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47 April 2020 / www.theengineer.co.uk
fuller understanding of challenges
throughout the GDF lifecycle.
NH: The main challenge is in assuring
the post-closure safety of the facility,
which requires a detailed and evidenced
safety case which has to predict the
evolution of the facility over several
hundred thousand years, considering
processes on the scale of the atom,
to the depth of the facility below the
surface. In the UK context, we have
been developing the basis of the safety
case over the last decade, but it will
need to be elaborated and tailored to the
selected site.
TM: The main challenges foreseen
during construction will be the
management of conventional hazards
associated with the construction and
operation of the underground workings.
Once constructed, ensuring suitable
long-term stability, and associated asset
management and maintenance of the
underground structures are likely to be
areas of key regulatory focus from an
engineering perspective.
There is no guarantee that a GDF will be
accepted in areas where it is proposed.
What contingencies should be in place?
AS: RWM is implementing a Concept
Selection Process to identify a number
of potential sites to locate a future
GDF and their approach to evaluating
multiple potential sites gives some
contingency to complete iterative
sitting process. They will need to
work with communities (locally and
regionally), offering a successive
programme of optioneering and
optimisation to ensure the ‘best fit’
disposal concepts are developed and
refined for each potential site and that
preferable solution is carried forward.
Presently, the main contingency
would be to increase the volume of
interim storage available within the UK
infrastructure, holding accumulated
wastes until and accepted GDF solution
is agreed upon.
TM: Higher Activity Radioactive Waste
(HAW) is currently safely and securely
stored at nuclear sites and will continue
to accumulate, both from existing and
new sources, where it will present
an on-going risk requiring active
management until a final disposal
solution is delivered. ONR agrees that
a safe permanent disposal route is
needed to resolve this situation and
supports government policy for longterm
management of HAW through
geological disposal.
NH: The contingency is continued
surface storage, which is the current
practice. Technically, it is feasible to
repackage the waste every few decades
and build new stores. However, this
is effectively kicking the waste can
down a never-ending road; it would be
leaving the cost, risk and responsibility
of managing and safely disposing of the
waste to future generations who did not
benefit from the energy generation. One
potential option for siting a GDF could
be just off-shore under the seabed, with
surface facilities and the access point
located on shore, which might, or might
not, be considered less contentious.
Could the waste be exported, or could
surface-level storage continue until
other disposal methods are available,
such as in Prism reactors?
BC: The import or export of radioactive
waste is not allowed, except in very
limited circumstances, so we must
manage our own waste. Whilst current
storage arrangements are safe and
secure in the short-term, some of
the waste will remain radioactive for
many thousands of years. A permanent
disposal solution is therefore needed
and there are currently no viable longterm
waste management options that
remove the need for a UK GDF. Whilst
some materials now in storage could
theoretically be re-used in some way,
most of our radioactive waste cannot,
and re-using those materials will
produce further waste to be disposed of.
Are there other feasible options other
than a GDF?
AS: There are a number of alternative
disposal options must be considered
and should be kept under review
throughout the GDF implementation
stages ensuring a fully comprehensive
decision is made. However, most of
the alternative disposal options are
either less feasible currently or have
been largely discounted in favour
of a GDF. Some of these are options
such as deep-sea disposal, disposal
at subduction zones, long term above
ground storage, rock melting, deep
well injection, disposal in ice-sheets
and even disposal into out of space.
Scotland currently favour Near Surface
Disposal which mimics the concept of
a GDF at less of a depth which would
also be a favourable option and has
pros and cons to it in comparison to a
GDF. Near surface disposal for short
lived intermediate level wastes are
under further investigation in the UK. A
consensus internationally found a GDF
to be the preferred disposal method
with most nuclear waste generating
countries opting for this option for
the safe disposal of heat generating
radioactive wastes. Therefore, in the
long-term the choice currently is
between near surface disposal and
geological disposal.
NH: Deep isolation borehole technology
is potentially suitable for a small
fraction of the UK’s radioactive waste
inventory such as spent nuclear fuel or
high level vitrified waste, and there are
some potential cost, safety and security
advantages that could arise from
application to these and other potential
wastes. That said, the technology is still
at an early stage of development and
needs considerably more in the way of
full-scale demonstration tests to build
confidence in the approach. However, it
will not change the need for a geological
disposal facility to accept the remainder
of the UK inventory of intermediate
level waste.
Dr Adam Sims
Radwaste
consultant
Bruce Cairns
Chief Policy
Advisor, RWM
Dr Tim Marshall
ONR geological
disposal lead
Prof Neil Hyatt
University of
Sheffield
Deep isolation borehole technology is
potentially suitable for a small fraction of
the uk’s radioactive waste Prof Neil Hyatt
a consensus internationally
found a gdf to be the preferred
disposal method Dr Adam Sims
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