4E ASSESSMENT on HEAT TRANSFER and OPTIMIZATION of A NOVEL COOLINGHEATING-POWER COGENERATION BRAYTON SYSTEM

High-Temperature gas-cooled fast reactors are fourth generation nuclear systems offering ultra-high heat source temperature and advanced safety features. When used in applications such as marine propulsion, delivery of cooling and hot water may be achieved by utilizing reactor heat rejection. The supercritical CO2 Brayton cycle is considered suitable for coupling with the fourth-generation nuclear systems due to the excellent thermophysical properties of supercritical CO2. In this study, a novel cooling-heating-power cogeneration Brayton system that can fully recover the reactor cooling heat is described. The prototype ALLEGRO demonstrator reactor operating conditions are used to design the supercritical CO2 combined cycle. The use of advanced, double-sided etched printed circuit heat exchanger with elliptical channel geometry is examined. Initially, the key thermodynamic and cost metrics are analyzed using energy, exergy, economy, and environment (4E) assessment. Subsequently, multi-objective optimization of the Brayton system is carried out using the 4E metrics. The results show that the economic and environment costs of the combined cycle can be reduced by 2.9% and 49.5%, respectively with respect to the base-case design.