International Radwaste Disposal: Post-Closure Safety, Monitoring and Intervention Bill Miller DOE LTS&M Conference Grand Junction November 2010

2 Spot the Difference – US and European Designs

3 Typical Multi-Barrier Designs (Spent Fuel – Sweden, Finland)

4 Typical Multi-Barrier Designs (Spent Fuel – KBS-3) Spent Fuel Cast Iron Copper Bentonite Rock Microfracture

5 Long-Term Safety Performance – HLW/SF Comparisons

6 Long-Term Safety Performance – Nirex ILW PA

7 Concern Hazard Long-Term Safety – Time in Perspective Years Dose/ Risk 1,00010,000100,0001,000,000100

8 Technical and Societal Expectations for Monitoring  From IAEA (2001) ̶ “... the long term safety of the disposal system should require no further actions on the part of future generations... the long term safety of the disposal system should not be based on the continual monitoring of its behaviour.”  From CoRWM (2006) ̶ “One of the key messages from stakeholders... was the desire to balance the wish to dispose of the waste with the wish to allow for getting the waste out again if this was considered necessary at some time in the future.”  From NEA (2010) ̶ “...lack of acceptance shows a desire of many stakeholders for the concept to accommodate monitoring... one common wish is for strategies that allow long-term monitoring, with the possibility of reversibility and retrievability.”

9 What Can be Monitored ? Complex, coupled THCM (B) processes  Thermal: ̶ radiogenic heat output  Hydraulic: ̶ resaturation of near-field rock ̶ saturation and swelling of bentonite  Chemical: ̶ mineral/water reaction (pH, Eh) ̶ copper then iron corrosion (chloride)  Mechanical: ̶ stress readjustment ̶ component failure  Biological: ̶ microbially mediated reactions

10 Time to Achieve Equilibrium – Spent Fuel, Thermal Posiva

11 Time to Achieve Equilibrium – Hydrostatic Pressure SKI, Decovalex

12 Time to Achieve Equilibrium – ILW, pH Nirex

13 Is Post-Closure Monitoring Meaningful ?  Short-term post-closure monitoring will record the repository ‘settling’ to a new equilibrium  But these results will not provide any significant information on long-term containment and safety  If it does, something has gone terribly wrong !  Therefore, we will need to compare actual monitoring results against predicted performance

14 Monitoring – Expected Performance Envelope X X X X X X X X X Natural baseline X X X X X X X X X X X X X X Construction operation X X X Closure Post-closure X X X X X X Trigger for intervention ?

15 Waste Emplacement is Hard Enough !!  People should not underestimate how hard post-closure retrieval would be – easy to promise, very hard to do...  Practical full-scale demonstrations of waste emplacement have shown the difficulties of disposal ̶ ESDRED “Engineering Studies and Demonstration of Repository Designs”

16 Retrieval Methods Under Development SKB, Äspö Andra, ESDRED Nirex, NRVB

17 NEA – Retrievability Scale

18 Some Final Key Messages  Deep geological disposal is intended to be passively safe, and should not reply on any post-closure human actions  The public is unlikely to be convinced by safety assessments and will demand post-closure monitoring as a prerequisite for hosting a repository  Post-closure monitoring will record all sorts of signals as the repository system achieves thermal, chemical, hydraulic and mechanical equilibrium  These signals will not directly correlate to any measure of waste containment or repository safety over the likely period of a monitoring programme  Monitoring will need to backed-up by sophisticated modelling and assessment capability to interpret the signals, against a predicted ‘performance envelope’  Monitoring is inextricably linked to public expectations that waste will and can be retrieved if anything ‘goes wrong’ – but this will be very hard to achieve  Decision makers need to balance the technical and societal expectations for monitoring and retrievability, and these should be realistic Thank you for listening !