Thermodynamic Analysis of Combined Supercritical Carbon Dioxide Brayton Cycle Applied to Lead-cooled Fast Reactor

In this paper, the thermodynamic analysis of the lead-cooled fast reactor composing recompression supercritical carbon dioxide(S-CO₂) Brayton cycle, steam Rankine cycle and He Brayton cycle as power block is introduced. The advantage of lead-cooled fast reactor composing recompression S-CO₂ Brayton cycle is explored through comparing the optimal thermodynamic performance of recompression S-CO₂ Brayton cycle with that of conventional power cycles. In order to improve the performance of S-CO₂ cycle, the recompression supercritical carbon dioxide/transcritical carbon dioxide(S-CO₂/T-CO₂) combined cycle is primarily constructed by using T-CO₂ as bottom cycle. The influences of the turbine inlet temperature, turbine inlet pressure and the compressor inlet temperature of the top cycle on the combined-cycle performance are further invesitgated. Finally, the performance of the S-CO₂ cycle and that of S-CO₂/T-CO₂ combined cycle are compared. The results are indicated as follows. First, the lead-cooled fast reactor comprising recompression S-CO₂ Brayton cycle has higher efficiency than the conventional systems. Second, the thermal efficiency and exergy efficiency of the S-CO₂/T-CO₂ combined-cycle can be maximally improved by 4.8% and 8.3% comparing to that of S-CO₂ cycle, separately. Third, the thermal performance of the S-CO₂ recompression cycle and that of S-CO₂/T-CO₂ combined cycle alter consistently with the changed crucial parameters of the top cycle.