Study on boiling heat transfer characteristics in debris beds, 4; Visualization of boiling behaviors on a heating surface

Kawakami, Taira*; Sakashita, Hiroto*; Ono, Ayako ; Yoshida, Hiroyuki  

Understanding the boiling heat transfer characteristics in debris beds is indispensable to assess the coolability of molten debris at severe accident. However, the trigger mechanism of the critical heat flux on the bottom heated debris beds has not been fully elucidated. This study performed the visualization measurements using a transparent heating surface on which small particles are accumulated. The boiling behaviors were observed via a total reflection technique, and effects of particle size on dryout and rewetting process of the heating surface were examined.