This report summarizes the issues discussed at the workshop and extracts the essential viewpoints that have been expressed. The report is not to consider as a comprehensive record of all the discussions at the workshop and individual statements made by workshop participants should be regarded as opinions rather than proven facts. This report includes, apart from the workshop synthesis, the review reports from the participating experts. The participants in the workshop identified a number of issues that not is fully understood and therefore suggested to be dealt with in more detail later on. However, it is necessary to look at these issues in the context of the overall safety case, in particular the key safety functions and threats, and to assess them in a quantitative fashion.