Investigation of reactivity control strategies for a micro-transportable gas-cooled thermal reactor

Micro nuclear reactors have gained increasing attention in recent years due to their high efficiency and long lifetime, making them an attractive solution for meeting the energy needs of remote and off-grid locations. Previous work has proposed a conceptual design for a micro solid nuclear reactor cooled by a helium-xenon mixture. The main aim of this study is to examine the effects of introducing burnable poisons on the neutronic performance of the designed micro nuclear reactor and to improve the design of the sliding reflector segment for reactivity control. The computational results indicate that the inclusion of burnable poisons can decrease the initial excess reactivity and radial power peaking factor, while not having a significant impact on the lifetime of the core. The use of 0.4%wt Gd2O3 and 0.75%wt ZrB2 as burnable poisons results in a reduction of 6.0 $ and 7.4 $ in the maximum reactivity of the core, respectively, while the core lifetime is reduced by 169 EFPD and 545 EFPD, respectively. By partitioning the sliding reflector, a linear introduction of reactivity can be achieved, and the influence of introducing burnable poisons on the reactivity control ability of the sliding reflector is relatively small.