Control rod driven long-term load-follow operation in small modular reactor

Abstract

The need for extensive load following with Small Modular Reactor (SMR) is increasing as its potential coupling with intermittent renewable energy sources increases. SMR is generally considered suitable for load following, though, its load maneuvering capability depends on the system design features and reactor control algorithm. In this study, it is shown that a control rod driving algorithm based on the core outlet temperature of a typical IPWR type of SMR, SMART100 facilitates the extensive load following operations (IAEA, 2018, Song et al., 2010, Lee et al., 2012). Addition of control parameter such as Axial Offset (AO) and Boron concentration change into the control algorithm makes a reactor control possible when the AO is close to the limit or control rod position is close to Power Dependent Insertion Limit(PDIL). Simulations for various scenarios were performed to verify the above algorithm Short-term simulations less than 2 days and Long-term simulations longer than 7 days were performed. For each simulation, random demand or scheduled demand considering demand changes incurred by renewable energy was used. In all simulations, it is confirmed that the reactor facilitates control rod driven load-following operation within the operation limit. Further, it is shown that more efficient load-following operation is achieved by additional adjustment of control band of outlet temperature.