First analysis of local fuel-coolant interactions in a molten pool by SIMMER-III using reactor materials

Cheng, S.; Matsuba, Kenichi  ; Isozaki, Mikio; Kamiyama, Kenji  ; Suzuki, Toru; Tobita, Yoshiharu

To clarify the mechanisms underlying local fuel-coolant interactions (FCI) in a molten pool, in this study, several latest calculations with reactor materials were performed using SIMMER-III, an advanced fast reactor safety analysis code. The performed SIMMER-III analyses suggest that despite of a comparatively larger temperature range of molten-fuel and sodium possibly varied during reactor accidents, the isolation effect of vapor bubbles generated at the melt-sodium interface seems to be the unique dominant mechanism that leads to the limited pressurization. Knowledge and fundamental data from this work might be utilized for future empirical-approach studies (e.g. those investigating the characteristics of critical coolant volume required for achieving the saturated pressurization at varied melt and coolant temperatures).