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Title: Disposal of HLW and ILW/LLW at the same site: challenges in an international contextAuthors: Maurer-Rurack, U.*, Poller, A., Hardie, S., Poppei, J., Voss, M. **, Smith, P. **** Federal Office for the Safety of Nuclear Waste Management (BASE), Berlin, Germany** CSD Ingenieure AG, Switzerland*** Safety Assessment Management GmbH, Switzerland Abstract:Germany is looking for the site with best possible safety for an HLW (high level waste) repository. In the site selection procedure of Germany three host rocks: rock salt, clay and crystalline rock are considered. In accordance with §1 (6) of the StandAG (German Site Selection Act), an additional disposal of ILM/LLW (intermediate level/low level waste) might be allowed at the same site, provided that its characteristics satisfy the best possible safety criteria for the sole disposal of HLW waste. This point will be addressed within the framework of preliminary safety investigations pursuant to §27 (5) of the StandAG in the individual phases of site selection process for the HLW repository, according to the current state of science and technology.The GemEnd research project (2022, in press) investigates the possible mutual influence of these different types of repositories at the same site and the resulting safety-relevant consequences for the HLW repository system in Germany.This contribution provides an overview of the currently existing international disposal programs of non-heat-generating waste (ILW/LLW) and heat-generating waste (HAW) at the same site in the following countries: Belgium, France, Finland, Germany, Japan, Sweden, Switzerland and the United Kingdom.The IAEA (International Atomic Energy Agency) also considers co-disposal of HLW and ILW/LLW as an option that has advantages over separate repositories. But particular critical interactions caused by gas formation and gas transport as well as interactions of cementitious materials with other engineered components and the host rocks should not be forgotten (IAEA 2009, 2018).On this basis, existing international disposal programs for HLW and ILW/LLW at the same site are compared with each other. Important similarities and differences for the transferability of the findings to the site selection procedure in Germany are presented. Finally, the approach of other countries can contribute to a better assessment of the safety implications in Germany.

The Federal Office for the Safety of Nuclear Waste Management (BASE – Bundesamt für die Sicherheit der nuklearen Entsorgung) is the German federal regulatory authority for radioactive waste disposal. It supervises the German site selection process and is responsible for the accompanying public participation. Task related research is an integral part of BASE's activities. The projects MessEr and übErStand compiled the state-of-the-art science and technology regarding surface based exploration methods suitable for addressing the criteria and requirements specified in the German Site Selection Act. The results support BASE to review and define the surface-based exploration programs to be executed by the national implementer BGE (Bundesgesellschaft für Endlagerung mbH). To support BASE in reviewing the application of the exclusion criteria “active fault zones” according to the Site Selection Act, the project KaStör reviewed the current knowledge on active faults and fault zones in Germany and recommends methodological approaches to date and identify the activity of faulting. For the time being, the Site Selection Act defines 100 ∘C as a draft limit on the temperature at the outer surface of a repository container for all host rocks. The project Grenztemperatur studied the temperature dependency of the different thermal-hydraulic-mechanical-chemical/biological (THMC/B) processes according to available features-events-processes (FEP) catalogues for rock salt, clay stone, and crystalline rock and describes ways to defining host rock specific maximum temperatures based on specific disposal and safety concepts. Safety oriented weighting of different criteria and comparison of different potential regions and sites are key challenges during the siting process. The project MABeSt studied and reviewed methodological approaches to this weighting and comparison problem with special emphasis on multi criteria analysis (MCA) and multi criteria decision analysis (MCDA). A key requirement for safe geological disposal of nuclear waste is barrier integrity. The project PeTroS performed the first triaxial flow-through experiments on natural rock salt samples at disposal relevant p−T conditions and studied potential percolation mechanisms of fluids within rock salt. The data substantiate that the minimum stress criterion and/or the dilatancy criterion are the prime “percolation thresholds” in rock salt. The research results support BASE in fulfilling its tasks as national regulator according to state-of-the-art science and technology and are also relevant to other stakeholders of the siting process.

The Site Selection Act stipulates a precautionary temperature limit of 100 ∘C on the outer surface of the containers with high-level radioactive waste (HLRW) in the final disposal site. This precautionary temperature limit should be applied in preliminary safety analyses provided that the maximum physically possible temperatures in the respective host rocks have not yet been determined due to pending research. Increasing temperatures in the deep geological underground, caused by the heat generation of the HLRW, can trigger thermal, hydraulic, mechanical, chemical and biological processes (THMCB) in the respective host rocks of a final disposal site and thus endanger safety. Furthermore, high temperatures may hamper the feasibility to retrieve and recover HLRW from a final disposal site. Such processes are described in detail in databases for features, events and processes (FEP) databases. Single components or barriers of a final disposal facility may require specific design temperatures for the preservation of their features once a concept for long-term safety of a final disposal site is established; however, the interactions of all relevant processes of a concept for a final disposal site must be considered when a specific temperature limit for the outer surface of the containers is derived. This temperature limit may vary for particular safety and final disposal concepts in the host rock: salt, clay and crystalline rock. The conclusion is that temperature limits regarding the outer surface of the containers should be derived specifically for each safety and disposal concept and should be supported by a solid safety analysis. Temperature limits without reference to specific safety concepts or the particular design of the final disposal site likely narrow down the possibilities for optimisation and could adversely affect the site selection process in finding the best suitable site.

The Federal Republic of Germany has decided to dispose its high-level radioactive waste in deep geological formations. Three types of host rock are considered: rock salt, clay rock and crystalline rock. The Site Selection Act (StandAG1), which came into effect on the 16th of May 2017, defines the successive steps of the repository siting process, which has to ensure the best possible safety conditions for a period of one million years. Based on precaution considerations, the StandAG (§27 (4) StandAG) sets a preliminary temperature limit of 100°C at the outer surface of a repository container for the preliminary safety assessment.This contribution provides an overview about the state of the scientific and technical knowledge on the limiting temperatures in the repository site selection process of Germany. It also illustrates the different treatments of the definition of temperature limits within other European siting processes. The findings highlight that, in Europe, the proposed criteria which consider temperature at the outer surface of a repository container get more and more into focus of research and discussion especially for the three different types of host rocks.After presenting the national regulatory frameworks, this contribution summarizes how the European countries address the different temperature related issues for their site selection, their repository concepts and how in turn these all can influence the German safety case strategy for the German site selection. Not at least, links to site selection criteria in other countries (e.g. USA, Japan, Russia) are provided.Reference1 StandAG: Standortauswahlgesetz vom 5. Mai 2017 (BGBl. I S. 1074), das zuletzt durch Artikel 2 Absatz 16 des Gesetzes vom 20. Juli 2017 (BGBl. I S. 2808) geändert worden ist.

The German Site Selection Act (Standortauswahlgesetz – StandAG) defines the search for and selection of the national German site with best possible safety for a disposal facility for high-level radioactive waste. The Federal Office for the Safety of Nuclear Waste Management (BASE) is the federal regulatory authority for radioactive waste disposal. BASE supervises the site selection process for a repository for high-level radioactive waste and is responsible for the accompanying public participation. To fulfill its tasks according to the state of science and technology, task related research forms an integral part of BASEs activities. Current research activities in the context of the site selection process address geoscientific questions, methodological aspects of the implementation of the site selection process, and public participation aspects. This contribution provides an overview on the current geoscientific and methodological research activities of BASE.According to § 16 StandAG , the national implementer (Bundesgesellschaft für Endlagerung mbH) has to execute surface-based exploration and BASE has to review and define the respective exploration program. Therefore, the two projects MessEr and übErStand compiled state of science and technology with regard to surface based exploration methods. The foci were on methods suitable for addressing the criteria and requirements set out in the German Site Selection Act.The project KaStör reviewed the current knowledge on active faults and fault zones in Germany and studied methodological approaches to date and identify the activity of faulting. The results support BASE to review the application of the exclusion criteria for areas with “active faults zones” according to § 22 (2) StandAG.For the time being, § 27 (4) StandAG defines 100 °C as precautionary maximum temperature at the outer surface of waste canisters for all host rocks. The project Grenztemperatur compiled and studied the temperature dependency of the different THMC/B processes according to available FEP catalogues for rock salt, clay stone, and crystalline rock. The project also identified open and pending research questions and describes ways to define host rock specific maximum temperatures based on specific disposal and safety concepts.During the site selection process, safety oriented weighting of different criteria and comparison of different potential regions and sites have to be performed. The project MaBeSt studied and reviewed methodological approaches to this weighting and comparison problem with special emphasis on multi criteria analysis (MCA) and multi criteria decision analysis (MCDA).Key requirement for safe geological disposal of nuclear waste is barrier integrity. The project PeTroS experimentally studied potential percolation mechanisms of fluids within rock salt at isotropic conditions at disposal relevant pressures and temperatures.

The INSPIRE Human Health and Safety (HH) theme describes ,,geographical distribution of dominance of pathologies (allergies, cancers, respiratory diseases, etc.), information indicating the effect on health (biomarkers, decline of fertility, epidemics) or well-being of humans (fatigue, stress, etc.) linked directly (air pollution, chemicals, depletion of the ozone layer, noise, etc.) or indirectly (food, genetically modified organisms, etc.) to the quality of the environment". Several components were identified within this broad theme description, including: human health data (on diseases, poisoning, injuries, etc.); biomarkers; health care/health services data; and determinants of health (focus on environmental data). While the definition in the Inspire Directive refers to direct or indirect links between pathologies and the quality of the environment, the HH data model is able to accommodate all health data, while linkage of specific health issues and the environment is a matter of a user decision. The data in the scope of HH theme are primarily statistical data/indices, expressed at different spatial levels, thus no specific spatial objects have been defined. For most applications, data are reported re-using spatial objects identified by TWG Statistical Units (SU); for health care/health services, spatial objects (Governmental Service) identified by TWG Utility and Government Services (US) were recommended to be used. A general model for environmental data, relevant as health determinant (envhealth), was also provided. No new spatial features were provided, and Statistical Units (SU) for aggregated data are reused. For primary or observed data, reuse of Environmental Monitoring Facilities has been proposed; however, alternatively O&M standard could be re-used for thematic environmental data. Feasibility of an approach most suitable to represent point data requires further discussion. This theme provides a generic data model applicable across statistical units (as presented in SU theme) available in the Member States. The human health theme contains mainly data attached to statistical units. Health data and biomarkers have no direct spatial features, and need to be linked to these features by the use of statistical units, for example NUTS-codes or grid coordinates. The following themes are particularly important in their relationships to Human Health and Safety, and these are: Statistical Units (SU): spatial objects identified by TWG SU are re-used Utility and Government Services (US): The use of spatial objects identified by TWG US are recommended to represent information about health care/health servicesEnvironmental Monitoring facilities (EF): Other themes relevant for HH include: Population Distribution - Demography (PD), as the theme HH addresses mainly aspects of health conditions of individuals and populations Production and industrial facilities (PF), Agricultural and aquaculture facilities (AF), Natural risk zones (NR), Soil (SO), Atmospheric conditions/Meteorological geographical features (AC), for analysing potential links with the quality of the environment, and safety issues. .... Some examples (use cases) are provided for environmental data in the context of human health; a case study (use case) focusing on human health, and possible linkages to other themes is considered for the next steps of DS development.