Dynamic modeling and simulation of supercritical carbon dioxide recompression Brayton cycle energy converter coupled with a 400MWth natural circulation lead-cooled reactor

The natural circulation lead-cooled fast reactor (NCLFR) possesses excellent neutron economy, thermal safety characteristics, and application potential. Meanwhile, the supercritical carbon dioxide recompression closed Brayton cycle (s-CO 2 -RCBC) has the merits of high thermal energy conversion efficiency, system compactness, environmental friendliness, safety, and notable economic benefits. Coupling the NCLFR with s-CO 2 -RCBC can integrate the advantages of both, representing a key development direction for future advanced clean-energy nuclear energy systems. However, the unique thermophysical properties of supercritical carbon dioxide, the complexity of the recompression Brayton cycle, and the intricate coupling with the NCLFR render the transient behavior and control strategies of the entire system highly complex. This paper establishes a dynamic model for a 400MW th small lead-cooled fast reactor coupled with a supercritical carbon dioxide conversion Brayton cycle system based on the reactor transient simulation code RESYS, and a control system for reactor power and s-CO 2 -RCBC system was established. The component model and closed-cycle dynamic model of the s-CO 2 -RCBC were validated using literature reference data. Subsequently, a detailed analysis is conducted on both the steady-state and transient operational characteristics of the integrated system. Firstly, the steady-state simulation is conducted to validate the precision of the integrated system model and serve as the initial condition for the transient simulation. Thereafter, three transient operational conditions are simulated, including reactor power perturbation, external load reduction, and fluctuations in cooling-water temperature and flow rate. The result shows that the automatic control system can effectively control the system and yield satisfactory system dynamic characteristics under the condition of these transients. The research findings presented in this paper can serve as an important reference for the design and evaluation of control methods for NCLFR systems coupled with s-CO 2 -RCBC.