Simulation Study of Mechanical Shim Control Strategy for Large Pressurized Water Reactor

One of the advantages of Mechanical Shim (MSHIM) operation technology is that it can realize partial decoupling between core power and axial offset (AO) in terms of control means. However, the original control strategy design does not make full use of this advantage. A new improved MSHIM control strategy is proposed through theoretical analysis in this paper. At the same time, a simulation platform for MSHIM control system is developed based on the multiple node reactor models. Upon this platform, the original control strategy of Westinghouse, Drudy’s control strategy of Westinghouse and the improved control strategy proposed in this paper are all simulated and compared carefully. The analysis results show that the improved MSHIM control strategy proposed in this paper not only can provide much tighter axial offset control but also can reduce the control rod movement, indicating its superiority than the original operation strategy. The study can be used as a reference for engineering implementation.