Part Strength Control Element Assemblies Effectiveness in APR1400 Reactivity Management During Transient Operation

This study investigates control methods for load following operation (LFO) in APR1400 nuclear reactors. While these reactors are primarily designed for baseload operation, there is an increasing interest to explore the LFO mode of operation to accommodate for changes in power demand. Effective LFO operation requires proper reactivity control strategies to maintain axial offset (AO) within the permitted band while operating at varying power levels. Part strength control element assemblies (PSCEAs) have been identified as potential solution for maintaining AO during LFO. To investigate the efficacy of PSCEAs, a 3D model of an APR1400 reactor core was developed in the CASMO-4/SIMULATE-3 code system. Different power manoeuvring scenarios were simulated to analyse reactor core behaviour and establish effective reactivity control strategies. The results of the study demonstrate that by utilizing PSCEAs, AO can be maintained within the permitted band during LFO operation. Specifically, a (1-6-1-16) or faster manoeuvring strategy was found to be more effective. The simulations showed that this strategy effectively managed the AO within the limits and boron concentration, ensuring stable reactor operation during LFO. This study provides valuable insights into the control methods required for successful LFO operation in APR1400 reactors. The findings have important implications for the nuclear industry, as they provide guidance on how to maintain stable reactor operation during variable power demand conditions. Further research may be needed to investigate the scalability and applicability of the findings to other reactor designs and operating conditions.