proposal for task 9: modelling of ltde and repro task force meeting 29, november 2012

Proposal for Task 9:Modelling of LTDE and REPRO

Task Force Meeting 29, November 2012

SKB Task Force Meeting 29 2

Outline of this presentation

• Overview of Task 9 proposal

• Summary of LTDE presentation at TF#28– Available data– Examples of results– Possible modelling cases


Proposal for Task 9:• Modeling of LTDE and REPRO

• LTDE is performed at Äspö HRL

• Long-Term Diffusion Experiment (sorption)

• Lots of data but the results need to be analyzed further

• REPRO is on-going and conducted by Posiva at ONKALO

• “A combination of LTDE and TRUE”

• Gives possibilities to predictive modeling


Motivation and features of proposal• LTDE: Large data set, deserves to be analyzed more

• Some odd results need to be explained

• Educational, training and demonstration

• Demonstrate what the Task Force can do e.g. in terms of predictive modeling

• Long time since we modeled solute transport

• Could fit into a PhD program

• Could be a benefit to show that the solute transport tools work

• Input to SA/PA modeling

• Could address scale issues e.g. transport in the matrix, channels and fractures i.e. give input to the near field transport

• Could give input to reactive transport modelling


Motivation and features of proposal• Other suggestions on topics that could be addressed?

• Would it be good if a pre-study is made first?

• Think about this until the parallel sessions on Thursday

• Summary LTDE

• REPRO

• How to start up a task successfully

• Task Force challenges

Summary of LTDE Sorption Diffusion Experiment(LTDE-SD)

Heterogeneously distributed diffusion and sorption in cm scale, a possible modelling case?

# 28 Int. Äspö Task Force Meeting, January 2012

Erik Gustafsson, Geosigma

# 28 Int. Äspö Task Force Meeting 7

LTDE-SD aims at:

• Increase knowledge of sorption and diffusion under in-situ conditions, in crystalline bedrock at depth representative for the final repository

• Obtain data on sorption properties and processes of individual radionuclides on natural fracture surfaces and internal surfaces in the matrix rock

• Compare laboratory derived diffusion constants and sorption coefficients for the investigated rock system with in-situ determined parameters

• Evaluate if laboratory scale/conditions sorption results are representative also for larger scales


LTDE-SD Main project tasks

• In-situ experiments in isolated test sections with known surface areas and without advection or dispersion effects– Functionality test with 8 short lived radionuclide tracers– Main test with 22 tracers (c. 6 ½ months)

• Laboratory program using LTDE-SD site specific rock material – Supporting laboratory program at AECL– Laboratory experiments at CTH using same tracer cocktail as in situ

experiment (c. 6 months)

Experimental set up at Äspö HRL



Borehole instrumentation and test section design in KA3065A03

Experimental concept

• In-situ sorption and diffusion, no advection or dispersion

• Natural fracture surface and matrix rock

• Ambient hydraulic pressure, rock stress and hydrochemistry at – 410 m level in Äspö crystalline rock

• Extraction and analysis of the rock at termination of experiment


Experimental rock volume retrieved by over core drilling


Sample cores extracted from large over core


Example on sample core (A6, from the fracture surface in stub section)

Handling procedure of all sample cores before slicing:1) scanning with scintillation detector2) detailed geological mapping3) stereo photography4) rough measurement of gamma emitting tracers with HPGe

Available data from LTDE-SD in situ experiment

• Tracer concentrations in the groundwater, i.e. input function

• Hydrochemical data and speciation of tracers

• Diffusion profiles (Na-22, Cl-36, Co-57, Ni-63, Ba-133, Cs-137)– From natural fracture into altered/unaltered rock (stub surface

section, 10 profiles) – From groundwater directly into matrix rock (slim hole section, 8

profiles)

• Penetration profiles ≤ 3 mm (Cd-109, Ag-110m, Gd-153, Ra-226, Np-237)

• Radionuclide distribution in each slice by autoradiograph measurements

• Geological characterisation of whole sample cores and the slices


Available data and results from the LTDE-SD laboratory program with site specific rock material

• Batch tests on crushed rock material and through-diffusion and sorption on intact drill core samples

• Porosity measurements by water saturation and PMMA• Specific surface area and electrical resistivity measurements• Parameters determined; Kd, Rd, De, Ff, ε, α, BET-area• Chemical analysis of rock samples• Rock material used in the laboratory tests

• Core samples from the slim hole test section in experimental borehole KA3065A03

• Counter part of the stub fracture surface in KA3065A03• Core samples from the exploration borehole KA3065A02

• Diffusion and through diffusion tests on 278 mm diameter core from experimental borehole KA3065A03 (De, ε)

• Permeability test on 22 mm diameter core sample from KA3065A03 (K)


Example of penetration profiles in matrix rockSample core D13 with relatively deep penetration


1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Ro

ck/W

ater

ph

ase

ratio

(m3/k

g)

Depth at center of slice (mm)

Na-22

Cs-137

Ba-133

Cl-36

Ni-63

Example of migration paths and mineral specific sorption in matrix rock

• Upper; sorption on biotite, chlorite, titanite in sample D7.1 (first slice in direct contact with radionuclide labelled groundwater)

• Lower; sorption mainly on biotite, but also in pore space at mineral grain boundaries in sample D5.2 (second slice, 1.5 mm from rock surface)



Some results of the in-situ experiment

• Out of 22 tracers injected, it was possible to follow 21 in the aques phase

• 11 tracers; Na-22, Cl-36, Co-57, Ni-63, Cd-109, Ag-110m, Ba-133, Cs-137, Gd-157, Ra-226, Np-237 were possible to follow in the rock fabric

• Species mainly sorbed by surface complexation (e.g. Gd-153, Ag-110m) is found in the first few millimetres

• The moderately sorbing tracers (Cs-137, Ni-63, Ba-133) are present in quite high concentrations in the first slices but have decreased to a level 3 – 4 orders of magnitude at 3 – 6 mm depth

• Non sorbing Cl-36 and weakly sorbing Na-22 has penetrated typically up to 30 mm during the 200 days of in situ experiment

Single-rate matrix diffusion modelThree modelling concepts to fit the experimental data (A16 core sample)


Penetration profile, Cs-137 in sample A16

1.0E-2

1.0E-1

1.0E+0

1.0E+1

1.0E+2

1.0E+3

1.0E+4

1.0E+5

0.0E+0 2.0E-3 4.0E-3 6.0E-3 8.0E-3 1.0E-2 1.2E-2 1.4E-2

d (m)

[Cs-

137]

Bq

/g

( )

( )

( )

K d= 2.5E-3 m3/kg (+3.5E-3 / -1.5E-3) , F f= 2.2E-5 (lab)

K d= 2.2E-2 m3/kg (lab), F f= 1.0E-3 (+7.6E-4 / -2.0E-4)

K d= 2.5E-3 m3/kg (+1.3E-4 / -1.2E-4) ,

F f= 2.3E-4 (+1.8E-5 / -4.1E-6)

Case 2

Case 3

Case 4


Some conclusions from the in-situ experiment

• Autoradiograph analyses of the sliced rock samples indicate that the radionuclides diffuse in a heterogeneous pattern. The migration paths can visually be associated with microfractures and with the biotite part of the rock.

• The general shapes of the penetration profiles (and forward tailing) indicates significant influence of heterogeneous distribution of porosity in micro scale creating migration paths were fast diffusion can take place.

• Difficult to fit a single-rate based homogeneous diffusion-sorption model to the penetration profiles.

• Further interpretation and modelling capable of handling heterogeneous porosity in micro scale is needed.


Possible modelling exercises based on data from the LTDE-SD experiment

1. Connection of the porosity distribution studies to the possible existence of heterogeneous diffusivity

2. Can the adsorption of the sorbing tracers be predicted using process based modelling (e.g., surface complexation/cation exchange) with literature data?

3. Testing the possibility of application of the results of the batch sorption experiment to predict and explain the behaviour of the sorbing tracers in the LTDE-SD experiment


Thank you for your attention!


Outline of this presentation

• Overview of project and experimental work

• Available data

• Examples of results

• Possible modelling cases


Cutting and slicing of sample cores

Comparison penetration profiles Natural fracture surface “stub”, core sample A6Tracers; Cs-137, Ni-63, Co-57, Cd-109, Gd-153Slices A6.1, A6.2 and A6.3 are 1 mm, slice A6.4 is 3mm thick


1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

A6.1 A6.2 A6.3 A6.4

C/C

(A6.

1)

Cs-137

Ni-63

Co-57

Cd-109

Gd-153

Example of migration paths continued


Sample core D13 with relatively deep penetration

Autoradiography of core slices D13.1, D13.2 and D13.3

16 x 16 mm

← D13.1

← D13.2

← D13.3

D13.1 D13.2 D13.3

Modelling Case 5, all retention parameters (Kd, Ff, ε) varied simultaneously to fit penetration profile and tracer loss in aqueous phase.


Concentration, aq. phase

0E+00

2E-04

4E-04

6E-04

8E-04

1E-03

0 50 100 150 200

Elapsed tim e (d)

C/A

tot

(1/m

L)

In-s itu data

Es tem ation

1E-02

1E+00

1E+02

1E+04

1E+06

0E+00 1E-02 2E-02Penetration depth (m)

Bq/g

In-s itu data

Es tem ationNi-63

Core A1

Fracture surface


0E+00

2E-04

4E-04

6E-04

8E-04

1E-03

0 50 100 150 200

Elapsed time (d)

C/A

tot

(1/m

L)

In-situ data

Estemation1E-02

1E+00

1E+02

1E+04

1E+06


Bq/g

In-s itu data

Estem ationNi-63

Core D12

Matrix rock

Modelling Case 5, all retention parameters (Kd, Ff, ε) varied simultaneously to fit penetration profile and tracer loss in aqueous phase.


Cs-137

Core A1

Fracture surface

Cs-137

Core D12

Matrix rock


0E+00

2E-04

4E-04

6E-04

8E-04

1E-03

0 50 100 150 200

Elapsed time (d)

C/A

tot

(1/m

L)

In-s itu-data

Estim ation

1E-02

1E+00

1E+02

1E+04

1E+06


Bq/g

In-s itu-data

Es tim ation


0E+00

2E-04

4E-04

6E-04

8E-04

1E-03

0 50 100 150 200

Elapsed time (d)

C/A

tot

(1/m

L)

In-s itu-data

Es tim ation

1E-02

1E+00

1E+02

1E+04

1E+06

0E+00 5E-03 1E-02

Penetration depth (m)

Bq/g

In-s itu-data

Es tim ation


Comparison of Kd ∙ Ff intervals, determined by different techniques

1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2

Cs+

Ni2+

Cd2+

Ra2+

Gd(III)

Hf(IV)

K d x F f (m3/kg)

Modelling, results both fromsolid and aqueous phase,Diffusivity and porosity fittingparameters (Case 5)

Modelling, results from solidphase, Diffusivity and porosityfitting parameters (Case 4)

Modelling, results from solidphase, Diffusivity and porosityfrom lab experiments (Case 2)

Modelling, only results fromthe loss in aqueous phase,Diffusivity and porosity fromthe laboratory experiments

Comparison laboratoryexperiments, modelling resultsonly from the loss in aqueousphase, Diffusivity and porosityfrom the laboratoryexperiments


Comparison of Kd value intervals, determined by different techniques

1E-5 1E-3 1E-1 1E+1 1E+3 1E+5

Cs+

Ni2+

Cd2+

Ra2+

Gd(III)

Hf(IV)

K d (m3/kg)

Batch laboratory experiment

Measured data from aq and solidphase, entire core, assumingpenetration < 5 mm

Measured data from aq and solidphase, first slice

Modelling, results both from solid andaqueous phase, Diffusivity andporosity fitting parameters (Case 5)

Modelling, results from solid phase,Diffusivity and porosity fittingparameters (Case 4)

Modelling, results from solid phase,Diffusivity and porosity from labexperiments (Case 2)

Modelling, only results from the lossin aqueous phase, Diffusivity andporosity from the laboratoryexperiments

Comparison laboratory experiments,modelling results only from the loss inaqueous phase, Diffusivity andporosity from the laboratoryexperiments


Comparison of sorption coefficients (Kd, m3/kg) recommended for SR-Site Forsmark and results from LTDE-SD

LTDE-SD results from modelling using data both from penetration profiles and

tracer loss in aqueous phase.

Tracer LTDE-SD in-situ data SR-Site

137Cs (I) 4.0 x 10-4 - 9.0 x 10-3 3.5 x 10-5 - 3.5 x 10-3

63Ni (II) 7.0 x 10-4 - 2.0 x 10-3 6.0 x 10-5 - 2.0 x 10-2

109Cd (II) 2.0 x 10-4 - 2.0 x 10-3 6.0 x 10-5 - 2.0 x 10-2

226Ra (II) 4.0 x 10-4 - 4.0 x 10-3 3.9 x 10-5 - 1.5 x 10-3

153Gd (III) 3.0 x 10-3 - 1.0 x 10-1 5.7 x 10-4 - 3.8 x 10-1

175Hf (IV) 1.0 x 10-2 - 3.0 x 10-2 2.8 x 10-3 - 9.8 x 10-1


Possible modelling exercises based on data from the LTDE-SD experiment Tentative modelling using a two pathway model for Cs-137

Matrix Fracture surface (A6 core sample from stub section)

Cs-137 diffusion in sample A6, tentative 2-pathway modelling

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

0 0.01 0.02 0.03 0.04 0.05 0.06

Depth [m]

C/ A

tot [

1/g

]

"Slow" process:

F f=7.5E-4 (D e=1.3E-12 m2/s)

K d=1.4E-2 m3/kge<< K d

r

"Fast" process:

F f=1.4E-5 (D e=2.4E-14 m2/s)e=3.7E-4K d

r< e


LTDE-SD Participating organisations• SKB Geosigma AB

» Project management, In-situ experiments, sample preparation and analysis, evaluation, modelling

» University of Helsinki » Rock core sample preparation and analysis

» Swedish Defence Research Agency

» Sample preparation and analysis

» Technical Research Institute of Sweden Sample preparation and analysis

» Chalmers University of Technology Supporting laboratory experiments

• OPG/NWMO AECL Whiteshell Supporting laboratory experiments, modelling


Tracers injected in main sorption diffusion experiment

Tracer Group Tracer Group Tracer Group

Na-22

B1 Nb-95 B2 Cs-137

B1

S-35

A Tc-99 B3 Gd-153 B2

Cl-36

A Pd-102 B2 Hf-175 B2

Co-57

B2 Cd-109 B2 Ra-226 B1

Ni-63

B2 Ag-110m B2 Pa-233 B2

Se-75

? Sn-113 B2 U-236 B3

Sr-85

B1 Ba-133

B1 Np-237 B3

Zr-95

B2

A non-sorbing tracer, B1 cation exchange, B2 mainly surface complexation, B3 electrochemical reduction dependent

Illustration of the dependence of the formation factor (Ff) on the Kd-value in the curve fitting procedure for the loss of Cs due to sorption on intact rock


0E+00

2E-01

4E-01

6E-01

8E-01

1E+00

0 50 100 150 200

C/C

0

Elapsed time (h)

Experiment

Min (I-)

H3HO

Mean (I-)

Max (I-)

All four

1E-06

1E-04

1E-02

1E+00

1E+02

1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00 1E+01

Kd

(m3/k

g)

Ff (-)

Fig. 4-6

Penetration profiles

1E-04

1E-02

1E+00

1E+02

1E+04

1E+06

1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00

C/(

Cto

t x L

) (m

-1)

L (m)

Min (I-), Ff=3E-6

H3HO, Ff=2E-5

Mean (I-), Ff=1E-4

Max (I-), Ff=3E-3

Experimental set- up at Äspö HRL



Some conclusions from the in-situ experiment

• Autoradiograph analyses of the sliced rock samples indicate that the radionuclides diffuse in a heterogeneous pattern. The migration paths can visually be associated with microfractures and with the biotite part of the rock.

• The general shapes of the penetration profiles (and forward tailing) indicates significant influence of heterogeneous distribution of porosity in micro scale creating migration paths were fast diffusion can take place.

• The interaction observed in this experiment (occurring mainly in the rock material less than 5 mm from the water-rock interface) seems to be influenced by a somewhat decreased Kd compared to batch sorption experiments and with an increased diffusivity compared to the results obtained by laboratory through diffusion experiments.

• Difficult to fit a single-rate based homogeneous diffusion-sorption model to the penetration profiles.

• Further interpretation and modelling capable of handling heterogeneous porosity in micro scale is needed.


Possible modelling exercises based on data from the LTDE-SD experiment

1. Connection of the porosity distribution studies to the possible existence of heterogeneous diffusivity

The penetration profile measurement of the tracers indicates that there are significant deviations from a homogeneous diffusivity pattern and also a significant variation in diffusivity rates of the different measured samples. An interesting task would be to investigate if the porosity distribution measurement could be used to explain and predict the shape of the penetration profiles, e.g., influence of microfractures

2. Can the adsorption of the sorbing tracers be predicted using process modelling (e.g., surface complexation/cation exchange) with literature data?

Using surface complexation models combined with the mineralogical data to make prediction of the adsorption and other processes (e.g., precipitation and co-precipitation) for the different sorbing tracers.


Possible modelling exercises based on data from the LTDE-SD experiment continued

3. Testing the possibility of application of the results of the batch sorption

experiment to predict and explain the behaviour of the sorbing tracers in the LTDE-SD experiment

How do the results of the batch sorption experiment relate to the losses in the aqueous phase and/or the penetration profile of the sorbing tracer of the experiment?


LTDE-SD project performance and results are presented in three reports:

• Widestrand H, Byegård J, Selnert E, Skålberg M, Höglund S, Gustafsson E, 2010. Äspö Hard Rock Laboratory. Long Term Sorption Diffusion Experiment (LTDE-SD). Supporting laboratory program - Sorption diffusion experiments and rock material characterisation. With supplement of adsorption studies on intact rock samples from the Forsmark and Laxemar site investigations. SKB R-10-66. Svensk Kärnbränslehantering AB.

• Widestrand H, Byegård J, Kronberg M, Nilsson K, Höglund S, Gustafsson E, 2010. Äspö Hard Rock Laboratory. Long Term Sorption Diffusion Experiment (LTDE-SD), Performance of main in situ experiment and results from water phase measurements. SKB R-10-67. Svensk Kärnbränslehantering AB.

• Nilsson K, Byegård J, Selnert E, Widestrand H, Höglund S, Gustafsson E, 2010. Äspö Hard Rock Laboratory. Long Term Sorption Diffusion Experiment (LTDE-SD). Results from rock sample analyses and modelling. SKB R-10-68. Svensk Kärnbränslehantering AB.

proposal for task 9: modelling of ltde and repro task force meeting 29, november 2012

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