Geosphere models as a tool for improving confidence in site characterisation and assessment of long-term evolution and safety (GEOSCALE)

Objective

The WP defines generic and real reference sites of increasing complexity for both crystalline and clay rocks and establishes benchmarking approaches for geosphere flow and transport models to improve transparency, credibility and robustness of geosphere models in support of siting and safety case.
 

Description of the WP

The WP aims to strengthen and harmonise the use of geosphere models in repository siting and site characterisation by developing an internationally aligned framework for benchmarking, validation and comparison of codes. GEOSCALE addresses the entire geosphere of a deep geologic repository including host rock and surrounding hydraulic systems. Rather than developing new numerical codes, the WP addresses the gap of missing validation and comparison of existing codes by developing tailored approaches and benchmarks following a bottom-up approach from simple to complex, and finally real-site systems. Thus, the WP will strengthen confidence in geosphere models, enhance transparency and social acceptance of repository siting procedures, and build public trust in geosphere models.
The reference sites developed within the WP will establish a durable framework beyond EURAD 2 for benchmarking and comparing codes, modelling approaches, and processes implementation strategies, thereby strengthening collaboration and knowledge exchange between modellers and end users at the European and international level.  The WP will further evolve the implementation of coupled THM processes as well as the coupling of landscape evolution with subsurface processes to evaluate their impact on flow and transport processes.
Well defined, coupled and validated geosphere models contribute to:
•    Site selection: Supporting efficient siting strategies based on site specific geosphere understanding, potentially reducing drilling, time, and costs.
•    Repository optimisation: Quantifying geosphere contributions to safety functions, reducing conservatism, improving risk understanding, and describing long term site evolution.
Overall, the WP will provide guidance on the application of tailored approaches and for robust model development. It will deliver workflows for quantitative modelling of long term geosphere evolution (flow, transport, thermal, geochemical and mechanical processes), expert knowledge, information on data requirements, and evaluation of model outcomes. This supports openness between organisations and the public, reducing costs for member states through harmonised siting practices and improved safety cases. Finally, lessons learned from advanced programmes will support Member States, particularly those in early siting phases.
 

Outcomes

SRA-Driver - Implementation safety: Improved quantification and understanding of geosphere flow and transport processes enhances confidence in geosphere models supporting site selection, site characterisation and post-closure safety assessment. This mitigates uncertainties, which is critical for building trust in society and with stakeholders.
SRA-Driver - Scientific Insight:  Novel establishment of reference sites, both generic and real, with increasing complexity for crystalline and clay host rocks will significantly help in the development of understanding and tools for current and future disposal programmes for all Member States and projects/communities beyond EURAD-2.  
The developed modelling approaches will enhance technical capabilities of geosphere flow and (reactive) transport models with respect to implementation of evolving boundary condition, coupling of subsidiary and different scale models and processes (thermal, hydrological, mechanical, chemical). These feed into recommendation of minimum and extended datasets for different siting stages and guidance on how to efficiently implement continuously generated data. 
SRA-Driver - Knowledge Management:  The WP develops skills, and expertise addressing the long timescales and challenges related to model development in the framework of radioactive waste management. Benchmark cases of the used sites—including data, models, and boundary conditions—will be made available to support shared learning and harmonised model development. The WP provides strong possibilities of training and exchange, particularly for early programme Member States and young scientists. It provides a structured training ground for the next generation, supporting capacity building and long-term retention of expertise by offering workshop-based exchange and networking opportunities.