Application of the general safety methodology of safety analysis and evaluation for fusion energy system (GEMSAFE) to Fast Breeder Reactor systems

General safety issues for Fast Breeder Reactor (FBR) systems have been examined along the framework of the GEMSAFE which was developed to establish a synthesized methodology of safety analysis and evaluation for nuclear energy systems. The safety characteristics of FBRs is investigated by constructing the General Descriptive Model (GDM) which is an integrated system model with five system elements constituted of functions, areas and boundaries. The crucial safety issues to be protected (IPs) in FBRs are found as (I) RI immobility, and (2) integrity of the boundaries. The safety ensuring principle is defined by considering the mechanism of the abnormal energy release against IPs together with the RI release structure. An event categorization has been proposed by mainly focusing upon the severity of loss of the IPs. The function based-safety analysis, which is performed for the GDM, has been carried out to obtain the qualitative event sequences by connecting abnormal states picked up. The candidates for the safety evaluation have been defined in each category by dividing the event sequences with the conditions of the IPs, corresponding to the proposed event category. The role assignment of the safety functions (SFs) is argued from the view of introducing form and achieving aspects against the abnormal states considered. An approach to introduce these SFs is proposed along the safety ensuring principle: the advantage of the GDM basis SFs, the role assignment of the Passive and Active SFs based on the time constant of the abnormal states, and the importance of the Engineered SFs depending on the phenomena of the abnormal event sequences are discussed to attain a rational safety design. (author)