Cycle Efficiency and Flowrates in a Supercritical Water Reactor: A Thermodynamic Analysis of the Effects of Final Feedwater Temperature and Number of Feedwater Heaters

Abstract

Cycle efficiency and flow rates are rough measures of power plant revenue and capital cost. A full thermodynamic analysis of a supercritical water reactor provides these and other parameters necessary to perform an economic analysis and optimize system design. A computer code has been developed that works with Excel to assist thermodynamic analysis of user-defined power plant designs and related operating parameters. A number of direct-cycle plant designs with steam reheat and possessing between 4 and 10 feedwater heaters were analyzed. All cycles analysed used a core coolant exit temperature of 550ºC, a HP turbine inlet pressure of 24 MPa, and turbine efficiencies of 92%. Maximum cycle efficiencies (excluding generator losses, cooling water pumping power, and station power consumption) ranged between 47.8% and 48.8%. Optimum final feedwater temperatures of 326 degrees C to 349 degrees C were observed, with variation mainly a function of extraction steam origin. Overall flow rates were observed to increase some 19% from a final feedwater temperature of 280 degrees C to 340 degrees C, while extraction steam increased 50% over the same range. It is concluded that optimum efficiency does not coincide with lowest capital cost and a detailed economic analysis is yet needed to optimize reactor design.