Development of simplified and inherently safe reactivity control mechanisms is still a challenge in many compact Small Modular Reactors (SMRs), despite significant progress. One such approach is the use of rotating reflector drums, which have been extensively employed in space reactor systems, but their application to light-water SMRs remains unexplored. This study investigates the application of rotating reflector drums as a primary reactivity control system in a light water SMR by quantifying achievable reactivity swing and shutdown margin. A 5 MWth nuclear heating reactor (NHR-5) design was used as a base design model, to analyze different configurations of reflector drums and to perform their neutronic simulations using Monte Carlo code. According to the current results, complete reflector drum rotation can provide sufficient reactivity swing to shut down the reactor and provides operational control within limits. This model uses beryllium filled reflector drums, with approximately 1224 pcm reactivity worth, which eliminates the rod ejection accidents, increases the fuel cycle length and reduces the risk of rapid reactivity insertion and mechanical complexity and consequently enhances the reactor safety as compared to the control rod mechanism.​