Numerical investigation on the influence of the type of PI controller combined with MAAP code on the steady-state performance of a nuclear power plant

The Advanced Boiling Water Reactor (ABWR) was adopted as a physical model in this work to investigate the influence of the type of PI controller combined with MAAP 5.03 code on the Core Shroud Water Level (CSWL). For all cases, the proportional gain (k(p)) is equal to 1. The numerical results reveal that when the integral gain (k(i)) and k(p) are the same, the feedwater flow modified by PI controller is sensitive. Accordingly, CSWL is always larger than the Level-2, which does not incur a scrammed reactor. Besides, CSWL modified by the PI controller also consists with the designed water level. However, k(i) << k(p) causes the feedwater flow modified by PI controller to be insensitive. To avoid a scrammed reactor, a P controller (k >> 1) is added in front of the PI controller to increase the response speed of CSWL, which improves the tardy speed of feedwater injected into the reactor. Although k(i) >> k(p) does not cause a scrammed reactor, a P controller (k << 1) added in front of the PI controller is able to reduce the vibration of CSWL; hence, CSWL is close to the designed water level. To exactly simulate the steady-state performance of a nuclear power plant under the normal operation, our results can offer MAAP code users an important reference to design the PI controller.