Probabilistic risk assessment model for released tritium into the environment for CFETR

The China Fusion Engineering Test Reactor (CFETR) is the next facility in the Chinese roadmap to realize sustainable-clean fusion energy. Because of the large tritium inventory of the CFETR, safety analyses are necessary. During the current design phase of the CFETR, performing the risk analysis of tritium released into the environment could reveal the design weaknesses and indicate improvements aimed at trtium risk (TR) reduction but also form a part of the licensing process for future CFETR construction and operation. Several CFETR safety analyses using deterministic approaches have been conducted, but relatively few studies based on probabilistic approaches are currently available. In this paper, a probabilistic risk assessment (PRA) model for tritium release into the environment for CFETR was proposed, in which the frequency and the radioactivity of the released tritium in accident sequences are considered. The event tree/fault tree (ET/FT) method was applied to investigate primary factors contributing to the tritium release into the environment and to estimate the frequency of accident sequences. We presented a model for preliminary and rapid assessment of the radioactivity of released tritium in accident sequences and developed a calculation code. The application process and validity of the model were demonstrated through the assessment of TR of the CFETR for selected postulated initiating events.