Design and evaluation of load-follow control schemes for a small district heating reactor LDR lite

Load following is needed in district heating networks, where heat demand varies significantly. LDR lite is a small light water reactor designed for flexible, low-temperature heat production. In this study two load-follow control schemes were designed for LDR lite. In the first option, control rods are used to regulate the power, while the secondary circuit temperatures are kept constant. The second option utilizes temperature feedback, adjusting the reactor power via secondary circuit pump control. The control schemes were evaluated by simulating a simplified load-follow scenario using coupled 3D neutronics and system thermal hydraulics. The control rod-driven scheme successfully followed the power demand within a narrow margin of error and reliably produced the required supply temperature to the district heating network. In contrast, the temperature feedback-driven control resulted in larger deviations, unpredictable temperature behaviour, and failed to meet the required supply temperature consistently. The results demonstrate that the control rod-driven power regulation is the more viable strategy for load following with LDR lite. Further optimization is still required, but the established control scheme provides a foundation for future research also in other fields.