1 Waste volumes and categories Low active waste Medium active waste High active waste Short livedCategory A Category C Long livedCategory B Category C VolumesCategory A +/ monolithes Category B +/ to monolithes Category C +/ to supercontainers

2 2 I – Isolate (geology) – 1My Reduce the Likelihood of inadvertent human intrusion or human action close to the facility and their possible consequences C – Contain for C-waste - 100’s to many 1000’s y Prevent contaminants’ dispersion from the waste forms during the thermal phase by using one or several impermeable engineered barriers. R – Retard (geology + EBS) – 1 My Retain the radionuclides for as long as required by: Limiting releases from the waste forms Limiting the water flow Retarding the migration of the radionuclides Isolate Contain Retard 2 How does the disposal system ensure safety ?

3 Presence of Boom & Ypresian Clay in Belgium

4 Transport properties of Boom Clay

5 Self-sealing

6 Current reference design Post-conditioning in super-container General view future repository Clay Gallery liner (concrete) Concrete container Cement filling Vitrified waste Steel overpack

7 Construction of HADES URL illustrates feasibility shafts galleries crossings

8 From manual … 8

...to industrial excavation in plastic clay with concrete lining

10 Feasibility: crossing between 2 galleries

12 Refinement of supercontainer (SC) design 2 half-scale tests  Development of a concrete composition for buffer and filler  Demonstration of construction feasibility of the buffer  Temperature and stress conditions in the buffer were measured and simulated  small fissures appearing at the outer surface of the buffer are further being examined (cause, extent and potential impact on operational and long-term safety)

13 The system is known It can be characterised Its evolution is bounded The safety functions can be relied upon Isolation Containment Retardation and low transport The system meets the requirements Radiological Environmental Conditions from the consultations We have confidence in the long-term safety because  the remaining uncertainties are manageable (there is also a tree with the feasibility statements (not shown))

14 Challenging the safety functions Open issues # 1  possible formation of H2S (agressive species) Open issues # 2 Argument # 1 Argument # 2 Argument # 3 Argument # 4 Substantiations Safety-pheno interaction team Assessment basis group The evolution of the overpack can be bound Safety assessment group The safety functions relied upon Safety Assessment can help in prioritisation of the remaining open issues Puts this into question the containment function? Scenarios with conservative values illustrate that the [S] at the overpack remains limited IsolationContainment Delay and attenuate

15 Burial history of Boom Clay at Mol Depth (m) Time (Million year) Boom Clay A very unrealistic and continuous uplift during 1 Million year is needed to bring the disposal up to the surface +7 The steepest movement in the burial history of the Boom Clay, would bring the disposal to the surface after about 7 Million years, if it would be continuous during whole this period In this time period about 10 ice ages occured Without unduly perturb the favourable Characteristics of Boom Clay 15

16 Long-term management of categories B&C waste In situ experiments in URL HADES (international collaboration) Geo-chemical, hydro-geological and geotechnical (constraints, pore water pressure, displacements) characteristics of Boom Clay Thermo-hydro-mechanical behaviour of Boom Clay Interaction between Boom Clay and artificial barriers and waste Excavation disturbed zone (EDZ) Radionuclides migration in the Boom Clay Development of measuring technics, …

17 a backfill which is easy to remove was developed the properties of the composition were determined (mainly by laboratory measurements) 2 backfill tests were successfully performed on small- scale mockups of a supercontainer disposal gallery (2 2 long; 60 cm diameter) Development and testing of a backfill composition