Stability Analysis of Total Power Control Loop of Large PHWRs

Safe, stable, and efficient operation of nuclear reactors is very necessary for the development of nuclear power industry. During the course of its operation, a nuclear reactor is subjected to many intentional or unintentional perturbations which tend to change the rector power from its steady operating value. Power-level regulation is a significant technique for guaranteeing both operation stability and efficiency of nuclear reactors. Therefore, thorough stability analysis of power control loop is necessary to demonstrate its ability to withstand the reactivity perturbations. In this paper, the stability of the total power control loop of a large pressurised heavy water reactor is investigated in discrete-time domain by linearizing the system around its equilibrium points and identifying eigenvalues of the closed-loop system. The dynamics of the system vary widely depending on factors such as operating power levels, core-fuelling states and cycle time of reactor regulating system. Hence, the input to the stability analysis are these system parameters and the output is a stability characterization in terms of the stability regions shown in G(P) (total power control gain)-G(H) (level tilt gain) plane. The results quantify the influence of these system parameters on the stability of the total power control loop.