Preliminary design and optimization of sCO2 nuclear-powered merchant vessel propulsion systems for the Northern Sea Route

This study investigates the potential of supercritical CO 2 (sCO 2 ) power cycles as alternatives to conventional steam Rankine cycles for the nuclear propulsion of commercial vessels operating along the Northern Sea Route (NSR). A numerical model is developed to simulate the performance of both a simple recuperative cycle (SRC) and a reheated recuperative cycle (RRC), using a pressurized water reactor (PWR) as the heat source, and to size the system heat exchangers. A preliminary sensitivity analysis is carried out to identify the most influential design parameters, which are then used in a multi-objective optimization employing the NSGA-II algorithm to maximize thermal efficiency and minimize the total heat exchanger volume. The resulting Pareto fronts are evaluated using the TOPSIS method, and the optimal solutions are further analyzed through a preliminary 1-D design of the turbomachinery. The results highlight that the RRC outperforms the SRC in both efficiency and compactness, achieving up to 30.1% efficiency with significantly reduced heat exchangers overall volumes. An additional analysis incorporating the reactor pressure vessel (RPV) volume indicates a moderate reshaping of the Pareto front, not significantly modifying the optimal design selection. Compared to conventional steam Rankine cycles, the sCO 2 -based systems demonstrate over 25 times higher volumetric power density, highlighting their substantial space-saving potential for marine propulsion applications.