Dans un site de stockage profond de déchets radioactifs, l’utilisation de matériaux à base de ciment Portland en association avec de l’argile pourrait se révéler inadaptée en raison de leur forte alcalinité. Une alternative serait de mettre en œuvre des ciments générant des solutions interstitielles de pH réduit (de l’ordre de 11 au lieu de 13,5 pour un CEM I). Les formulations étudiées dans cette thèse font appel à des ciments composés (également appelés « liant bas pH ») élaborés à partir de mélanges binaires (CEM I / fumée de silice) ou ternaires (CEM I / fumée de silice / cendres volantes ou laitier), avec de forts taux de substitution du CEM I (de 30% à 80%). Le travail réalisé répond à un double objectif : (i) étudier l’évolution chimique des liants bas pH à 50°C ou 80°C, températures qui pourraient être rencontrées dans certaines zones du stockage, et (ii) préciser les mécanismes à l’origine de la bonne rétention des alcalins par ces liants hydratés. (i) Le suivi sur une période d’un an de pâtes de liant bas pH montre que l’accroissement de la température de 20 à 80°C accélère l’hydratation des liants et favorise la consommation de la portlandite. L’allongement et la réticulation des chaînes de silicates des C-A-S-H est mise en évidence par RMN de l’27Al et du 29Si. L’ettringite observée dans les pâtes conservées à 20°C est par ailleurs déstabilisée. Les sulfates ainsi relâchés sont pour partie adsorbés sur les C-A-S-H et dissous dans la solution interstitielle. Le pH de cette dernière est réduit de 1,7 à 2,2 unités selon les formulations. En revanche, les fractions solubles d’alcalins n’évoluent pas de façon importante. Le liant ternaire T1 composé de 37,5% de CEM I, 32,5% de fumée de silice et 30% de cendres volantes est le seul des ciments étudiés à conduire à un pH de solution interstitielle inférieur à 11 aux trois températures considérées (20, 50 et 80°C - échéances 6 mois et 1 an). Son évolution à plus long terme a pu être simulée à l’aide de systèmes modèles reproduisant sa composition chimique à partir d’oxydes réactifs. A l’équilibre thermodynamique, l’assemblage minéralogique est constitué de C-A-S-H (rapports Ca/Si et Al/Si de 0,75 et 0,15 respectivement) ainsi que d’hydroxyde d’aluminium et de silice amorphes, et il impose un pH de 10,3 à 20°C. (ii) Ce sont les C-A-S-H qui jouent le rôle essentiel dans la rétention des alcalins. Le mécanisme mis en jeu est celui d’une compensation des charges négatives des C-A-S-H par interaction électrostatique. Il existe une sélectivité de sorption : le potassium est mieux retenu que le sodium. Celle-ci pourrait être attribuée en première approche à la différence de rayon solvaté entre ces ions. Une modélisation Monte Carlo des interactions électrostatiques entre des particules de C-S-H et un électrolyte contenant des ions sodium et potassium montre cependant que cette hypothèse ne suffit pas à elle seule à expliquer la sélectivité observée expérimentalement. / Because of their high alkalinity, Portland cement (OPC)-based materials may have deleterious effects in an underground waste repository. A solution would be to use low-alkalinity cements (also referred as low-pH cements) generating interstitial solutions with a reduced pH (11 instead of 13.5 for OPC), and thus showing an improved chemical compatibility with the repository environment. In this work, the investigated formulations were based on binary (OPC / silica fume) or ternary (OPC / silica fume / slag or fly ash) blends, with high substitution levels of CEM I (from 30% to 80%). This research project met two main objectives: (i) study the chemical evolution of low-pH cements at 50°C or 80°C, since such temperatures could be encoutered in certain zones of the waste repositories, and (ii) determine the mechanisms of alkali retention by hydrated low-pH cements. (i) Investigation of low-pH cement pastes with ongoing hydration over one year showed that increasing the temperature from 20°C to 80°C accelerated cement hydration and favoured the depletion of portlandite. A lengthening of the C-A-S-H silicate chains was also detected by 27Al and 29Si NMR analyses. Besides, ettringite precipitated at 20°C, but was destabilised at higher temperature. The released sulphates were partly adsorbed on the C-A-S-H and dissolved in the interstitial solution. The pH of this solution was reduced from 1.7 to 2.2 units depending on the formulations. The soluble fractions of alkalis did not significantly change with temperature. Among the five investigated blends, ternary binder T1 (37.5% CEM I, 32.5% silica fume, 30% fly ash) was the only one giving a pore solution pH lower than 11 at 20, 50 and 80°C (curing time of 6 months and 1 year). Its long-term evolution was simulated by model systems reproducing its chemical composition with reactive oxides. At equilibrium, the hydrate assemblage comprised C-A-S-H (Ca/Si and Al/Si ratios of 0.75 and 0.15 respectively), amorphous silica and aluminium hydroxide. It led to a pH of 10.3 at 20°C. (ii) C-A-S-H hydrates played a major role in the retention of alkalis. Sorption of potassium was higher than that of sodium and mainly resulted from electrostatic interactions with C-A-S-H. Monte Carlo modelling of these interactions showed that the difference of solvated radii between these ions could not explain by itself the sorption selectivity experimentally observed.

Actuellement, bien que la plupart des pays nucléaires converge vers la même solution technique: le stockage profond pour la gestion des déchets radioactifs de haute activité et à vie longue, les objectifs calendaires divergent d'un pays à l'autre. Grâce au calcul économique, nous souhaitons apporter des éléments de réponse à la question suivante : En termes de temporalité, comment les générations présentes, qui bénéficient de la production d'électricité nucléaire, doivent-elles supporter les charges de la gestion des déchets radioactifs en tenant compte des générations futures ? Cette thèse se propose d'analyser spécifiquement la décision française en tenant compte de son contexte. Nous proposons un ensemble d'outils qui permet d'évaluer l'Utilité du projet de stockage profond en fonction des choix de temporalité. Notre thèse étudie également l'influence en retour des choix de stockage sur le cycle du combustible nucléaire. Au-delà, nous prenons en compte les interactions entre le stockage profond et les choix de parc nucléaire et de cycle du combustible qui constituent un « système complet ». / Nowadays, the deep geological repository is generally considered as the reference solution for the definitive management of spent nuclear fuel/high-level waste, but different countries have decided different disposal deployment schedules. Via the economic calculation, we hope to offer some answers to the following question: In terms of disposal time management, how should the present generations, benefiting from the nuclear power generation, bear the costs of radioactive waste management, while taking into account future generations? This thesis proposes to analyze specifically the French decision in its context. We propose a set of tools to evaluate the Utility of the deep geological repository project according to the deployment schedule choices. Our thesis also studies the influence of disposal choices on the nuclear fuel cycle. Beyond, we also take into account the interactions between the deep geological repository, nuclear fleet and cycle choices which constitute a "complete system".

The focus of this work is to investigate the dissolution of MW25, a non-radioactive simulant of UK high-level nuclear waste borosilicate glass, and to predict its performance in the near field of a geological repository. A single-pass flow-through (SPFT) experimental system was used to measure the forward dissolution rates of MW25. Experiments were conducted in two parts. Experiment Part 1 considers the dissolution of the waste glass in deionised water at 40 and 90 oC and circum-neutral pH. Experiment Part 2 considers the dissolution of the waste glass in simulant groundwaters, with similar compositions to groundwaters of Callovo-Oxfordian clay (lower-strength sedimentary rock (LSSR)) and Borrowdale Volcanic Group rocks (higher-strength rock (HSR)), at 40 oC and pH 7. The forward dissolution rate measured in deionised water was found to be approximately one order of magnitude higher at 90 oC than at 40 oC. A similar release was observed for Si, Mg and Al at 40 oC and 90 oC, whereas the B, Cs, Na, Li and Mo showed an order of magnitude increase when the temperature was increased from 40 to 90 oC for low q/S values. The activation energy (Ea) of the reactions shows that the dissolution process is a surface phenomenon. At 90 oC the net effect of the processes governing MW25 dissolution led to the preferential release of boron and alkali metals relative to the release of Si during the transient dissolution stage, accompanied by an increase in the concentration of silicic acid. This suggests that the solution activity of silicic acid at a higher temperature has a weak influence on the release of the mobile elements. The forward dissolution rate measured in LSSR simulant groundwater was found to be slightly higher than that measured in HSR simulant groundwater. The dissolution behaviour of MW25 in both groundwaters is consistent with its behaviour in deionised water at 40 oC, with the dissolution rates of elements increasing as flow rates were increased. However, forward dissolution rates measured in the simulant groundwaters were lower than the forward dissolution rates measured in deionised water under these experimental conditions. This is attributable to the interaction of the components of the simulant groundwaters with the glass, as revealed by post-reaction surface analyses, and a consequential lower alkalinity of the leachates collected in the experiments with simulant groundwater than in deionised water. Reactive chemical transport simulations of waste glass dissolution and radionuclide release in a hypothetical near field were conducted over a time span of a million years with GoldSim. The results showed that enclosing the waste glass in a steel canister covered by a copper canister and emplacing the waste package in a granite host rock is optimal for the long-term isolation of the radionuclides. The waste glass was found to play a significant role in the overall performance of the near field. This study features a new method for estimating the surface area of reacted glass powder more accurately than the geometric surface area estimate, which is the preferred standard method among researchers.

Deep geological repository (DGR) for disposal of high-level radioactive waste (HLW) is designed to rely on successive superimposed barrier systems to isolate the waste from the biosphere. This multiple barrier system comprises the natural geological barrier provided by the repository host rock and its surrounding and an engineered barrier system (EBS). The EBS represents the synthetic, engineered materials placed within the natural barrier, comprising array of components such as waste form, waste canisters, buffer materials, backfill and seals. The buffer will enclose the waste canisters from all directions and act as a barrier between canisters and host rock of the repository. It is designed to stabilise the evolving thermo-hydro-mechanical-chemical stresses in the repository over a long period (nearly 1000 years) to retard radionuclides from reaching biosphere. Bentonite clay or bentonite-sand mix have been chosen as buffer materials in EBS design in various countries pursuing deep geological repository method. The bentonite buffer is the most important barrier among the other EBS components for a geological repository. The safety of repository depends to a large extent on proper functioning of buffer over a very long period of time during which it must remain physically, chemically and mineralogically stable. The long term stability of bentonite buffer depends on varying temperature and evolution of groundwater composition of host rocks in a complex way. The groundwater in the vicinity of deep crystalline rock is often characterized by high solute concentrations and the geotechnical engineering response of bentonite buffer could be affected by the dissolved salt concentration of the inflowing ground water. Also during the initial period, radiogenic heat produced in waste canisters would radiate into buffer and the heat generated would lead to drying and some shrinkage of bentonite buffer close to canister. This could alter the dry density, moisture content and in turn the hydro-mechanical properties of bentonite buffer in DGR conditions. India has variety of bentonite deposits in North-Western states of Rajasthan and Gujarat. Previous studies on Indian bentonites suggest that bentonite from Barmer district of Rajasthan (termed as Barmer-1 bentonite) is suitable to serve as buffer material in DGR conditions. Nuclear power agencies of several countries have identified suitable bentonites for use as buffer in DGR through laboratory experiments and large scale underground testing facilities. Physico-chemical, mineralogical and engineering properties of Kunigel VI, Kyungju, GMZ, FoCa clay, MX-80, FEBEX and Avonseal bentonites have been extensively studied by Japan, South Korea, China, Belgium, Sweden, Spain, Canada. It is hence essential to examine the suitability of Barmer-1 bentonite as potential buffer in DGR and compare its physico-chemical and hydromechanical properties with bentonite buffers identified by other countries. The significant factors that impact the long-term stability of bentonite buffer in DGR include variations in moisture content, dry density and pore water chemistry. With a view to address these issues, the hydromechanical response of 70 % Barmer-1 bentonite + 30 % river sand mix (termed bentonite enhanced sand, BES specimens) under varying moisture content, dry density and pore water salt concentration conditions have been examined. The broad scope of the work includes: 1) Characterise the physico-chemical and hydro-mechanical properties of Barmer-1 bentonite from Rajasthan, India and compare its properties with bentonite buffers reported in literature. 2) Examine the influence of variations in dissolved salt concentration (of infiltrating solution), dry density and moisture content of compacted BES specimens on their hydro-mechanical response; the hydro-mechanical properties include, swell pressure, soil water characteristic curve (SWCC), unsaturated hydraulic conductivity, moisture diffusivity and unconfined compression strength. Organization of thesis: After the first introductory chapter, a detailed review of literature is performed to highlight the need for detailed characterisation of physico-chemical and hydromechanical properties of Barmer-1 bentonite for its possible application in DGR in the Indian context. Further, existing literature on hydro-mechanical response of bentonite buffer to changes in physical (degree of saturation/moisture content, dry density) and physico-chemical (solute concentration in pore water) is reviewed to define the scope and objectives of the present thesis in Chapter 2. Chapter 3 presents a detailed experimental programme of the study. Chapter 4 characterises Barmer-1 bentonite for physico-chemical (cation exchange capacity, pore water salinity, exchangeable sodium percentage) and hydro-mechanical properties, such as, swell pressure, saturated permeability, soil water characteristic curve (SWCC) and unconfined compression strength. The properties of Barmer-1 bentonite are compared with bentonite buffers reported in literature and generalized equations for determining swell pressure and saturated permeability coefficient of bentonite buffers are arrived at. Chapter 5 describes a method to determine solute concentrations in the inter-lamellar and free-solutions of compacted BES (bentonite enhanced sand) specimens. The solute concentrations in micro and macro pore solutions are used to examine the role of osmotic flow on swell pressures developed by compacted BES specimens (dry density 1.50-2.00 Mg/m3) inundated with distilled water and NaCl solutions (1000-5000 mg/L). The number of hydration layers developed by the compacted BES specimens on inundation with salt solutions in constant volume swell pressure tests is controlled by cation hydration/osmotic flow. The cation hydration of specimens compacted to dry density of 2.00 Mg/m3 is mainly driven by matric suction prevailing in the clay microtructure as the number of hydration layers developed at wetting equilibrium are independent of the total dissolved solids (TDS) of the wetting solution. Consequently, the swell pressures of specimens compacted to 2.00 Mg/m3 were insensitive to the salt concentration of the inundating solution. The cation hydration of specimens compacted to dry density of 1.50 Mg/m3 is driven by both matric suction (prevailing in the clay micro-structure) and osmotic flow as the number of hydration layers developed at wetting equilibrium is sensitive to the TDS of the wetting solution. Expectedly, the swell pressures of specimens compacted to 1.50 Mg/m3 responded to changes in salt concentration of the inundating solution. The 1.75 Mg/m3 specimens show behaviour that is intermediate to the 1.50 and 2.00 Mg/m3 series specimens. Chapter 6 examines the influence of initial degree of saturation on swell pressures developed by the compacted BES specimens (dry density range: 1.40- 2.00 Mg/m3) on wetting with distilled water from micro-structural considerations. The micro-structure of the bentonite specimens are examined in the compacted and wetted states by performing X-ray diffraction measurements. The initial degree of saturation is varied by adding requisite amount of distilled water to the oven-dried BES mix and compacting the moist mixes to the desired density. The montmorillonite fraction in the BES specimens is responsible for moisture absorption during compaction and development of swell pressure in the constant volume oedometer tests. Consequently, it was considered reasonable to calculate degree of saturation based on EMDD (effective montmorillonite dry density) values and correlate the developed swell pressure values with degree of saturation of montmorillonite voids (Sr,MF). XRD measurements with compacted and wetted specimens demonstrated that if specimens of density series developed similar number of hydration layers on wetting under constant volume condition they exhibited similar swell pressures, as was the case for specimens belonging to 1.40 and 1.50 Mg/m3 series. With specimens belonging to 1.75 and 2.00 Mg/m3 series, greater number of hydration layers were developed by specimens that were less saturated initially (smaller initial Sr,MF) and consequently such specimens developed larger swell pressures. When specimens developed similar number of hydration layers in the wetted state, the compaction dry density determined the swell pressure. Chapter 7 examines the influence of salt concentration of infiltrating solution (sodium chloride concentration ranges from 1000- 5000 mg/L) on SWCC relations, unsaturated permeability and moisture diffusivity of compacted BES specimens. Analysis of the experimental and Brooks and Corey best fit plots revealed that infiltration of sodium chloride solutions had progressively lesser influence on the micro-structure and consequently on the SWCC relations with increase in dry density of the compacted specimens. The micro-structure and SWCC relations of specimens compacted to 1.50 Mg/m3 were most affected, specimens compacted to 1.75 Mg/m3 were less affected, while specimens compacted to 2.00 Mg/m3 were unaffected by infiltration of sodium chloride solutions. Variations in dry density of compacted bentonite impacts the pore space available for moisture flow, while, salinity of wetting fluid impacts the pore structure from associated physico-chemical changes in clay structure. Experimental results showed that the unsaturated permeability coefficient is insensitive to variations in dry density and solute concentration of wetting liquid, while, the effective hydraulic diffusivity is impacted by variations in these parameters. Chapter 8 summarises the major findings of the study.

Deep geological repository (DGR) for disposal of high-level radioactive waste (HLW) is designed to rely on successive superimposed barrier systems to isolate the waste from the biosphere. This multiple barrier system comprises the natural geological barrier provided by the repository host rock and its surrounding and an engineered barrier system (EBS). The EBS represents the synthetic, engineered materials placed within the natural barrier, comprising array of components such as waste form, waste canisters, buffer materials, backfill and seals. The buffer will enclose the waste canisters from all directions and act as a barrier between canisters and host rock of the repository. It is designed to stabilise the evolving thermo-hydro-mechanical-chemical stresses in the repository over a long period (nearly 1000 years) to retard radionuclides from reaching biosphere. Bentonite clay or bentonite-sand mix have been chosen as buffer materials in EBS design in various countries pursuing deep geological repository method. The bentonite buffer is the most important barrier among the other EBS components for a geological repository. The safety of repository depends to a large extent on proper functioning of buffer over a very long period of time during which it must remain physically, chemically and mineralogically stable. The long term stability of bentonite buffer depends on varying temperature and evolution of groundwater composition of host rocks in a complex way. The groundwater in the vicinity of deep crystalline rock is often characterized by high solute concentrations and the geotechnical engineering response of bentonite buffer could be affected by the dissolved salt concentration of the inflowing ground water. Also during the initial period, radiogenic heat produced in waste canisters would radiate into buffer and the heat generated would lead to drying and some shrinkage of bentonite buffer close to canister. This could alter the dry density, moisture content and in turn the hydro-mechanical properties of bentonite buffer in DGR conditions. India has variety of bentonite deposits in North-Western states of Rajasthan and Gujarat. Previous studies on Indian bentonites suggest that bentonite from Barmer district of Rajasthan (termed as Barmer-1 bentonite) is suitable to serve as buffer material in DGR conditions. Nuclear power agencies of several countries have identified suitable bentonites for use as buffer in DGR through laboratory experiments and large scale underground testing facilities. Physico-chemical, mineralogical and engineering properties of Kunigel VI, Kyungju, GMZ, FoCa clay, MX-80, FEBEX and Avonseal bentonites have been extensively studied by Japan, South Korea, China, Belgium, Sweden, Spain, Canada. It is hence essential to examine the suitability of Barmer-1 bentonite as potential buffer in DGR and compare its physico-chemical and hydromechanical properties with bentonite buffers identified by other countries. The significant factors that impact the long-term stability of bentonite buffer in DGR include variations in moisture content, dry density and pore water chemistry. With a view to address these issues, the hydromechanical response of 70 % Barmer-1 bentonite + 30 % river sand mix (termed bentonite enhanced sand, BES specimens) under varying moisture content, dry density and pore water salt concentration conditions have been examined. The broad scope of the work includes: 1) Characterise the physico-chemical and hydro-mechanical properties of Barmer-1 bentonite from Rajasthan, India and compare its properties with bentonite buffers reported in literature. 2) Examine the influence of variations in dissolved salt concentration (of infiltrating solution), dry density and moisture content of compacted BES specimens on their hydro-mechanical response; the hydro-mechanical properties include, swell pressure, soil water characteristic curve (SWCC), unsaturated hydraulic conductivity, moisture diffusivity and unconfined compression strength. Organization of thesis: After the first introductory chapter, a detailed review of literature is performed to highlight the need for detailed characterisation of physico-chemical and hydromechanical properties of Barmer-1 bentonite for its possible application in DGR in the Indian context. Further, existing literature on hydro-mechanical response of bentonite buffer to changes in physical (degree of saturation/moisture content, dry density) and physico-chemical (solute concentration in pore water) is reviewed to define the scope and objectives of the present thesis in Chapter 2. Chapter 3 presents a detailed experimental programme of the study. Chapter 4 characterises Barmer-1 bentonite for physico-chemical (cation exchange capacity, pore water salinity, exchangeable sodium percentage) and hydro-mechanical properties, such as, swell pressure, saturated permeability, soil water characteristic curve (SWCC) and unconfined compression strength. The properties of Barmer-1 bentonite are compared with bentonite buffers reported in literature and generalized equations for determining swell pressure and saturated permeability coefficient of bentonite buffers are arrived at. Chapter 5 describes a method to determine solute concentrations in the inter-lamellar and free-solutions of compacted BES (bentonite enhanced sand) specimens. The solute concentrations in micro and macro pore solutions are used to examine the role of osmotic flow on swell pressures developed by compacted BES specimens (dry density 1.50-2.00 Mg/m3) inundated with distilled water and NaCl solutions (1000-5000 mg/L). The number of hydration layers developed by the compacted BES specimens on inundation with salt solutions in constant volume swell pressure tests is controlled by cation hydration/osmotic flow. The cation hydration of specimens compacted to dry density of 2.00 Mg/m3 is mainly driven by matric suction prevailing in the clay microtructure as the number of hydration layers developed at wetting equilibrium are independent of the total dissolved solids (TDS) of the wetting solution. Consequently, the swell pressures of specimens compacted to 2.00 Mg/m3 were insensitive to the salt concentration of the inundating solution. The cation hydration of specimens compacted to dry density of 1.50 Mg/m3 is driven by both matric suction (prevailing in the clay micro-structure) and osmotic flow as the number of hydration layers developed at wetting equilibrium is sensitive to the TDS of the wetting solution. Expectedly, the swell pressures of specimens compacted to 1.50 Mg/m3 responded to changes in salt concentration of the inundating solution. The 1.75 Mg/m3 specimens show behaviour that is intermediate to the 1.50 and 2.00 Mg/m3 series specimens. Chapter 6 examines the influence of initial degree of saturation on swell pressures developed by the compacted BES specimens (dry density range: 1.40- 2.00 Mg/m3) on wetting with distilled water from micro-structural considerations. The micro-structure of the bentonite specimens are examined in the compacted and wetted states by performing X-ray diffraction measurements. The initial degree of saturation is varied by adding requisite amount of distilled water to the oven-dried BES mix and compacting the moist mixes to the desired density. The montmorillonite fraction in the BES specimens is responsible for moisture absorption during compaction and development of swell pressure in the constant volume oedometer tests. Consequently, it was considered reasonable to calculate degree of saturation based on EMDD (effective montmorillonite dry density) values and correlate the developed swell pressure values with degree of saturation of montmorillonite voids (Sr,MF). XRD measurements with compacted and wetted specimens demonstrated that if specimens of density series developed similar number of hydration layers on wetting under constant volume condition they exhibited similar swell pressures, as was the case for specimens belonging to 1.40 and 1.50 Mg/m3 series. With specimens belonging to 1.75 and 2.00 Mg/m3 series, greater number of hydration layers were developed by specimens that were less saturated initially (smaller initial Sr,MF) and consequently such specimens developed larger swell pressures. When specimens developed similar number of hydration layers in the wetted state, the compaction dry density determined the swell pressure. Chapter 7 examines the influence of salt concentration of infiltrating solution (sodium chloride concentration ranges from 1000- 5000 mg/L) on SWCC relations, unsaturated permeability and moisture diffusivity of compacted BES specimens. Analysis of the experimental and Brooks and Corey best fit plots revealed that infiltration of sodium chloride solutions had progressively lesser influence on the micro-structure and consequently on the SWCC relations with increase in dry density of the compacted specimens. The micro-structure and SWCC relations of specimens compacted to 1.50 Mg/m3 were most affected, specimens compacted to 1.75 Mg/m3 were less affected, while specimens compacted to 2.00 Mg/m3 were unaffected by infiltration of sodium chloride solutions. Variations in dry density of compacted bentonite impacts the pore space available for moisture flow, while, salinity of wetting fluid impacts the pore structure from associated physico-chemical changes in clay structure. Experimental results showed that the unsaturated permeability coefficient is insensitive to variations in dry density and solute concentration of wetting liquid, while, the effective hydraulic diffusivity is impacted by variations in these parameters. Chapter 8 summarises the major findings of the study.

L'objectif de cette thèse est de fournir des modèles et des outils de simulation pour décrire les échanges de masse entre les circuits de ventilation (galeries) et les milieux poreux des ouvrages souterrains d'enfouissement des déchets nucléaires. La modélisation prend en compte le couplage à l'interface poreux-galerie entre les écoulements liquide gaz compositionnels dans le milieu poreux constituant le stockage et les écoulements gazeux compositionnels dans le milieu galerie libre. / 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.