TRANSIENT ANALYSES OF S-CO2 COOLED KAIST MICRO MODULAR REACTOR WITH GAMMA+ CODE

Abstract

Existing Small Modular Reactors (SMR), which have been usually cooled by water, haven’t achieved a full modularization because of large steam power system and following balance of plant. However, if the working fluid of the SMR uses supercritical CO2 (S-CO2) as the working fluid, the SMR could be more compact and achieve better modularization. From the characteristic of S-CO2, KAIST research team has developed a SMR targeting portable and perfectly modular reactor, namely the KAIST Micro Modular Reactor (MMR). Until now, the design work of reactor core, major components, and cycle configuration have been performed for the MMR. In this paper, transient analyses of the designed MMR are performed to check whether the designed reactor can conceptually secure satisfactory safety margin when some events occur, which could lead to severe accident. Among many events, load rejection is selected as one of important events for developing power system control logic because load rejection event can lead to SBO (Station black out) accident if any active safety features are not working after the event. Moreover, SBO accident became widely known to the even non- nuclear industry people after the Fukushima accident. In certain aspect, load rejection event response became a quantitative measurement of how the designed nuclear system can withstand such initial event. Moreover, once load rejection transient results of the MMR are obtained, the results could suggest new design criteria of the MMR. This study can provide perspective of the performance of the MMR during the load rejection event as well as the information of the control logics of the newly proposed nuclear system.