MODELING REACTIVE TRANSPORT IN NUCLEAR WASTE GEOLOGICAL DISPOSAL: 2 benchmark problems : - Glass/iron/clay interactions - Atmospheric Carbonation of concrete SES BENCH – OCT NOV O. Bildstein, P. Thouvenot, J.E. Lartigue, I. Pointeau CEA (French Alternative Energies and Atomic Energy Commission) B. Cochepin, I. Munier ANDRA (French Radioactive Waste Management Agency) 11 novembre 2015 | PAGE 1 CEA | 10 AVRIL 2012

DISPOSAL CONCEPT IN A CLAYSTONE FORMATION AT 500 m DEPTH Current design of deep underground repository for high and intermediate level long-lived waste S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 2

Just a few words about the glass/iron/clay benchmark… S.S.BENCH - November DRD/EAP/

HLW DISPOSAL CELL 11 novembre th Andra International Conference - Montpellier | 22 Oct 2012 | PAGE 4 different types of material in physical contact, technological gaps  long term calculations of geochemical evolution ( years) Vitrified waste packages Cross section 3 cm gap steel liner disposal package 0.8 cm gap 3 cm gap scale

1D radial domain transport: diffusion only water saturated, constant porosity glass Φ = 0.42 m, H = 1 m porosity = 0.12 metallic components total thickness = 0,095 m, porosity = 0.25 connected fractured zone 0.4 * excavation diameter = m porosity = 0.20; D eff (25°C) = m 2 /s undisturbed claystone (50 m) porosity = 0.18; D eff (25°C) = 2, m 2 /s GEOMETRY AND TRANSPORT PROPERTIES 5 th Andra International Conference - Montpellier | 22 Oct 2012 | PAGE 5 - reactive-transport codes: Crunch/Hytec Isothermal conditions - H 2 (g) produced from anoxic corrosion p(H 2 )max = 60 bar

RESULTS IN THE BASE CASE (2) 11 novembre th Andra International Conference - Montpellier | 22 Oct 2012 | PAGE 6 Corrosion products (volume%, yrs, end of corrosion) magnetite, Ca-siderite, and greenalite dominate (oxide) (carbonte) (silicate) also smaller amounts of aluminosilicates (nontronites and saponites) no significant changes after corrosion phase POROSITY CLOGGING modeling vs. experimental results (Schlegel at al. 2007) iron/claystone at 90°C for 1 year small amount of magnetite siderite(-Ca), Fe-silicates  more phenomenological model for corrosion Canister zone 0,1 µm

Now to the concrete carbonation benchmark… S.S.BENCH - November DRD/EAP/

DESIGN: ILLW CELLS, SHAFTS (AND SEALS), ILLW DISPOSAL OVERPACK Atmospheric carbonation of overpack during the operating period S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 8 Bitumized waste Compacted metallic waste Organic waste

CARBONATION ISSUE FOR RADWASTE DISPOSAL S.S.BENCH - November Overpack carbonation pH decrease Corrosion increase Overpack cracking What about reversibility ? SeS BENCH – Taipei, Taiwan | NOV | PAGE 9 Ventilation (100 years)

DRYING AND CARBONATION PROCESSES OF ILLW OVERPACK S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 10

MODELING ISSUES S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 11 CO2 gas diffusion and reactivity

MODELING ISSUES S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 12 benchmark emphasizes the coupling aspects CO2 gas diffusion and reactivity

GEOMETRY 1D Cartesian – 5.5 cm divided in 11 x 5 mm cells Boundary conditions (EOS 4) S.S.BENCH - November Concrete Symmetry axis Dry air Wall package 110 mm SeS BENCH – Taipei, Taiwan | NOV | PAGE 13

CASE 1 DRYING OF CONCRETE OVERPACK S.S.BENCH - November DRD/EAP/

DRYING PHENOMENON (TOUGHREACT EOS4) Flow law: Generalized Darcy law Lowering of the dew point due to capillary effects (Kelvin equation in EOS 4) Water relative permeability (Van Genuchten) Gas relative permeability (Corey) Klinkenberg effect (gas flow at low pressure) S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 15

DRYING PHENOMENON (TOUGHREACT) Air and water gases diffusion CO2 and other gases Aqueous diffusion Effective diffusion Tortuosity S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 16

DRYING PHENOMENON (TOUGHREACT) Air and water gases diffusion CO2 and other gases Aqueous diffusion Effective diffusion Tortuosity S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 17

DRYING PHENOMENON : PARAMETERS IN REFERENCE CASE BHP CEM I S.S.BENCH - November ROCK1 Density (kg/m 3 )2700 Porosity0.12 Intrinsic permeability to liquid (m ² ) 1e-19 Intrinsic permeability to gas (m ² ) 1e-17 Relative permeability m – Slr – Sls - Sgr – 0.0 – 1.0 – 0.0 Capillarity pressure m – P 0 (MPa) – Pmax (MPa) – Molecular diffusion coefficient in gaseous phase (m ² /s) 2.4e-5 Molecular diffusion coefficient in aqueous phase (m ² /s) 1.9e-9 Millington-Quirk a parameter2 Millington-Quirk b parameter4.2 Klinkenberg parameter (MPa)0.45 SeS BENCH – Taipei, Taiwan | NOV | PAGE 18

RESULTS S.S.BENCH - November Drying results SeS BENCH – Taipei, Taiwan | NOV | PAGE 19

RESULTS with RICHARDS’ EQUATION S.S.BENCH - November Drying results SeS BENCH – Taipei, Taiwan | NOV | PAGE 20  OK to use Richards’ equation for benchmarking exercise

CASE 2 CARBONATION WITH CONSTANT SATURATION S.S.BENCH - November DRD/EAP/

PHENOMENOLOGY Constant saturation but unsaturated + diffusion of gas S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 22

CHEMICAL PARAMETERS Primary phases Secondary phases Kinetics of dissolution / precipitation Phase Volume % Calcite72.12 Portlandite5.73 CSH Monocarboaluminate2.26 Ettringite3.60 Hydrotalcite0.39 Hydrogarnet-Fe (C3FH6)2.05 Phase typePhases OxidesMagnetite, Amorphous silica HydroxidesBrucite, Gibbsite, Fe(OH) 3 Sheet silicatesSepiolite Other silicatesCSH 1.2, CSH 0.8, Straetlingite, Katoite_Si Sulfates, chlorides, other saltsGypsum, Anhydrite, Burkeite, Syngenite, Glaserite, Arcanite, Glauberite, Polyhalite CarbonatesCalcite, Nahcolite OtherHydrotalcite-CO 3, Ettringite, Dawsonite

CHEMICAL PARAMETERS Primary and Secondary phases characteristics SeS BENCH – Taipei, Taiwan | NOV | PAGE 24

CASE 3 FULLY COUPLED CARBONATION S.S.BENCH - November DRD/EAP/

Input parameters Combination of parameters from the 2 previous cases: Flow and transport from case 1 Chemical reactions from case 2 Maximum time step: 20 s (limitation due to reactive diffusion of CO 2 ) Coupling limitations No dependence of reactivity with the saturation state No shielding effect (potential decrease of portlandite reactivity with calcite precipitation)

CARBONATION RESULTS pH decrease, portlandite dissolution and calcite formation over a thickness of about 2 cm after 100 years

CARBONATION RESULTS Dissolution of CSH 1.6, ettringite, monocarboaluminate and hydrotalcite on 2 cm after 100 years Precipitation of CSH 1.2, CSH 0.8, straetlingite, amorphous silica and gypsum on the same thickness Precipitation of small amounts of sepiolite, gibbsite and katoïte-Si is also predicted

CARBONATION: CPU CONCERNS… CO2 diffusion (gas phase) and reactivity are very fast! No SIA  small time steps  CPU times go up!

POSSIBLE EXTENSION: SATURATION DEPENDENT REACTIVITY Considerable reduction in the amplitude of carbonation (less dissolution of portlandite and CSH 1.6 and less precipitation of amorphous silica and other secondary CSH) Lower reactivity accompanied by a greater penetration of carbonation front due to lower consumption of CO 2 at the surface Effect of water content on reactivity (Bazant type function)

CONCLUSIONS Drying process of 11 cm thick waste packages depends strongly on the concrete nature and slightly on the flow model (Richards or full multiphase) Considering full multiphase model, carbonated depth is about 2 cm after 100 years for the Intermediate Performance Concrete.  degraded thickness is totally carbonated (total dissolution of primary mineral phases) If we consider a chemical reactivity depending on the liquid saturation (Bazant type function), a considerable reduction in the amplitude of carbonation and a greater penetration of carbonation front are observed. Progress areas include: taking into consideration a protective effect of secondary minerals improving knowledge on kinetics parameters and thermodynamic data, especially for CSH with low Ca/Si ratio coupling this system with corrosion of rebars

NUMERICAL RESOURCES Carbonation during the operation period TOUGHREACT EOS 4 Few numerical implementations CEA/ANDRA Thermodynamic database S.S.BENCH - November SeS BENCH – Taipei, Taiwan | NOV | PAGE 32 And now: - EOS9 - Crunchflow - Hytec - … more?

Direction de l’Energie Nucléaire Département des Technologies Nucléaires Service de Modélisation des Transferts et de Mesures Nucléaires Commissariat à l’énergie atomique et aux énergies alternatives Centre de Cadarache | Saint Paul-lez-Durance T. +33 (0) | F. +33 (0) Etablissement public à caractère industriel et commercial | RCS Paris B novembre 2015 | PAGE 33 CEA | 10 AVRIL 2012 Acknowlegement Toughreact development team (LBNL) C. Steefel ( LBNL, Crunchflow) Hytec developement team (Mines Paristech, PGT consortium) for technical support on codes THANK YOU FOR YOUR ATTENTION