the pHcatholyte. The results demonstrated that electro-activation process is capable of neutralizing the acidity of RMS alone or mixed with COP and also to achieve alkaline pH conditions (pHcatholyte 8.0 – 10.0). In addition, the electro- activation process using three compartments can remove up to 80% of ferrous iron from an aqueous FeSO4·7H2O solution.
Gaillard, Clotilde. "Étude de la migration thermique des produits de fission molybdène, technétium et iode dans les apatites". Lyon 1, 2000. http://www.theses.fr/2000LYO10253.
Esnault, Loïc. "Réactivité géomicrobiologique des matériaux et minéraux ferrifères : impact sur la sureté d'un stockage de déchets radioactifs en milieux argileux". Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10139/document.
This thesis sought to describe the dynamic concept of a viable and sustainable microbiological activity under deep geological disposal conditions and to assess its impact on containment properties and storage components. Thus, in this study, a model based on the bacterial ferric reduction was chosen for its sustainability criteria in the system and its ability to alter the materials in storage conditions. The main results of this work demonstrated the capability of the environment to stand the iron-reducing bacterial activity and the conditions of its development in the deep clay environments. The bio-availability of structural Fe (III) in clay minerals and iron oxides produced during the process of metal corrosion was clearly demonstrated. In this system, the corrosion appears to be a positive factor on bacterial activities by producing an energy source, hydrogen. The iron-reducing bacterial activities can lead to a resumption of metallic corrosion through the consumption of iron oxides in the passive film. The direct consequence would be a reduction of the lifetime of metal containers. In the case of ferric clay minerals, the consequences of such an activity are such that they can have an impact on the overall porous structure both in terms of chemical reactivity of the materials or physical behavior of the clayey barrier. One of the most significant results is the crystallization of new clay phases at very low temperatures, below 40°C, highlighting the influence of the anaerobic microbial activity in the mineralogical transformations of clay minerals. Furthermore, these experiments also allowed to visualize, for the first time, a mechanism of bacterial respiration at distance, this increases the field of the availability of essential elements as Fe3+ for bacterial growth in extreme environment. In conclusion, these results clearly showed the impact of the microbiological factor on the reactivity of clay and metal minerals, while relying on control parameters on bacterial activity. The relevance of taking into account these microbiological activities in the case of safety assessments of a repository is then established
Camps, Guillaume. "Etude des interactions chemo-mécaniques pour la simulation du cycle de vie d'un élément de stockage en béton". Toulouse 3, 2008. http://thesesups.ups-tlse.fr/324/.
In order to achieve acceptable safety condition during the concrete package handling and to ensure the nuclear waste confinement over several decades, Andra plans to develop fibre reinforced concrete package. The research program presented in this work aims to develop the chemo-mechanical constitutive model for the fibre reinforced concrete. The model considers both the early age behaviour of the concrete and the long term behaviour. The first part of this study consists in performing an experimental program to characterise the physical properties of concrete. The second part was devoted to the development of behaviour laws for plain and fibre-reinforced concrete in a finite element code. We are now able to predict the complete life cycle of nuclear waste packages
Limery, Anasthase. "Étude et réalisation d’un lidar Raman pour la détection d’hydrogène et de vapeur d’eau dans une alvéole de stockage de colis radioactifs". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV005/document.
The CIGEO project, led by the ANDRA agency, aims at enabling future deep geological disposal of french nuclear waste packages. Those packages could be stored in hundred-meters long underground galleries, and may release hydrogen gas (H2), which is explosive at concentrations above 4% in the air. For safety concerns, it is important to ensure that H2 concentration remains well below the lower explosive limit. The objective of this thesis work, conducted at the ONERA agency, is to design and build a lidar which enable high-resolution (3 m) remote profiling of H2 concentration (0-4%) over hundreds of meters. Such a lidar could perform nonintrusive H2 detection and then prevent H2-related explosion risks. This lidar measures vibrational Raman scattering in the UV domain (355 – 420 nm). Its design takes into account the specific conditions expected in storage galleries. A highspeed and sensitive detection stage has been chosen, based on SiPM (Silicium Photomultiplier) technology in photon counting mode. Due to a spectral overlap between molecular hydrogen and water vapor Raman spectra, the need of a H2O measurement channel has been demonstrated. A three-channel spectral analyzer (H2, H2O and N2 used as reference) has been designed and implemented. Signal processing in real time has been developed to display H2 and H2O concentration profiles. This lidar has been tested in a reduced range scene (100 m) enabling hydrogen gas releases. Simultaneous measurements of concentration profiles of natural water vapor and hydrogen gas (0-2%) have been performed at 85 m with 1-meter and 1-minute resolution and a 600 ppm detectivity
Mialle, Sébastien. "Développements analytiques en spectrométrie de masse à thermo-ionisation pour l'analyse isotopique de faibles quantités". Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1507/.
In the framework of the French transmutation project of nuclear wastes, experiments consisted in the irradiation in a fast neutron reactor of few milligrams of isotopically enriched powders. Hence, the isotopic analysis of very small amount of irradiation products is one of the main issues. The aim of this study was to achieve analytical developments in thermal ionization mass spectrometry in order to accurately analyze these samples. Several axes were studied including the new total evaporation method, deposition techniques, electron multiplier potentialities and comparison between different isotope measurement techniques. Results showed that it was possible to drastically decrease the amounts needed for analysis, especially with Eu and Nd, while maintaining an uncertainty level in agreement with the project requirements
Wantz, Olivier. "A study of in-package nuclear criticality in possible Belgian spent nuclear fuel repository designs". Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211019.
The main achievements of this work are:
*A first set of in-package criticality scenarios for different design options for a Belgian spent fuel repository in the Boom clay layer.
*A large number of criticality calculations with different parameters (fuel type, fuel burnup, fuel enrichment, distance between the fuel assemblies, distance between the fuel rods, water fraction inside the overpack) for the different design options.
*A preliminary study of the effects of the spent fuel assemblies isotopic evolution with time on the multiplication factor.
*For the first time, a coupling between the in-package criticality scenarios and the criticality calculations has been performed.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Bourdoiseau, Jacques-André. "Rôle des espèces sulfures sur le comportement d’un acier non allié en milieu de stockage des déchets radioactifs de type C : interaction sulfures / produits de corrosion". Thesis, La Rochelle, 2011. http://www.theses.fr/2011LAROS328/document.
This PhD work deals with the nuclear waste disposal. In France, it is envisaged byAndra (French national radioactive waste management agency) that high-level radioactivewastes will be confined in a glass matrix, stored in a stainless steel canister, it self placed in a carbon steel overpack. The wastes will then be stored at a depth of ~500 m in a deep geological repositery, drilled in a very stiff (indurated) clay (argillite) formation. The kineticsof corrosion expected for the overpack in this disposal concept are low and will stay low if the somehow protective rust layer that will develop initially on the steel surface remains undamaged. Local changes of the physico-chemical conditions may however degrade this layer and induce accelerated kinetics of corrosion. In particular, the growth of sulphate reducing bacteria (SRB) close to the steel overpack cannot be excluded and the sulphid especies these micro-organisms produce may modify the corrosion process. The aim of this work was then to achieve a better understanding of the corrosion system constituted with steel, its rust layer mainly made of siderite FeCO3, and a sulphide-containing electrolyte.First, it proved necessary to characterise the iron sulphides involved in the corrosion processes by Raman micro-spectroscopy so as to study their formation and transformation mechanisms in various conditions of Fe(II) and S(-II) concentration, pH, temperature andaeration. It could be demonstrated that the Raman spectrum of mackinawite FeS, thecompound that precipitated in any case from dissolved Fe(II) and S(-II) species with the experimental conditions considered here, depended on the crystallinity and oxidation state.Moreover, the mechanisms of the oxidation of mackinawite into greigite Fe3S4 in acidicanoxic solutions at 80°C could be described. Finally, iron sulphides, often present on archaeological artefacts, could be identified using Raman micro-spectroscopy. The compounds present were mainly mackinawite and greigite.Secondly, to investigate the nature and properties of carbonated rust layers, carbonsteel electrodes were polarised anodically in NaHCO3 electrolytes continuously de-aerated byan argon flow. The experiments were performed at room temperature. The carbonated greenrust was observed to form at 0.003 and 0.1 mol L-1 NaHCO3 whereas FeCO3 was obtained atthe largest concentrations (0.5 and 1 mol L-1). Additional experiments were performed similarly in solutions of NaHCO3 and Na2SO4. Chukanovite, the Fe(II) hydroxycarbonate with formula Fe2(OH)2CO3, could be obtained in solutions containing 0.03 mol L-1 of eachsalt.Finally, interactions between sulphide species and corrosion products were studied.Siderite, goethite and lepidocrocite proved to be reactive towards sulphide. So, it seems clear that sulphide species produced by SRB should interact with the rust layer before to reach the metal underneath. Tests were performed with ferrous archaeological artefacts immersed 2months in anoxic sulphide-containing electrolytes to demonstrate it. The main effect of theimmersion was the formation of iron sulphide at the interface between the dense corrosion products layer, mainly constitute of siderite, and the transformed medium, where minerals ofthe soil are mixed with corrosion products. Sulphide species were not detected at the vicinityof the iron surface
Citli, Pinar. "Molecular modeling of hydrogen gas adsorption in hydrated clay environments in the context of geological disposal of radioactive waste". Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2024. http://www.theses.fr/2024IMTA0392.
Clay-rich formations are considered as optimal host rock for deep geological repository facilities for high-level radioactive waste. Gas, particularly H2, may form during long-term storage through mechanisms such as anoxic corrosion and water radiolysis, potentially leading to gas pressure buildup and fractures in the surrounding host rock. Molecular-scale understanding of H2 behavior in clay is essential for safe geological disposaland storage, and for the developing effective strategies. In this thesis, montmorillonite, which is widely found in host rock compositions and used as an engineered barrier, is chosen as the clay model. Atomistic simulations of H2 adsorption within the interlayers of hydrated Na-, Ca-, and Cs-montmorillonites are conducted at 25, 50, and 90◦C, up to 120 bar using Monte Carlo and hybrid methods. To this end, the impact of several other factors factors, including the presence of water and pore size are investigated, aiming to improve the fundamental understanding of the physical and chemical processes governing interactions among H2, aqueous solutions, and clay. Furthermore, hydrogen adsorption under extreme conditions is explored to determine the point of saturation in clays
Liu, JiangFeng. "Etanchéité de l’interface argilite-bentonite re-saturée et soumise à une pression de gaz, dans le contexte du stockage profond de déchets radioactifs". Thesis, Ecole centrale de Lille, 2013. http://www.theses.fr/2013ECLI0011/document.
In France, the deep underground nuclear waste repository consists of a natural barrier (in an argillaceous rock named argillite), associated to artificial barriers, including plugs of swelling clay (bentonite)-sand for tunnel sealing purposes. The main objective of this thesis is to assess the sealing efficiency of the bentonite-sand plug in contact with argillite, in presence of both water and gas pressures. To assess the sealing ability of partially water-saturated bentonite/sand plugs, their gas permeability is measured under varying confining pressure (up to 12MPa). It is observed that tightness to gas is achieved under confinement greater than 9MPafor saturation levels of at least 86-91%. We than assess the sealing efficiency of the bentonite-sand plug placed in a tube of argillite or of Plexiglas-aluminium (with a smooth or a rough interface). The presence of pressurized gas affects the effective swelling pressure at values Pgas from 4MPa. Continuous gas breakthrough of fully water-saturated bentonite-sand plugs is obtained for gas pressures on the order of full swelling pressure (7-8MPa), whenever the plug is applied along a smooth interface. Whenever a rough interface is used in contact with the bentonite-sand plug, a gas pressure significantly greater than its swelling pressure is needed for gas to pass continuously. Gas breakthrough tests show that the interface between plug/argillite or the argillite itself are two preferential pathways for gas migration, when the assembly is fully saturated
Gérard, Bruno. "Contribution des couplages mécanique-chimie : transfert dans la tenue à long terme des ouvrages de stockage de dechets radioactifs". Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0017.
Aburto, Mardones Danitza. "Filtrage géostatistique de données géophysiques en vue de la cartographie de l’impédance d’une formation argileuse : exemple du Callovo-Oxfordien de Meuse". Electronic Thesis or Diss., Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0012.
In the framework of researches carried out by ANDRA (the French agency for nuclear waste), which aim at evaluating the feasibility of creating a repository of radioactive waste in the Callovo Oxfordian clay formation. This thesis studies two key steps to obtain a 3D image of the formation: its geometry and its internal heterogeneity. The geometry of the sedimentary formation is determined from seismic time picking along profiles. These profiles are oriented along two main directions. At the intersections, the values registered by two profiles are different. The low number of intersections does not allow a precise study of the spatial behavior of these differences; they are analyzed via the pseudo-cross-variogram. The variography analysis allows the choice of a coherent model for all the profiles, from which an estimation of the corrected time is presented. The internal heterogeneity is performed through the study of the impedance, a variable linked to the intrinsic properties of the rock. Two types of measurements are available. On one hand, the seismic impedance resulting from the geophysical inversion of the amplitude recorded along seismic reflection profiles is densely distributed in the area of interest. On the other hand, the impedance log, resulting from the product of rock density and P wave velocity, is known at only few wells. Bivariate spatial behavior along the vertical direction has allowed the formulation of the following hypothesis: each impedance measurement can be decomposed into a sum of a variable Z (common to both measures) and a residual specific to each measure. Under certain supplementary hypotheses, it is possible to estimate the common component along the seismic sections. Some complements to these studies are mentioned, for example the correspondence between geophysical and geostatistical methods or the consideration of uncertainty in the amplitudes
Chautard, Camille. "Interactions fer/argile en conditions de stockage géologique profond : Impact d'activités bactériennes et d'hétérogénéités". Electronic Thesis or Diss., Paris, ENMP, 2013. http://www.theses.fr/2013ENMP0044.
This study focuses on the interactions between two materials that may be introduced in a geological disposal of radioactive waste: metallic materials such as the high-level waste overpack, and clay materials such as the clay host rock. Indeed, the interactions between these two materials in such conditions could induce a change of their initial confinement properties. This work aimed at determining the influence of heterogeneities (technological gaps and fractures) and bacterial activities on these interactions, in terms of evolution of chemical and hydraulic properties of clayey materials. To this end, two percolation cells have been conducted during 13 months: the first one with two bacteria (SRB, IRB), the second one without bacteria. These experiments, carried out at 60°C, involved circulating synthetic water representative of the Tournemire pore water through iron powder and through Toarcian artificially cracked argillite from Tournemire. An iron rod was also placed into the argillite. Thus, solid characterizations (SEM, SEM/EDS, Raman, XRD, X-ray tomography) allowed the study of both interfaces: the iron powder/argillite interface and the iron rod/argillite interface.The water probably circulated into the crack during the entire test, which was confirmed by reactive transport modeling with the HYTEC reactive transport code. However, no secondary phase was identified in the crack. In addition, bacteria survival in the biotic cell was confirmed during the experiment by monitoring their population and by analyzing their genetic diversity at the end of the experiment. A strong decrease in sulfate concentration was measured in the output, which confirms the SRB activity.Solid characterization conducted at the end of the experiments have highlighted, with and without bacteria, the occurrence of magnetite and chukanovite in the iron powder, the latter being mainly located close to the argillite interface. In the argillite, a Fe-enriched zone (10 µm) was identified. The mean corrosion rate was estimated at 0.2 µm/y (lower bound). At the iron rod/argillite interface, two corrosion facies were observed. The first, identified in both cells, is mainly constituted of chukanovite in the inner layer and siderite in the outer layer. Extent of the argillite perturbation reaches about 30 µm. The second, only observed with bacteria, highlights the presence of iron sulfide precipitation (mackinawite) and localized corrosion patterns. Finally, HYTEC simulations have enabled us to better understand the observed biogeochemical processes, such as the pH effect, and to better quantify some key kinetic parameters
Badet, Hugues. "Effet de la radiolyse sur les systèmes de corrosion anoxiques à très long terme des alliages ferreux". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00945974.
Acher, Loren. "Etude du comportement sous irradiation γ et électronique de matrices cimentaires et de leurs hydrates constitutifs". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX045/document.
In order to treat the technological waste arising from the dismantling of the Marcoule Vitrification facility of the French Atomic Energy Commission (CEA), conditioning in a cement matrix is being put forward. Within this context, the impact of ionizing radiation produced by the nuclear waste on the confinement matrix ought to be investigated in order to ensure both the integrity of the package and the limitation of the radiolytic gas production. This thesis investigates the behavior of three types of cement compounds with distinct constituents under gamma and electronic radiation. This study deals with both the radiolytic gas production and the physical resistance of the materials using a structural modification examination. A double and complementary approach is used treating cement pastes and synthetic cement compounds together. It clearly appears that the pore water and the hydrates themselves both contribute to the radiolytic hydrogen production, with a significant variation depending on the nature of the materials. As far as radiolysis is concerned, calcium aluminate-based cements and magnesium phosphate cements are of considerable interest in comparison with the usual calcium silicate cements. At very high doses (GGy range), the structural resistance under electron irradiation was evaluated by X-ray diffraction. The constituent hydrates of the three cement types studied exhibit a good structural resistance. Despite the presence of dimensional variations at the unit cell scale as well as microstructural evolution, no amorphization is observed under irradiation, which is an interesting result with respect to the intended industrial application
Saba, Simona. "Comportement hydromécanique différé des barrières ouvragées argileuses gonflantes". Phd thesis, Université Paris-Est, 2013. http://pastel.archives-ouvertes.fr/pastel-00985466.
Codina, Maud. "Les bétons bas pH - Formulation, caractérisation et étude à long terme". Phd thesis, INSA de Toulouse, 2007. http://tel.archives-ouvertes.fr/tel-00199021.
Plusieurs liants incorporant du ciment Portland, de la fumée de silice, des cendres volantes et / ou du laitier sont comparés. Tous ces systèmes sont caractérisés par des teneurs en ajouts très importantes, la fraction de clinker n'étant comprise qu'entre 20 et 60 %.
Après un an d'hydratation, la solution interstitielle des pâtes de liants bas pH présente des pH compris entre 11,7 et 12,2 selon la formulation, réduit de plus d'une unité par rapport aux témoins à base de CEM I ou CEM V. Cette chute de pH (comparé à celui d'un CEM I (13,5)) est concomitante i) d'une forte réduction de la concentration en alcalins dans la solution porale, ii) de la disparition ou de la diminution de la teneur en portlandite dans les matériaux, iii) et de l'enrichissement en silice des C-S-H.
Ces liants ont été utilisés avec succès pour mettre au point des bétons bas pH haute performance (pH de la solution interstitielle compris entre 10,7 et 11,6 selon les liants) avec les outils classiques du génie civil.
Enfin, des études de lixiviation en eau désionisée montrent que les pâtes de liants bas pH se décalcifient environ 4 fois moins vite que celle à base de ciment Portland. Les évolutions minéralogiques et les flux lixiviés par l'eau pure (pH 7) à 25 °C ont pu être modélisés à l'aide du code HYTEC en associant deux modules de réactivité chimique et de transport par diffusion.
Echevarria, Guillaume. "Contribution à la prévision des transferts sol-plante des radionucléides". Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL116N.
Liang, Yue. "Comportement du béton sous sollicitations multiaxiales en fonction de la saturation et de la température". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10198/document.
Studies of this paper are focused on the experimental characterization of concrete durability for Andra (National Agency for Radioactive Waste Management), and notably in order to study the feasibility of radioactive waste storage in deep geological rocks. In that context, the concretes are subjected to coupled mechanisms: stress variation due to cavity excavation, change of water saturation degree due to ventilation and gas pressure, variation of temperature due to exothermic waste… Therefore, it is necessary to acquire new experimental data for an adequate characterization of short and long-term thermo-hydro-mechanical couplings. Researches are carried out on Andra reference concretes made from cement CEM I and CEM V/A. In the short term, various tests highlight the evolution of multiaxial mechanical behaviour of concrete as a function of saturation and temperature. In a long-term view, creep tests (uniaxial and multiaxial) are performed to study the delayed effects of mechanical behaviour under temperature or during drying by small controlled steps in relative humidity
Chautard, Camille. "Interactions fer/argile en conditions de stockage géologique profond : Impact d'activités bactériennes et d'hétérogénéités". Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2013. http://pastel.archives-ouvertes.fr/pastel-01058325.
Aburto, Mardones Danitza. "Filtrage géostatistique de données géophysiques en vue de la cartographie de l’impédance d’une formation argileuse : exemple du Callovo-Oxfordien de Meuse". Thesis, Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0012/document.
In the framework of researches carried out by ANDRA (the French agency for nuclear waste), which aim at evaluating the feasibility of creating a repository of radioactive waste in the Callovo Oxfordian clay formation. This thesis studies two key steps to obtain a 3D image of the formation: its geometry and its internal heterogeneity. The geometry of the sedimentary formation is determined from seismic time picking along profiles. These profiles are oriented along two main directions. At the intersections, the values registered by two profiles are different. The low number of intersections does not allow a precise study of the spatial behavior of these differences; they are analyzed via the pseudo-cross-variogram. The variography analysis allows the choice of a coherent model for all the profiles, from which an estimation of the corrected time is presented. The internal heterogeneity is performed through the study of the impedance, a variable linked to the intrinsic properties of the rock. Two types of measurements are available. On one hand, the seismic impedance resulting from the geophysical inversion of the amplitude recorded along seismic reflection profiles is densely distributed in the area of interest. On the other hand, the impedance log, resulting from the product of rock density and P wave velocity, is known at only few wells. Bivariate spatial behavior along the vertical direction has allowed the formulation of the following hypothesis: each impedance measurement can be decomposed into a sum of a variable Z (common to both measures) and a residual specific to each measure. Under certain supplementary hypotheses, it is possible to estimate the common component along the seismic sections. Some complements to these studies are mentioned, for example the correspondence between geophysical and geostatistical methods or the consideration of uncertainty in the amplitudes
Song, Yang. "Rétention d'eau et microstructure fine de l'argilite de Bure". Thesis, Ecole centrale de Lille, 2014. http://www.theses.fr/2014ECLI0008/document.
In the context of deep underground storage of radioactive nuclear waste, it is important to identify the saturation hysteresis of the host rock, i.e. of Callovo-Oxfordian (COx) claystone, and its porosity and pore size distribution. Firstly, six different cycles of relative humidity are applied for saturation hysteresis, which is not observed in the cycles with low magnitude. Secondly, a new method is proposed for measuring porosity, which uses injection of gas to evaluate the pore volume. In contrast to porosity given by water adsorption, the gas injection method provides larger porosity values of around 5%. The gas injection method is also used to quantify the sorption-desorption isotherms of COx claystone, which are significantly different from those obtained by the gravimetric method, with a bigger pore volume accessible to gas in relative humidities < 43%. Finally, by Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM), we obtain 2D image stacks and 3D reconstructed pore volumes, by which porosity and pore size distribution are quantified down to 20nm, as well as pore orientation and anisotropy. At a higher resolution (below 1nm), Transmission Electron Microscopy (TEM) imaging reveals significant amounts of smaller pores (of a few nm) between clay aggregates
Depierre, Sara. "Etude des mécanismes d'altération du verre par des eaux cimentaires". Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20152/document.
In the French deep geological repository concept, intermediate-level vitrified wastepackages could be disposed of concrete medium. Chemical composition and pH of the interstitialleaching water are expected to influence the chemical durability of glass. Investigations have thusbeen carried out to study glass dissolution mechanisms and kinetics in contact with cement waters.Three cement pore waters were studied: the first two correspond to two stages of the Portlandcement aging and the third corresponds to equilibrium with a low pH concrete. The S/V ratio(glass-surface-area-to-solution-volume ratio) and the chemistry of cement waters are the two mainparameters that control glass alteration mechanisms.If the leaching flow from the glass allows a degree of supersaturation to be reached and maintainedwhich leads to nucleation of secondary phases, then precipitation of these phases drives glassdissolution. At a very low S/V ratio, the calcium uptake into the alteration layer increases itspassivating properties. Conversely, at a high S/V ratio, the calcium precipitates as cementitiousphases consuming elements which form the alteration layer. The glass dissolution is maintained ata high rate.This study contributes to highlighting the beneficial role of low pH cement in glass alteration, andis a first step towards understanding the mechanisms between the glass and the cement medium
Martin, Philippe. "Etude des mécanismes de diffusion thermique et de diffusion sous irradiation alpha des terres rares dans les apatites". Lyon 1, 1999. http://www.theses.fr/1999LYO10026.
Molinero, Guerra Agustin. "Caractérisations expérimentale et numérique du comportement hydro-mécanique d'un matériau hétérogène : mélange de poudre/pellets de bentonite". Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1022/document.
The present investigation deals with the hydro-mechanical behavior of a mixture composed of pellets and powder of MX80 bentonite with a proportion of 80/20 in dry mass. This is one of the studied materials by the French Institute for Radiation protection and Nuclear Safety (IRSN) within the SEALEX project, which aims at investigating the long-term performance of swelling clay-based sealing systems in the context of geological high-level radioactive waste disposal. This study has been conducted by following an experimental program covering different scales. Firstly, the microstructure changes while wetting of a single pellet was investigated by combining MIP results with μ-CT observations. Results revealed that swelling of a pellet is due to the development of cracks, with significant development between 38 and 9 MPa of suction, combined to swelling of bentonite grains, which is governed by the hydration mechanisms of smectite at nano-scale. The application of suctions below 9 MPa leads to a significant decrease of the platelet thickness and to an increase in the disorder of the platelet assembly. Water retention tests, swelling pressure tests and suction controlled oedometer tests on the pellet/powder mixture were performed. Similar water retention properties were observed for the mixture under constant-volume condition and pellet under free swelling condition under suctions higher than 4 MPa, suggesting that physico-chemical suction prevails on capillary suction. At lower suctions, constant-volume condition defined a lower water retention capacity because of the disappearance of macro-pores. Lower yield stress values than the common pure bentonite mixtures were found for the pellet/powder mixture for non-zero suctions, showing that the volume change behavior is governed by the rearrangement and crushing of pellets, and the loss of the granular structure in the case of zero suction. Two mock-up tests were performed, aiming at studying two extreme cases at a global dry density of 1.49 Mg/m3: a homogeneous pellet/powder mixture fabricated by following a special protocol, and a strong heterogeneous sample. Results revealed that the radial swelling pressure depends strongly on the local pellet/powder distribution combined with the evolution of the hydration front. An anisotropy swelling was found in both cases, being the axial swelling pressure lower than the radial one. Moreover, different values of axial pressure were found between the two tests, even though they have the same global dry density of samples. In parallel, μ-CT observations were carried out on the mixture while wetting, revealing a homogeneous sealed sample after 100 days of hydration. No density gradients were identified at the investigated resolution (50 μm/voxel) after this long time of hydration. A new damage model, which takes into account the development of fissures within a pellet while wetting, was proposed an included to the well-IVknown double porosity Barcelona Expansive Model (BExM) to carry out numerical simulations of one mock-up test. The initial heterogeneous porosity distribution was also considered to reproduce the anisotropy swelling. The experimental results obtained in this study will greatly help well understand the response of seals made up of pellets/powder bentonite mixture in the SEALEX in situ experiment. Moreover, the constitutive model developed taking into account the pellet cracking damage and the initial sample heterogeneity allows significantly improving the prediction of hydomechanical behavior of seals/plugs made up of this mixture, constituting thus an useful tool for the safety assessment of the nuclear waste disposal system
Rolland, Alexandra. "Rhéologie, localisation de la déformation et histoire des contraintes dans les calcaires du site de Bure". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00853208.
Wang, Qiong. "Hydro-mechanical behaviour of bentonite-based materials used for high-level radioactive waste disposal". Phd thesis, Université Paris-Est, 2012. http://pastel.archives-ouvertes.fr/pastel-00806392.