S-CO2 cycle design and control strategy for the SFR application

Abstract

As a part of Sodium-cooled Fast Reactor development in Korea, the supercritical CO2 Brayton cycle is studied as an alternative power conversion system to the steam Rankine cycle. The benefits of the S-CO2 cycle are relatively high efficiency under the mild turbine inlet temperature condition, simple layout and compact size. In addition, the safety of the SFR system can be potentially enhanced as the violent sodium-water reaction can be replaced with the benign sodium-CO2 reaction. The power output of the reference SFR is 150MWe, and two modules of 75MWe S-CO2 recompression cycle will be used for the reference SFR application. The main components including turbomachineries and heat exchangers are designed with in-house codes which have been validated with experiment data. Based on the cycle and component design condition, the pipe system is designed and the component module arrangement and respective size are assessed. Due to the high mass flow rate and pressure drop in pipes, some portion of the cycle efficiency is reduced. To deal with the leakage flow from turbomachineries, the recovery system design condition is also assessed. Based on the designed components, the S-CO2 cycle performance under part load condition is analyzed with an in-house developed quasi-static cycle analysis code. Furthermore, the control logics including inventory control, turbine bypass and throttle valve control are compared under the cycle part load performance.