Integrated design and off-design hybrid control strategy of supercritical CO2 recompression cycle for nuclear power

Abstract

The supercritical CO2 power cycle has attracted extensive attention for its potential application in next-generation nuclear reactors. In this study, the integrated design and off-design control strategies of supercritical CO2 recompression cycle for a small-scale lead-cooled fast reactor were investigated. After determining the optimal design conditions of the system through thermodynamic and exergoeconomic models, the off-design operating states of the compressors of the system controlled by four strategies were evolved. According to the compressor operation map under each control strategy, a series of hybrid control strategies based on inventory control were proposed. The design results indicate that the system has the highest efficiency of 42.12% and the lowest total production unit cost of 11.67 $∙GJ−1 when the split ratio is 0.37. The off-design results indicate that the re-compressor of the turbine bypass-controlled systems faces chock with decreasing load due to the increase of the optimal split ratio, which can be alleviated by adopting an inventory-bypass hybrid control strategy. Moreover, this hybrid control strategy both improves the thermal efficiency of the bypass-controlled system and protects the re-compressor of the inventory-controlled system away from the stall boundary. Because of the analogous operation footprints on the compressor map, a hybrid strategy consisting of inventory control and turbine inlet temperature control can achieve a similar effect as inventory-bypass hybrid control. The analysis results provide theoretical guidance for the selection of off-design control strategies for the supercritical CO2 recompression cycles applied in various energy fields.