Eventos Anais de eventos
COBEM 2017
24th ABCM International Congress of Mechanical Engineering
Largest Lyapunov Exponent and Attractors Applied to Stability Study of Nuclear Reactors
Submission Author:
Antonella Lombardi Costa , MG
Co-Authors:
WILMER ARUQUIPA COLOMA, Antonella Lombardi Costa, Claubia Pereira
Presenter: WILMER ARUQUIPA COLOMA
doi://10.26678/ABCM.COBEM2017.COB17-0653
Abstract
Nuclear reactors are susceptible to instability, causing oscillations in reactor power in specific working regions characterized by determined values of power and coolant mass flow. During reactor startup, there is a high probability that these regions of instability will be present; another reason may be due to transient processes in some reactor parameters. The main aim of the instability phenomena studies in nuclear reactors is to try to identify points or regions of operation that can lead to power oscillations conditions. The problems of instability were analyzed using the classical concepts of non-linear systems, such as largest Lyapunov exponents, phase space and attractors. The Lyapunov exponents quantify the exponential divergence of the trajectories initially close to the phase space and estimate the amount of chaos in a system; the phase space and the attractors describe the dynamic behavior of the system. This method was applied to a set of signals coming from stability tests of the reactors Forsmark 1 and 2. In this work, there were calculated the largest Lyapunov exponents and also reconstructed the attractors for each signal considered. In the analyzed cases, all the largest Lyapunov exponents that were found are positive; this implies that system presents chaos.
Keywords
BWR Instability, Large Lyapunov Exponent, Attractor
