Safety Issues of VHTR RCCS Design

The concept of passive safety is emphasized in VHTR (Very High Temperature Reactor) to accomplish the enhanced safety goal of future reactors compared to the reactors of previous generation. The Reactor Cavity Cooling System (RCCS) is the passive safety system in VHTR designed to remove the residual and decay heat. Large thermal margin, low power density and core configuration with large heat transfer surface in VHTR make passive cooling effective. In addition, RCCS in VHTR is the only safety-related system which should have a high reliability. Therefore, it is important to study the design characteristics of RCCS and derive safety issues to assure the passive safety of VHTR. In this paper, several safety issues related with RCCS in VHTR were identified and reviewed