Design of a Supercritical Carbon Dioxide Power Generation Cycle for Small Modular Reactors Thank you to: Bechtel Corporation– Stephen Routh, James Haldeman, John Gülen, Steven Kline, Desmond Chan Penn State Mechanical and Nuclear Engineering Department ME Senior Design Director, Dr. Frecker and Section Professor, Mr. Rose Conclusions Kelsa Benensky, Karen Bobkowski, Hardik Jasani, John Merlino The Pennsylvania State University Department of Nuclear and Mechanical Engineering Heat Exchanger Selection A plate heat exchanger was chosen because of its compatibility with SCO 2 and large surface area that maximizes heat transfer efficiency Working Fluid SCO 2 has the potential for 20x smaller turbine size and less stages compared to steam for given power output Proposed Design Problem Statement Current SMRs use steam in the secondary loop to rotate the turbine blades and produce power. This working fluid requires a high flow volume through large, multi-stage turbines to achieve required power output. Background The mission of small modular reactors (SMRs) is to provide safe and reliable small scale power to developing areas by maximizing the efficiency, transportability, and manufacturability of power plant design. System Components The proposed design incorporates a supercritical carbon dioxide (SCO 2 ) secondary loop to decrease size and increase efficiency. The entire system is made up of: • Primary Pressurized Water Loop • Intermediate Steam Loop • Secondary SCO 2 Loop o Steam-SCO 2 Heat Exchangero Turbine o Circulating Water-SCO 2 Loop o Compressor• Circulating Water Loop Heat Balance The heat balance of the system was determined by Ther moflow software using component inputs. The results produce d the temperature, pressure, mass flow rate, and enthalpy for each of the following state points: 1. Inlet of Compr essor2. Inlet of S team-SCO 2 HxR 3. Inlet of Tu rbine 4. Inlet of Cir cula ting Wa ter-SCO 2 HxR These state points follow the Brayton cycle model, depicted to the right Results are shown in the table to the left The proposed system design with a SCO 2 working fluid provides a net power output of 65 MW e and can be improved to 73 MW e by adding a recuperation cycle. This analysis proves that a SCO 2 working fluid has greater electrical power output potential than a steam power conversion cycle of similar size. Future Considerations • The secondary SCO 2 loop is capable of being modelled with a recuperator to provide additional power from the turbine. A low and high temperature recuperator provides additional heat to the cycle and results in an 18% increase in net power output. • In order for the proposed design to be competitive with steam cycles, heat exchanger design must allow for high efficiencies. Heat exchanger sizing also limits the viability of the system. • Turbo machinery materials research and sizing must be proven for a system on the scale of MWe power output. State Point Enthalpy (BTU/lb) Temperature (F) Pressure (psi) Mass Flow Rate (lb/s) 1 -27.2 82 1000 4922 2 -4.141 268.9 3060 4922 3 77.75 520 3000 4922 4 42.25 328.2 1000 4922
