The article describes the founding principles, work program, and accomplishments of a Reference Group with both expert and layperson stakeholders for the corrosion of copper canisters in a proposed deep repository in Sweden for spent nuclear fuel. The article sets the Reference Group as a participatory effort within a broader context of stakeholder and public participation. It is argued that for the future it will be necessary to more precisely define the roles of different approaches to public participation in relation to the actual societal decision-making procedures, and the issue is raised whether an increasing level of their institutionalization is required. In particular, the focus is set on the safe-space approach to stakeholder participation designed to suit situations where independence and autonomy are crucial elements for the participants. To illustrate this we compare experiences from Sweden and the Czech Republic.