Identification of the Postulated Initiating Events of Accidents of a CPS-Based Liquid Metal Divertor for the EU DEMO Fusion Reactor

A preliminary but systematic safety analysis of a liquid metal divertor (LMD) for the EU DEMO performed by means of the Functional Failure Mode and Effect Analysis (FFMEA) is presented. This methodology is suitable for the analysis of the LMD, which is undergoing preconceptual design. In fact, the FFMEA compensates for the lack of detailed design information by postulating the loss of a system function, rather than a specific component failure. The implementation of the FFMEA led to a better understanding of the safety and operational issues associated with the system and to the identification of a list of postulated initiating events (PIEs), i.e., the most challenging conditions for the plant. The PIEs, together with their possible consequences, represent an input for future quantitative safety analyses. Due to the early design stage of the LMD and the iterative nature of the methodology, this list will evolve alongside the design detail and with improvements in the understanding of phenomena driving reactor behavior. The study highlighted some safety-relevant issues, e.g., those related to materials compatibility and system modularity, to be addressed in the perspective of a safety-driven design evolution