The paper presents the design of state feedback control for a large pressurized heavy water reactor (PHWR) by developing a reduced-order model for the same. The nonlinear mathematical model of the PHWR is linearized around an operating point corresponding to full-power operation of the reactor. The linear model has 14 inputs and outputs each and 56 states. Application of the reduction technique leads to a simplified model characterized by only 14 states. This 14th-order simplified model is used to design a linear quadratic regulator, and state feedback gains for the original 56th-order system are obtained without any significant difficulty. The transient performance of the closed-loop system is tested by simulation of the original nonlinear model of the PHWR.