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Chatenay - Malabry, France

Shen W.Q.,Lille University of Science and Technology | Shao J.F.,Lille University of Science and Technology | Kondo D.,University Pierre and Marie Curie | Gatmiri B.,Andra Inc
International Journal of Plasticity | Year: 2012

This paper is devoted to mesomechanical modeling of plastic deformation in a clayey rock. The material contains linear-elastic mineral grains embedded in a porous clay matrix at mesoscale. The clay matrix itself is composed of a solid phase containing spherical micropores. A two-step homogenization procedure, from micro to meso and from meso to macro, is proposed to estimate the macroscopic elastoplastic behavior of the clayey rock. The meso-macro upscaling is performed considering the incremental approach initially proposed by Hill (1965) which allows to account for the effects of mineral inclusions. For the micro-meso transition, the pressure sensitive behavior of the solid phase of clay matrix is described using a Drucker-Prager yield criterion and an associate flow rule. The effects associated with the presence of micropores are taken into account using a limit analysis-based homogenization approach. It is shown that, although the macroscopic model based on an associated plastic solid phase correctly predicts the non linear response and failure stress of the clayey rock under conventional triaxial compression tests, it fails to quantitatively reproduce volumetric deformation. By considering a non-associated flow rule for the solid phase, the agreement with experimental data is significantly improved. Comparisons between the numerical results and experimental data show that the proposed micro-macro model is able to capture the main features of mechanical behavior of heterogeneous clayey rocks. © 2012 Elsevier Ltd. All rights reserved. Source

Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: Fission-2009-1.1.2 | Award Amount: 1.55M | Year: 2010

The overall objective of CatClay is to provide a scientifically well grounded answer to the following question: Can the migration of actinides and other strongly sorbing radionuclides in clayrock be predicted by coupling models of (i) their sorption equilibria on representative clay minerals and (ii) the diffusion-driven mass transport of radionuclide sorbed and dissolved species in compacted masses of these clay minerals? The answer is of prime importance for Safety Cases for clayrock formation-based radioactive waste disposal concepts. The project takes as its starting point experimental observations showing that certain cations known to form highly stable surface complexes with sites on mineral surfaces, migrated more deeply into clayrock than expected. This suggests that current models may not be correct for these cations. CatClay calls upon a number of innovative approaches. It provides i) high resolution experimental methods leading to high quality, low analytical uncertainty data sets, ii) innovative conceptual, and corresponding numerical, models in order to represent the coupled diffusion-sorption behavior of surface complexing radionuclide. CatClay is structured along 3 RTD workpackages, combining modeling and experimental studies from the simpler, analogous system (clay) to real materials (clayrocks). The sorption-diffusion behavior of 3 cations will be studied selected according to their known differences in sorption reactions with clay mineral surfaces. CatClay combines the forces of 5 research institutions having proven expertise in experimentally studying and modelling the above described processes; the developer of a widely used coupled transport code; one waste management organisation for the application to safety case. The transfer of knowledge to a broader community, scientists and end-users, is also done through publication in peer reviewed journals and publically-available reports.

Agency: Cordis | Branch: FP7 | Program: CP | Phase: Fission-2012-1.1.1 | Award Amount: 15.74M | Year: 2012

DOPAS aims to improve the adequacy and consistency regarding industrial feasibility of plugs and seals, the measurement of their characteristics, the control of their behavior over time in repository conditions and also their hydraulic performance acceptable with respect to the safety objectives. This DOPAS project addresses the design basis, reference designs and strategies to demonstrate the compliance of the reference designs to the design basis, for plugs and seals in geological disposal facilities. The project focuses on shaft seals for salt rock (German repository concept), tunnel plugs for clay rock (French and Swiss repository concepts), and tunnel plugs for crystalline rock (Czech, Finnish and Swedish repository concepts). Five different demonstration experiments are part of the project and will take place in Sweden, France, Finland, Czech Republic and Germany. They are in different state-of-development. The Swedish demonstrator will be constructed prior to start of the DOPAS project and will basically provide experience on demonstration of compliance of reference design to the design basis. German demonstrator will be installed after the DOPAS project and will focus on demonstration of suitability by performance assessment. The French, Finnish, Swedish,German and the Czech experiments will address developments in all phases of design basis, reference designs and strategies to demonstrate compliance of reference designs to design basis. The studied concepts will be developed in the DOPASs five thematic scientific/technological work packages, which each integrate the results of the individual experiments. The DOPAS project is derived from the IGD-TPs Strategic Research Agenda that points out the topic of plug and seals as a first priority issue for joint European RTD projects.

Agency: Cordis | Branch: FP7 | Program: CSA-SA | Phase: Fission-2012-1.1.2 | Award Amount: 1.42M | Year: 2013

The Implementing Geological Disposal of Radioactive Waste Technology Platform (IGD-TP) was established in 2009. This project through a Secretariat, aims at further deepening integration and coordination of the activities of the IGD-TP participants. This project includes activities involving all committed participants (80) and beyond all interested entities through Exchange Forums. The proposed Work Packages have been set up in order to: Provide an efficient management of the IGD-TP and its operation so that the mission and objectives are achieved and the benefits from the work are widely spread, Network, structure and develop Research, Development and (RD&D) programmes and competences in countries with less advanced geological disposal programmes. Public events will be organized to foster the RD&D activities in countries with less advanced programmes are proposed, Contribute to fulfilling the requirements, including advice and expertise, laid down in the new EU Directive on the management of radioactive waste, and Develop, implement and coordinate education and training activities in geological disposal in Europe within the Terms of Reference set for the IGD-TPs Competence Maintenance, Education and Training Working Group. For the period 2013-2015 the main objective of the IGD-TP is to deploy the Joint Activities identified in the Deployment Plan (DP) with the support of the Secretariat according to the timeframes set in the Vision Document, the Strategic Research Agenda 2011 (SRA) and in the Deployment Plan (DP). IGD-TP and its Secretariat do have a programmatic role which goes far beyond FP7 projects and encompasses the coordination of RD&D activities related to geological disposal from 11 Member States (and Switzerland). The Secretariat will promote the scientific and technical quality of the Research, Development and Demonstration (RD&D) by fostering interactions between national programmes. In this dissemination function, it maintains a website where e.g. progress reports and announcements for future events are published.

Agency: Cordis | Branch: H2020 | Program: RIA | Phase: NFRP-06-2014 | Award Amount: 5.95M | Year: 2015

The HORIZON 2020 EURATOM Collaborative Project Cement-based materials, properties, evolution, barrier functions (Cebama) is developed with the overall objective to support implementation of geological disposal of nuclear waste by improving the knowledge base for the Safety Case. Cement-based materials are highly relevant in this context, being used as waste forms, liners and structural components or sealing materials in different types of host rocks and disposal concepts. Specific objectives of Cebama are (i) experimental studies of interface processes between cement based materials and host rocks or bentonite, and assessing the specific impact on transport properties, (ii) quantifying radionuclide retention under high pH cement conditions, and (iii) developing comprehensive modeling approaches. Modeling will support interpretation of results and prediction of the long-term evolution of key transport characteristics such as porosity, permeability and diffusion parameters especially in the interface between cement based materials and the engineered and natural barriers. Further objectives cover dissemination of results to scientific and non-scientific stakeholders as well as training and education of young professionals for carrying over the expertise into future implementation programms. To a large extent, the experimental and modelling work will be part of PhD theses, aiming at high scientific-technical impact and quality with respect to peer-reviewed publications. The 4 years project is implemented by a consortium of 27 partners consisting of large Research Institutions, Universities, one TSO and one SME from 9 EURATOM Signatory States, Switzerland and Japan. National Waste Management Organizations support Cebama by co-developing the work plan, participation in the End-User Group, granting co-funding to some beneficiaries, and providing for knowledge and information transfer.

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