agence nationale pour la gestion des dÉchets radioactifs © andra b. cochepin direction...

AGENCE NATIONALE POUR LA GESTION DES DÉCHETS RADIOACTIFS© Andra

B. Cochepin

Direction Scientifique – Evaluation et Analyse de Performances

Results and new challenges in reactive transport simulations

Journées Scientifiques du GNR MoMaS 23-25

Novembre 2009

DS/EAP/09-0081

AGENCE NATIONALE POUR LA GESTION DES DÉCHETS RADIOACTIFS© Andra© Andra

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

Journées Scientifiques du GDR MoMaS 23-25 Novembre 2009

DS/EAP/09-0081


Chemical transport simulations at Andra: schedule

Objectives DAC 2014

2007-20091st iteration of a chemical simulations for phenomenological behavior (PARS): conceptualization of problems and feasibility study (tools, model…) identifications of development of toolsUse of reactive transport tolls for PA: to reduce conservatism, to define and quantify simplifications

2010-2012Reference run of chemical simulations for PARS (convergence with data acquisition programs)PA simulations dedicated to chemical processes

Retention Degradation RN Source term

2013-2014Complementary studies in support to safety analysis and safety calculations for DAC


DS/EAP/09-0081


Chemical transport simulations at Andra: a local description of complex processes

Role of chemical transport simulations for AndraTo 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


Chemical transport simulations at Andra: Main processes

Concrete degradation / alkaline plumeSafety operating

Durability

HLW Iron corrosion

Glass degradation

Specific ILLWBituminized waste

ILLW/HLWRN integration


DS/EAP/09-0081


Chemical transport simulations at Andra: Calculation specific features

Interfacial problemsShort distances

A question of number of unknowns with highly non-linear equations

Over a long periodNot a matter of mesh with millions of elements

Performance of algorithms


DS/EAP/09-0081


Chemical transport simulations at Andra: numerical tools

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 calculationsDrawbacks: kinetic treatment

Toughreact (LBNL)Advantages: unsaturated chemical transport simulations Drawbacks: coupling, numerical convergence


DS/EAP/09-0081

Feedback from ANDRA, CEA and BRGM


New challenges: alkaline plume (Phreeqc)

Concrete-clay interactions

~7000 cells, 30 minerals, 100 000 years 40 CPU days

Progress axesFeedback on porosity, parallelization, solving methods (C. de Dieuleveult thesis)


DS/EAP/09-0081

t = 0 t = 105 years


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



Chemistry of carbonationNear 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...


DS/EAP/09-0081

0,00

0,04

0,08

0,12

0,16

0 0,01 0,02 0,03 0,04 0,05 0,06Distance (m)

Calcite - 5 y

Portlandite - 5 y

Calcite - 20 y

Portlandite - 20 y

fraction vol.

COLIS_1

0,00

0,04

0,08

0,12

0 0,01 0,02 0,03 0,04 0,05 0,06Distance (m)

CSH 1.6

Si02 amorphe

CSH 1.2

CSH 0.8

Straetlingite

fraction vol.

COLIS_1 20 y

Trotignon et al. 2009 (CEA)



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 axesSolving 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


New challenges: organic matter/ bituminized waste

Conceptual problems concerning the source termFlux control (need to be representative), degradation kinetics

A complex chemistryhigh concentrations, redox, microbial activity

Progress axesEfficiency of algorithms concerning the kinetically controlled chemistry


DS/EAP/09-0081


New challenges: corrosion (glass, steel)

GlassPhenomenological models still need to be adjusted with experimental evidences

How to represent a non crystallized material (gel)? Solid solution?

SteelNon porous medium

Progressive consumption/expanding secondary products

H2 production (gas bubbles?)

Progress axesUnsaturated simulations

Kinetics of processes


DS/EAP/09-0081


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 axesMechanic feedback on transport properties (cracking)

Adapting mesh

Efficiency of dedicated solving methods


DS/EAP/09-0081


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 dimensioningExample : Influence of organic matter on radionuclide migration


DS/EAP/09-0081


Conclusion and prospects

Advances since 2005Enhanced 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 comeMore efficient solving method/coupling algorithms

New coupling (adding of unsaturated conditions/mechanics)

High performance (parallelization, optimization,…)


DS/EAP/09-0081

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