High Temperature Bentonite Project Ideas · Florian Kober (Nagra, on behalf of interested parties)...

Florian Kober (Nagra, on behalf of interested parties)

IGD-TP Exchange Forum, Cordobá; 25/26 October 2016

GTS Phase VI

HotBENT High Temperature Bentonite Project Ideas Studying the effects of high temperatures on clay buffers/nearfield

HotBENT Motivation to study THMC behavior under high T

Kober HotBENT IGD-TP Exchange Forum 25/26 Oct 2016 2

Thermal limit is an important design and cost-optimisation parameter: - repository footprint - storage time at the surface

A higher thermal limit is especially beneficial for the: - disposal of dual-purpose canisters - disposal in host rocks with high background temperature (steep geothermal

gradients)

Bentonite exposed to much higher temperature a proof of robustness is needed from a safety point of view optimal and shared allocation of resources should be pursued

Bentonite behaviour is a common thread In order to do so a substantial database and experience still needs to be gathered which is likely to be an international multi-annual exercise

Previous or running higher temperature experiments have been only up to < 150°C (LOT, ABM 130 ⁰C, PEBS/HE-E 140 ⁰C, TBT ~ 150 ⁰C)

HotBENT What to expect in the buffer for T > 150 °C Due to the high temperature it is expected that the following physico-

chemical effects will occur: - cementation possibly affecting mechanical properties - illitization (under certain conditions, e.g. high potassium concentrations) affecting mechanical

properties (reduced swelling, increased hydraulic conductivity and diffusivity)

Due to the strong thermal gradients: - complex moisture transport process, including convection of vapor - delayed saturation - heterogeneous, time-dependent density distribution (differential swelling)

Kober HotBENT IGD-TP Exchange Forum 3

Laboratory scale

Large scale (Mock-up/URL)

Numerical models developed, or being under development, can be used to simulate the thermal period of a repository, but database for T > 150 °C limited (laboratory) or non-existent (large scale)

Pellet- based buffer

25/26 Oct 2016

HotBENT Kickoff Meeting (Baden, CH, Feb 12th, 2016): “HotBENT - Studying the effects of high temperatures on clay buffers / nearfield - Brainstorming”

Kober HotBENT IGD-TP Exchange Forum 4 25/26 Oct 2016

HotBENT - Kickoff Meeting – gathering and formulating the interests

Interested / participating organizations

And various interested universities: EPFL, UdC, KIT, CTU, ..

https://www.numo.or.jp/en/

http://www.grs.de/

HotBENT Aims (from first meeting) Increase data base on buffer / host-rock performance under high T (up

to 200°C and demonstration at realistic scales/conditions upscaling) vs process understanding

Broad interest in: what are the T- limits (max) to assure safety function of buffer (and host rock) …

Need of repository optimisation with respect to design, space and costs …

Compare different materials, concepts/designs, boundary conditions (e.g. types of bentonite and canister materials, water chemistries, temperatures, …)

Evaluation of microbial activities / corrosion (e.g. buffer/canister)

Integrating of modelling (e.g. THMC) and lab activities (and also mock-up experiments)

Availability of data and samples must be possible not only after 20 years, preferred are ~5 years … develop and implement suitable monitoring/sampling strategies


HotBENT - Potential location - GTS, FEBEX-gallery

At Grimsel Test Site (GTS) - Old/former FEBEX-DP tunnel (70 m long, geologically and hydrologically well

characterized gallery, multiple boreholes,…)

- Availability of GBM and bentonite blocks MX80 - Auger machine


HotBENT - FEBEX gallery – well characterized boreholes


Water content Data from: Villar et al.(2016) FEBEX-DP: Onsite determinations report. NAB 16-012


NAB 16-012, Villar et al.

HotBENT since ISCO 2015 (4) - FEBEX gallery – onsite analysis

HotBENT - Scoping calculations


Liange Zheng & Jens Birkholzer, LBNL

0

20

40

60

80

100

120

140

160

180

200

0 2000 4000 6000 8000

Tem

eper

atur

e (o C

)

Time (day)

R = 0.48 m

TSE2-01TSF2-02TSF2-03TSF2-04FEBEX, 100 °CHotBENT 200 °C

0

10

20

30

40

50

60

70

80

90

100

0 2000 4000 6000 8000

Tem

eper

atur

e (o C

)

Time (day)

R = ~1.05 m

WPSF2-05 WPSF2-08

WPSF2-06 WPSE2-05

FEBEX, 100 °C HotBENT 200 °C

Temperature

0

10

20

30

40

50

60

70

80

0 1000 2000 3000 4000 5000 6000 7000 8000

Rela

tive

hum

idity

(%)

Time (day)

R = 0.52 m

WCSE2-03 WCSE2-04WCSE1-03 WCSE1-04FEBEX, 100 °C HotBENT 200 °C

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000 6000 7000 8000

Rela

tive

hum

idity

(%)

Time (day)

R = ~1.1 m

WCSE2-07 WCSE2-08WCSE1-01 WCSE1-07WCSE1-08 WCSE1-10WCSF1-01 WCSF1-05WCSF1-06 WCSF1-08FEBEX, 100 °C HotBENT 200 °C

Relative humidity

Comparison with FEBEX modelling and data


Liange Zheng & Jens Birkholzer, LBNL

0

5

10

15

20

25

30

35

40

0.4 0.6 0.8 1 1.2

Wat

er co

nten

t (%

)

Radial distance (m)

Data 5.3 yrs FEBEX, 5.3 yrs,

HotBENT, 200 °C, 5.3 yrs HotBENT, 200 °C, 10.3 yrshe

ater

gran

ite

1.4

1.45

1.5

1.55

1.6

1.65

1.7

1.75

1.8

0.4 0.6 0.8 1 1.2

Dry

den

sity

(%)

Radial distance (m)

Data 5.3 yrsFEBEX, 5.3 yrs, HotBENT, 200 °C, 5.3 yrsHotBENT, 200 °C, 10.3 yrs

heat

er

gran

ite

0

50

100

150

200

250

0.4 0.6 0.8 1 1.2

Tem

pera

ture

(°C

)

Radial distance (m)

HotBENT, 200 °C, 5 yrsHotBENT, 200 °C, 5.3 yrsHotBENT, 200 °C, 10 yrsHotBENT, 200 °C, 10.3 yrs

heat

er

gran

ite

HotBENT - Scoping calculations

Observations: After 10 years, the majority part of bentonite is still unsaturated.

Observations: HotBENT undergoes significant re-distribution of moisture during the cooling period

Com

paris

on w

ith F

EB

EX

mod

ellin

g an

d da

ta

Water content & Dry Density AFTER COOLING

Temperature & Water content AFTER COOLING


HotBENT – Possible Designs

Possible set-ups

…

Czech bentonite

HotBENT – Potential Modules


Wyoming

Steel B

125…175°C

Module 1 Module 2 Module 3 Module 5

… …

Not to scale

Con

cret

e Pl

ug

Concrete

Cu Steel A

FEBEX, Wyoming bentonite

Concrete high pH

Copper

…200…°C …

Wyoming /FEBEX bentonite

steel

…200…°C

Concrete high pH

Module 4

… … steel

150….200°C

Concrete low pH

Japanese bentonite

… … … Carbon cast iron steel

….200°C

Concrete low pH

saline water chemistry

Not specified

… … … Steel or COpper

125…175°C

Module 6

To be run for 5…10…15 years

HotBENT – Initial “Designs” for first very preliminary cost estimates


“half-tunnel”/”half-pipe” model “long-sampling-pipe” model

“classic” model “HE-E type” model

HotBENT - Next Actions Technical refinements for further design optimizations on

- General risk assessment, project risks and risk mitigation - Monitoring at high temperatures - Material evaluation (bentonite, heater, …)

- Gas/steam/vapor-evolution and risk of overpressure, interaction with hydrosphere, boiling effects

- Sampling and sampling techniques - Artificial hydration (compositions) options and limitations - …


thank you for your interest

HotBENT - timeline (proposal)


2019 2020 2021 2022 2023 2024 2025Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Excavation/ analysis/

modelling/ reporting1- 2 yeras

Experiment construction

7 month

Experiment runing/monitoring

5 years (-->2023)

2016 2017 2018

Conceptual design and modelling

(budget)

Formalise partici-pation

6 month 2 month

Site and experiment preparation

6- 8 month

High Temperature Bentonite Project Ideas · Florian Kober (Nagra, on behalf of interested parties)...

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