Thermal hydraulic responses of the Primary Heat Transfer System of the WCCB blanket to accident cases for CFETR

The Water Cooled Ceramic Breeder (WCCB) blanket is one of the blanket candidates for Chinese Fusion Engineering Test Reactor (CFETR). In this work, the Primary Heat Transfer System (PHTS) of the WCCB blanket was designed based on the configuration of the blanket sectors, employing two identical loops at this stage. Each loop consists of a steam generator, a pressurizer and two pumps, feeding water coolant into each blanket modules individually of 8 blanket sectors. One of the loop was modeled using RELAP5/MOD3.3 under normal condition and accident cases. The operational mode of PHTS was carefully chosen so as to obtain a more stable hydraulic behavior under steady state, due to the anisotropy of geometry structures and heat sources. Enveloping accidental cases, including Loss of Flow Accident (LOFA), in-vessel Loss of Coolant Accident (LOCA), and ex-vessel LOCA, were selected to preliminarily evaluate the safety performance of the system. The results show that the integrity of the confinement barriers can only be ensured in limited period of time during LOCAs. Additional safety facilities are needed and mitigation methods: are discussed.