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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