Keywords: boiling water reactors, BWR, nonlinear behaviour, bifurcation analysis, Gear', s method, regional oscillations, global oscillations, ordinary differential equations, ODE, nuclear energy, nuclear power
Boiling water reactors as dynamic complex systems
The research studied and analysed the nonlinear behaviour of Boiling Water Reactors (BWRs) using a new analytical reduced-order model. This model was applied to analyse global and regional oscillations in BWRs. Stability and semi-analytical bifurcation analyses were performed using this model in conjunction with the bifurcation code BIFDD to determine the stability limits for both in-phase and out-of-phase oscillation modes and the nature of Hopf bifurcation. The results obtained show that both sub- and supercritical Hopf bifurcations are encountered in different regions of the parameter space. Furthermore, numerical integrations of the set of Ordinary Differential Equations (ODEs) were carried out in the MATLAB environment using the so-called Gear's method. Results confirm the predictions of the bifurcation analyses.