Validation and improvement of a numerical model for freezing and blockage formation of solid-liquid flow of molten fuel in the core disruptive accident of FBR

Aoyagi, Mitsuhiro ; Kamiyama, Kenji  ; Tobita, Yoshiharu; Suzuki, Toru

A numerical model for freezing and blockage formation of solid-liquid flow in the SIMMER code was validated in order to improve the accuracy in evaluating fuel discharge behavior in the core disruptive accident of FBR. The THEFIS experiment which investigated fuel discharge behavior was chosen as reference data in this study. The numerical conditions were set according to the experimental system. Although the experimental result was well simulated by using the existing numerical model of SIMMER, the melt flow was suppressed excessively in some cases. Overestimation of flow resistance by the solid particles in the numerical model was discovered though the comparison between the numerical model and the physical phenomenon in the experiment. The numerical model caused the excessive melt flow suppression. Therefore, we improved the numerical model to adapt to the actual phenomenon. Then, it was confirmed the improved numerical model brought more appropriate numerical results.