Coordinated control system design and verification of HTR-PM plant

The modular high temperature reactor (MHTGR), which uses helium as coolant and graphite as both moderator and structural material, has inherent safety features. It is multi-modular, i.e. the superheated steam produced by multiple MHTGR-based nuclear supplying system (NSSS) modules are combined to drive a common thermal load. The inherent safety feature of MHTGR can applied to a large-scale nuclear plant of any desired power ratings by adding modules. Since the plant power control technique of classical single-modular plants cannot be directly applied to multi-modular plants, it is necessary to design a new power control system for multi-modular plants. In this paper, the coordinated control system is presented for the two-module HTR-PM plant, the first multi-modular high temperature gas-cooled nuclear plant to be constructed in the world. The control system design is tested on the full-scale simulator of HTR-PM plant for the cases of power and high ramp down pressure heater bypass. The results demonstrate the feasibility of control system design and the acceptable transient performance of the multi-module plant.