challenges for reactive transport modeling … · challenges for reactive transport modeling in the...
TRANSCRIPT
CHALLENGES FOR REACTIVE TRANSPORT
MODELING IN THE CONTEXT OF DEEP
GEOLOGICAL STORAGE
PREDICTIVE GEOSCIENCES FOR GEORESOURCES
EXPLORATION/MANAGEMENT AND ENVIRONMENTAL ISSUES
BRGM/ISTO - ORLÉANS - OCTOBER 24-25, 2016
O. Bildstein CEA (French Alternative Energies and Atomic Energy Commission)
| PAGE 1 CEA | 10 AVRIL 2012
DISPOSAL CONCEPT IN CLAYSTONES FORMATION
Current design of deep underground repository for
high and intermediate level long-lived waste
| PAGE 2
HLW disposal
ILW disposal
U/G facilities
Surface Facilities
Preliminary design
Glass-iron-
clay
interactions
Redox
control in
claystones
~ 100 m
COx claystones
500 m
Predictive Geosciences – Orléans | Oct. 2016
HLW DISPOSAL CELL
9 mars 2017
• different types of material in physical contact,
technological gaps, large amount of iron (~1 ton
/linear meter of cell)
long term calculations of geochemical
evolution (100 000 years)
Vitrified waste
packages
Cross section
3 cm gap steel liner
disposal
package
0.8 cm gap
3 cm gap
scale
| PAGE 3 Predictive Geosciences – Orléans | Oct. 2016
• 1D radial domain
• transport: diffusion only
• water saturated
• H2(g) from anoxic corrosion
pH2(max) = 60 bar
• 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 = 0.268 m
porosity = 0.20; Deff(25°C) = 5.2 10-11 m2/s
• undisturbed claystone (50 m)
porosity = 0.18; Deff(25°C) = 2,6 10-11 m2/s
GEOMETRY AND TRANSPORT PROPERTIES
argilites (50 m – 183 cells)
glass (21cm – 21 cells)
overpack + lining + gaps
(13,8cm – 14 cells)
Alteration rate for glass and iron
Porosity in iron cells
Porosity evolution in altered zones?
| PAGE 5 Predictive Geosciences – Orléans | Oct. 2016
PHYSICOCHEMICAL PROCESSES
| PAGE 6
Iron corrosion for ~45 000 years
Glass alteration in the presence
of corrosion products (and
residual steel?)
magnetite, Ca-siderite, and greenalite dominate
(oxide) (carbonate) (silicate)
also smaller amounts of aluminosilicates
(nontronites and saponites)
POROSITY CLOGGING
modeling vs. experimental results
iron/claystone at 90°C for 1 year
siderite(-Ca), Fe-silicates
small amount of magnetite (corrobated by
archaeological analogues)
canister zone
(Schlegel et al. 2007)
claystone
iron
corrosion
claystones
alteration
0,1 µm
Glinet nails; Neff et al. 2014
STEEL CORROSION “GEOCHEMICAL” REACTION
Corrosion in reactive transport codes
Fe(s) + 2 H2O Fe2+ + H2 + 2 OH-
perturbation in pH and Eh
mineralogical changes
| PAGE 7
base case
claystone
zone iron zone
claystone
zone
iron zone
corrosion rate /10
Predictive Geosciences – Orléans | Oct. 2016
9 mars 2017 | PAGE 8 Predictive Geosciences – Orléans | Oct. 2016
BUT WHAT DO EXPERIMENTAL RESULTS SHOW?
9 mars 2017
ArCorr experiments (C. Bataillon, CEA Saclay)
COx claystone block
Triaxial cell @40 bars
3 « electrodes »
2 interfaces :
- Armco iron/claystone
- (glass/claystone)
100 µm
Experimental observations
2 years at 90°C
data from Schlegel et al. 2014
iron claystone
STEEL CORROSION “GEOCHEMICAL” MODELING
To match the observed mineralogical paragenesis, we have to modify:
- (very low) diffusional properties in the corroded layer
- (high) magnetite precipitation rate
| PAGE 9
claystone
zone iron zone
from Schlegel et al. 2014
iron claystone
… the paragenesis of secondary minerals is not predicted correctly
Predictive Geosciences – Orléans | Oct. 2016
IN SITU STEEL CORROSION RATE
| PAGE 10
« MCO » in situ experiments in Bure (2 years @ 80°C)
Motivited a change of concept : addition of bentonitic cement at the liner extrados
Relative humidity (%)
Co
rro
sio
n r
ate
(µ
m/y
r)
very high corrosion rates
(probably due to transient oxidizing conditions)
COUPLED RTM WITH CORROSION:
ELECTROCHEMICAL REACTIONS
Corrosion: an electrochemical model
redox reactions occurring at the interface
non-equilibrium reactions
involving electrons in the
conduction band
corrosion generates fluxes
of Fe2+, Fe3+, H2, H+, …
| PAGE 11
Diffusion Poisson Coupled Model (DPCM)
from Bataillon et al. Electrochem. Acta 2010
iron solution oxide layer
Predictive Geosciences – Orléans | Oct. 2016
Take surface charge into account?
use fluxes for Fe2+ and Fe3+ and aqueous kinetics?
9 mars 2017 | PAGE 12 Predictive Geosciences – Orléans | Oct. 2016
CALIBRATING PARAMETERS…
BACK TO CORROSION RATE IN THE ARCORR EXPERIMENT
from Schlegel et al. 2014
THE REDOX SYSTEM IN THE HLW DISPOSAL CELL
Vitrified waste packages
Cell cross section
3 cm gap steel liner
disposal
package
0.8 cm gap
3 cm gap
scale
| PAGE 14 Predictive Geosciences – Orléans | Oct. 2016
Claystones: celestite (sulfates)
pyrite, Ca-siderite
goethite if temperature increases
structural Fe(III) micas/chlorite
Steel: Iron
magnetite (Fe3O4)
Production of H2
Glass: elements considered in oxidized for: :
Fe(III), U(VI), Pu(IV), Tc(VII), Np(V),…
potentially sufficient contraints for redox
REDOX REACTIONS IN THE CLAYSTONES
redox reactions in claystones is limited
in tiny ~20 nm connected pores
significant reactivity only at interfaces in repository?
what about redox control in claystones? Especially once the H2 has diffused away?
implication for RN migration? | PAGE 15
• Corrosion production of hydrogen:
Theoritically : pH = 10,5 and Eh = -800mV @ 25°C - 1 bar (close to iron surface)
• Hydrogen reactions:
pyrite pyrrhotite (Truche et al., 2010)
no significant clay structural Fe(III) reduction (Michelin et al., 2012, 2014)
no significant sulfate reduction (without microbes) (Truche et al., 2011)
no U(VI) reduction (Trummer et al. 2008; Riba et al., 2012)
pore size
pore
volu
me
Predictive Geosciences – Orléans | Oct. 2016
pH AND Eh EVOLUTION IN HLLW SIMULATION
-700
-600
-500
-400
-300
-200
-100
0,01 0,1 1 10 100
Eh cas 1_1ka_1ka Eh cas2 1ka Zone Fer
6,00
6,50
7,00
7,50
8,00
8,50
9,00
9,50
10,00
0,01 0,1 1 10 100
pH cas 1_1ka_1ka pH cas2 Zone Fer
-700
-600
-500
-400
-300
-200
-100
0,01 0,1 1 10 100
Eh cas 1_45_5ka Eh cas 2_45_5ka Zone fer
6
6,5
7
7,5
8
8,5
9
9,5
10
10,5
0,01 0,1 1 10 100
pH cas 1_45_5ka pH cas 2_45_5ka Zone fer
6,6
6,8
7
7,2
7,4
7,6
0,01 0,1 1 10 100
pH cas 2_100ka pH cas 1_100ka Zone fer
pH Eh (mV)
-400
-350
-300
-250
-200
-150
0,01 0,1 1 10 100
Eh cas 2_100ka Eh cas 1_100ka Zone fer
glass
claystones
With sulfates/sulfides reaction Without sulfates/sulfides reaction
1 ky
45 ky
100 ky
iron
log distance (m)
Hytec
pH AND pH2 EVOLUTION IN HLLW SIMULATION
| PAGE 17
pH and hydrogen perturbations migrate further
in the absence of sulfate reduction
With sulfates/sulfides reaction Without sulfates/sulfides reaction
pH2
pH
Crunch
MINERALOGY EVOLUTION IN HLLW SIMULATION
| PAGE 18
Hydrogen + S(VI)/S(-II) reactivity in COx :
pyrite pyrrhotite
celestite strontianite
Impact on RN migration if not reacting with H2?
With sulfates/sulfides reaction Without sulfates/sulfides reaction
claystones claystones
Crunch
perturbation 2 m perturbation 0.2 m
HOW TO GO FURTHER WITH REDOX IN
CLAYSTONES?
| PAGE 19
Albrecht, 2013
Difficult to interpret measured
Eh values
Effect of transient redox potential
(H2 fast diffusion away from
cells)
Which redox couples are
actually active?
sulfide / sulfate ?
H2 / H+?
Fe(II) / Fe(III) ?
Potential reducing agents for RN?
Reconstruct a complete non-equilibrium redox system?
(RECOSY program 2008-2012; Altmaier et al. 2011; Duro et al. 2014)
at neutral pH
Conditions in the
claystones:
Eh = -180 mV
Oxydized conditions
CONCLUSIONS
Redox control in claystones still remains a challenging question
RN speciation and migration will depend on active reducing species present at the interfaces/in the claystones = scenario dependent
Coupling of electrochemical corrosion reactions with reactive transport codes
Dedicated experiments to improve understanding and calibrate coupled RTM/corrosion models
| PAGE 20 Predictive Geosciences – Orléans | Oct. 2016
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 | 13108 Saint Paul-lez-Durance
T. +33 (0)4 42 25 37 24 | F. +33 (0)4 42 25 62 72
Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019
| PAGE 21
CEA | 10 AVRIL 2012
THANK YOU FOR YOUR ATTENTION
Acknowledgement:
J.E. Lartigue, P. Thouvenot, C. Bataillon, … CEA (French Alternative Energies and Atomic Energy Commission)
B. Cochepin, I. Munier, B. Madé, D. Crusset, ...
Andra (French Radioactive Waste Management Agency)
F. Foct, X. Crozes, ...
EDF
13 DECEMBRE 2012 | PAGE 22
EXPERIMENTAL CORROSION PARAMETERS
| PAGE 22
• Prescribed corrosion rate
• Thermodynamical and kinetics data, diffusion coefficients at 90°C
• Dissolution kinetics from Palandri & Kharaka, precipitation = kdiss/100 with BET
surfaces area
(Bataillon et al.)
(Brucker et Schlegel)
iron 3 1 2 clayston
es
RESULTS OF RTM
9 mars 2017 | PAGE 23
Evolution of mineral volume fraction as a function of time
in the iron
zone
magnetite
greenalite
Fe-saponite
Magnetite
dominates!