Survey of Research Activities for Passive Safety System of AC600

The use of passive safety system in AC600, the Chinese advanced 600 MWe PWR proposed by NPIC, together with other improvements, such as simplification and advanced I&C etc., makes the plant more safe, economic and reliable. The core damage frequency (CDF) decreases from less than 10−4 of conventional PWR to less than 10−5 to 10−6 and the plant available factor increases to ∼90%. The passive safety system of AC600 consists of three complete independent systems. They are passive containment cooling system (passive CC system), passive core residual heat removal system (passive CRHR system) and passive safety injection system (CMT). To verify and demonstrate the AC600’s innovative passive safety features and to obtain an experimental database for system design modification and optimizing, and for computer code development and assessment, the experimental studies on these systems were finished in NPIC during the eighth national Five Year period under the national support. In this paper, the experimental research activities on passive containment cooling system, passive CRHR system and CMT injection system, including test rigs and main results are summarized. These experiments proved the design of all these passive systems are feasible and reliable and can meet basically the required safety functions. Some undesired thermal hydraulic phenomena, for example, “water hammer”, which may have bad impacts on its safety functions and to which high attention should be given, was found and identified in these studies. All data obtained have already been used in the design improvement and next R&D program planning.