In the framework of the CORTEX EU project, several measurements from different KWU and VVER reactors
have been analyzed. The goal of this project is to develop and test core monitoring techniques to
detect possible anomalies and better characterize the information provided by the neutron detectors.
In this article, three different signal processing methods are presented: coolant velocity estimation,
Singular Spectrum Analysis (SSA) and Operational Modal Analysis (OMA). The first method is based on
detecting travelling perturbations by cross correlating different detectors and obtaining the impulse
response function. The second method, SSA, reduces the noise and allows a better estimation of the frequency
content with a high resolution. SSA has been tested both in simulated and plant data. The last
method permits distinguishing closely spaced resonances and a multivariate analysis of all the detectors.
In this work, the details of each methodology are explained step by step, and the results on each reactor
are also presented. Testing these methods during CORTEX project gives valuable information and orientation
for further investigations in reactors diagnostics.