A phenomenological model for the interpretation of velocities measured in BWRs by cross-correlation techniques

We present a simple phenomenological analytical model for the interpretation of the velocities measured in BWR rod bundles by cross-correlation techniques. Additionally, we shall show that the peaks of the cross-correlation function can give a better estimate of the velocities than the slope(s) of the phase. The model is based on the assumption that at a given axial elevation, the radial two-phase flow velocity profile is due to the different independent velocities in the different types of subchannels, rather than to a radially continuously changing profile. This assumption is realistic, and helps us to formulate a simple analytical model and understand the experimental results, which is the main scope of the present work. Our model can explain qualitatively the origin of the velocities measured either by neutron or gamma cross-correlation techniques as we)) as interpret a number of experimental results