Control system design of very high temperature gas cooled reactor for start, stop and load follow operations

Very High Temperature Gas Cooled Reactor (VHTR) is one of future reactors for multi-purpose use. The reactor core has large amount of graphite moderator with much heat capacity. So the response of the core outlet gas temperature has very long time constant for disturbances. In this report, the control system design has been studied for the start up, the shut down and the load follow operations using PID controllers that have been applied for 100 % power operation. The system consists of the reactor power controller and the reactor outlet and inlet gas temperature controllers. At the start up operation, VHTR system is controlled successfully by the reactor power controller. At the shut down and the load follow operations, the reactor power control and the manipulation of the primary gas flow rate are needed for the control of the system. In these operations, it is found to be very important to use both the power controller and the primary gas flow rate controller for the simultaneous control of the reactor power and the outlet gas temperature. (author)