Thermoeconomic analysis and inter-stage pressure ratio optimization of nuclear power supercritical CO₂ multi-stage recompression

Implemented optimization and full life cycle economic analysis on the inter-stage pressure ratio were rarely paid attention to in supercritical carbon dioxide multi-stage recompression. In this article, a thermodynamic model of supercritical carbon dioxide recompression Brayton cycle was established based on gas-cooled fast reactor and the sensitivity analysis was performed. With the aim of seeking the optimal pressure ratio for two-stage, three-stage, and four-stage recompression configuration, the full life cycle economic indicators were predicted, respectively. Parameter sensitivity analysis indicated that the thermodynamically optimized result could not coincide with that of the economically optimized. The optimal PR distribution scheme may result in the improvement of the initial cycle system efficiency from 46.89% to 48.07%. Meanwhile the levelized cost of electricity decreased from 57.40$/MWh to 55.87$/MWh. The approaching equilibrium trend of thermoeconomic parameters confirmed the existence of the optimal number of recompression stages, which could also be derived from the prediction tendency based on full life cycle economic indicators. Furthermore, it was discovered that reducing the year of repayment and the loan proportion enhanced the net present value of nuclear power plant, but the former method gave rise to longer payback period and lower internal rate of return. The present work preserves the guiding significance for nuclear power plant investors and the utilization of the supercritical carbon dioxide Brayton system.