Dynamic characteristics of a recompression supercritical CO₂ cycle against variable operating conditions and temperature fluctuations of reactor outlet coolant

The transient performance of an inventory-controlled supercritical CO₂ recompression cycle under synchronous adjustment of parameters has rarely been studied. In this study, a one-dimensional design of a supercritical CO₂ recompression cycle with a 10 MW output power was completed for a lead-cooled fast reactor. The dynamic characteristics of the system power, which decreased from full load to half load under three ramp signals, were compared. Furthermore, the effect of the fluctuating reactor outlet coolant temperature on the transient performance of the system was investigated. Steady-state analysis revealed that the maximum design efficiency of the system was 43.40% at a split ratio of 0.37. The dynamic results showed that the shorter the ramp signal for parameter adjustment, the more significantly the transient performance of the system degraded. When the load decreased significantly, a secondary efficiency trough appeared in the system. These poor phenomena were improved by appropriately extending the action time of the ramp signal. Additionally, the influence of coolant temperature fluctuation on the temperature at both ends of the recuperator differed owing to the difference in the heat capacity. Moreover, the reduction in the target load of the system made the fluctuation range wider for efficiency but narrower for power.