Methodologies for boiling water reactors stability analysis based on the study of neutronic power signals.

摘要

The present PhD Thesis deals with the Boiling Water Reactors (BWR) stability characterization by means of neutronic power signals analysis. The main objective is to detect the stability-related neutron flux oscillations in order to be suppressed before exceeding specified acceptable fuel design limits. In this context, the present PhD Thesis makes contributions by means of tools and methodologies that allow to determine the stability regime in a robust way, using the lineal stability parameters, Decay Ratio (DR) and natural frequency.; Firstly, the identification of the natural frequency associated with the neutronic oscillation is revised using spectral analysis. Once the natural frequency is determined, the DR estimation is studied. In order to estimate the DR, autoregressive (AR) models and dynamics reconstruction techniques are revised, making contributions in order to improve the stability regime characterization. Also a previous treatment of the neutronic power signals based on the singular system analysis (SSA) is proposed to improve the signals characteristics and better determine the stability regime of the reactor. Furthermore, the linear approximation of the BWR behaviour is analysed by means the linear stability parameters variation during the measuring time of the neutronic power signals.; In order to validate the tools and methodologies presented and compare their performance, analytic signals and the neutronic power signals from the Forsmark 1&2 Stability Benchmark are used. The purpose of this international benchmark was the intercomparison of the different time series analysis methods that can be applied to study BWR stability regime using neutronic power signals.