Analyses of the load following capabilities of Brayton Helium gas turbine cycles for generation IV nuclear power plants

The control system for Generation IV Nuclear Power Plant (NPP) design must ensure load variation when changes to critical parameters affect grid demand, plant efficiency and component integrity. The objective of this study is to assess the load following capabilities of cycles when inventory pressure control is utilised. Cycles of interest are Simple Cycle Recuperated (SCR), Intercooled Cycle Recuperated (ICR) and Intercooled Cycle without recuperation (IC). Firstly, part power performance of the IC is compared to results of the SCR and ICR. Subsequently, the load following capabilities are assessed when the cycle inlet temperature is varied. This was carried out using a tool designed for this study. Results show that the IC takes ~2.7% longer than the ICR to reduce the power output to 50% when operating in Design Point (DP) for similar valve flows, which correlates to the volumetric increase for the IC inventory storage tank. However, the ability of the IC to match the ICR’s load following capabilities is severely hindered because the IC is most susceptible to temperature variation. Furthermore, the IC takes longer than the SCR and ICR to regulate the reactor power by a factor of 51 but this is severely reduced, when regulating NPP power output. However, the IC is the only cycle that does not compromise reactor integrity and cycle efficiency when regulating the power. The analyses intend to aid the development of cycles specifically Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs), where helium is the coolant.