Measurement of Transient Flow Pattern by High Speed Scanning X-Ray Void Fraction Meter

In order to measure void distributions across pipe flow and to determine the transient flow pattern during blowdown from a high pressure water vessel to atmosphere, we have developed a high-speed scanning X-ray void fraction meter. The scanning X-ray beam is collimated by 8 hole-slits on a rotating disc. An X-ray beam scans across a pipe from top to bottom, according to the hole-slit movement. The maximum scanning frequency is 200 Hz. A void distribution curve can be obtained every 5.0 ms. Void signals are sent to a void distribution color display system that make it easy to recognize even a slug flow. Experimental results show that the system is very effective to determine how flow patterns change during blowdown.