The strategic approach and structuring of safety cases for nuclear waste repositories have seen marked improvements over the past ten to fifteen years as a result of the collective experience of national agencies in developing their safety cases and their efforts, under the auspices of the OECD Nuclear Energy Agency (NEA), to develop a systematic and thorough approach, as well as through systematic reviews by regulators and expert teams. A safety case can be developed at any stage in a program and it provides a remarkably effective method for reassessing design and siting requirements and refocusing R&D needs. The process of developing a safety case for a repository is the critical test of the quality of understanding that exists for a given repository concept, because it forces an integration of the siting and design strategies and the assessment approach. This integration demands that one evaluates all relevant R&D results available and addresses the questions i) is the system good? and ii) is the understanding sufficient, taking the stage of the programme into account?

Here we address some questions on the relationship between R&D work and the development of a safety case, including:

1) Is the R&D performed in Europe evolving in concert with safety case development for European repositories?

2) How much generic work is still needed when robust site-specific repository concepts obviously lead to much more focused R&D?

3) How good is good enough and how do we measure this at each successive stage of repository development?

There are no easy answers to such questions, but they must increasingly be addressed as national programs progress.