Modeling the DR-A in-situ diffusion experiment (Opalinus Clay):

Ionic strength effects on solute transport

Josep M. Soler (IDAEA-CSIC, Catalonia, Spain)

Carl I. Steefel (LBNL, USA)

Olivier X. Leupin (NAGRA, Switzerland)

Thomas Gimmi (PSI & Univ. Bern, Switzerland)

Mont Terri ProjectDisturbances, diffusion and retention (DR-A)

Nagra, Switzerland

NWMO, Canada

DOE, USA

In-situ diffusion experiments, Mont Terri URL (15 years)

• DI: HTO, I-

• DI-A: HTO, I-, 22Na+, Cs+ DI-B: 2H, I-, 6Li+, 87Rb+

• DI-A2: HTO, I-, Br-, 85Sr2+, Cs+, 60Co2+, Eu3+

• DR: 2H, 18O, 133Ba2+, 60Co2+, 137Cs+, Eu3+, 152Eu3+

HTO, Br-, I-, SeO42-, 22Na+, 85Sr2+, Cs+

injection line

re-circulation line

tracer injection vial

flow meter

Nitrogen

balance

overpressurevalve

manometer

sampling port

detector

data acquisition for-detection

3 m

5 m

8 m

9 m

PVC liner

steel linerdiam. 350 mm

packer

Screen(Teflon)

central tube PFA coated

76 mm

circulation pump

plexi glasscabinet

Packer system control unit

electric cooler

injection lineinjection line

re-circulation line

tracer injection vial

flow meter

Nitrogen

balance

overpressurevalve

manometer

sampling port

detector

data acquisition for-detection

3 m

5 m

8 m

9 m

PVC liner

steel linerdiam. 350 mm

packer

Screen(Teflon)

central tube PFA coated

76 mm

circulation pump

plexi glasscabinet

Packer system control unit

electric cooler

Proven experimental setup

Circulation of synthetic solution at equilibrium with rock (OPA)+ tracers

Data: (1) monitoring (2) rock profiles

Successful for conservativeand moderately-sorbing tracers

Anion exclusionSorption of cations(Effect of filters)(BDZ)

1 m

DR-A: Objectives

• Induce a perturbation in the system

• Check the capabilities of reactive transport codes

DR-A: Concept

(1) Conventional in-situ diffusion experiment (189 days) Synthetic OPA pw + tracers

HTO, I-, Br-, Cs+, 85Sr2+, 60Co2+, Eu3+

(2) Replace synthetic OPA pw with high-salinity solution 0.5 M NaCl + 0.56 M KCl 85Sr2+

Modeling by different teams:PSI, Univ. Bern (T. Gimmi), Univ. British Columbia (U. Mayer, M. Xie),Lawrence Berkeley Natl. Lab. (C. Steefel), IDAEA-CSIC, T. Appelo

Nov. 2011 – Nov. 2013

Basis: Modeling with CrunchFlow, 1D – radial

• r = 4.16 cm (circle with same perimeter as ellipse)• Excess volume of ca. 1%. Borehole capacity decreased by the same factor for same volume as ellipse.

Diffusion domain(bedding plane)

x

y

BoreholeDip = 32.5o

1D

cDtc

etot

c = concentration in solution [mol.m-3]

t = time [s]

De = effective diffusion coefficient [m2.s-1]

ctot = total concentration of tracer [mol.m-3]

scc dtot

f = diffusion accessible porosity

rd = bulk dry density [kg.m-3]

s = sorbed tracer conc. [mol.kg-1]

sd )1( 3/2700 mkgs

filter

gap

Modeling with CrunchFlowMC, 1D – radial

All chemical species modeled simultaneouslyNo decay in the model (decay-corrected data)

(1) Dynamic calculation of bulk porosity and microporosity (EDL)

Microporosity

Aclay (m2/m3rock), lDL: n. of Debye lenghts

Total porosity (fixed) = bulk porosity + microporosity

IADA DL

DLclayLDLclayEDL

(2) Concentrations in EDL related to concs. in bulk water through the meanelectrical potential of the diffuse layer ( )

Mean electrical potential calculated from charge balance between surface chargeand diffuse layer.

Tkez

CCB

miBi

EDLi

exp

m

Micropor. (EDL), CiEDL

Micropor. (EDL), CiEDL

Bulk porosity, CiB

Micropor. (EDL), CiEDL

Micropor. (EDL), CiEDL

Bulk porosity, CiB BBB

e DD 0

EDLEDLEDLe DD 0

EDLEDLEDLe DD 0

t = 1 in the rockD0 = Dp

(3) Different De values in the microporosity (EDL) and bulk porosity.

iiei

iiei CDRTFz

CDJ ,, Nernst-Planck equation

run 17b

PARAMETERS

Borehole: well mixed, De = 1e-4 m2/s, a = 3.262(tank, lines, inner gap: 10243 mL; Gimmi, 2003, PSI AN 44-13-03)

Filter: well mixed, De = 1e-5 m2/s, f = 0.445

Gap: De = 2e-9 m2/s, f = 0.989

Rock: total porosity f = 0.15

Bulk porosity Cations, HTO: Dp = 1e-9 m2/s Anions: Dp = 3e-10 m2/s

Microporosity (EDL) Cations, HTO: Dp = 9e-11 m2/s (except Cs+, Dp = 1e-9 m2/s) Anions: Dp = 2e-11 m2/s lDL = 6 Surf. charge on illite: 0.2 eq/kg (B&B, 2000) (25 vol%, 200 m2/g)

Sorption of K had to be decreased (logK(PS-K)=-0.4 instead of -1.1)

Calculation up to 729 days (final 6-day back-diffusion not included)

INITIAL SOLUTION COMPOSITIONSTotal concentrations in mol/kg_H2O

Rock/filter/gap Borehole (1) Borehole (2)

T (°C) 18 18 18

pH 7.6 7.6 7.6

Na+ 2.59×10-1 2.59×10-1 5.00×10-1

K+ 1.64×10-3 1.64×10-3 5.60×10-1

Mg2+ 1.80×10-2 1.80×10-2 1.47×10-2

Ca2+ 1.88×10-2 1.88×10-2 2.30×10-2

Sr2+ 5.10×10-4 5.10×10-4 4.54×10-4

Cl- 3.00×10-1 3.00×10-1 1.12×100 charge

SO42- 1.37×10-2 1.37×10-2 2.37×10-4

HCO3- 7.25×10-3 charge 8.19×10-3 charge 5.63×10-4 PCO2,atm

Cs+ 2.00×10-8 2.069×10-4 6.23×10-6

SiO2(aq) 6.71×10-5 quartz 6.71×10-5 quartz 5.76×10-5 quartz

Al3+ 1.18×10-8 illite 1.18×10-8 illite 2.88×10-9 illite

I- 1.00×10-12 1.09×10-2 8.60×10-3

Br- 7.15×10-4 1.09×10-2 8.86×10-3

40 species in solution

CATION EXCHANGE – Opalinus Clay(Bradbury & Baeyens, 2000; Jakob et al., 2009;Van Loon et al., 2009)

  log KSite capacity (eq/kg)

FES-Cs + Na+ = FES-Na + Cs+ -7-01.05×10-4

FES-K + Na+ = FES-Na + K+ -2.4

II-Cs + Na+ = II-Na + Cs+ -3.28.4×10-3

II-K + Na+ = II-Na + K+ -2.1

PS-Cs + Na+ = PS-Na + Cs+ -1.6

9.5×10-2

PS-K + Na+ = PS-Na + K+ -0.4 (-1.1)

PS2-Ca + 2 Na+ = 2 PS-Na + Ca2+ -0.67

PS2-Mg + 2 Na+ = 2 PS-Na + Mg2+ -0.59

PS2-Sr + 2 Na+ = 2 PS-Na + Sr2+ -0.59

RESULTSBorehole

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

0 100 200 300 400 500 600 700

C/C

0

t (d)

HTO model

HTO data

I model

I data

Br model

Br data

HTO, I-, Br-

0.0

0.2

0.4

0.6

0.8

1.0

0 100 200 300 400 500 600 700

C/C

0

t (d)

Cs+

0.0E+00

1.0E-01

2.0E-01

3.0E-01

4.0E-01

5.0E-01

6.0E-01

0 100 200 300 400 500 600 700

K (

mo

l/L

)

t (d)

0.0E+00

1.0E-01

2.0E-01

3.0E-01

4.0E-01

5.0E-01

6.0E-01

0 100 200 300 400 500 600 700

Na

(m

ol/

L)

t (d)

0.0E+00

1.0E-02

2.0E-02

3.0E-02

4.0E-02

5.0E-02

0 100 200 300 400 500 600 700

Mg

(m

ol/

L)

t (d)

0.0E+00

1.0E-02

2.0E-02

3.0E-02

4.0E-02

5.0E-02

6.0E-02

0 100 200 300 400 500 600 700

Ca

(m

ol/

L)

t (d)

Ca2+ Mg2+

Na+ K+

0.0E+00

2.0E-03

4.0E-03

6.0E-03

8.0E-03

1.0E-02

1.2E-02

1.4E-02

1.6E-02

0 100 200 300 400 500 600 700

SO

4 (

mo

l/L

)

t (d)

0.0E+00

2.0E-01

4.0E-01

6.0E-01

8.0E-01

1.0E+00

1.2E+00

1.4E+00

0 100 200 300 400 500 600 700

Cl

(mo

l/L

)

t (d)

0.0E+00

3.0E-04

6.0E-04

9.0E-04

1.2E-03

1.5E-03

1.8E-03

0 100 200 300 400 500 600 700

Sr

(mo

l/L

)

t (d)

Sr2+

Cl-SO4

2-

?

RESULTSRock

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0.0 10.0 20.0 30.0 40.0

Poro

sity

(%)

d (cm)

Bulk por.

Micropor.

Model porosities, t = 729 d(total por. = 15%, fixed)

EDL

Bulk

0.0E+00

1.0E-03

2.0E-03

3.0E-03

4.0E-03

5.0E-03

6.0E-03

7.0E-03

0 5 10 15 20

I (m

ol/L

)

d (cm)

11.60

11.80

11.85

Model-b

Model-mp

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0 5 10 15 20

H-3

(Bq/

g_pw

)d (cm)

11.60

11.80

11.85

Model-b

Model-mp

I-

Aqueous extract data (PSI)

HTO

Back-diffusion signal(final 6 days)

1.0E-03

2.0E-03

3.0E-03

4.0E-03

5.0E-03

6.0E-03

7.0E-03

0 5 10 15 20

Br (m

ol/L

)

d (cm)

11.60

11.80

Model-b

Model-mp

2.0E-01

3.0E-01

4.0E-01

5.0E-01

6.0E-01

7.0E-01

8.0E-01

0 5 10 15 20

Cl (m

ol/L

)d (cm)

11.60

11.80

Model-b

Model-mp

Aqueous extract data(U. Bern)

Cl-

Br-

0

10

20

30

40

50

60

70

80

0 5 10 15 20

C (m

eq/k

g)

d (cm)

Ca

K

Mg

Na

Sr

Ca model

K model

Mg model

Na-model

Sr model

Ni-en extract data (U. Bern) – exchange complex

Prof. 11.60

Prof. 11.80

0

10

20

30

40

50

60

70

80

0 5 10 15 20

C (m

eq/k

g)

d (cm)

Ca

K

Mg

Na

Sr

Ca model

K model

Mg model

Na-model

Sr model

BOREHOLE• Good match of borehole concentrations (some overestimation of Cs+ right after solution exchange; also problem with SO4

2-)• Clear effect of increased salinity on anions: Reduced microporosity (EDL), Dp(B) > Dp(EDL), CB > CEDL • Also effect on HTO: Dp(B) > Dp(EDL)

PROFILES – aqueous extracts• Anions, HTO: approximate match of profiles, concentrations on the low side• Cations: good match for Na+, K+; no match for Ca2+, Mg2+

PROFILES – Ni-en extracts• Good match of transport distances and composition of the exchange complex• K sorption had to be decreased (logK(PS-K)=-0.4 instead of -1.1)

Summary and conclusions

Thank you for your attention