Three-dimensional void fraction measurement of two-phase flow in a rod bundle by neutron radiography

Three-dimensional void fraction distribution and one-dimensional cross-sectional averaged void fraction distribution of air-water two-phase flow in a 4 × 4 rod bundle near a spacer was measured by neutron radiography using a CT method. Two-phase flow behavior in the rod bundle near the spacer, which is important to study from the safety considerations of nuclear reactors and which is difficult to observe by other methods, was clearly visualized.