Ph' Lalieux, J' Bel, M' Demarche, C' De Bock

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The PRACLAYProject An Evolving Cornerstone in
the Belgian Deep Disposal Programme

• Ph. Lalieux, J. Bel, M. Demarche, C. De Bock
• HLW/MLW Disposal Programme Coordinator

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Content

• Introduction
• Original aims and current achievements
• Current design review
• Redefining PRACLAY
• PRACLAY Components
• Conclusions

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Introduction (i)

• PRACLAY Project as a pivot between
• Phase of methodological RD
• Pre-project phase
• Initially set up as an in situ, large-scale
  demonstration of the technical, industrial and
  economic feasibility of disposing of
  heat-emitting vitrified HLW in Boom Clay

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Introduction (ii)

• However
• Numerous design developments
• Review of the functions to be ensured by EBS
• Increased consideration of operational issues
• Complete review of the SAFIR 2 design
• Requires long-term preparatory work
• Sufficient underground access
• Adequate phenomenological understanding
• Rethinking PRACLAY

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Original aims and current achievements (i)

• Dig a gallery using industrial techniques
  representative for a full-size repository
• Successful realisation of the connecting gallery
  (2001-2002) using TBM and wedge blocks
• Realise a crossing between main and disposal
  galleries
• Partially met by the crossing between the second
  shaft and the connecting gallery
• To be fully met by the construction of the
  crossing between the connecting gallery and the
  PRACLAY gallery study of its behaviour under
  different constraints such as thermal load

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Original aims and current achievements (ii)

• Establish and observe a set up which is identical
  to a planned disposal gallery for vitrified HLW
• SAFIR 2 design
• VHLW simulated by electrical heater
• Not been met yet
• However, experimentally prepared through the
  OPHELIE Mock up

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Original aims and current achievements (iii)

• Improve EBS knowledge
• Some parts included in the OPHELIE works
• On-surface, large-scale hydration test of
  pre-fabricated bentonite blocks under a thermal
  load (1995-2003)
• Contributed extensively to the current design
  revision
• Contributed to further refine instrumentation

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Phases of the HADES URF
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SAFIR 2 Design OPHELIE Mock-Up (dismantling)
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Current design review

• Current preferred option supercontainer
• OPC Ordinary Portland Cement buffer
• Carbon steel overpack
• Still many issues to be solved
• Behaviour under thermal stress
• Alkaline effect (within EBS and Boom Clay)
• Overall feasibility

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Supercontainer design (radial)
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Supercontainer design (radial)
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Redefining PRACLAY (i)

• Considering notably
• Current evolution of the reference design
• Flexibility approach (incl. vis-à-vis regulatory
  or other stakeholder requirements)
• Remaining open issues with SC/OPC
• Need for further characterisation work
• No need to test everything now and in situ
• Clear that the realisation of a unique large
  scale demonstration specific to one (nearly
  definitive) design may not be the most adequate
  option

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Redefining PRACLAY (ii)

• Support to stepwise design development
• Confirmation aspects of the feasibility and
  understanding of some EBS elements
• Testing issues that are generic to, and key for,
  all potential designs (i.e. that are
  design-independent) e.g.
• Thermal impact on the Boom Clay and its EDZ, the
  gallery lining and crossing
• Efficiency of gallery plugs
• Starting as soon as possible
• Extended experimental duration needed to ensure
  representativeness

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Redefining PRACLAY (iii)

• Combining surface and in situ
• Surface when
• No added value of going underground e.g.
• Overpack construction
• Supercontainer construction and handling
• In situ conditions not imposing key requirements
  on the short term performances
• EBS internal interactions
• Help
• Better control experimental conditions
• Ease follow up
• Increase cost effectiveness

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PRACLAY Components (i)

• In situ experiments
• Crossing and gallery
• Heater (and EDZ) test
• Backfill test
• Plug test
• Witness test
• On surface experiments
• EBS material characterisation
• EBS construction and handling
• EBS interaction experiments

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PRACLAY Components (ii)

• PRACLAY gallery and crossing (2005-06)
• Large-scale heater test (over 10 y duration)
• THM perturbation might be the most severe
  transient (large spatial scale, short time)
• Thermal impact on Boom Clay (EDZ whole
  thickness), lining, crossing and backfill
• Combined excavation thermal effects
• Confirmation of THM behaviour predictions
• C (oxidation, pCO2, )

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PRACLAY Components (iii)

• Backfill test (EC IP ESDRED)
• Definition in situ installation and testing of
  annular space between the supercontainer and the
  gallery lining
• Plug test
• PA poor plug performances do not contribute
  significantly to overall RN releases
• However e.g. limit interactions between
  repository zones, increase resilience to
  intrusion, avoid gas migration
• Focus on
• Cutting hydraulic connection along lining and EDZ
• Horizontal emplacement

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PRACLAY Components (iv)

• Witness test
• Check the long term behaviour (several decades)
  of the EBS and the host rock in conditions
  representative of the planned ones
• Test long term monitoring devices
• Engineered analogue
• Could only be installed after interpretation and
  (partial) dismantling the previously mentioned
  in-situ tests (not before 2017)

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Schematic and preliminary overview of the PRACLAY
in situ experiments
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Conclusions

• Original objective demonstration of design for
  vitrified HLW
• Reduced (more realistic expectations) to
• Take into consideration design reviews and
  evolution
• Tackle design-independent open issues
• Enlarged to
• Fully support iterative design development
• Foster complementarity between small surface and
  large in situ experiments