Development of safety analysis methodology for fusion systems. 1

One of the most important safety characteristics of a fusion energy system is the fact that energy and RI (radioisotope) sources as a hazard potential are distributed over and some of them move around the system. Abnormal release of these energy sources result in abnormal state of the system and may induce another energy release, an increase of vulnerable RI (source term) or a formation of flow path from system to environment (RI leak path). Moreover, these relationship is complex and extended over the system. Then, in this study, I will arrange these relationship in order and develop safety analytical model to be able to analyze system behavior quantitatively under abnormal conditions. In this report, I constructed a system model as the first stage of development of a comprehensive analytical model. The system model is composed of conceptual system elements such as control functions, spaces and boundaries. This model describes the characteristics of general fusion systems in an overall sense. Then, I arranged in order the system model mass and/or energy transport or storage processes between system elements on normal and/or abnormal conditions and defined the inter-relationship precisely. Based on the system model, a mathematical model is being developed. This mathematical model enables us to analyze system behavior quantitatively and to survey parameters controlled by safety features. The mathematical model will be the basis to develop a computer program which will be a good tool for selection of dominant event sequences and request for rational safety features. (author)