A COMPARATIVE ASSESSMENT OF PASSIVE SAFETY SYSTEMS IN INTEGRAL PRESSURIZED WATER REACTOR TYPE SMALL MODULAR REACTOR

The new generation reactors, including small modular reactors (SMRs) have long been argued as a way to provide a safe, clean and sustainable energy future. Innovative SMR concepts are in particular seen as attractive in terms of its unique features, simplified design, and flexible power generation and applications. Here we focus our attention on integral pressurized water reactor (iPWR) type SMRs. We identified and reviewed eleven (11) iPWR-type SMR designs in various developmental phases, including the possibility of near-term deploy ability. This class of SMRs integrates the major primary reactor coolant system components within a single pressure vessel; the intended purpose of which is to minimize the design basis accidents (DBAs) to the extent possible. Additionally, iPWRs designs employ passive safety systems (PSSs) to enhance the safety margin, and subsequently reduce the predicted core damage frequency (CDF). PSSs take advantage of natural physical laws, thus negating reliance on external power nor human intervention to assure a safe end state. A comparative assessment of PSSs in iPWR-type SMRs is presented featuring surveyed safety features. A generic classification of PSSs based on the class, operating mechanism and functions is presented. We limit our discussion to four (4) key functional PSSs namely: the decay heat removal system, safety injection system, reactor depressurization system and containment cooling system. These four (4) functional systems largely determine the path to safe shutdown given a spectrum of initiating events. The comparative assessment contributes to a better understanding of the differences in PSS designs which helps to improve the safety and reliability of new generation reactors.