Thermal Efficiency of Alternative Supercritical CO2 Combined Cycle

Abstract

In the global Nuclear-Power-Plant (NPP) fleet with Light Water Reactors (LWRs) and Pressurized Heavy Water Reactors (PHWRs) make up 95% of the total number of reactors. These reactors have thermal efficiency within 26-38%. Comparing NPPs to the most advanced thermal power plants, which have thermal efficiencies up to 62.5%, the gap between the two technologies is clear. In the global transition to clean energy, Generation-IV reactors, such as Very High Temperature Reactors (VHTRs) and Gas-cooled Fast Reactors (GFRs), which have the highest temperature of the helium reactor coolant, will need to utilize alternative power cycles in order to make them cost competitive with thermal power plants. The objective of this paper is to demonstrate the maximum theoretical thermal efficiency of an indirect combined cycle for GFRs (primary— SuperCritical Pressure (SCP) Brayton gas-turbine cycle (working fluid - SC carbon dioxide at 20 MPa) and secondary—SCP Rankine cycle (working fluid - SC CO₂ at 21 MPa)).