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 GeomechanicsClausthal University of Technology

September 7-9, 2016Washington, DC

2Fluid dynamic processes within a closed repository

with or without long-term monitoring

Outline

• Long-Term Monitoring Options

• Fluid Dynamic Processes within a Closed Repository

• TH2M-Coupled Simulation Tool FTK

• Numerical Simulation Results

• Conclusions



Outline





• Conclusions



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?




Swiss Monitoring ConceptSource: Nagra-Webpage

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/HLW2 ILW repository3 Pilot facility4 Test zones5 Access tunnel6 Ventilation shaft and construction shaft




2-Level Repository Concept

Emplacement Level Monitoring Level Monitoring Boreholes

Monitoring of every single emplacement drift is possible!




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



Outline





• Conclusions



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



Outline





• Conclusions



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P : pore pressureT : temperatureSl : liquid saturation

k : permeabilityf : porosity

s : stresse : straint : 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.



Constitutive Model Lux/Wolters

Dilatancy Boundary ss ,3 332 JF ds

Additional Creep Rate in Sealed/Healed Zones

modLubby2: D 1ss

1,11

11

23 ij

mv

ktr

k

vpij

sT

Gss

ses

e

0or0 dzds FF

DamageRate

17

16

1

**

15 a

adzds

D

FF

FF

aD

Additional CreepRate in Damaged Zones

ij

dz

a

adz

ij

ds

a

ads

dzij

dsij

dij

QD

FF

aQ

DFF

ass

eee

2

1

2

1

11

*

3

*

3

Sealing/Healing Boundary

Sealing/Healing Rate

ieij

eijij eee

no further damage orsealing/healing

0D

0&0&0,or

0&0,,

DFFF

DFFF

hdzds

hdzds

0and0 hFD

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vkk kGG

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vkk k ss

vk

tr Gse

1max

modLubby2 (without damage)

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TH2M-Coupled Simulation Tool FTK



Outline




• Numerical Simulation Results• Process Modelling• System Modelling

• Conclusions



Numerical Simulation Results – Process Modelling

3D-Simulation of TSDE-Experiment FLAC3D-Berechnungsmodell Voronoi-Diskretisierung für TOUGH2

FLAC3D-Berechnungsmodell Voronoi-Diskretisierung für TOUGH2

Blanco-Martín, L., Wolters, R., et al. (2016)

FLAC3D-Model

Voronoi-Discretization for TOUGH2



3D-Simulation of TSDE-ExperimentBlanco-Martín, L., Wolters, R., et al. (2016)




3D-Simulation regarding the Monitoring Borehole Concept


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



3D-Simulation regarding the Monitoring Borehole Concept


1 Waste Canister (5,5m) 1/2 Waste Canister

Backfill Material

(5,5m)

Monitoring Borehole

Monitoring Borehole (0,1m2)

Crushed Salt

Main Components of the 3D-Model Monitoring Drift

Emplacement Drift

A

B

1/2 Waster Canister

Crushed Salt

B

A

Emplacement DriftMonitoring Borehole

Crushed Salt



Outline




• Numerical Simulation Results• Process Modelling• System Modelling

• Conclusions



3D-Simulation of a Repository System in Rock Salt Masswithout Monitoring Level

Numerical Simulation Results – System Modelling



Time-dependent Temperature Evolution


2. Panel 3. Panel1. Panel

→ Schachtt = 0,274 a


→ Schacht

t = 0,671 a


→ Schacht

t = 1,05 at = 0,85 a


→ Schacht




→ Schacht

t = 1,23 a


→ Schacht

t = 1,57 a


→ Schacht

t = 1,76 a


→ Schacht

t = 1,94 a






→ Schacht

t = 2,13 a


→ Schacht

t = 2,47 a


→ Schacht

t = 2,81 a


→ Schacht

t = 3,15 a






→ Schacht

t = 3,28 a


→ Schacht

t = 3,41 a

2. Panel 3. Panel1. Panel→ Schacht

t = 3,54 a


→ Schacht









t = 6,24 a


→ Schacht

t = 6,37 a


→ Schacht

t = 5,53 a


→ Schacht

t = 5,67 a


→ Schacht





t = 7,66 a


→ Schacht

t = 7,79 a


→ Schacht

t = 6,95 a


→ Schacht

t = 7,08 a


→ Schacht





t = 9,07 a


→ Schacht

t = 9,21 a


→ Schacht

t = 8,37 a


→ Schacht

t = 8,50 a


→ Schacht





t = 10,49 a


→ Schacht

t = 10,62 a


→ Schacht

t = 9,78 a


→ Schacht

t = 9,91 a


→ Schacht





t = 11,90 a


→ Schacht

t = 12,04 a


→ Schacht

t = 11,20 a


→ Schacht

t = 11,33 a


→ Schacht





t = 13,32 a


→ Schacht

t = 13,45 a


→ Schacht

t = 12,61 a


→ Schacht

t = 12,74 a


→ Schacht





t = 14,74 a


→ Schacht

t = 15,31 a


→ Schacht

t = 14,03 a


→ Schacht

t = 14,16 a


→ Schacht





t = 17,04 a


→ Schacht

t = 19,04 a


→ Schacht

t = 15,89 a


→ Schacht

t = 16,46 a


→ Schacht





t = 30 a nach Verschluss


→ Schacht



→ Schacht



→ Schacht



→ Schacht







→ Schacht



→ Schacht



→ Schacht



→ Schacht







→ Schacht



→ Schacht



→ Schacht



→ Schacht









→ Schacht



→ Schacht



→ Schacht



→ Schacht







→ Schacht



→ Schacht



→ Schacht



→ Schacht

t = 1.000 a nach Verschluss


→ Schacht



→ Schacht



→ Schacht



→ Schacht





→ Schacht



→ Schacht



→ Schacht



→ Schacht







→ Schacht



→ Schacht



→ Schacht



→ Schacht







→ Schacht



→ Schacht



→ Schacht



→ Schacht





0

20

40

60

80

100

120

140

160

1 10 100 1000 10000 100000 1000000

Tem

pera

tur [�C

]

Zeit nach Verschluss [a]



1

4

5

2 3



Time-dependent Porosity Evolution


0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

1 10 100 1000 10000 100000 1000000

Poro

sitä

t [-]


1

4

5

2 3



0

2

4

6

8

10

12

14

16

18

20

1 10 100 1000 10000 100000 1000000

Pore

ngas

druc

k [M

Pa]


Time-dependent Gas Pressure Evolution


1

4

5

2 3



Gas Flow within Repository System (t = 10 a after repository closure)


↑ Schacht

↓ 1. & 2. Einlagerungsfeld← weitere Einlagerungskammern im 3. Einlagerungsfeld

ca. 0,0043 N-m³/a/m²

ca. 0

,057

N-m

³/a/m

²

ca. 0

,0 N

-m³/a

/m²



ca. 0,1356 N-m³/a/m²

ca. 0

,072

2 N

-m³/a

/m²

ca. 0

,035

N-m

³/a/m

²↑ Schacht


Gas Flow within Repository System (t = 1.000 a after repository closure)




ca. 0,046 N-m³/a/m²

ca. 0

,041

N-m

³/a/m

²

ca. 0

,023

N-m

³/a/m

²↑ Schacht






ca. 0,00159 N-m³/a/m²

ca. 0

,0 N

-m³/a

/m²

ca. 0

,001

13 N

-m³/a

/m²↑ Schacht






Gas Infiltration into Salt Rock Mass (t = 8.000 a after repository closure)


t = 8.000 Jahrenach Verschluss des Endlagers


0

2

4

6

8

10

12

14

16

18

20

1 10 100 1000 10000 100000 1000000

Pore

ngas

druc

k [M

Pa]






0

2

4

6

8

10

12

14

16

18

20

1 10 100 1000 10000 100000 1000000

Pore

ngas

druc

k [M

Pa]



with or without long-term monitoringt = 8.000 Jahrenach Verschluss des Endlagers




0

2

4

6

8

10

12

14

16

18

20

1 10 100 1000 10000 100000 1000000

Pore

ngas

druc

k [M

Pa]




3D-Simulation of a Repository System with Monitoring Level




Gas Flow within Repository System (t = 900 a after repository closure)


ca. 0,0014 N-m³/a/m²

ca. 0

,24

N-m

³/a/m

²

ca. 0

,238

N-m

³/a/m

²

ca. 0,000885 N-m³/a/m²

ca. 0,0144 N-m³/a/m²

Einlagerungssohle

Überwachungssohle

Bohrlöcher



Outline





• Conclusions



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 .- 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 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.



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.