Measurement of radial void fraction distribution of two-phase flow in a metallic round tube using neutrons as microscopic probes

As a part of the development of the neutron radiography technique, a method was proposed to measure a radial void fraction distribution of a two-phase flow in a metallic round tube. The measurement was performed by (1) assuming an appropriate function so as to approximate the radial void fraction distribution α_r, (2) deriving a function for the void fraction distribution projected on the plane perpendicular to the incident neutron beam and along the transversal direction (x-direction) by integrating the function of the radial void fraction distribution, and (3) determining parameters in the function α_r by the least-squares method with measured α_x. It was pointed out that the test section should be placed at an appropriate distance from a converter to validate this method. It was shown that this method could apply to measure both of the power-law and saddle-shaped void fraction distributions.