Analyses of the Control System Strategies and Methodology for Part Power Control of the Simple and Intercooled Recuperated Brayton Helium Gas Turbine Cycles for Generation IV Nuclear Power Plants

Abstract

An important requirement for Generation IV Nuclear Power Plant (NPP) design is the control system, which enables part power operability. The choices of control system methods must ensure variation of load without severe drawbacks on cycle performance. The objective of this study is to assess the control of the NPP under part power operations. The cycles of interest are the simple cycle recuperated (SCR) and the intercooled cycle recuperated (ICR). Control strategies are proposed for NPPs but the focus is on the strategies that result in part power operation using the inventory control method. First, results explaining the performance and load limiting factors of the inventory control method are documented; subsequently, the transient part power performances are also documented. The load versus efficiency curves were also derived from varying the load to understand the efficiency penalties. This is carried out using a modeling and performance simulation tool designed for this study. Results show that the ICR takes ∼102% longer than the SCR to reduce the load to 50% in design point (DP) performance conditions for similar valve flows, which correlates with the volumetric increase for the ICR inventory tank. The efficiency penalties are comparable for both cycles at 50% part power, whereby a 22% drop in cycle efficiency was observed and indicates limiting time at very low part power. The analyses intend to aid the development of cycles for Generation IV NPPs specifically gas cooled fast reactors (GFRs) and very high-temperature reactors (VHTRs), where helium is the coolant.

Analyses of the Load Following Capabilities of Brayton Helium Gas Turbine Cycles for Generation IV Nuclear Power Plants

“…Thus the regulation takes place down stream of the compressor(s). The preceding study documented in [1], mathematically demonstrated that the power output regulation is almost linear to the flow, up to a certain level due to the changes in working fluid density.…”

“…However, NPPs need to demonstrate part load operational capability to meet grid demand and eliminate the negative impact on the environment by displacing polluting energy sources. Control strategies are discussed in detail in the preceding paper [1] to this study, as part of this research work. Thus, the focus of this paper is on strategies, which are required to meet grid demand, maintaining reactor thermal power and high cycle efficiencies in ODP operation.…”

“…Inventory pressure control requires a storage tank, where helium is delivered to for part power performance and released from, if the power needs to be increased [1]. The flow is controlled using valves (CV) to an acceptable limit.…”

“…The approach was considered satisfactory for the analysis conducted in this study. The equations implemented within the code environment are described in the preceding paper to this study in [1]. It is worth remembering that IC does not have a recuperator, thus the calculations for the recuperator do not apply.…”

“…The objective of this study is to demonstrate the load following capabilities of the cycles when using inventory pressure control to manage NPP power output and reactor thermal power including assessing the effects on cycle efficiency. A set of control strategies were recommended as part of this research work and is documented in [1]. The intent is for this study to be aligned with the applicable strategies.…”