Abstract
Optimal control of a two-core coupled nuclear reactor system is considered. The mathematical description of this system leads to an eighth-order nonlinear time delay model. This model is written in such a way that when a scalar parameter is perturbed, it reduces to a second-order model without time delays. Using the recently developed singular perturbation theory, an approximate solution valid for the eighth-order time delay model is obtained by solving only reduced-order models. Computational advantages of this method over the second variation method are discussed.