Decay Ratio estimation in boiling water reactors based on the empirical mode decomposition and the Hilbert-Huang transform

In this paper a new method based on the empirical mode decomposition (EMD) to estimate a parameter associated with instability in boiling water reactors (BWR), is explored. This instability parameter is not exactly the classical Decay Ratio (DR), but it will be associated with this. The proposed method allows to decompose the analyzed signal in different levels or intrinsic mode functions (IMF). One or more of these different modes can be associated to the instability problem in BWRs. By tracking the instantaneous frequency (obtained through the Hilbert-Huang transform) and the autocorrelation function of the IMF associated to the instability of the BWR, the estimation of the proposed instability parameter can be achieved. The methodology was validated with two events reported in the Forsmark stability benchmark.