On the application of singular perturbation techniques to nuclear engineering control problems

Using a linear state regulator problem for the control of xenon-induced spatial flux oscillations in a nuclear reactor it is shown that model simplifications may cause the system equations to behave like singularly perturbed ones. An example illustrates that an attempt to transform the system equations to standard singular perturbation form also transforms the performance index and raises the possibility of cheap control, which is physically not possible with mechanical control systems in a nuclear reactor. Another example demonstrates that the stiffness of the system equations is improved dramatically by making the model less approximate. It is concluded that care must, therefore, be exercised while applying singular perturbation techniques to problems which are ill-conditioned as a result of model simplification