13 th exchange meeting the role of cementitious materials for deep disposal of high-level waste in...
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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
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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
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), …
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
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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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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Construction feasibility
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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Construction feasibility
Use of cementitious materials in HADES mainly linked to the lining Second shaft Prefab segments + shotcrete + cast concrete
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Construction feasibility
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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Construction feasibility
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
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 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