13 th exchange meeting the role of cementitious materials for deep disposal of high-level waste in...

13th Exchange MeetingThe role of cementitious

materials for deep disposal of high-level waste in Boom Clay

Use of cementitious materials in the PRACLAY experimental programme

Wim BastiaensESV EURIDICE GIE

Mol, 29 January 2009

13th Exchange Meeting29 January, 2009

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Introduction

PRACLAY: PReliminAry demonstration test for CLAY disposal of highly radioactive waste

Aim: to demonstrate the feasibility of the reference design for deep disposal of HLW


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The PRACLAY project

PRACLAY In SituPRACLAY Surface(Generic)(Design specific)

Demonstration experiments

Repository construction feasibility

Demonstration Experiments

Construction, handling and performance of EBS (Engineered Barrier Systems)

Examples: Ophelie mock-up, supercontainer construction, backfill test ESDRED (EC)

Confirmation experiments The PRACLAY Heater Test

Supporting studies (T-H-M)Atlas, CLIPEX (EC), SELFRAC (EC),TIMODAZ (EC), …


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The PRACLAY project









Ophelie Day10/06/2004

www.euridice.be

Presentations byBart Craeye &

Lou Areias


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Section to be backfilled• ~30 m long• ~90 m³ of material

PRACLAY surface: ESDRED (EC)


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Prevent collapse of the gallery lining (and potential damage of the supercontainer)

Prevent/limit creep of Boom Clay(with potential destabilization of the surrounding host formation)

Main requirement is a high filling ratio There are some constraints on the materials

The backfill material has two main roles/functions


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Two backfilling techniques tested in the scope of ESDRED Backfilling by pumping a grout

Backfilling by projecting a granular material


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Programme objectives: ‘grout technique’

Development of a grout with specific requirements (related to operational and LT safety aspects): High pH (corrosion protection) Sufficiently high thermal conductivity (> 1 W/mK) Compressive strength between 3 and 10 MPa

(retrievability) Limited quantity of chemical additives (RN complexes)

and no sulfur containing species (corrosion) Hardening time < 4 days (operation) Fluidity sufficient to fill a 30 m long section


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Programme objectives: ‘grout technique’

Verify preparation aspect (logistics) at large scale

Verify emplacement aspect at large scale

Verify that grout properties (emplacement and behaviour) are maintained under thermal load

Reduced scale test: 2/3, Ø2.5m Full scale test: Ø3.5m


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Grout composition Binding medium

Portland cement (CEM I) High compressive strength (52.5 N) High Sulphate Resisting (HSR) Low Alkali level (LA)

Limestone powder Additive

Superplasticizer Glenium® Sand

Calibrated river sand 0 - 4 mm, washed and dried


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Design of the reduced-scale mock-up


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Reduced-scale test (June 2006)

Flow rate ~ 3 m³/h Hardening < 4 days No segregation observed Hardened material homogeneous

Rheological properties of grout were suitable

100 % filling ratio obtained Main injection tube was sufficient

Design of main injection tube was suitable

Properties of hardened material Density = 2200 kg/m³ λ = 1.6 W/mK (fully dried) k = 10-12 m/s (water)

.Grout composition was found

to be suitable for full-scale test


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Construction and design of the full-scale mock-up

Main injection(at 25m depth)

Back-up injection

Vent


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Full-scale test: grout preparation and tests (April

2008)

2 cranes 3 trucks (10 m³)

1 pump + reserve

240 big bags(1T, pre-mix)

88 m³ grout

On-site tests


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Grout injection

Temperature: ~65°C Time needed: +/- 7 hours Average flow rate: 15.1 m³/h (11.7 24

m³/h)

Pump breakdown (replacing it took ~1h) Main injection tube is sufficient

Back-up was used after pump breakdown About 2-3 m³ of water/grout was ejected

through the vent


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Grout injection

4 days after the test ~99 % filled Small gap at the top (filled with water)

About 900 l was removed (1.1 % of total volume) Gap dimensions from 0.5 cm (end cover) to 5 cm

(front cover)

5 cm0.5 cm


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Grout behaviour The grout hardened partially and very slowly ( small scale test)

NOT caused by Difference of compositions (chemical analyses) Problem with cement quality (chemical analyses) Segregation during pumping (not likely according to Magnel, CSTC, Glaser)

Different boundary conditions

W/C ratio during full scale test at the high end of the functioning range

Reduced scale test Full scale test

Temperature 45°C 65°C

Diameter 2.5 m 3.5 m

Reinforcement of the setup

Bars ( not impervious) Metal sheet ( impervious)


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Lessons learnt from backfill tests

Material development based on industrial knowledge; properties +/- OK

Backfilling 30 m: yes we can! The design of the mock-up and internal components

was OK (cf. injection tubes) Logistic aspects are important The saturation and design of the concrete lining of

the disposal galleries could have an influence Further need to tailor the grout: larger functioning zone Continuing theoretical/design studies (for SFC-1) to translate

knowhow from tests to repository configuration


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The PRACLAY project










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Construction history

Phase 1 1980 - ’87 pioneering + R&D

Phase 2 1997 - ’07 demonstration


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Construction feasibility

Use of cementitious materials in HADES mainly linked to the lining First shaft

Poured concrete


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Use of cementitious materials in HADES mainly linked to the lining Experimental works / Test Drift

Unreinforced concrete segments Wooden interlayers to limit ground pressure Installed manually


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Use of cementitious materials in HADES mainly linked to the lining Second shaft Prefab segments + shotcrete + cast concrete


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Use of cementitious materials in HADES mainly linked to the lining Connecting gallery / PRACLAY gallery

Unreinforced concrete segments Wedge block technique Installed with erector


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Construction feasibility Evolution of the properties of the lining

Higher strength Lower thickness Manual mechanised installation Lower host rock disturbance

Limit overexcavation Avoid additional convergence after lining installation

1st shaft 2nd shaft (sand) 2nd shaft (clay) Test drift Connecting gallery PRACLAY galleryConstruction end 1982 1999 1999 1987 2002 2007

External diameter 4.3 m 4.5 m 4.5 m 4.7 m 4.8 m 2.5 m

Lining thickness 2 x 40 cm 30 cm * 40 cm * 60 cm 40 cm 30 cm

Installation method Poured Segments (mechanised) PouredShotcrete + segments

(manual)Segments (mechanised) Segments (mechanised)

Rigidity Rigid Rigid Rigid Wooden interlayers Rigid Rigid / INOX interlayers

Host rock disturbance Very large NA Large Large Small Small

Compressive strength C40/50 ** C40/50 C45/55 C45/55 C65/80 C80/95 and >C125/150 ***

* Secondary lining thickness, primary lining is present** Based on test cube results

*** C125/150 is not an official strength class; >150MPa on a normalised cilinder was required


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Monitoring of strains in lining (CG) Correction for creep phenomena is important

External ground pressures Test Drift: 1.6 – 2.4 MPa (De Bruyn et al. 1995)

Connecting Gallery: 2.1 – 3.1 MPa (Ramaeckers & Van Cotthem 2003)

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The PRACLAY project










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The PRACLAY heater test Demonstrate that thermal loading doesn’t compromise the

role of Boom Clay in the disposal system Combination of excavation (EDZ) and thermal loading Study the interaction between the host rock and the lining

(cf. retrievability) Verify current knowledge of THM(C) processes Large scale heated section ~35m (~80°C) Long term heat during 10 years


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The PRACLAY heater test Some tailor-made concrete applications Lining

C80/95 (“normal” wedge blocks) Very high-strength concrete (Ceracem®, Eiffage)

End plug Compressive concrete (Solexperts) Grout


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PRACLAY heater test: lining

Geotechnical load case Host rock 2.5 MPa Anisotropy 1.1 (1.4)

Thermal load Temperature increase ~70°C Temperature gradient ~10°C

Conservative calculation (no possibility for dilation) leads to stresses in the lining up to 110 MPa during the thermal phase


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PRACLAY heater test: lining

C80/95 unreinforced concrete Expansions joints to allow thermal dilation

Stainless steel foam panels, silicone rubber sheets


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PRACLAY heater test: lining Stainless steel foam panels

Elasto-plastic behaviour Small compression before thermal phase Start to compress before the concrete

fails (allow thermal dilation) Compression tests have confirmed the

elasto-plastic behaviour Test necessity of joints: rings without

Special concrete: > 125MPa on cylinder Fibre reinforced concrete (Ceracem®)


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PRACLAY heater test: end plug


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Conclusions

EIG EURIDICE uses cementitious materials in on surface and in-situ tests

Backfill experiments (ESDRED) Demonstrate the feasibility of grouting technique Give important input for future design

Cementitious materials are important construction materials for a disposal site / URF

Concrete (lining) technology has evolved over time

Some tailor made concrete solutions were necessary to cope with the specific experimental conditions of the PRACLAY heater test

13 th exchange meeting the role of cementitious materials for deep disposal of high-level waste in...

Documents

th exchange meeting

esdred ec slide

praclay project praclay

praclay heater test

selfrac ec

timodaz ec

clipex ec

test esdred ec confirmation