A fuzzy-logic-based pressure setpoint modification method for pressurized water reactor pressurizers

•Correlations between pressure setpoint and operating conditions of pressurizers are studied.•Fuzzy rules are generalized to clarify the correlations with no analytic expression.•A fuzzy-logic-based pressure setpoint modification (FPSM) system is developed.•The pressurizer control performance is improved by implementing the FPSM system. For pressurized water reactors, the pressurizer pressure is expected to be maintained constant to limit adverse impacts on the reactor due to pressure variations. To achieve this, a constant pressure setpoint is usually adopted in the pressurizer pressure control system. But it may not guarantee satisfactory pressure control performances especially under severe transient conditions. A feasible solution may be adjusting the pressure setpoint during transient processes and then restoring it to the initial value. For this purpose, the paper proposes a fuzzy-logic-based pressure setpoint modification (FPSM) method for pressurizers. A simulation platform was developed in MATLAB/Simulink implementing a nonequilibrium three-region pressurizer model, the pressure and waterlevel control systems and the FPSM system. Simulation studies of the AP1000 pressurizer during typical load change transients were performed, and responses of the pressurizer implementing the FPSM system are compared with those employing constant pressure setpoint to demonstrate feasibility and effectiveness of the system.