Parameters analysis and techno-economic comparison of various ORCs and sCO2 cycles as the power cycle of Lead–Bismuth molten nuclear micro-reactor

Organic Rankine cycle (ORC) and supercritical CO2 (sCO2) Brayton cycle are two key and competition technology routes as the power cycle of Lead–Bismuth micro-reactor (LBMR). However, few studies focus on the comparison of thermodynamic and economic performance between ORCs and sCO2 cycles in nuclear micro-reactor. The objectives in this study are to perform parameters analysis and techno-economic comparison in ORCs and sCO2 cycles with various configurations as the power cycle of LBMR, so as to provide the technical support for the selection of power cycle and its operating conditions in different scenarios. Several high/low-temperature working fluids are screened for ORCs in view to achieve high net efficiency (ηth) and low electricity production cost (EPC). Multi-objective optimization is performed to solve the trade-off between ηth and EPC, and then to compare the comprehensive performance of various cycles from thermodynamic, compact and economic aspects. Results show that, the ηth and EPC of ORCs are comparable or superior to that in sCO2 cycles when the two cycles have similar structures (simple/regenerative). Among the ORCs, the cascade ORC with two-side regeneration using N-Dodecane/Pentane as working fluid pair has the best performance. In all cycles, recompression sCO2 cycle performs best, but only when the heat source temperature is higher than 460 °C, the performance of the recompression sCO2 cycle are overall better than the cascade ORC.