Loss of flow accident and loss of heat sink accident analyses of the WCCB primary heat transfer system for CFETR

The Primary Heat Transfer System (PHTS) of the Water Cooled Ceramic Breeder (WCCB) blanket was designed to fulfill multiple operation modes of Chinese Fusion Engineering Testing Reactor (CFETR) with the fusion power of 200 MW in Phase I and 1.5 GW in Phase II. One PHTS loop was modeled using RELAP5. Loss of Flow Accident (LOFA) and Loss of Heat Sink (LOHS) were analyzed to evaluate the reliability of the PHTS design. Both accidents were simulated under two phases of CFETR with two postulations. The first postulation was that accidents happened without detection. Results showed that the blanket was overheated. The second postulation was to verify the effectiveness of corresponding counter-measures. For LOFA, if the plasma shuts down in time, the system can establish natural circulation and remove the decay heat effectively. For LOHS, plasma shutdown in time and feed water restoration at appropriate time are effective mitigation measures.