Void Fraction Distribution Patterns of Steady Air-Water Two-Phase Flow in a Rod Bundle With a Spacer

Abstract

Abstract Void fraction distributions of a steady air-water two-phase flow in a 4 × 4 rod-bundle with circular ferrule type spacers were visualized by neutron radiography. A high flux thermal neutron radiography system at JRR-3M in Japan Atomic Energy Research Institute and a fast neutron radiography system at Yayoi reactor in the University of Tokyo were used. Thermal neutron radiography was suitable for high void fraction two-phase flow and fast neutron radiography was suitable for low void fraction two-phase flow. Visualization with high spatial resolution up to 0.1 mm was carried out by using a cooled Charge Coupled Device (CCD) camera. The Computed Tomography (CT) reconstruction was carried out to obtain three-dimensional (3-D) void fraction distributions by a filtered back projection method. Cross-sectional averaged one-dimensional (1-D) void fraction distributions were also calculated for many experimental conditions by image processing methods. The 1-D and 3-D void fraction distributions were clearly visualized by neutron radiography. The void fraction distribution patterns in the rod bundle were discussed.