Auxiliary feedwater reheating to mitigate primary and secondary side thermal stressors

A consequence of operating steam cycles under time varying loads, is the variability of the feedwater temperature entering the bottom of the steam generators. This variability is a direct result of changes in turbine impulse pressure and subsequently turbine tap pressures in response to the load changes, with a reduction in feed temperature during periods of low turbine demand. These fluctuations over time will increase thermal cycling and threaten the integrity of the tube bundle as well as other components in the feed system. Sensible heat, TES systems have been shown to be an effective load management strategy allowing nuclear reactor systems to operate at effectively 100% full power while storing excess thermal energy for recovery later. A byproduct of the TES system is the availability of large amounts of low grade waste heat that can be used for ancillary applications, including auxiliary feed heating during periods of low turbine demand. The addition of an auxiliary feed heater at the end of the traditional feed train can minimize feed temperature variations during periods of low turbine demand, reducing the effects of thermal cycling and increasing overall thermodynamic efficiency. This paper discusses the design, operation and control strategies for an auxiliary feed water system as an integral component of a coupled Thermal Energy Storage system and Integral Pressurized Water Reactor. The impact on system performance, particularly as it affects reactor dynamic response and reductions in thermal cycling will be addressed. In addition to the improved thermal efficiency, a benefit of this approach is the relocation of thermal stressors from the reactor coolant system to more easily managed Balance of Plant systems.