16 wolters lux

Fluid dynamic processes within a closed repository
with or without long-term monitoring
7th US/German Workshop on Salt Repository Research, Design, and Operation
R. Wolters, K.-H. Lux, U. Düsterloh
Chair in Waste Disposal and Geomechanics
Clausthal University of Technology
September 7-9, 2016
Washington, DC

2
Outline
• Long-Term Monitoring Options
• Fluid Dynamic Processes within a Closed Repository
• TH2M-Coupled Simulation Tool FTK
• Numerical Simulation Results
• Conclusions

3
Outline
• Conclusions

4
Long-Term Monitoring Options
Motivation
In Germany, according to its recommendations, the Repository Commission
prefers the disposal of high-level waste within a repository built in deep
geological formations.
But:
Reversibility of decisions as well as retrievability of the waste canisters
should be possible for future generations because there might be a
significant improvement of scientific knowledge and technology concerning
the handling of high-level waste or there might occur an unexpected
development of the repository system.
For this reason, a long-term monitoring option should be implemented into
the repository concept to provide data about the time-dependent physical as
well as chemical situation within the repository system.
How could a long-term monitoring option be realized?

5
Swiss Monitoring Concept
How can the measured data be transferred from
the pilot facility to the main facility?
How to be sure that the main facility works
correctly if the pilot facility works correctly?
1 Main facility SF/HLW
2 ILW repository
3 Pilot facility
4 Test zones
5 Access tunnel
6 Ventilation shaft and construction shaft

6
2-Level Repository Concept
 Emplacement Level
 Monitoring Level
 Monitoring Boreholes
Monitoring of
every single
emplacement
drift is
possible!

7
2-Level Repository Concept
 Emplacement Level
- backfilled and sealed like in repository concept without monitoring option
 Monitoring Level
- access to monitoring boreholes
- kept open during monitoring phase
- backfilled and sealed after monitoring phase (including shaft closure)
 Monitoring Boreholes
- drilled to emplacement drifts and instrumented before waste emplacement
- provide access to measurement equipment for repair, energy supply, and data
transfer
- kept internally open during monitoring phase, but covered by some kind of moveable
sealing construction at the upper end of the boreholes
- lined to prevent borehole convergence during monitoring phase
- (unlined?,) backfilled, and sealed after monitoring phase

8
Outline
• Conclusions

9
Fluid Dynamic Processes
within a Closed Repository
Mechanical Processes
 Salt rock mass:
- Creep behaviour
- Thermomechanically induced damage leading to an increase of secondary porosity as well
as of secondary permeability
- Sealing/healing of microfissures
- Stress redistribution
 Crushed salt:
- Compaction leading to a reduction of porosity and permeability as well as to increasing
compaction stresses
Hydraulic Processes
 Flow of liquids and gases (2-phase flow)
 Increase of gas pressure due to temperature increase, gas compression, and gas
generation
 Hydraulically induced damage in salt rock mass / pressure-driven fluid infiltration
Thermal Processes
 Heat conduction considering non-constant thermal properties

10
Outline
• Conclusions

11
, ,
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, ,
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,
,
, ,
, ,
, ,
, ,
,
,
, ,
, ,
, ,
, ,
P : pore pressure
T : temperature
Sl : liquid saturation
k : permeability
f : porosity
s : stress
e : strain
t : time
Legend:
TH2M-Coupled Simulation Tool FTK
 The TH2M-coupled simulation tool FTK is based on the two numerical
codes FLAC3D and TOUGH2.
 Mechanical and thermohydraulic processes are sequentally simulated.

12
Constitutive Model Lux/Wolters
Dilatancy Boundary
   ss ,3 332  JFds
Additional Creep Rate in Sealed/Healed Zones
modLubby2:  D 1ss
 
   
   

















 

1,
11
1
1
2
3 ij
mv
k
tr
k
vp
ij
s
T
G
ss
se
s
e
0or0  dzds
FF
Damage Rate
  17
16
1
**
15 a
a
dzds
D
F
F
F
F
aD









Additional Creep Rate in Damaged Zones
    ij
dz
a
adz
ij
ds
a
ads
dz
ij
ds
ij
d
ij
Q
D
F
F
a
Q
D
F
F
a
ss
eee









 2
1
2
1
11
*
3
*
3

Sealing/Healing Boundary
Sealing/Healing Rate
ie
ij
e
ijij eee  
no further damage or
sealing/healing
0D
0&0&0,
or
0&0,,


DFFF
DFFF
hdzds
hdzds
0and0  h
FD
h
ij
d
ij
vp
ij
ie
ij eeee  
D
D
2
01
1
1











p
p
vol v
v
D
e
, mod , modkG m
a
v
vmm TlmT 





 *
**
)exp()exp(),(
s
s
ss
b
v
vkk kGG 





 *1
*
)exp()(
s
s
ss
)exp()( 2
*
vkk k ss 
v
k
tr
G
se 
1
max
modLubby2 (without damage)
ij
mtr
tr
k
vp
ij s












e
e

e
1
1
1
2
3
max

Dilatancy
hhhddd
vol 321321 eeeeeee 
     v
h
MaaaMa
a
a
F s





 8765
11
4
expexp1










2121 fsfs
F
fcfc
M
DD
h
h


ij
hh
vol
h
ij
Q
fs
F
fc
M
s
ee
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







11

 with














  12
3
6
2
1
s



s
R
M
T-M
T-M ↔ H
H
Darcy-tr
INFIL
TH2M-Coupled Simulation Tool FTK

13
Outline
• Process Modelling
• System Modelling
• Conclusions

14
Numerical Simulation Results –
Process Modelling
3D-Simulation of TSDE-Experiment FLAC3D-Berechnungsmodell Vorono
FLAC3D-Berechnungsmodell Voronoi-Diskretisierung für TOUGH2
Blanco-Martín, L., Wolters, R., et al. (2016)
FLAC3D-Model
Voronoi-Discretization for TOUGH2

15
3D-Simulation of TSDE-Experiment
Blanco-Martín, L., Wolters, R., et al. (2016)
Process Modelling

16
3D-Simulation regarding the Monitoring Borehole Concept
Process Modelling
z = -560 m
z = -800 m
z = -400 m
z = -600 m
L = 50 mB = 11 m
Monitoringstrecke
Bohrlöcher
Einlagerungsstrecke
Stahlmann et al. (2016)
Shape of Emplacement Drift Shape of Monitoring Drift
Emplacement Drifts
Monitoring Boreholes
Monitoring Drift

17
3D-Simulation regarding the Monitoring Borehole Concept
Process Modelling
Monitoring Borehole
Monitoring Borehole (0,1m2)
Main Components of the 3D-Model Monitoring Drift
Emplacement Drift
A
B
B
A
Emplacement Drift
Monitoring Borehole

18
Outline
• Process Modelling
• System Modelling
• Conclusions

19
3D-Simulation of a Repository System in Rock Salt Mass
without Monitoring Level
System Modelling

20
Time-dependent Temperature Evolution
System Modelling
2. Panel 3. Panel1. Panel
→ Schacht
t = 0,274 a
→ Schacht
t = 0,671 a
→ Schacht
t = 1,05 at = 0,85 a
→ Schacht

21
→ Schacht
t = 1,23 a
→ Schacht
t = 1,57 a
→ Schacht
t = 1,76 a
→ Schacht
t = 1,94 a
System Modelling

22
→ Schacht
t = 2,13 a
→ Schacht
t = 2,47 a
→ Schacht
t = 2,81 a
→ Schacht
t = 3,15 a
System Modelling

23
→ Schacht
t = 3,28 a
→ Schacht
t = 3,41 a
→ Schacht
t = 3,54 a
→ Schacht
System Modelling

24
System Modelling

25
t = 6,24 a
→ Schacht
t = 6,37 a
→ Schacht
t = 5,53 a
→ Schacht
t = 5,67 a
→ Schacht
System Modelling

26
t = 7,66 a
→ Schacht
t = 7,79 a
→ Schacht
t = 6,95 a
→ Schacht
t = 7,08 a
→ Schacht
System Modelling

27
t = 9,07 a
→ Schacht
t = 9,21 a
→ Schacht
t = 8,37 a
→ Schacht
t = 8,50 a
→ Schacht
System Modelling

28
t = 10,49 a
→ Schacht
t = 10,62 a
→ Schacht
t = 9,78 a
→ Schacht
t = 9,91 a
→ Schacht
System Modelling

29
t = 11,90 a
→ Schacht
t = 12,04 a
→ Schacht
t = 11,20 a
→ Schacht
t = 11,33 a
→ Schacht
System Modelling

30
t = 13,32 a
→ Schacht
t = 13,45 a
→ Schacht
t = 12,61 a
→ Schacht
t = 12,74 a
→ Schacht
System Modelling

31
t = 14,74 a
→ Schacht
t = 15,31 a
→ Schacht
t = 14,03 a
→ Schacht
t = 14,16 a
→ Schacht
System Modelling

32
t = 17,04 a
→ Schacht
t = 19,04 a
→ Schacht
t = 15,89 a
→ Schacht
t = 16,46 a
→ Schacht
System Modelling

33
t = 30 a nach Verschluss
→ Schacht
→ Schacht
→ Schacht
→ Schacht
System Modelling

34
→ Schacht
→ Schacht
→ Schacht
→ Schacht
System Modelling

35
→ Schacht
→ Schacht
→ Schacht
→ Schacht
System Modelling

36
System Modelling
→ Schacht
→ Schacht
→ Schacht
→ Schacht

37
System Modelling
→ Schacht
→ Schacht
→ Schacht
→ Schacht
t = 1.000 a nach Verschluss
→ Schacht
→ Schacht
→ Schacht
→ Schacht

38
→ Schacht
→ Schacht
→ Schacht
→ Schacht
System Modelling

39
→ Schacht
→ Schacht
→ Schacht
→ Schacht
System Modelling

40
→ Schacht
→ Schacht
→ Schacht
→ Schacht
System Modelling

41
0
20
40
60
80
100
120
140
160
1 10 100 1000 10000 100000 1000000
Temperatur[C]
Zeit nach Verschluss [a]
System Modelling
1
4
5
2 3

42
Time-dependent Porosity Evolution
System Modelling
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
1 10 100 1000 10000 100000 1000000
Porosität[-]
1
4
5
2 3

43
0
2
4
6
8
10
12
14
16
18
20
1 10 100 1000 10000 100000 1000000
Porengasdruck[MPa]
Time-dependent Gas Pressure Evolution
System Modelling
1
4
5
2 3

44
Gas Flow within Repository System (t = 10 a after repository closure)
System Modelling
↑ Schacht
↓ 1. & 2. Einlagerungsfeld← weitere Einlagerungskammern im 3. Einlagerungsfeld
ca. 0,0043 N-m³/a/m²
ca.0,057N-m³/a/m²
ca.0,0N-m³/a/m²

45
ca. 0,1356 N-m³/a/m²
ca.0,0722N-m³/a/m²
ca.0,035N-m³/a/m²
↑ Schacht
Gas Flow within Repository System (t = 1.000 a after repository closure)
System Modelling

46
ca. 0,046 N-m³/a/m²
ca.0,041N-m³/a/m²
ca.0,023N-m³/a/m²
↑ Schacht
System Modelling

47
ca. 0,00159 N-m³/a/m²
ca.0,0N-m³/a/m²
ca.0,00113N-m³/a/m²
↑ Schacht
System Modelling

48
Gas Infiltration into Salt Rock Mass (t = 8.000 a after repository closure)
System Modelling
0
2
4
6
8
10
12
14
16
18
20
1 10 100 1000 10000 100000 1000000
Porengasdruck[MPa]

49
System Modelling
0
2
4
6
8
10
12
14
16
18
20
1 10 100 1000 10000 100000 1000000
Porengasdruck[MPa]

50
System Modelling
0
2
4
6
8
10
12
14
16
18
20
1 10 100 1000 10000 100000 1000000
Porengasdruck[MPa]

51
3D-Simulation of a Repository System with Monitoring Level
System Modelling

52
Gas Flow within Repository System (t = 900 a after repository closure)
System Modelling
ca. 0,0014 N-m³/a/m²
ca.0,24N-m³/a/m²
ca.0,238N-m³/a/m²
ca. 0,000885 N-m³/a/m²
ca. 0,0144 N-m³/a/m²
Einlagerungssohle
Überwachungssohle
Bohrlöcher

53
Outline
• Conclusions

54
Conclusions
 Capabilities of the simulation tool FTK to evaluate the barriers integrity over time
including TH2M-coupled processes like rock mass convergence, backfill
compaction, heat production, gas production, 2-phase flow, and pressure-driven
infiltration have already been demonstrated in former works, e.g. at SaltMech 8 or at
5th US/German Workshop on Salt Repository Research, Design, and Operation.
 The simulation tool FTK can be used to analyze the long-term TH2M-coupled
behaviour of a repository system in salt rock mass without or with monitoring option.
 Numerical simulation of fluid dynamics in a closed repository in rock salt without
monitoring option shows:
- Maximum temperature stays below 200 °𝐶.
- Temperature field reaches primary temperature after about 10,000 years.
- Primary pore air within crushed salt as well as corrosion gases are squeezed out through drifts
and shafts as well as through the geologic barrier due to the pressure-driven gas infiltration
process.
 Numerical simulation of fluid dynamics in a closed repository in rock salt with
monitoring option via monitoring boreholes shows:
- Temperature at monitoring level amounts about 50 °𝐶 in maximum.
- Gas escapes from the emplacement level to the monitoring level through the monitoring boreholes
resulting in a less intensive gas pressure build-up within the repository system.

55
Conclusions
Some benefits of the implementation of a monitoring level in combination with
monitoring boreholes:
 Monitoring boreholes enable direct measurement of physical parameters during
post-closure transition phase.
 Monitoring boreholes give a possibility to indicate measurement errors and to
replace measurement equipment in case of cancellation.
 Direct monitoring may increase confidence as well as public acceptance.
But:
 Direct monitoring via monitoring level in combination with monitoring boreholes may
influence the site selection criteria (e.g. thickness as well as lateral extension of
geological barrier formation) and has therefore to be implemented in the site
selection process.

16 wolters lux

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