Standard for Prevention of Gas Entrainment Phenomena in Fast Reactors<br/>(II) Proposal of Gas Entrainment Evaluation Method

概要

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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. However, such a method has not yet been established, especially for the vortex-type GE. 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 the velocity gradient tensor, and GE evaluation parameters, e.g., gas core length, are calculated by using the Burgers vortex model. In addition, the standard method for the prevention of three kinds of vortex-type GE is shown by considering experimental data, evaluation results obtained by the proposed method and comparison results. Finally, it is confirmed that the onset conditions of the vortex-type GE can be evaluated by the proposed method.