More information on our screening work, and its relevance to the siting of a GDF
Approach to higher activity radioactive waste across the UK
The framework for implementing the GDF siting process in England is set out in the 2018 White Paper Implementing Geological Disposal – Working with communities. This policy describes a consent-based approach to finding a suitable site within a willing host community.
Radioactive waste disposal is a devolved matter. Welsh Government policy is set out in two documents: Management and Disposal of Higher Activity Waste; and Geological Disposal of Higher Activity Radioactive Waste: Community Engagement and Siting Processes. These documents describe a consent-based siting process with the same broad policy commitments as are made in England.
The geological screening outputs include Northern Ireland, because this was a commitment in the 2014 White Paper - ‘Implementing Geological Disposal’ - which was issued jointly by the UK Government and the Northern Ireland Executive. Future policy decisions in relation to geological disposal in Northern Ireland would be a matter for the Northern Ireland Executive, which is currently suspended. Accordingly, in the continued absence of the Executive, no further policy commitments can be given at this time.
The Scottish Government has a separate higher activity radioactive waste policy. Scottish Government policy is that the long-term management of higher activity radioactive waste should be in near-surface facilities which are located as near as possible to the sites where the waste is produced.
The National Geological Screening provides a high level summary of the existing geological information of relevance to the safety of a Geological Disposal Facility (GDF) for England, Wales and Northern Ireland. It is possible to have a subsurface facility extending under the sea at depths of hundreds of metres in rock, with the surface works on-shore. In Sweden, their GDF will extend under the sea. For this reason, the screening has considered the geology up to 20km from the shore to account for such an inshore facility.
Relevance to the safety of a GDF
The long term safety of a GDF will be achieved by using a multi-barrier approach comprising both engineered components and the natural rock at a site.
Based upon work in the UK and overseas we have identified three broad types of potential host rock for a geological disposal facility. Click on the links below to see how each of these different rock types could contribute to the safety of a GDF.
- Lower Strength Sedimentary Rocks like clays and mudstones.
- Higher Strength Rocks like granites and slates.
- Evaporites like rock salt.
The screening will provide a high level summary of the geological information which is of relevance to the safety of a GDF, to inform initial discussions with communities who may wish to be involved in the siting process. During the siting process our evaluation and selection of potential sites will consider the relevant geological attributes in a detailed manner that takes into account international guidelines and meets international safety requirements set out by the International Atomic Energy Agency.
The approach to geological screening has been developed based on an understanding of long-term safety requirements, in particular the contribution to safety provided by the geological environment. We worked closely with the British Geological Survey (BGS) and other technical experts to compile information that is available at the national scale which is of relevance to the safety of a GDF .
The draft guidance was reviewed by an Independent Review Panel (IRP) and a public consultation was carried out between September and December 2015. We published a formal response to the feedback received during this consultation in both English and in Welsh. The Final Guidance which takes this feedback into account was published in April 2016, also in English and in Welsh.
Screening identifies where rock with the appropriate geological attributes can be found. It brings together existing information on:
These topics were selected because the information enables an understanding of how effectively the geology could contain and isolate radioactive waste.
Information used for screening
Geological screening is a desk-based exercise, primarily using publicly available information from geological mapping, geophysical surveys and boreholes:
- geological mapping involves study of the rocks where they occur at the surface or are otherwise accessible for direct examination (e.g. mines)
- geophysical investigations include studies of the Earth’s gravity and magnetic fields and seismic surveys to image the subsurface.
- boreholes allow access to the sub-surface and the collection of rock and water samples.
Additional information includes historical records from mines, studies of earthquakes and past glaciations, and data from environment agencies.
In order to cover the area of England, Wales and Northern Ireland, the resolution of the screening has been kept at a high level – using base maps at a 1:625,000 scale at which one centimetre represents about 6 kilometres. This means that local variations in the geological attributes at a level of detail greater than this have not been included.
For the purposes of this work the BGS only used data which was publicly available at the end of February 2016. The one exception to this was the extent of Oil and Gas Authority licensing which was updated to include data to the end of June 2018.
Technical Information Reports (TIRs)
The underpinning geological information has been collated and reported by the British Geological Survey (BGS) as Technical Information Reports (TIRs) following the Final Guidance and implementing Detailed Technical Instructions (DTIs) that were developed for the purpose. The BGS is the UK’s premier provider of geoscientific data, information and knowledge and provides expert services and impartial advice in all areas of geoscience. The TIRs can be found on the BGS website.
TIRs have been produced for each of the 13 geological regions used by the BGS in its Regional Guides. The Regional Guide publication series provides a structure for which there is a well-established source of more detailed information for those who would like to know more. The TIRs are technical reports which are intended for a geological audience, but RWM has produced summaries of the geological attributes for each region intended for a wider technical but less geological audience.
National Geological Screening outputs
We then used our knowledge and understanding of geological disposal to interpret the geological information provided by the BGS for each region in terms of its relevance to the safety of a GDF. The screening outputs are in the form of narratives, maps and videos.
To present these conclusions in a concise and accessible way, we have divided regions into subregions. We have selected subregions with broadly similar geological attributes although there is still considerable variability within each subregion. The boundaries between subregions may locally coincide with the extent of a particular rock type of interest or may correspond to discrete features such as faults.
For each subregion, a non-technical summary of the relevance of the geology to the safety of a GDF is provided. They are supported by more detailed summaries intended for a technical but non-geological audience.
The approach to screening and its application by RWM and the BGS have been reviewed by an Independent Review Panel (IRP), established by the Geological Society of London, to give confidence in the robustness of the outputs. The IRP operated independently of the Geological Society, the Department for Business, Energy & Industrial Strategy (BEIS) and RWM. It first engaged with RWM and its contractors, members of the public and interested stakeholders during the development of the screening guidance in 2015. The IRP was made up of individuals with a broad range of geoscience expertise including experts from the UK, Sweden and Canada, with backgrounds in both industry and academia.
More details about the IRP and their oversight of the National Geological Screening exercise can be found here.
Screening in the context of siting
Geology in the context of wider siting
The high-level screening information has been made publicly available to provide a basis for discussions about the suitability of local geology for siting a GDF.
The results will also inform the planning of further work in areas where communities are interested in hosting a GDF.
The National Geological Screening only considers the geological attributes which have relevance to the siting of a GDF. A number of other factors need to be considered in the siting of a GDF, including:
- community interest
- engineering feasibility
RWM has developed a Site Evaluation public consultation to consider these factors.
Next steps for geological attributes
Our screening work has only used national scale geological information. Where communities are interested further work on the geology would be needed to develop the understanding needed to decide whether an area is suitable.
Desk studies would be undertaken first, incorporating detailed local information. This would include looking at any information on the depth of principal aquifers and the consideration of secondary aquifers which are of local importance and so have not been considered as part of this national exercise.
Where communities are interested and the geology has potential, RWM will then commission new investigations to address gaps in geological understanding. Initially these may include airborne geophysical surveys. Land-based geophysical surveys and the drilling of boreholes will be needed to provide the level of information needed to identify a preferred site for a GDF.
Suitability can only be finally established when RWM and the independent regulators are satisfied that the geology is sufficiently well understood to support the design and safety of a GDF at a specific site.
More details about the wider Siting Process can be found here.
Details on how other countries have approached siting and screening can be found here.
The National Geological Screening outputs indicate that suitable rock for a GDF is likely to be found under a large part of England, Wales and Northern Ireland. Visit the NGS landing page to find out more information about your region.
If you have a question about NGS, please email firstname.lastname@example.org.
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