A Supercritical CO2 Brayton Cycle Power Converter for a Sodium-Cooled Fast Reactor Small Modular Reactor

Abstract

Although a number of power conversion applications have been identified or have even been developed (e.g., waste heat recovery) for supercritical carbon dioxide (S-CO2) cycles including fossil fuel combustors, concentrated solar power (i.e., solar power towers), and marine propulsion, the benefits of S-CO2 Brayton cycle power conversion are especially prominent for applications to nuclear power reactors. In particular, the S-CO2 Brayton cycle is well matched to the Sodium-Cooled Fast Reactor (SFR) nuclear power reactor system and offers significant benefits for SFRs. The recompression closed Brayton cycle is highly recuperated and wants to operate with an approximate optimal S-CO2 temperature rise in the sodium-to-CO2 heat exchangers of about 150 °C which is well matched to the sodium temperature rise through the core that is also about 150 °C. Use of the S-CO2 Brayton cycle eliminates sodium-water reactions and can reduce the nuclear power plant cost per unit electrical power. A conceptual design of an optimized S-CO2 Brayton cycle power converter and supporting systems has been developed for the Advanced Fast Reactor – 100 (AFR-100) 100 MWe-class (250 MWt) SFR Small Modular Reactor (SMR). The AFR-100 is under ongoing development at Argonne National Laboratory (ANL) to target emerging markets where a clean, secure, and stable source of electricity is required but a large-scale power plant cannot be accommodated. The S-CO2 Brayton cycle components and cycle conditions were optimized to minimize the power plant cost per unit electrical power (i.e., $/kWe). For a core outlet temperature of 550 °C and turbine inlet temperature of 517 °C, a cycle efficiency of 42.3 % is calculated that exceeds that obtained with a traditional superheated steam cycle by one percentage point or more. A normal shutdown heat removal system incorporating a pressurized pumped S-CO2 loop slightly above the critical pressure on each of the two intermediate sodium loops has been developed to remove heat from the reactor when the power converter is shut down. Three-dimensional layouts of S-CO2 Brayton cycle power converter and shutdown heat removal components and piping have been determined and three-dimensional CAD drawings prepared. The S-CO2 Brayton cycle power converter is found to have a small footprint reducing the space requirements for components and systems inside of both the turbine generator building and reactor building. The results continue to validate earlier notions about the benefits of S-CO2 Brayton cycle power conversion for SFRs including higher efficiency, improved economics, elimination of sodium-water reactions, load following, and smaller footprint.

Thermodynamic analysis and preliminary design of closed Brayton cycle using nitrogen as working fluid and coupled to small modular Sodium-cooled fast reactor (SM-SFR)

“…It is based on the selection of two dimensionless numbers, specific speed (ns) and specific diameter (ds), in conjunction with the use of Balje's ns-ds diagrams [57]. ns and ds can be determined from equation (31) and equation 32:…”

“…Recent times has witnessed a renewed interest in s-CO2 cycle [16] as PCS for nuclear power [17][18][19] and other heat sources such as concentrated solar power [20][21][22], fuel cell [23], coal [24] and waste heat [25]. In literature, s-CO2 cycle has been investigated as alternative to steam cycle for SFR application [3,[26][27][28][29][30][31][32]. All the studies agreed on the benefits of s-CO2 CBC power conversion system for SFR including higher efficiency (about 44%) and smaller footprint.…”

The application of supercritical CO2 in nuclear engineering: A review

“…The researchers demonstrated that SCO 2 power conversion system allows an achievement of well plant efficiencies at moderate core outlet temperatures and makes it easier to eliminate contamination if fission product leakage. 1 Sienicki et al 18 concentrated on the SCO 2 Brayton cycle power conversion for a sodium-cooled fast reactor (SFR) and stated that recompression closed Brayton cycle can offer a reasonable temperature and significant benefits to the SFR. Moreover, they demonstrated that the SCO 2 Brayton cycle power converter can eliminate sodium-water reactions as well as can reduce the space requirements and cost.…”

Counter flow induced draft cooling tower option for supercritical carbon dioxide Brayton cycle

“…Analysis was performed for S-CO 2 cycles developed for advanced fast reactor (AFR-100) and advanced burner reactor (ABR-1000) reactor applications [3], [4]. Detailed calculations for the AFR-100 plant will be presented and the ABR-1000 plant is used for comparison between different cooling options.…”

“…shows the effect of water flow rate and temperature on the cooling tower parameters for lowest power consumption option assuming that power plant is setup in Idaho Falls. For constant ambient air and water conditions, the optimum calculated from Equations(4) and(5)is constant irrespective of the water flow rate. Hence, as the water flow rate decreases the required volumetric flow rate of air decreases leading to a total reduction of floor area (A floor ) as can be seen inFig.…”