Passive Decay Heat Removal System with Unlimited Operating Time for S-CO2 Cooled Micro Modular Reactor

Abstract

S-CO2 cooled MMR (Micro Modular Reactor) is a 36 MWth gas cooled fast reactor and has very small system size enough to be transported by a trailer. The SCO2 has good heat transfer performance and the MMR achieves compact core design with the coolant. Waste heat removal system of the MMR is dry cooling system therefore the reactor has wide construction site such as water shortage region. The MMR adopts PDHR (Passive Decay Heat Removal) system with unlimited operation time for enhancing its advantages, and in accidents the MMR doesn't require any external supports, and isolated regions can be considered as construction sites. At the early stage of the accidents, the reactor core is cooled by pressurized CO2 in inner containment rapidly and reliable dry cooling system conducts long-term cooling of the reactor core. Safety assessment by MARS-KS code is conducted with conservative initial and boundary condition and the results show that the core temperature and the coolant system pressure are maintained under the design limitation at all DBAs (Design Basis Accidents) and secure integrity of the MMR.