Evaluation of start-up characteristics for heat pipe-cooled nuclear reactor coupled with recuperated open-air brayton cycle using hardware-in-the-loop

The heat pipe-cooled nuclear reactor (HPR) holds great importance for the low-carbon transition period and can be applied flexibly and stably in numerous scenarios. However, studies on the dynamic performance of the HPR coupled with the open-air Brayton cycle (OBC) are scarce, and achieving a balance between economy and accuracy has proven challenging. In this work, a hardware-in-the-loop (HIL) method is proposed and implemented for the coupled HPR-OBC prototype by combining the benefits of experimental measurements and numerical simulations. A sodium heat pipe test rig is heated in the real world, while neutronics and OBC dynamics are synchronously solved using Simulink models. A transient HIL test lasting for 12000 s is conducted to explore the start-up process of HPR-OBC. The coupled system successfully reaches steady-state by regulating reactivity and shaft speed. The results indicate a strong coupling effect between the shaft speed, the heat transfer rate of the heat pipes, and the air flow state in the OBC. The turbomachine operates within reasonable regions and no surge or choke phenomena occur. The final reached OBC efficiency is 20 %, and the generated electricity power output is 0.16 MWe.