IGSC perspective on human intrusion

Hiroyuki Umeki, Chairman of the IGSC, indicated that when updating its programme of work, in 2007, the IGSC raised a number of issues that the group recommended RWMC-RF to consider for further discussion. The conclusions from different IGSC studies were that there is agreement at a conceptual level on the treatment of human intrusion, but a range of approaches are adopted for addressing it in safety assessment, and the degree to which these are specified in regulations also varies considerably among national programmes. The requirements and constraints for considering human intrusion are stylised and, therefore, are largely specified in regulations; in many national programmes, relatively few (or no) aspects are left to the discretion of the implementer. Human intrusion is considered as a sensitive issue for many programmes since it can be an issue of high interest to stakeholders and decisions on approaches are normally undertaken after extensive consultation; those who have already taken decisions are generally satisfied with the outcome and would not welcome work that might undermine or re-open the issue. Thus, a detailed re-examination of safety assessment of human intrusion and of the conclusions that have been reached previously is not a priority. This issue remains of interest to IGSC, however, as it must be addressed in some fashion within all safety cases. The key questions are: - Should regulations require measures to reduce the likelihood or consequences of human intrusion? What 'credit' can be taken for such measures? Is there new thinking or methods in terms of memory and markers? - What types of stylised human intrusion should be considered in a safety case? What are the roles of the regulator and implementer in doing so? - What consequences should be considered? What are the protection criteria against which to assess human intrusion scenarios? - Are the answers to any of these questions site-, culture-, concept- or waste-specific? A concluding question may be: Is there still consensus on the areas of agreement, or has thinking evolved?