Experiment on gas entrainment evaluation method from free liquid surface in a sodium-cooled fast reactor, 1; Measurement of velocity distributions in the experimental flow area by PIV method

Kobayashi, Shunsuke*; Endo, Kazuki*; Jasmine, H.*; Sakai, Takaaki*; Matsushita, Kentaro  ; Ezure, Toshiki ; Tanaka, Masaaki  

Assuming gas entrainment (GE) to the main coolant circulation system from cover gas which is an inert gas to cover sodium coolant in a reactor vessel of the sodium cooled fast reactor, there is a concern that reactivity disturbance will occur when bubbles pass through the reactor core. Conventionally, an evaluation method based on static vortex extension theory has been employed for the GE prediction. However, it is known that the method gives rather overestimation for the GE occurrence from the unsteady traveling vortex dimple at the wide liquid surface. In order to contribute to understand the phenomena, experimental data have been accumulated by the basic water experiment. In this study, the velocity distributions were measured under the conditions where GE occurs by particle image velocity (PIV) measurement in an experimental system to observe the gas cores that grow from the unsteady traveling vortex dimple.