Modelling of the long-term evolution and performance of engineered barrier system

Components of the so-called “multiple-barrier system” from the waste form to the biosphere include a combination of waste containers, engineered barriers, and natural barriers. The Engineered Barrier System (EBS) is crucial for containment and isolation in a radioactive waste disposal system. The number, types, and assigned safety functions of the various engineered barriers depend on the chosen repository concept, the waste form, the radionuclides waste inventory, the selected host rock, and the hydrogeological and geochemical settings of the repository site, among others. EBS properties will evolve with time in response to the thermal, hydraulic, mechanical, radiological, and chemical gradients and interactions between the various constituents of the barriers and the host rock. Therefore, assessing how these properties evolve over long time frames is highly relevant for evaluating the performance of a repository system and safety function evaluations in a safety case. For this purpose, mechanistic numerical models are increasingly used. Such models provide an excellent way for integrating into a coherent framework a scientific understanding of coupled processes and their consequences on different properties of the materials in the EBS. Their development and validation are supported by R&D actions at the European level. For example, within the HORIZON 2020 project BEACON (Bentonite mechanical evolution), the development, test, and validation of numerical models against experimental results have been carried out in order to predict the evolution of the hydromechanical properties of bentonite during the saturation process. Also, in relation to the coupling with mechanics, WP16 MAGIC (chemo Mechanical AGIng of Cementitious materials) of the EURAD Joint Programming Initiative focuses on multi-scale chemo-mechanical modeling of cementitious-based materials that evolve under chemical perturbation. Integration of chemical evolution in models of varying complexity is a major issue tackled in the WP2 ACED (Assessment of Chemical Evolution of ILW and HLW Disposal cells) of EURAD. WP4 DONUT (Development and improvement of numerical methods and tools for modeling coupled processes) of EURAD aims at developing and improving numerical models and tools to integrate more complexity and coupling between processes. The combined progress of those projects at a pan-European level definitively improves the understanding of and the capabilities for assessing the long-term evolution of engineered barrier systems

Temperature effect on the Portland cement/argillite interface – Main results gained from the CEMTEX project

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CONCRETE AGING IN CONTAINMENT BUILDING AND DEEP GEOLOGICAL DISPOSAL FACILITIES: THE ODOBA PROJEC

International audienceConcrete is widely used in nuclear facilities (Nuclear Power Plants, Deep Geological Repository) andparticipate to ensure their safety. Aging may deeply impact the mechanical and containment properties ofstructures made ofeither concrete orreinforced concrete. Present knowledge regarding concrete pathologiesis mainly based upon small-scale and separate effect experiments at laboratory level. Within this context,IRSN started the ODOBA international program. Its main objective is to improve the understanding ofphenomena related to aging, to assess and qualify Non Destructive Examination and to develop and validatenumerical models to predict pathologies evolutions at structural scale. ODOBA experimentation is mainlyperformed in Cadarache (South-East of France) on the ODE platform and consists oflarge-scale concretespecimenspecimen, highly instrumented. As today, 17 specimens representing containment building issue,were cast. DEF, ASR and coupled ASR/DEF are studied. The majority ofthe specimens will be submittedto accelerated aging by immersion in heated water pool. Some specimenspecimens are reinforced with steel rebars. First deformations are foreseen at the beginning of 2020. Today, ODOBA partners include USNRC, CNSC (Canada), Bel V (Belgium), VTT (Finland) and NRA (Japan). NSC (China) should soon sign the ODOBA agreements

CONCRETE AGING IN CONTAINMENT BUILDING AND DEEP GEOLOGICAL DISPOSAL FACILITIES: THE ODOBA PROJEC

International audienceConcrete is widely used in nuclear facilities (Nuclear Power Plants, Deep Geological Repository) andparticipate to ensure their safety. Aging may deeply impact the mechanical and containment properties ofstructures made ofeither concrete orreinforced concrete. Present knowledge regarding concrete pathologiesis mainly based upon small-scale and separate effect experiments at laboratory level. Within this context,IRSN started the ODOBA international program. Its main objective is to improve the understanding ofphenomena related to aging, to assess and qualify Non Destructive Examination and to develop and validatenumerical models to predict pathologies evolutions at structural scale. ODOBA experimentation is mainlyperformed in Cadarache (South-East of France) on the ODE platform and consists oflarge-scale concretespecimenspecimen, highly instrumented. As today, 17 specimens representing containment building issue,were cast. DEF, ASR and coupled ASR/DEF are studied. The majority ofthe specimens will be submittedto accelerated aging by immersion in heated water pool. Some specimenspecimens are reinforced with steel rebars. First deformations are foreseen at the beginning of 2020. Today, ODOBA partners include USNRC, CNSC (Canada), Bel V (Belgium), VTT (Finland) and NRA (Japan). NSC (China) should soon sign the ODOBA agreements

MODELLING OF THE LONG TERM EVOLUTION AND PERFORMANCE OF ENGINEERED BARRIER SYSTEM

International audienceComponents of a so-called “multiple-barrier system” between the waste matrix and the biosphere include a combination of waste containers (e.g. metal canisters, concrete), engineered barriers such as bentonite or cementitious materials and natural barriers such as salt formation, clayey, volcanic or granitic rocks. The engineered Barrier System (EBS) is a crucial component for containment and isolation in a radioactive waste disposal system. The number, types and assigned safety functions of the various engineered barriers depend on the chosen repository concept, the waste form, the radionuclides inventory in the waste, the selected host rock, the hydrogeological and geochemical settings of the repository site among others. EBS properties will evolve with time in response to the thermo, hydro, mechanical, radiological and chemical gradients and interactions between the various constituents of the barriers and the host rock. Therefore, assessing how these properties evolve over long time frames is highly relevant for evaluating the performance of a repository design and safety function evaluations in a safety case. For this purpose, mechanistic numerical models are increasingly used. Such models provides an excellent way for integrating in a coherent framework scientific understanding of coupled processes and their consequences on different properties of the materials in the engineered barrier system. Their development and validation are supported by R&D actions at European level. For example, the aim of the HORIZON 2020 project BEACON (Bentonite mechanical evolution) is to develop, test and validate numerical models against experimental results in order to predict the evolution of the hydromechanical properties of bentonite during the saturation process. Also in relation to the coupling with mechanics, WP16 MAGIC (chemo Mechanical AGIng of Cementitious materials) of the EURAD Joint Programming Initiative focuses on multi-scale chemo-mechanical modelling of cementitious-based materials that evolve under chemical perturbation (including bacterial impact). Integration of chemical evolution in models of varying complexity (from complex description to its abstraction) is a major issue tackled in the WP2 ACED (Assessment of Chemical Evolution of ILW and HLW Disposal cells) of EURAD. WP4 DONUT (Development and improvement of numerical methods and tools for modelling coupled processes) of EURAD aims at developing and improving numerical models and tools to integrate more complexity and coupling between processes. The combined progress of those projects at a pan-European level will definitively improve our understanding of and our capabilities for assessing the long-term evolution of engineered barrier systems and will encourage collaboration between scientific communitie

Etude multi-échelle de l'influence de la précipitation de M-S-H sur le comportement chemo-mécanique de matériaux cimentaires

International audienceL’Agence nationale pour la gestion des déchets radioactifs (ANDRA) s’est vue confier la responsabilité, au travers du projet Cigéo, de concevoir un stockage en couche géologique profonde de déchets radioactifs. L’IRSN est en charge d’évaluer la sûreté du projet. L’un des axes d’expertise de ce dossier concerne le système de fermeture des galeries. Celui-ci est composé d’un noyau de bentonite bloqué entre deux massifs d’appui en béton bas-pH. De précédentes études ont montré un potentiel enrichissement de lamatrice cimentaire en magnésium dû au contact avec l’eau porale des roches hôtes. Les analyses précédemment menées ont montré la formation de brucite et de silicate de magnésium hydraté (M-S-H) dans le matériau cimentaire. Les mêmes phénomènes (précipitation de M-S-H et de brucite) ont été observés au niveau de barrages et de structures marines au contact d’eaux plus ou moins riches en magnésium. L’objectif de la thèse est d’étudier l’influence de la précipitation des M-S-H sur le comportement chemo mécanique des matériaux cimentaires. Pour cela, une caractérisation chimique des matériaux sera réalisée pour comprendre les mécanismes de précipitation des M-S-H, couplée à une caractérisation mécanique permettant d’appréhender l’impact de l’enrichissement en magnésium sur les changements structuraux et sur les propriétés mécaniques au sein de la matrice cimentaire. L’étude multi-échelle se concentrera dans un premier temps sur des matériaux modèles puis s’étendra aux matériaux industriels au fur-et-à-mesure de l’acquisition de connaissances. Les matériaux modèles envisagés sont des pâtes de M-S-H synthétiques et des pâtes de C-S-H synthétiques. Les pâtes de M-S-H serviront à la caractérisation de l’hydrate seul tandis que les pâtes de C S-H seront immergées dans du MgCl2 pour permettre d’étudier l’ensemble de la zone enrichie en magnésium. Les résultats obtenus permettront d’enrichir les modèles numériques existants qui seront également utilisés pendant la thèse (Hytec notamment)

Modelling of temperature impacts on cement paste in clayey environment constrained by field experiments

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Tournemire argillite/carbon steel evolution under bacterial influence after 10 years of in situ interaction

International audienceThe purpose of the present study was to characterise the physicochemical evolution of argillite/carbon steel coupons after 10 years of interaction inside the Tournemire Underground Research Laboratory (France). Carbon steel coupons were introduced in boreholes drilled in the geological formation in contact with the argillite, and were overcored 10 years later to study the interfaces. The iron release by steel corrosion induced mineralogical dissolutions (Ca phases) and precipitations (iron oxides and hydroxides), leading to a partial clogging of the argillite porosity. A sulphur enrichment was observed in the corrosion area, linked to a potential microbial activity. The biodiversities differed depending on the steel type, indicating the influence of iron-clay interactions. This analysis has shown the presence of bacteria known for their involvement in corrosion processes and isolates able to develop at elevated temperatures. © 2014 Institute of Materials, Minerals and Mining

Modelling of the evolving contributions of gas transport, cracks and chemical kinetics during atmospheric carbonation of hydrated C3S and C-S-H pastes

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