This paper explores the concept of instability suppression system and its performance in a BWR plant. The key idea adopted from the work of Aleksakov et al. (1980) is to utilize information provided by the in-core power monitoring detectors to guide movement of control rods in a way that suppress the global, regional and local instability. In the paper, effectiveness of a simplified suppression algorithm is characterized by implementing it on a real BWR model, using the RELAP5/PARCS coupled thermal-hydraulics and neutron kinetics code. Both forced power oscillations and realistic reactor transients (feedwater temperature transients, control rod drop) were analyzed. The results suggest that, without requiring any modifications for the in-reactor diagnostics and equipment, the proposed suppression system is capable of significantly mitigating the impact of core instability events on plant performance by maintaining the core parameters within the safe operational range.