Investigation on heat transfer characteristics of reactor cavity cooling system for HTGR

Hosomi, Seisuke*; Yamaguchi, Shuhei*; Akashi, Tomoyasu*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Takamatsu, Kuniyoshi  

After Fukushima Daiichi nuclear disaster by TEPCO, a cooling system to prevent core damage became more important from the perspective of defense in depth. Therefore, a new, highly efficient RCCS with passive safety features without a requirement for electricity and mechanical drive is proposed. Employing the air as the working fluid and the ambient air as the ultimate heat sink, the new RCCS design strongly reduces the possibility of losing the heat sink for decay heat removal. The RCCS can always stably and passively remove a part of the released heat at the rated operation and the decay heat after reactor shutdown. After building the scale-down heat removal test facility, we conducted experiments and analyses to understand the heat-transfer characteristics. As a result, we could assess effect of radiation and natural convection quantitatively for passive decay heat removal from the RPV.