Development of evaluation method of gas entrainment on the free surface in the reactor vessel in pool-type sodium-cooled fast reactors; Gas entrainment judgment based on three-dimensional evaluation of vortex center line and distribution of pressure decrease

Matsushita, Kentaro ; Ezure, Toshiki ; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki  

Development of evaluation method for cover gas entrainment (GE) by vortices generated at free surface in upper plenum of sodium-cooled fast reactor (SFR) is required. GE evaluation tool, named StreamViewer, based on method using numerical results of three-dimensional computational fluid dynamics analysis for loop-type SFRs has been developed. In this study, modification of evaluation method of StreamViewer to rationalize conservativeness in evaluation results was examined by identifying vortex center lines and calculating three-dimensional distribution of pressure decrease along vortex center lines. The applicability of modified method was checked using water experimental result in rectangular open channel where unsteady vortices are generated. As the result, it was indicated that evaluation results on gas core depth which were excessive in current method were improved in modified method, and it is confirmed that modified method may discriminate onset of GE with appropriate criteria.