What is a Geological Repository and what would it look
like?
A Geological Repository is an engineered underground containment
facility or ‘geological disposal facility’, which is designed in
such a way that natural and man-made barriers work together to
prevent and/or minimise the escape of radioactivity. It is
inevitable that some radioactivity from the facility will
eventually reach the surface. But the disposal facility is designed
to ensure that this will not happen for many thousands of years,
and even then only in quantities that are insignificant compared to
the levels of radioactivity all around us in the environment from
natural background sources.
At this early stage in the process it is not possible to specify
exactly what a geological disposal facility will look like. The
detailed layout and design of the basic geological disposal
facility, both above and below ground, will be tailored to the
waste inventory for disposal and the geography and specific
geological characteristics at the site in question.
The dimensions of the underground areas of a geological disposal
facility will be determined by the exact inventory for disposal,
the properties of the host rock and the geometry of features within
it. Nevertheless indicative geological disposal facility dimensions
have been estimated for an inventory similar to the ‘CoRWM
baseline’. Those estimates indicate that the underground area of
host rock required (i.e. the ‘footprint’) for an Intermediate level
waste/low level waste disposal facility would be of the order of
1km², and for a HLW and spent fuel disposal facility (assuming that
the latter were treated as a waste) would be of the order of 3km².
In practice it may be possible to build a geological disposal
facility over a smaller area, by building deposition tunnels or
vaults on different levels. This would however depend on the
geology of the site.
Timescales
An estimated timescale for developing a disposal facility is
outlined in the diagram below. This timescale covers the period up
until the facility becomes available for the first waste
emplacement. After that point waste emplacement and construction of
additional vaults and tunnels would continue in parallel for a
number of decades, depending on the decommissioning process and the
waste to be managed. Once waste emplacement is complete the
facility could be closed and the surface facilities dismantled.
The estimated duration is between 20-30 years, however,
sequencing and the makeup of the different stages may be affected
by a number of factors and/or scenarios over the coming years, as
the MRWS programme proceeds.