Standard for prevention of gas entrainment phenomena in fast reactors, 2; Proposal of gas entrainment evaluation method

Ohshima, Hiroyuki; Eguchi, Yuzuru*; Kunugi, Tomoaki*; Kamide, Hideki ; Sakai, Takaaki; Ito, Kei

For the stable operation of fast breeder reactors (FBRs), the occurrences of gas entrainment (GE) phenomena should be suppressed below an allowance level. Therefore, a reliable evaluation method for the GE phenomena is necessary to determine the operating conditions of FBRs. In this paper, the authors propose a GE evaluation method in which free surface vortices are identified from velocity fields by using the second invariant of velocity gradient tensor, and the GE evaluation parameters, e.g. gas core length, are calculated by using the Burgers vortex model. In addition, the standard for prevention of three kinds of the vortex-type GE are shown in consideration of experimental data, evaluation results with the proposed method and the comparison results of them. Finally, it is confirmed that the onset conditions of the vortex-type GE can be evaluated by the proposed method.