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Results and new challenges in reactive transport simulations

Results and new challenges in reactive transport simulations. B. Cochepin Direction Scientifique – Evaluation et Analyse de Performances. Presentation outline. Main Andra’s goal: License Application (DAC) for HLW/ILLW repository in 2014 Reactive transport simulations at Andra

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Results and new challenges in reactive transport simulations

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  1. Results and new challenges in reactive transport simulations B. Cochepin Direction Scientifique – Evaluation et Analyse de Performances DS/EAP/09-0081

  2. Presentation outline • Main Andra’s goal: License Application (DAC) for HLW/ILLW repository in 2014 • Reactive transport simulations at Andra • Current limitations and progress axes DS/EAP/09-0081

  3. Chemical transport simulations at Andra: schedule • Objectives DAC 2014 • 2007-2009 • 1st iteration of a chemical simulations for phenomenological behavior (PARS): conceptualization of problems and feasibility study (tools, model…) identifications of development of tools • Use of reactive transport tolls for PA: to reduce conservatism, to define and quantify simplifications • 2010-2012 • Reference run of chemical simulations for PARS (convergence with data acquisition programs) • PA simulations dedicated to chemical processes • Retention • Degradation • RN Source term • 2013-2014 • Complementary studies in support to safety analysis and safety calculations for DAC DS/EAP/09-0081

  4. Chemical transport simulations at Andra: a local description of complex processes • Role of chemical transport simulations for Andra • To acquire a detailed description of interfacial chemical processes of the repository and its surrounding geological media over 1 million years: Phenomenological simulations • To participate to waste conditioning and design concept • To contribute to performance assessment: Preliminary simulations DS/EAP/09-0081

  5. Chemical transport simulations at Andra: Main processes • Concrete degradation / alkaline plume • Safety operating • Durability • HLW • Iron corrosion • Glass degradation • Specific ILLW • Bituminized waste • ILLW/HLW • RN integration DS/EAP/09-0081

  6. Chemical transport simulations at Andra: Calculation specific features • Interfacial problems • Short distances • A question of number of unknowns with highly non-linear equations • Over a long period • Not a matter of mesh with millions of elements • Performance of algorithms DS/EAP/09-0081

  7. Chemical transport simulations at Andra: numericaltools Feedback from ANDRA, CEA and BRGM • Phreeqc (USGS) • Advantages: robustness, flexibility in kinetic law definition, chemical processes (ion exchange, solid solution, high ionic strength…) • Drawbacks: problems with many kinetically defined minerals, 1D transport (may be adjusted), porosity feedback • Crunch (LBNL) • Advantages: specifically made for minerals defined with kinetic laws, various solving methods (OS3D, GIMRT) • Drawbacks: absence of equilibrium chemistry and high ionic strength treatment • Hytec (Ecole des Mines) • Advantages: multi-D, robustness of thermodynamic calculations • Drawbacks: kinetic treatment • Toughreact (LBNL) • Advantages: unsaturated chemical transport simulations • Drawbacks: coupling, numerical convergence DS/EAP/09-0081

  8. New challenges: alkaline plume (Phreeqc) • Concrete-clay interactions • ~7000 cells, 30 minerals, 100 000 years  40 CPU days • Progress axes • Feedback on porosity, parallelization, solving methods (C. de Dieuleveult thesis) t = 0 t = 105 years DS/EAP/09-0081

  9. New challenges: carbonation 1/3 • Diphasic simulations – Toughreact • Drying physics • Assessed phenomena: • Gas phase diffusion of vapor • Gas phase flow of vapor (under pressure gradient) • Capillary flow of water • Thermodynamic equilibrium liquid water/vapor • Gas diffusion in liquid phase • Influence of the temperature DS/EAP/09-0081

  10. New challenges: carbonation 2/3 • Chemistry of carbonation • Near 40 mineral phases kinetically controlled, temperature • Need new expressions of kinetic laws /approximations due to the unsaturated conditions Mineral reactivity depending on saturation state, CO2 instantaneous solubilization, influence of the water released from carbonation processes on hydraulics, precipitation of other minerals... Trotignon et al. 2009 (CEA) DS/EAP/09-0081

  11. New challenges: carbonation 3/3 • Simulation performances • ~100 cells (concrete/argillites, water/air/CO2), 1 processor: 100 years simulated in 6 months CPU (time step limited by gas diffusion) • Coupling algorithm SNIA /SIA • Progress axes • Solving method/numerical coupling more efficient • Chemistry feedback on transport (porosity, hydraulics,…) • Evolution of material texture (passivating precipitation, saturation control of kinetic laws…) • … DS/EAP/09-0081

  12. New challenges: organic matter/ bituminized waste Conceptual problems concerning the source term • Flux control (need to be representative), degradation kinetics A complex chemistry • high concentrations, redox, microbial activity • Progress axes • Efficiency of algorithms concerning the kinetically controlled chemistry DS/EAP/09-0081

  13. New challenges: corrosion (glass, steel) Glass • Phenomenological models still need to be adjusted with experimental evidences • How to represent a non crystallized material (gel)? Solid solution? Steel • Non porous medium • Progressive consumption/expanding secondary products • H2 production (gas bubbles?) • Progress axes • Unsaturated simulations • Kinetics of processes DS/EAP/09-0081

  14. New challenges: chemical-transport-mechanics coupling 3 applications: • Degradation of argillaceous materials  swelling properties of chemically degraded clays • Degradation of cementitious materials/steel corrosion  mechanic behaviour of waste disposal components • Carbonation shrinkage, cracking  mechanic behaviour of waste disposal components (B. Bary, CEA) Preliminary studies Chemical transport simulations supplies mechanic simulations: • Mineral dissolution/precipitation  volume variation, deformation (LMS) • Progress axes • Mechanic feedback on transport properties (cracking) • Adapting mesh • Efficiency of dedicated solving methods DS/EAP/09-0081

  15. Chemical transport simulations at Andra: performance assessment • “PRELIMINARY” Simulations • Assessment of error impacts made by phenomenon simplification in performance calculations • PAMINA European project: comparison of Cs transfer represented either by Kd/SL or thermodynamic models • Calculation helping to radioactive waste package dimensioning • Example : Influence of organic matter on radionuclide migration DS/EAP/09-0081

  16. Conclusion and prospects • Advances since 2005 • Enhanced capacity to take into account integrated and complex geochemical systems • Alimented by experimental programs which provides up to date conceptual models • A huge step is about to be made with unsaturated chemical transport simulations • Confidence in safety calculations is increased by “preparatory” simulations • Still to come • More efficient solving method/coupling algorithms • New coupling (adding of unsaturated conditions/mechanics) • High performance (parallelization, optimization,…) DS/EAP/09-0081

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