Hydraulic testing in search for nuclear waste repository
Exploring deep geology for safe nuclear waste disposal in Switzerland
AFRY supported Nagra with hydraulic test and fluid logging analysis for safe nuclear waste repository siting.
The Swiss National Cooperative for the Disposal of Radioactive Waste - Nagra - is responsible for identifying suitable locations for a deep geological repository for nuclear waste in Switzerland. This requires detailed knowledge of the host rock and surrounding formations to ensure long-term containment of the radioactive waste.
Between 2018 and 2024, Nagra conducted extensive hydraulic testing in deep boreholes reaching depths of up to ~1,400 m. The investigations quantified key hydraulic parameters - including permeability and hydraulic conductivity. This was to assess the barrier capacity of geological formations, including the host rock Opalinus Clay, for long-term nuclear waste disposal. Complementary fluid logging and hydraulic test analyses in aquifers identified and quantified active inflow and outflow zones along the boreholes, providing critical insight into the location and hydraulic significance of conductive structures.
Key facts about the project
- Project: TBO (short for German “TiefBOhrung” = “deep drilling” in English)
- Client: Nagra (Nationale Genossenschaft für die Lagerung radioaktiver Abfälle)
- Location: Switzerland
- Duration: 2018–2024 (hydraulic testing), 2020–2022 (fluid logging)
Testing to assess the subsurface
AFRY supported Solexperts AG, a specialist in geotechnical and hydrogeological instrumentation and field testing, as a subcontractor. AFRY contributed expertise in test design, hydraulic testing, and fluid logging analysis to derive key hydraulic parameters of the subsurface.
AFRY’s scope included:
- Supporting the design and planning of hydraulic packer and fluid logging tests
- Analyzing testing activities during execution
- Running numerical simulations on and off-site using our in-house developed borehole simulator MULTISIM
- Quantification of uncertainty ranges by applying novel uncertainty techniques such as perturbation and sampling analysis
- Delivering Quick Look and Detailed Reports
In-house developed borehole simulator MULTISIM
MULTISIM is an interactive well test analysis software and numerical simulator for single-phase hydraulic testing (water or gas), integrating data management, diagnostic analysis, and test simulation within a single tool - from raw field data to final formation characterization.
The software was specifically developed by AFRY for major underground research and disposal programs (Andra, Nagra, BGE) and is widely used for the interpretation of hydraulic tests in low to very low permeability formations.
MULTISIM4 enables advanced simulation of transient single-phase flow (under complex hydraulic boundary conditions, including multi-rate/pressure tests, wellbore storage, skin effects, temperature variations, and interference testing).
Built on a finite-volume numerical scheme, the tool supports automated parameter calibration, statistical uncertainty analysis, and database-driven workflows, allowing robust estimation of key hydraulic properties of the subsurface.
“By combining advanced numerical simulations with high-quality field data, we help reduce uncertainty in the interpretation of complex hydraulic test data. This supports reliable safety assessments for the long-term disposal of radioactive waste,” says Dominik Rätz, Head of Nuclear EMEA & APAC at AFRY
By combining field data with advanced numerical modeling, AFRY provided reliable insights into subsurface conditions. The results supported:
- Identification of suitable repository host rock
- Reduced uncertainty in safety assessments
- Robust technical documentation for authorities.
