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Paul Skelton Head of Assessments for Sellafield and Spent Fuel and Nuclear Materials
The multi-barrier concept for
the disposal of spent fuel to
a geological disposal facility
Scope of presentation
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• To describe the multi-barrier
approach to disposability of spent
fuel and international experience
in this area
• To highlight the current and future
work activities being undertaken
by RWM in support of options for
disposal of spent fuel
Implementing Geological Disposal
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• The scope of the GDF is established
within the Government White Paper
which sets out the UK Government’s
framework for managing higher
activity radioactive waste
• This also aligns with the
recommendations of the CORWM
report on Managing Radioactive
Waste Safely
• This includes ensuring that materials
not currently defined as wastes, could
be safely managed within the GDF
concept, this includes spent fuel.
Deep Geological Disposal of Spent Fuel
• The generic design
concept for the GDF
includes the capability
to dispose of an
inventory of spent fuel.
• Disposal of spent fuel
is not unique to the UK
GDF concept as such
we collaborate with a
number of our
international sister
organisations in this
area.
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International Experience - Sweden
• SKB the Swedish repository organisation are developing a facility at Forsmark on the east coast of Sweden
• The facility which is being constructed within a hard rock will be the repository for a proposed inventory of
~12,000 tonnes of spent fuel
• The disposal system utilises a multi-barrier approach to provide containment of the inventory,
• SKB have undertaken many years of underground in-situ experimental work to demonstrate feasibility and
safety with in excess of 40 years underpinning through research and development.
• The Swedish government is scheduled to consider SKBs approach for an environmental licence this autumn
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International Experience - Finland
• Posiva the Finnish repository organisation
are developing a facility on the West coast of
Finland. In 2016 a licence was granted to
begin construction of the facility
• The facility which is being constructed within
a hard rock will be the repository for a
proposed inventory of ~5,500 tonnes of
spent fuel
• As with the Swedish methodology the
Finnish approach utilises a multi barrier
approach with canisters placed vertically.
• Since 2004 they have been constructing and
utilising their underground rock
characterisation facility ONKALO to support
the underpinning and implementation of the
national repository.
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Images are used by courtesy of “Posiva Oy”
POSIVA – Underground Rock Characterisation
Facility ONKALO
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Images are used by courtesy of “Posiva Oy”
Isolation and Containment - The multi-
barrier approach
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• Fuel properties
– Ceramic nature of the fuel pellet results in
very slow rate of leaching when immersed
in water
• High Integrity Disposal Canister
– Very high integrity corrosion resistant
container, providing isolation of the fuel from
water and resisting mechanical stresses
• Bentonite Barrier and tunnel backfill
– Protects the canister from movement in the
bedrock and minimises canister corrosion
• Bedrock (Distance)
– Changes are slow, predictable and isolated
from changes occurring above ground. This
also distances the packages from human
intrusion and the surface environment
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Isolation and containment: multi-barrier system
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–The multi-barrier concept
is not specific to the
management of spent fuel.
• The same multi-barrier proposal is
also applied to High Heat
Generating vitrified wastes
• A similar approach is also in place
for the management of low heat
generating wastes.
Disposal of Spent Fuel – Current Activities
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• Disposability Assessment
– RWM is currently updating the assessment base for spent AGR against the recently
updated safety case for the Geological Disposal Facility to confirm feasibility of safe
transport and disposal
– Assessments of disposability have also been completed for other types of UK spent fuel in
support of new build, as well as for vitrified HLW.
• Research and Technology development (Providing further underpinning)
– Leach testing of AGR pellet samples to underpin performance assumptions as part of a
wider series of international tests on ceramic fuel performance
– Modelling assessment has been undertaken on container corrosion tests with ongoing
underpinning through a material testing programme
– Bentonite re-saturation trials are ongoing to further underpin barrier performance as part of
the multi-barrier argument
– Significant collaboration with international counterparts on modelling and experimental
work to establish further underpinning on the underpinning science, this includes FEBEX
(the Full-scale Engineered Barrier Experiment) an 18 year + experiment to underpin the
performance of the bentonite under high heat conditions.
Disposal of Spent Fuel – Current Activities
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• Engineering and concept development
– Engineering studies continue to mature the engineering design of the HHGW disposal
system
– RWM continues to work with international sister organisations to learn from international
developments, particularly those with highly matured HHGW disposal systems.
– RWM has an ongoing programme of work based on international practice looking at
“developing concepts” to consider their applicability to the management of the wider UK
inventory (including that of spent fuel)
Keeping in touch
• Visit our website at:
www.gov.uk/rwm
• Subscribe for regular updates via our
homepage or directly at:
https://public.govdelivery.com/accounts/
UKRWM/subscriber/new
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