Model reduction of AHWR space–time kinetics using balanced truncation

Abstract

Study of transient behavior and design of control for large reactors, such as the Advanced Heavy Water Reactor (AHWR) requires accurate mathematical models. An 80th order space–time kinetics model which describes the core neutronics behavior of AHWR is available but it is nonlinear and stiff. The modern control design and analysis studies with this model are accompanied by serious numerical ill-conditioning problems. Hence, there is a strong motivation for obtaining a reduced order model which preserves the input–output behavior accurately.In this paper, we have explored the application of balanced truncation technique to obtain a reduced order model from the original high order model of the AHWR. The reduced order model thus obtained was examined from the view point of transient performance by comparing its response with that of the original model and it is found to yield a very good approximation. We also carried out the comparative study between different reduced order models of AHWR, namely, Davison’s technique, Marshall’s technique, singular perturbation analysis and balanced truncation by comparing their performances with respect to each other and with the original model. All of these methods are found to be effective, however the overall accuracy in the approximation using the balanced truncation approach is found to be far more superior.