Study on design method for gas entrainment prevention from a liquid surface based on a computational fluid dynamics method; 1st proposal of the design guideline

Sakai, Takaaki; Ito, Kei; Uchibori, Akihiro ; Kimura, Nobuyuki; Ezure, Toshiki ; Kamide, Hideki ; Ohshima, Hiroyuki

Japan Atomic Energy Agency has conducted a conceptional design study of a sodium-cooled fast reactor in a frame work of the FBR feasibility study. The plant system concept for a commercial step is intended to minimize a vessel diameter to achieve an economical competitiveness. Therefore, the coolant in the vessel has relatively higher velocity than conventional designs. Because of the high velocity, gas entrainment prevention from a liquid surface in the reactor vessel becomes one of important issues for the thermal-hydraulic design. Gas entrainment may cause the core power fluctuation or heat transfer reduction. Therefore, it is necessary to clarify the avoidance of the phenomena in the design conditions with sufficient allowance. The prevention of gas entrainment phenomena was prospectively confirmed by a 1/1.8 scale model water experiment. The large scale sodium experiment, however, needs very high costs to validate the design. The design method by a utilization of a computational fluid dynamics (CFD) method is one of possible choices for the gas entrainment prevention design. In this study, the gas entrainment prevention from vortex dimples at the liquid surface was investigated by a working group that consists of members from Universities, Research institutes, Utilities and Manufacturers, in order to establish a design method for the gas entrainment prevention by a CFD method. The research work was commenced from 2002 and performed for four years. This report is the first proposal of the design guideline for the gas entrainment prevention using CFD methods, from the achievements of the working group activity.