Design considerations of the supercritical carbon dioxide Brayton cycle of small modular molten salt reactor for ship propulsion

Recently, many studies on nuclear-powered ships as replacements for ships using fossil fuels are attracting worldwide attention. Among fourth-generation reactors, molten salt reactors (MSRs) are a suitable candidate as a power source for nuclear-powered ships because of its high efficiency and safety features. In addition, a small modular reactor (SMR) design using MSR can be developed by adopting the supercritical CO2 Brayton cycle (SCBC) as a power conversion system. The SCBC is an appropriate system for MSR-powered ships in terms of its operating temperature and compact size. In this study, we compare the design considerations of SCBC with the design requirements of a reference ship and reactor. Sensitivity studies were conducted with optimization variables, i.e., flow split ratio and pressure ratio, to determine the optimal design of the SCBC. An optimal cycle efficiency of 47.78% was obtained when the flow split ratio was 0.7 and the pressure ratio was 2.94. Finally, the SCBC was compared to a reference design using a pressurized water reactor based steam Rankine cycle. The SCBC was evaluated to be a better design for an MSR-based ship, with approximately 12% higher cycle efficiency than the reference design.