Measurements of Boiling Two-Phase Flow Dynamics in a Heated Tube Using Neutron Transmission Imaging

Abstract

In BWRs, the boiling two-phase flow structure determines the heat transfer characteristics in the core. It is also crucial for evaluating cooling characteristics during severe accidents. Therefore, the boiling two-phase flow has been studied by many researchers for reactor core design and safety assessment. In this study, neutron imaging is applied to visualize the boiling two-phase flow dynamics in a heated tube, and the flow structure is evaluated by the void fraction distributions estimated from the neutron transmission images. The test section is a stainless-steel circular pipe, and it is installed vertically in the neutron beam. A high-speed neutron imaging system with a high-speed camera and an image intensifier is applied to observe fast two-phase flow phenomena. The axial flow development in the heated tube could be visualized, and the spatio-temporal characteristics were evaluated.