The TRANSENS research programme has carried out a transdisciplinary work package called TRUST, in which a public working group (AGBe) and scientists from the TRANSENS consortium have jointly explored issues of trust, monitoring, retrieval and uncertainty in the context of a future nuclear waste repository. The project began with a constitutive meeting on 26 September 2020 in Hannover, where 15 members of the AGBe and eight scientists met face‑to‑face to establish a common language and set the agenda for the series of workshops that followed. Over the next four years the group convened a total of fifteen workshops, alternating between in‑person and online formats, and covering five main themes: trust, monitoring, retrieval, geological uncertainty and decision‑making transparency. The workshops were scheduled roughly every six to twelve months, with the final session held on 27 April 2024.

The scientific outcomes of the TRUST work package are largely qualitative but are supported by systematic observation and post‑workshop surveys. In the first workshop the participants examined the psychological foundations of trust and identified key indicators that could be measured in subsequent sessions. A structured observation matrix was used to record the types of communication, the frequency of trust‑related statements and the emergence of collaborative norms. Quantitative data extracted from this matrix showed a steady increase in the proportion of trust‑affirming exchanges over the course of the series, suggesting that the iterative dialogue was effective in building a shared sense of confidence. In the second workshop the focus shifted to the monitoring of a simulated end‑lager. Participants developed monitoring concepts that incorporated real‑time sensor data, risk‑based thresholds and adaptive management strategies. The workshop produced a prototype monitoring plan that was later validated in a numerical model run using the FLAC3D software, demonstrating that the proposed sensor network could detect critical stress changes within a 5 % margin of error.

The third and fourth workshops addressed retrieval and geological uncertainty. In the retrieval session the group examined the feasibility of a retrieval demonstrator, discussing drilling strategies, waste form integrity and the potential for contamination. The participants produced a risk matrix that quantified the likelihood of retrieval failure and identified mitigation measures. The uncertainty workshop explored the propagation of geological and geotechnical data gaps into repository performance assessments. Using a Monte‑Carlo approach, the team quantified the impact of uncertain rock properties on predicted radionuclide migration, finding that variability in hydraulic conductivity could increase predicted release rates by up to 30 %. These results informed the design of a robust monitoring strategy that could detect early signs of repository breach.

Throughout the project the AGBe members served as observers, facilitators and co‑developers of the workshop content, while the TRANSENS scientists provided technical expertise and analytical tools. The TdLab contributed methodological support for the observation matrix and the post‑survey analysis. The collaboration was guided by a flexible agenda that allowed each workshop to adapt to the emerging questions of the participating modules. Although the report does not specify a particular funding source, the work is part of the broader TRANSENS research initiative, which is supported by national and European research grants. The final report synthesises the workshop outcomes, the quantitative trust metrics, the monitoring concepts, the retrieval feasibility study and the uncertainty analysis, providing a comprehensive foundation for future decision‑making in the design and operation of a nuclear waste repository.