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ATLAS III results and relevance to the Safety Case X. Sillen – X.L.Li – J. Verstricht – P. Van Marcke

ATLAS III results and relevance to the Safety Case X. Sillen – X.L.Li – J. Verstricht – P. Van Marcke. ATLAS III results and relevance to the Safety Case. The challenge: disposal of heat-emitting waste The experiment: ATLAS III Experimental results to date Modelling results to date

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ATLAS III results and relevance to the Safety Case X. Sillen – X.L.Li – J. Verstricht – P. Van Marcke

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  1. ATLAS III results and relevance to the Safety Case X. Sillen – X.L.Li – J. Verstricht – P. Van Marcke Exchange Meeting XII, September 30, Mol

  2. ATLAS III resultsand relevance to the Safety Case • The challenge: disposal of heat-emitting waste • The experiment: ATLAS III • Experimental results to date • Modelling results to date • Provisional conclusions from the experiment • Relevance to the Safety Case Exchange Meeting XII, September 30, Mol

  3. ATLAS III resultsand relevance to the Safety Case • The challenge: disposal of heat-emitting waste • The experiment: ATLAS III • Experimental results to date • Modelling results to date • Provisional conclusions from the experiment • Relevance to the Safety Case • Significance for the PRACLAY experiment • do not miss Xiang Ling's presentation today ! Exchange Meeting XII, September 30, Mol

  4. Disposal of heat-emitting waste • VHLW: ~ 1 kW per supercontainer • 2 x COGEMA canisters per supercontainer • after cooling time 50 years (after 60 years: ~ 0.8 kW) • supercontainer length: 4.2 m • Spent fuel: ~ 1.4 kW per supercontainer • 4 fuel assemblies, burn-up 45 GWd/tHM per SC. • after cooling time 50 years (after 60 years: ~ 1.2 kW) • supercontainer length: > 6 m SUPERCONTAINERS Exchange Meeting XII, September 30, Mol

  5. Disposal of heat-emitting waste How hot will it be ? • Waste • Engineered BarriersSystem (EBS) • Clay • Aquifers • Reports are available • Near Field (R-4277, Weetjens & Sillen, 2005) • Far Field (ER-38, Sillen & Marivoet, 2007) • Mostly based on SAFIR-2 clay thermal conductivity + sensitivity studies Exchange Meeting XII, September 30, Mol

  6. Disposal of heat-emitting waste What could be the consequences of DT ? • Processes ( system evolution) • Chemical/geochemical ? • Thermal degradation/dissolution rate of waste / EBS components ? • Thermal decomposition of organic matter in Boom Clay, CO2 ? • Migration parameters, solubility ? (RN's, others) • Mechanical ? • Near field: Thermo-Hydro-Mechanics of EBS, host rock ? • Far field: uplift ? • Hydrogeology ? • Impact on the aquifer ? • Time frames ( safety strategy) • perturbations limited to thermal period ? • long-lasting (irreversible) changes ? Exchange Meeting XII, September 30, Mol

  7. The ATLAS III experimentat the Mol URL • Thermal transient affects many processes • several of these processes have been / are investigated within the Belgian R&D programme (OM, aquifers,...) • ATLAS III objectives: • Confirm/update thermal properties of Boom Clay • Especially the thermal conductivity l [W/(m∙°C)] • Test of some PRACLAY-like instrumentation • Investigate THM coupling in Boom Clay Exchange Meeting XII, September 30, Mol

  8. THM coupling ? • Clay = porous media • Terzaghi's analogyadapted to THM • DT thermal expansion • awater > aclay ! Exchange Meeting XII, September 30, Mol

  9. Layout of ATLAS III 8 m 11 m 2.7 m Test drift Heater Observation boreholes 1.5 m 2.7 m 1.3 m Exchange Meeting XII, September 30, Mol

  10. Picture of ATLAS Heater borehole Installation of instrumentation in observation borehole (ATLAS I, 1993) Exchange Meeting XII, September 30, Mol

  11. The ATLAS III experimentas a member of the ATLAS family • ATLAS: Admissible Thermal Loading for Argillaceous Storage • 1 Heater, 2 × observation boreholes • Part of the EC INTERCLAY-II project (1990-1994) • An experiment for modellers (blind predictions) • A simpleTHM experiment • No radioactive source (CERBERUS) • No backfill material (BACCHUS) or simulated EBS • Focus is on the behaviour of the Boom Clay • ATLAS: a modeller's dream • simple geometry • "clean" boundary conditions • simple loading Exchange Meeting XII, September 30, Mol

  12. The ATLAS III experiment:"the last remake of ATLAS" • ATLAS I & II limitations • Initial conditions after drilling ? • Deviations of boreholes not taken into account • Relatively little (working) instrumentation • Low data acquisition rate (manual) • Sharp heating transients • ATLAS III improvements • System initially at equilibrium • Deviations of boreholes recovered • Additional boreholes, many additional T & p sensors • High data acquisition rate (fully automatic) • Stepwise, initially limited, heating • ATLAS III complementary to PRACLAY • Small DT, scale  representative of far field Exchange Meeting XII, September 30, Mol

  13. ATLAS III T & p sensors Linear heating source, L=8m, max. 4×450W • AT97E • Inclined • only T sensors • Dz ~ 2.7 m close to heater • ATLAS III (2007): Two new boreholes • in addition to ATLAS I & II boreholes (1993): Heater + T & p sensors + total stresses (?) • AT98E • Horizontal • T and p sensors • distance: ~ 2.7 m Exchange Meeting XII, September 30, Mol

  14. ATLAS III test programme:Thermal power at the heater Start: 02 Apr 2007 Stop:17 Apr 2008 Exchange Meeting XII, September 30, Mol

  15. Experimental results:DT at R85 and R93 (ATLAS I & II sensors) Exchange Meeting XII, September 30, Mol

  16. Experimental results:DT at R98 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  17. Experimental results:DT at R98 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  18. Experimental results:DT at R97 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  19. Experimental results:DT at R97 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  20. Experimental results:pore water pressures (R85, R93 & R98) Interesting feature(not an artefact, canalso be seen in HE-D) Exchange Meeting XII, September 30, Mol

  21. Experimental results: temporary drop of pressure at start of heating steps Not a local effect: pp drops before local temperature increase ! Exchange Meeting XII, September 30, Mol

  22. sx = sy = sz = p0 s sr sq r r0 q sz sq p0 ps sr y ps x r0 r z Explanation of pressure drop:anisotropy of mechanical properties ? • Lamé's solution (cylindrical hole in isotropic elastic media) • ps : confinement pressure (excavation, thermal expansion,...) • (sr + sq + sz )/3 = p0 no volume change (porewater: Duw = 0) • BUT: not anymore the case for anisotropic media ! Exchange Meeting XII, September 30, Mol

  23. Modelling ATLAS III • Thermo-hydro-poro-elastic model • Heat transport (conduction) • Thermal expansion, thermal stresses • Effective stresses • Porewater pressure dissipation, drainage • COMSOL multiphysics model • General-purpose FEM toolbox • 3D • Transverse isotropic • Use of symmetry • Model parameter values • Initial: consistent with previous lab/in situ studies • Limited optimisation Exchange Meeting XII, September 30, Mol

  24. Modelling results:DT at R85 and R93 (ATLAS I & II sensors) Exchange Meeting XII, September 30, Mol

  25. Modelling results:DT at R98 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  26. Modelling results:DT at R98 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  27. Modelling results:DT at R97 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  28. Modelling results:DT at R97 (ATLAS III sensors) Exchange Meeting XII, September 30, Mol

  29. Modelling results & prediction:pore water pressures (R85, R93 & R98) pressure increase predicted at start of cooling pressure drops can be reproduced(only if mech.anisotropy !) Exchange Meeting XII, September 30, Mol

  30. Experimental results:pore water pressures (R85, R93 & R98) pressure increase observed ! permeability test Exchange Meeting XII, September 30, Mol

  31. Modelling vs. experimental results:pore water pressures (R85, R93 & R98) Exchange Meeting XII, September 30, Mol

  32. Provisional conclusions from experiment and modelling • ATLAS III provides a lot of good-quality data • Observed temperature evolution can be very well modelled • Evidence of transverse anisotropy of thermal conductivity • 1.23 < lv < 1.33 ; 1.65 < lh < 1.75 [W/m/K] • Observed pore pressure evolution can be modelled as well • Assumption: anisotropy of hydro-mechanical parameters • E, n transverse isotropic • 5 parameters: Ep, Et, upp, utp, Gpt • Constitutive model ? • Poro-elastic already gives reasonable results... • ...1.3 m away from heater and more • Kh ~= 2 x Kv • known for a long time, Put & Henrion... • Mechanical anisotropy of Boom Clay deserves characterisation Exchange Meeting XII, September 30, Mol

  33. Relevance of ATLAS III resultsto the Safety Case • ATLAS III improved our knowledge of the thermal conductivity of Boom Clay • An improved description of T evolution of repository is possible • Good news: impact of updated thermal conductivity values on expected Boom Clay temperatures around repository is rather limited Exchange Meeting XII, September 30, Mol

  34. Relevance of ATLAS III resultsto the Safety Case • The "mystery" of long range hydraulic perturbations around HADES during various excavation phases (2nd shaft, CLIPEX) • Many theories have been proposed • EDZ extents  apparent size of excavation larger ? • µ-fracturation and permeability increase ? • pre-existing fractures ? • viscous behaviour of clay (creep) ? • ATLAS III gives us a clue about what could be the explanation • ATLAS is somewhat similar to a dilatometer test • Anisotropy of mechanical characteristics (deformability) is a tempting assumption ! • Other possible hypotheses ? • anisotropy of in situ stresses • thermo-osmosis (?) • An additional observation borehole with pressure measurement above the heater is foreseen to verify the current assumption Exchange Meeting XII, September 30, Mol

  35. Thank YOU for your attention. Thanks go also to • Frédéric Bernier for initial support of ATLAS III • ONDRAF/NIRAS for continued support & funding • The EC & ANDRA for the MODEX-REP project • led us to suspect the effect of anisotropy ofin situ stresses on far field H-M behaviour Exchange Meeting XII, September 30, Mol

  36. Thank YOU for your attention. Thanks go also to • Frédéric Bernier for initial support of ATLAS III • ONDRAF/NIRAS for continued support & funding • The EC & ANDRA for the MODEX-REP project • led us to suspect the effect of anisotropy ofin situ stresses on far field H-M behaviour Exchange Meeting XII, September 30, Mol

  37. Modelling results:D pore pressures after 350 days Exchange Meeting XII, September 30, Mol

  38. Modelling results:D pore pressures after 450 days Exchange Meeting XII, September 30, Mol

  39. Modelling results:DT & Dpore pressure close to heater Exchange Meeting XII, September 30, Mol

  40. Modelling results:pore pressures after 450 days Exchange Meeting XII, September 30, Mol

  41. Modelling results:DT, Ds1 & Ds3 close to heater Exchange Meeting XII, September 30, Mol

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