Study on Reactor Power Control Strategies Based on Mode-C Operation and Control Mode

At present, the operation control modes of pressurized water reactor (PWR) nuclear power plants in service mainly include Mode-A, Mode-G, and MSHIM. Mode-A is mainly applicable to base load operation and cannot realize load tracking. In the process of Mode-G load tracking, it is necessary to adjust boron, and it cannot realize load tracking without boron regulation. Although MSHIM implements unregulated boron load tracking, a large number of control rods are inserted into the core during base load operation, which reduces the safety margin and causes certain economic losses. In recent years, China National Nuclear Corporation Limited proposed the Mode-C operation control mode, which attempts to concentrate the advantages of the above operation mode and avoid its disadvantages. When Mode-C is adopted, only one set of control rods is inserted into the reactor core to complete the nuclear power plant control task for the base load and other operations that do not require frequent reactor power regulation. For load tracking and other operations requiring frequent reactor power regulation, control rods are used instead of adjusting soluble boron to control core reactivity. Reactivity compensation and power distribution control in the load-tracking process are completed through control rods. When Mode-C mode is adopted, the reactivity control method under base load and load tracking conditions is different from other mature operating modes. It is impossible to directly adopt the ready-made reactor power control system scheme, which brings challenges to the practical engineering application of Mode-C. To solve the above problems, based on the idea of single-variable automatic control and bivariable automatic control in Mode-C under different load demand conditions, this paper carries out research on the strategy of the reactor power control system and puts forward two specific control schemes. Through the control simulation program based on the one-dimensional core model, the simulation model of the control object and control system is established, and the closed-loop simulation verification of the control strategy is completed. The simulation results show that the designed reactor power control system can realize automatic control of the full power operating range and non-adjustable boron load tracking, reduce the operator’s burden, and meet the expected operation effect of the Mode-C operating mode.