The state feedback assisted control (SFAC) uses the concept of state feedback to modify the demand signal for an embedded classical output feedback controller to achieve an optimal control objective. It has been shown that the SFAC concept can improve the performance of primary coolant temperature control in a nuclear reactor. How the embedded classical controller assists a state feedback controller in achieving improved performance and stability robustness, which play an important role in implementing optimal control algorithms for reactor control over a wide range of operations, including possible faulted conditions, is demonstrated. While the state feedback component improves system performance, the classical output feedback component enhances stability robustness.