Abstract
One of the key technology requirements to achieve the non-nuclear-grade hydrogen plants coupled to the HTTR is the development of control methods mitigating the effect of IS process-abnormal thermal load transients on the reactor operation. This study focused on developing the control methods for the thermal mitigation system in the HTTR-IS system. The control methods are developed to stabilize the steam generator helium gas outlet temperature increase against the high-temperature helium gas inflow. The key parameters and equipment are determined and the control operations are simulated. The simulation results show that the steam generator water temperature can be effectively decreased by interfacing the actuation of the air cooler inlet shut-off valve with the actuation of the diverter valve. Furthermore, the air cooler outlet shut-off valve is activated as the pressure difference approaches zero between the steam generator bottom and the down comer from the air cooler to the steam generator. It is demonstrated that the control methods developed enable the continuation of the nuclear reactor normal operation under IS process abnormal conditions and without operator intervention.
