Dynamics and Control of a Load-Following Nuclear Power Plant for Grid with Intermittent Sources of Energy

Intermittent renewable energy sources such as solar and wind are still in their early stages of market penetration. However, fraction of electricity coming from these sources continues to increase, putting pressure on the stability of the new grid, which is best characterized as a hybrid energy system (HES). Generation II nuclear power plants (NPPs) were designed to supply base load to the grid, making it necessary for the new generation of NPPs to have some level of load following capability to respond to the needs of the new grid with varying load and frequency needs. NPPs that can follow load need new kind of hardware and control strategy. One of the newer reactors, AP1000, is designed to load follow, thus permitting its easy integration into a modern HES electricity grid. The advanced Mechanical Shim (MSHIM) control system is used in the AP1000 reactor design to regulate power. This control system consists of two separate rod controllers that control the core reactivity and axial power distribution using the “gray and black M control banks” (M-banks) and the “axial offset control bank” (AO-bank), respectively. In this chapter, past works on the development of the modeling of AP1000 will be reviewed first. This will include nodal model for reactor, pressurizer and UTSG dynamics, and corresponding models for their control. This will be followed by a discussion of load following capability of AP1000 with original MSHIM strategy and a revised one.