International Radwaste Disposal: Post-Closure Safety, Monitoring and Intervention
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Transcript of International Radwaste Disposal: Post-Closure Safety, Monitoring and Intervention
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International Radwaste Disposal:
Post-Closure Safety, Monitoring and Intervention
Bill Miller
DOE LTS&M ConferenceGrand Junction
15-18 November 2010
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Spot the Difference – US and European Designs
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Typical Multi-Barrier Designs (Spent Fuel – Sweden, Finland)
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Typical Multi-Barrier Designs (Spent Fuel – KBS-3)
Spent Fuel
Cast Iron
Copper
Bentonite
Rock
Microfracture
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Long-Term Safety Performance – HLW/SF Comparisons
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Long-Term Safety Performance – Nirex ILW PA
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Concern
Hazard
Long-Term Safety – Time in Perspective
Years
Dose/ Risk
1,000 10,000 100,000 1,000,000100
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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.”
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What Can be Monitored ?
Complex, coupled THCM (B) processes
Thermal:̶' radiogenic heat output
Hydraulic:̶' resaturation of near-field rock̶'saturation and swelling of bentonite
Chemical:̶'mineral/water reaction (pH, Eh)̶'copper then iron corrosion (chloride)
Mechanical:̶'stress readjustment̶'component failure
Biological:̶'microbially mediated reactions
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Time to Achieve Equilibrium – Spent Fuel, Thermal
Posiva
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Time to Achieve Equilibrium – Hydrostatic Pressure
SKI, Decovalex
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Time to Achieve Equilibrium – ILW, pH
Nirex
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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
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Monitoring – Expected Performance Envelope
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Natural baseline
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Construction operation
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Closure
Post-closure
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Trigger for intervention ?
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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 disposal̶'ESDRED “Engineering Studies and Demonstration of Repository Designs”
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Retrieval Methods Under Development
SKB, Äspö
Andra, ESDRED
Nirex, NRVB
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NEA – Retrievability Scale
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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 !