Autonomous load following behavior of a sodium-cooled fast reactor with a supercritical carbon dioxide Brayton cycle

The control of a nuclear power plant incorporating a Sodium-Cooled Fast Reactor (SFR) and a Supercritical Carbon Dioxide (S-CO2) Brayton power converter was investigated using a combination of the ANL Plant Dynamics Code (PDC) for the S-CO2 side and the SAS4A/SASYSYS-1 code for the reactor side. To investigate the autonomous load following, capabilities of the SFR with a S-CO2 cycle transient system level simulations were carried out without any active control on the reactor side such that the reactor power is regulated only by means of the inherent reactivity feedbacks of the metallic-fuelled sodium-cooled fast neutron spectrum core. The system response to a linear change in the grid demand from 100 to 0 % at the rate of 5 % nominal power per minute was analyzed. The results of the analysis demonstrate that a small temperature variation is calculated in the reactor core during the load following transient. Since the reactor behavior in response to the assumed 100 % change in grid demand is achieved without any need for deliberate control action on the reactor side, the calculations demonstrate the potential for autonomous load following for a SFR coupled to a S-CO2 cycle power converter. (authors)