Determination of the maximum speed of WWER-1000 nuclear reactor control rods

In this study, a transfer function model of Bushehr WWER-1000 nuclear reactor is developed based on point kinetics equations with six delayed neutron groups and lumped thermal-hydraulic balance equations. The stability of the system is investigated by the root locus method. In addition, the control rod is modeled as a linear and non-linear system. The reactor model together with the control rod model is implemented on a personal computer using MATLAB/Simulink. To verify the model a rod drop accident is simulated in full power state of Bushehr WWER-1000 nuclear reactor. The trends of all parameters are correct, the steady-state error is in an acceptable range and the simulated values are in good agreement with those reported in the FSAR. Then, the transient behavior of the reactor is simulated at full power for identical displacement of control rods with different speeds along with linear and nonlinear models for the control rods. The results of the transients are analyzed and the maximum speed of control rods is determined for both of them.