A multi-coloured map

Large areas of orange, a lot of lilac, a touch of green: the map of Germany on which the Bundesgesellschaft für Endlagerung (BGE) – the Federal Company for Radioactive Waste Disposal – shows possible sub-areas is a colourful one. Its radiant hues show where there are claystone, granite or rock salt formations and, above all, which regions in Germany – according to current knowledge – may be suitable as a site for a future repository for high-level radioactive waste. The sub-areas were assessed against legally stipulated criteria and finally made public in the BGE’s Sub-areas Interim Report in September 2020. The Oeko-Institut is involved in a number of projects which examine the bases and content of the Interim Report and consider the implications for various regions in Germany.

According to the Interim Report, a total of 90 sub-areas in Germany are suitable in principle for consideration as a repository site; this means that based on current knowledge, they have suitable geological conditions as stipulated in the Repository Site Selection Act (Standortauswahlgesetz – StandAG). They include the Fichtelgebirge mountain range in Bavaria, Alb-Donau-Kreis county in Baden-Württemberg, the Mecklenburg Lake District, and the district of Friesland, as well as cities such as Berlin and Stuttgart.

The Repository Site Selection Act defines three groups of criteria. In a first step, exclusion criteria were applied in order to identify areas that cannot be considered. Characteristics that put a site out of the running for a future repository are seismic or volcanic activity and large-scale vertical movements. “These are caused by very gradual processes, such as plate tectonics, within the Earth,” says Dr Saleem Chaudry, a geologist from the Oeko-Institut’s Nuclear Engineering & Facility Safety Division. “Areas that have active geological fault zones where there are fractures in the rock strata, for example, and areas with young groundwater in direct exchange with the biosphere are also excluded.” The Act also stipulates minimum requirements for a possible final repository, which were applied in the second step for the Interim Report. “For example, the host rock must have very low-level permeability, the rock formation must have a thickness of at least 100 metres and be located at least 300 metres below ground surface, and it must be large enough for a repository that can accommodate all of Germany’s nuclear waste,” Dr Chaudry explains. In a third step in this part of the process, the identified areas were evaluated according to 11 geoscientific weighing criteria, including the rock’s temperature compatibility, protection of the effective containment zone by the overburden, and hydrochemical conditions.

One million years

All these criteria are intended to ensure that the high-level radioactive waste – mainly consisting of spent fuel elements and vitrified fission products from reprocessing – remains safely contained in the future repository for a period of at least one million years. “From a scientific perspective, there is currently no alternative to underground storage of this waste. Over the long term, geological barriers can prevent the radioactive materials from reaching the surface again,” says Dr Chaudry. “They will of course be reinforced by technical and geotechnical barriers, including those created when the repository is sealed.”

Even after the application of these criteria and requirements, that still leaves a total of 54 per cent of Germany’s national territory as a designated sub-area; the details are published in the Interim Report. In a self-funded project, the Oeko-Institut is tracking the process from a scientific perspective, for example by producing analyses and participating in the relevant sub-areas conferences (for more details, see “An ongoing task” on p. 8). “We also publish statements and articles about the Interim Report in order to address current issues, and we provide background information for all interested parties,” says Dr Chaudry. Overall, the researchers regard the Interim Report as an important step in keeping the public informed and offering them an opportunity to participate in the process early on. “Many elements of the report have been handled well; the criteria were applied sensibly and addressed in a transparent manner.” Elsewhere, however, the experts are critical of the Interim Report’s methodology. “For example, before making any predictions on volcanic activity in a given region, the indicators need to be reviewed as there are differences in scientific opinion here.” Dr Chaudry is also critical of the fact that much of the available data relating to previous drilling was not utilised in the production of the report. “This is due to the principle of comparability, because the data may have been available for one region but not for another. However, in the further process, this information should be used for site-specific evaluation.”

In addition, the Oeko-Institut considers the very detailed report to be insufficiently structured, especially given the complexity of its content. “A non-professional would find it almost impossible to navigate,” says Dr Chaudry. “And there are many sections where even scientists working on this topic on a daily basis find it difficult to follow the decisions that the report documents.” In his view, this is partly due to the short timeframe for the production of the report. “However, it is neither necessary nor sensible for the persons responsible to be working under time pressure here.”

Impact in the regions

From Dr Saleem Chaudry’s perspective, the Interim Report requires interpretation as a matter of urgency for anyone who is not an expert but will be using it in their work. “Sooner or later, local government representatives in particular will need the capability to deal with this topic.” The Oeko-Institut has already provided this service for Bevensen-Ebstorf municipality in Lower Saxony by “unpacking” the report and providing short-term consultancy. “The municipality wanted to know why it was being considered as a site for a repository, so we looked at the reasons for this decision.” Two salt domes and a claystone distribution area were designated as sub-areas in the Interim Report. “In our analysis, we found that with regard to the weighing criteria, for example, only very general information about the rock formations, their location, scale and thickness had been used,” says Saleem Chaudry. “In our view, detailed information from the municipal area was left out of the assessment.”

The Oeko-Institut has already provided advice to Emsland as well. “In total, there are 10 possible sub-areas across this rural district, including three salt domes, which lie adjacent to each other,” says Dr Chaudry. “The officials responsible for dealing with this issue wanted to know whether these domes were likely to be considered for a repository. We also helped them set up their own advisory panel.” In its report, entitled “Specialised Consultancy for Emsland Rural District on the Findings of the Sub-areas Interim Report as Part of the Process for the Selection of a Repository Site” (Fachliche Beratung des Landkreises Emsland zu den Ergebnissen des Zwischenberichts Teilgebiete im Standortauswahlverfahren für ein Endlager), the Oeko-Institut notes that the methodology that led to the selection of the salt domes was transparent. However, the report also identifies a need for additional information and review on certain points. “For example, pre-existing site-specific data from prospection drilling by the oil industry were not used in the assessment – that needs to change as the process continues,” says Dr Chaudry. “There also need to be further checks on which active fault zones exist in the salt domes and how this influences their suitability as a sub-area.” The report further notes that the minimum requirements pertaining to the size of the future repository – three square kilometres for rock salt, six for crystalline rock and 10 for claystone – should be reviewed, “also with a view to establishing whether the stated area is sufficient to guarantee retrievability of the high-level radioactive waste, if desired.”

On behalf of the Citizens’ Initiative for Environmental Protection Lüchow-Dannenberg (Bürgerinitiative Umweltschutz Lüchow-Dannenberg), the researchers also produced a “Short Report on the Implementation of the Criteria pursuant to Sections 22-24 of the Repository Site Selection Act: Methodology for the Application of the Criteria by the Federal Company for Radioactive Waste Disposal (BGE)” (Kurzgutachten zur Umsetzung der Kriterien nach den §§ 22-24 StandAG in Methoden zur Kriterienanwendung durch die Bundesgesellschaft für Endlagerung mbH). “The Citizens’ Initiative had already commissioned us to assess the suitability of the criteria applied in the Interim Report prior to its publication,” the geologist explains. “We concluded that for the most part, the requirements and criteria defined in the Repository Site Selection Act were translated into a methodology in a transparent and appropriate manner.”

Losing colour

The search for a repository site will soon enter the next phase. For the BGE, this will involve conducting surface explorations in potential siting regions and narrowing the choice further, based on analyses of seismic activity, for example. This will be followed by subsurface explorations in a third phase and a site proposal, which is subject to final approval by the German Bundestag. The aim is to have identified a site by 2031. So instead of its current broad sweep, the BGE’s map of Germany will gradually become focused on individual areas – and will become much less colourful in the process.

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Geologist Dr Saleem Chaudry works on various aspects of radioactive waste management. Based in the Oeko-Institut’s Nuclear Engineering & Facility Safety Division, his specialist areas include the geochemistry of marine evaporites and inter- and transdisciplinary research in the field of radioactive waste management.