On the stability of the point reactor kinetics equations

As the basic neutronic problem is unstable by nature, maintaining a reactor critical is a task that requires a lot of effort. This work presents and discusses some aspects related to the stability of the basic physics behind a nuclear reactor core based on the well-known point reactor kinetics equations. First, the linear non-feedback case is studied where differences between Lyapunov and BIBO stability are found. These differences are shown both numerically and analytically, and explained using a reactor physics based reasoning. Finally, a simple model is used to analyse the intrinsic stability of the point reactor equations when reactivity feedbacks are taken into account. A method for constructing conceptual stability design maps is proposed and a basic interpretation of the simple results obtained is given.