Icone15-10736 Experimental Study on Liquid Film Behavior in 3x3 Rod Bundle Channel Simulated Nuclear Fuel Assembly

Abstract

An accurate knowledge of hydro-dynamic behavior of a liquid film flow on nuclear fuel rods is indispensable for analysis of the CHF under postulated loss-of-coolantaccidents in boiling water reactors. Despite of this importance, the microscopic knowledge of liquid film flow in the rod bundle is still not enough for us to construct the physical model for CHF analysis. Especially flow near the spacer is very unstable and complicated, so it is very difficult to obtain its information experimentally.The objective of the present work is to investigate on the liquid film flow in rod bundle channel experimentally, and to obtain the details of the behavior of liquid film and droplets with high resolutions of time and space. Liquid film flow in a 3x3 bundle channel simulated nuclear fuel assembly was visualized with about less 10µm and 100 µsec resolutions by using high speed video camera with the Cassegrain optical system. The shape and motion of liquid droplets in the rod bundle were observed directly, and the surface of liquid film were also visualized. Several interesting behaviors of liquid droplets and liquid film were observed and are reported in the present work. Image analysis were also conducted for evaluating the size of liquid droplet quantitatively.