international radwaste disposal: post-closure safety, monitoring and intervention

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

XX

XX

X

XX

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

XX

X

X

X

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 !