The investigation of thermo-economic performance for dry-cooled closed Brayton cycle coupled to nuclear microreactors using different coolants

Dry -cooled closed Brayton cycle (CBC) coupled to gas-cooled nuclear microreactors offers a compact structure and can be deployed in water -deficient areas. The gas-cooled reactor utilizes coolants including supercritical carbon dioxide (S - CO 2 ), helium, and He - Xe mixture. The choice of working fluids for CBC strongly affects its size and performance, where smaller plant sizes, higher thermal efficiency, and lower investments are preferred. This study investigates the thermo-economic performances of dry -cooled CBC coupled to nuclear microreactors using different coolants. A design method for dry -cooled CBC is developed based on the integration of thermodynamic modeling and component preliminary design. Baseline designs are first established, followed by an analysis of the effects of key design parameters. Furthermore, a multi -object optimization is conducted to compare the Pareto frontiers of CBC using different working fluids. The results demonstrate that the helium simple cycle exhibits superior efficiency and precooler size due to its higher reactor outlet temperature, though with a larger capital cost. The Pareto frontier of the He - Xe cycle is worse than that of the helium cycle. The S - CO 2 recompression cycle has a comparable efficiency with a smaller capital cost at mediate reactor outlet temperatures but suffers from large precooler sizes. The findings revealed that the S - CO 2 recompression cycle is a more promising choice if the reactor outlet temperature can be further elevated.