Real-time neutron radiography as a flow visualization and measurement tool for nuclear thermal hydraulics researches

Visualization and measurement results are presented on multiphase flows in a metallic tube and container and liquid metal flows by real-time neutron radiography. A liquid metal flow was visualized by a tracer method and the vector field was obtained by an image processing method. A solidification interface in a liquid metal was visualized by a dye injection method. Flow patterns of nitrogen gas-water two-phase flows in a metallic tube and container and a water flashing flow in a nozzle were visualized. A flow pattern map in a vertical tube was obtained and compared with a flow pattern transition model. One-dimensional void fraction distributions were obtained by an image processing method and the results were used for testing the constitutive equations in a two-phase flow prediction code. Two-dimensional void fraction distributions in a rectangular container were also obtained. It is shown that the real-time neutron radiography is a very useful tool to study thermal hydraulics in nuclear engineering. (author)