A control design scheme is formulated for a pressurized water type nuclear power plant by integrating the optimal linear quadratic Gaussian (LQG) control with the robust integral sliding mode (ISM) technique. A novel robust-optimal hybrid control scheme is further proposed by integrating the LQG-ISM technique with the loop transfer recovery approach to enhance the effectiveness and robustness capability. The control architecture offers robust performance with minimum control efforts and tracks the reference set-point effectively in the presence of disturbances and parametric uncertainties. The multi-input multi-output nuclear power plant model adopted in this work is characterized by 38 state variables. The nonlinear plant model is linearized around steady-state operating conditions to obtain a linear model for the controller design. The efficacy of the proposed controllers is demonstrated by nuclear power plant subsystem simulations. The control performance of the proposed technique is also compared with other classical control design schemes. Numerical measures are employed to quantitatively analyse and compare the performance of the different controllers that are studied in the work.