Stability Analysis of Chemical Fine-Control Reactor in State Space

Abstract

Stability is studied of a nuclear reactor system which is controlled by the concentra-tion change of poison solution circulating through the pipe installed in the reactor. Particular attention is paid to: (1) nonlinearities due to the reactivity feedbacks, (2) rigorous treatment of nonlinear control elements without employing approximate methods such as the describing function and (3) nonlinear characteristics of the concentration change of poison solution.
The stability of this complex reactor system is analyzed in the state space by apply-ing the technique based on Lyapunov's method. A special technique is employed to cope with the difficulty such that the stability of a system with time lag depends on the pre-sent state as well as on the past history of the state which is usually indeterminable. Analysis is carried out for both simplified and realistic models. For the former model, one stability region is compared with another by varying the lag time, characteristics of nonlinear elements and the power at equilibrium point. Similar results are also ob-tained for the latter model.