CHALLENGES FOR REACTIVE TRANSPORT MODELING … · CHALLENGES FOR REACTIVE TRANSPORT MODELING IN THE...

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

Modeling

glass & steel

corrosion

in claystones

DRD/EAP/11-0219

• 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?


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


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


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


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

Redox control

in claystones

DRD/EAP/11-0219

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


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


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


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?


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


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!

RESULTS IN THE BASE CASE (3)

9 mars 2017 | PAGE 24

in the glass

zone

RESULTS IN THE BASE CASE (4)

9 mars 2017 | PAGE 25

in the clay

zone

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