Neutron Wave Propagation in Heterogeneous Media and the Interpretation of Neutron Noise in BWRs

摘要

Experimental data from boiling water reactors (BWRs) show that the phase of the cross-power spectral density between pairs of axially separated neutron detectors varies linearly with frequency (characteristic of a pure delay process) for frequencies greater than approx. 1 Hz. The interpretation of this fact is of relevance to application of noise techniques to measure the average velocity of the vapor phase in the moderator. It is shown that the homogeneous approximation is inadequate to interpret the noise field in the BWRs despite the number of energy groups used. To show this point, a single-energy-group, neutron diffusion model which accounts explicitly for the heterogeneities of the system is presented. (ERA citation 06:004849)