The role of the PRACLAY programme in the RD&D programme of ONDRAF/NIRAS

1. Ph. Lalieux, M. Van Geet, A. Dierckx, H. Van Humbeeck The role of the PRACLAY programme in the RD&D programme of ONDRAF/NIRAS

2. 11th Exchange Meeting Overview The Belgian RD&D programme: from SAFIR 2 towards SFC 1 The PRACLAY Demonstration & Confirmation Experiment PRACLAY within the Belgian RD&D programme PRACLAY success criteria

3. 11th Exchange Meeting Over 30 years of RD&D on geological disposal of HLW/ILW-LL in clay • Reference host rock is Boom Clay • Summarized in SAFIR 2 report (2001) and peer reviewed (NEA, 2003)‏ • Disposal in Boom Clay has the potential to be safe and feasible • Boom Clay has excellent barrier properties as regards the migration of radionuclides • Industrial mining feasibility is established (but crossings between galleries)‏ • The programme is well developed and sufficiently advanced to address the siting issue, even though several uncertainties must still be reduced • However, disposal in Boom Clay lacks formal political and societal legitimacy

4. 11th Exchange Meeting Therefore, further development is based on complementary approaches • Reducing scientific and technological uncertainties for increased safety margins • Progressively turning working hypotheses into legitimated choices / policy through decision-oriented documents • Geological disposal • Argillaceous formations as host • Poorly indurated clays • Boom Clay • Site Waste Plan (~ 2010)‏ Safety & Feasibility Case 1 – SFC 1 (~ 2013) Safety & Feasibility Case 2 – SFC 2 (~ 2020) Licence application + conditions to be guaranteed

5. The PRACLAY Demonstration & Confirmation Experiment PRACLAY surface programme PRACLAY in-situ programme (PRACLAY witness programme)‏ 5 11th Exchange Meeting 13 December 2007

6. 11th Exchange Meeting PRACLAY SurfaceProgramme (supercontainer design specific)e.g. ESDRED (EC)‏

7. The PRACLAY Demonstration & Confirmation Experiment PRACLAY surface programme PRACLAY in-situ programme (PRACLAY witness programme)‏ 7 11th Exchange Meeting 13 December 2007

8. The PRACLAY Demonstration & Confirmation Experiment PRACLAY In situ Programme Gallery & Crossing Test Heater Test Seal Test TIMODAZ ATLAS III 8 11th Exchange Meeting 13 December 2007

9. 11th Exchange Meeting PRACLAY in-situ

10. 11th Exchange Meeting Overall objectives of the PRACLAY Heater Experiment Demonstrate several mining feasibility aspects, esp. crossings Assess the impact of a thermal stress on the Boom Clay originating from heat emitting waste (vitrified waste and spent fuel) Most penalizing conditions of thermal transient THM behaviour, self-sealing capabilities, influence on RN transport parameters Not a “prototype” type of demonstration Not specific to the Supercontainer design

11. 11th Exchange Meeting The place of PRACLAY Heater Experiment within the Belgian programme • PRACLAY is part of the assessment basis for both feasibility and safety evaluations • Delivers substantiation of key safety and feasibility statements • One of the drivers for SFC’s planning • SFC 1 (2013) : first input, with the most important information from the transient phase  no major flow • SFC 2 (2020) : full input • Takes a central place because uniqueness (large-scale, long-term)

12. These objectives are linked with safety strategy, RD&D priorities and SFC goals Assess adherence to requirements: Bottom – Up Approach from scientific and technical assessment basis Disposal System Design Requirements: Top – Down Approach from safety strategy

13. 0 103 104 – 105 106 years Isolation (I) EBS Boom Clay and environment Eng. Cont. (C) Delay and attenuate (R) Boom Clay Thermal phase Engineered Containment phase System containment phase (retarded) System containment phase (non retarded) Stable geological barrier phase BC temp. in accept. Range + Loss of integrity of ECB Possible release of non retarded contaminants to beiosphere Heat-emitting waste Closure of disposal

14. 11th Exchange Meeting “Top-down” to “bottom-up” Design should show sufficient promise to proceed to next stage Require-ments top - down Repository should provide long-term safety Repository should be technologically and economically feasible Engineered containment barrier should provide C for at least the duration of the thermal phase Boom Clay should delay and attenuate releases (R)‏ for at least a million year … Boom Clay provides diffusion and retention up - bottom Well-substantiated claims Permeability is low Sorption capacity is high …

15. 11th Exchange Meeting Feasibility statements to be substantiated The disposal facility can be constructed, operated and closed with adequate funding provided constructed operated closed packages costs

16. 11th Exchange Meeting Safety statements to be substantiated The disposal system and environment conform to regulatory standards of long-term safety isolation containment delay and attenuate Waste form spreads the release Transport is diffusion dominated Host rock (+EBS) retard components dilution evaluations Environmental impact

17. DEMONSTRATION FEASIBILITY constructed Disposal galleries can be constructed using wedge blocks with reliable and safe techniques Crossings between access and disposal gallery can be constructed using reliable and safe techniques

18. 11th Exchange Meeting Demonstration objectives Demonstrating the feasibility in constructing a crossing between galleries Crossing of disposal and access gallery Without starting chamber (expensive + strong disturbance)‏ At representative ratio (≤ 2)‏ Demonstrating the feasibility of a stop & go with the tunnelling machine with shield Demonstrate that interruption of excavation process does not pose a problem to use preferred excavation method Demonstrating the absence of liquefaction of Boom Clay Based on our current knowledge, this will not occur, but PRACLAY will enable confirmation at large scale

19. PROCESS UNDERSTANDING SAFETY Delay and attenuate Transport is diffusion dominated THM properties known Self-sealing Effects of excavation known Effects of thermal stress known Chemical changes do not limit sealing Environmental impact Temperature increase of the aquifers is acceptable Thermal expansion of the soil is acceptable

20. 11th Exchange Meeting Objectives regarding process understanding Capability to assess the heat dissipation from a repository containing heat-emitting waste Mainly the thermal conductivity of the Boom Clay Can have a direct influence on the repository layout and associated costs Capability to assess the consequences of a THM impact on the damaged/disturbed zone of the host rock Major focus on the diffusion Allow describing the evolution of the damaged and disturbed zone (Selfrac – Timodaz) Multiple lines of evidence gathered and remaining uncertainties identified Capability to assess the stability of concrete lining under thermal stress Need and performances of compressive materials (not needed in current reference design as no retrievability requirement)‏

21. 11th Exchange Meeting Objectives regarding process understanding (Ctd)‏ SAFETY Host rock (+EBS) retard components • Increase capabilities to substantiate the limited influence of thermal loading on RN transport-related parameters • Understanding of the effects on Boom Clay characteristics after a thermal pulse with main focus on retention safety function • Post-mortem analyses Chemical disturbances related to temperature increase are known and will not jeopardise the favourable characteristics

22. Objectives regarding process understanding (Ctd)‏ FEASIBILITY closed Progressive closure can be monitored in line with strategy • Progress in monitoring in realistic conditions to help elaborating a monitoring strategy • Increasing the capability to provide an effective range of reliable and validated systems to monitor disturbances within the clay as a result of gallery excavation and heat-emitting waste emplacement • Input to the development of a monitoring plan and monitoring objectives

23. Risk analysis PRACLAY Belgian programme Crossing Stop/postpone Major issue Liquefaction Stop Showstopper Stop & go None Re-evaluate design Heat dissipation Major objective not obtained Large uncertainties THM impact Major objective not obtained Large uncertainties Stability of lining Dismantling more difficult Retrievability excluded for this solution Effect on RN transport None Large uncertainties Monitoring Partial reinstallation Important missed input Communication Missed opportunity Missed opportunity 11th Exchange Meeting

24. 11th Exchange Meeting Assessment of success Assessment Crossing Feasibility Liquefaction Presence/absence Stop & go Feasibility Heat dissipation Reduction of uncertainty THM impact Answers and multiple lines of evidence on evolution and uncertainties of DZ Stability of lining Compressible materials needed? Effect on RN transport RN transport related parameters remain within natural variability Monitoring 50% of PW and T° sensors function during experiment Communication Scientific publications + actions to selected target public

25. 11th Exchange Meeting Conclusions Important step with respect to substantiating feasibility and safety statements Aims at confirming the absence of undue impact of thermal stress on (long-term) safety First result on THM to be available by Safety & Feasibility Case 1 (2013) No « full prototype » Communication opportunity