A control system design for the Modular High Temperature Gas-Cooled Reactor Gas Turbine power plant (MGR-GT) is presented. The control system is designed to provide full-scale automated control functions for power output regulation and plant protection in accordance with utility requirements for modular nuclear power plants. Control of the plant power output is based on a unique integration of inventory control and bypass control, which not only enables required load following capabilities but also offers 45% electric generating efficiency over the power ranges from 100% to 50% of the rated level. The reactor power is controlled based on the strategy of maintaining constant core outlet temperature. This approach minimizes the occurrence of thermal transients and temperature redistribution in the core during reactor power changes. In addition, the control system also provides emergency protective control to protect the plant components and to mitigate the likelihood of bounding safety events in case of severe accidents. The operation of the control system is automated by controllers implemented based on the state-space feedback control methodology. A spectrum of transients in both normal and far-off normal conditions has been simulated to evaluate the operability of the plant. The simulation results for a few selected events will be described. The design demonstrates that the MGR-GT is a highly efficient and robust controllable power plant.

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