Local steam transit time estimation in a boiling water reactor

A new correlation method, the so-called "rehocence" [1] or "smoothed coherence transform" (SCOT) [4], for transit time estimation is applied in a boiling water reactor (BWR). The transit time of a propagating perturbation of the coolant density between two points along the propagation path could be measured by noise analysis technique. This is usually performed by directly observing the peak in the cross-correlation function of the stochastic signals measured at two points in the propagation path, or indirectly by determining the slope of the phase. The used rehocence method presents the transit time directly in the same way as in the ordinary cross correlation technique, but with a better resolution, even when the measured signals are contaminated by a narrow-band limited internal noise coming from the global noise of the neutron flux fluctuation.