102 103. june 9 overview gwfts task force-and_ufd r&d activites related to gwfts task force_viswanathan

1. Used Fuel Disposition Campaign
Swedish Task Force
Ground Water Flow and Transport
of Solutes (GWTFS)
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of
Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-
94AL85000. SAND2016-nnnnn
Hari Viswanathan, Nataliia Makedonska, Satish
Karra, Jeffrey Hyman
Los Alamos National Laboratory
Collaborators: SKB, AMPHOS, Royal Institute of
Technology Stockholm
2016 UFDC Annual Working Group Meeting
June 9, 2016 Las Vegas, NV

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Ground Water Flow and Transport of
Solutes (GWTFS)
• The Task Force reviews all modeling work on fracture flow and solute transport
made by the Äspö Hard Rock Laboratory.
• The work in the TF is tied to the experimental work performed at Äspö and/or in-
situ data from Äspö.
• The work is performed within the framework of well defined and focused
Modeling Tasks. Several Modeling Teams should preferably address each Task.
• The TF tries to evaluate different concepts and modeling approaches. This is
achieved by several Modeling Teams performing the same task followed by
evaluation of the modeling work by the TF Delegates.
• Uncertainty quantification and rolling up the results from the different efforts were
suggestions made by Stefan Finsterle and myself and in the latest Prague
meeting this has now become a major focus of future work

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Task 9
 Key processes:
 Rock Volumes:
 Scientific Areas:
 Matrix diffusion in the microporous system
 Sorption and immobilization at mineral surfaces
 Reactions of solutes in the groundwater or pore water
 Interface between flowing and stagnant water
• The undisturbed rock matrix (REPRO, LTDE-SD)
• Fracture adjacent rock surrounding flow paths (LTDE-SD)
 Radionuclide transport and retention
 Groundwater evolution
 Rock/engineered barrier interface

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Task 9A: REPRO experiment
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Rock matrix rEtention PROperties
(experiment is carried out by Posiva at the ONKALO, Finland)
 WPDE – Water Phase Diffusion Experiment
 TDE – Through Diffusion experiment
• A borehole drilled into non-fractured
rock matrix;
• Dummy is inserted into a borehole,
creating 1 mm gap;
• Low steady-state water flow is applied in
the gap;
• A tracer cocktail is injected as a pulse
into the water flow.
• Three parallel boreholes: 324, 326, 327;
• The tracer cocktail is injected in one borehole
326.

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Task 9B: LTDE-SD
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Long Term Sorption Diffusion Experiment
(experiment is conducted in Sweden at the Äspö Hard Rock)
LTDE-SD site
410 m below see level
The decline in tracer concentration in the water
phase was monitored. Thereafter the rock was
overcored and analyzed in regard to tracer
concentration profiles in the rock matrix.
A cocktail tracer (in the
boreholes) is in a contact with
a natural fracture surface and
the unaltered rock matrix for a
time period of 200 days.

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Task 9B: LTDE-SD
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Numerous core samples from the
overcored rock volume were first
cut into 1 to 10 mm slices and
subjected to autoradiographs.
Thereafter, the tracer activities of
the slices were obtained by
various laboratory methods
ultimately allowing for the
compilation of tracer penetration
profiles.

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Penetration Profile in LTDE
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A cocktail of both sorbing and non-sorbing tracers was allowed to contact
a natural fracture surface, as well as the unaltered rock matrix, for a time
period of 200 days.
The measured experimental shapes of Cs penetration profile (symbols)
DO NOT SATISFY modeled penetration profile (dashed line)
(mm)

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Possible Solution
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Hypothesis:
The LTDE tests were strongly influenced by heterogeneity in the micro-
structure.
LANL Modeling Approach:
Include micro-structure directly into a high fidelity simulation using
discrete fracture networks
From Maikki Siitari-Kauppi. TF #32Fracture network (2D slice)

9. Used
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DFN Realization is Mapped
Into Continuum
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 Fracture intensity: P32 = 864.718 1/m
 Fracture porosity: P33 = 0.0032 m3/m3
(0.32%)
 Total number of fractures: 36169
• The fracture network structure of the
DFN is mapped into regular voxel
mesh.
• Each voxel in the hexahedral mesh has
dimensions of 0.5 mm.
• 4x smaller than the smallest fracture
(2mm)

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DFN based Continuum Model
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Permeability Field Porosity Field
Three models set up:
• Pure diffusion: homogeneous continuum
• Pure diffusion: continuum fractured media, heterogeneous porosity
• Diffusion + Advection: continuum fractured media, heterogeneous permeability and porosity

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Results
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Tracer is injected
uniformly on a top
face
Shown time
1-25 days

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Results
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Uncertainties:
• Flow rate: working with SKB to determine if advection is a
possible mechanism
• An alternative conceptual model is fracture damage near
the inlet and diffusion further in
(mm)