Self-leveling onset criteria in debris beds

Bin Zhang, Tetsushi Harada, Daisuke Hirahara, Tatsuya Matsumoto, Koji Morita, Kenji Fukuda, Hidemasa Yamano, Tohru Suzuki, Yoshiharu Tobita

研究成果: Contribution to journalArticle査読

40 被引用数 (Scopus)


In a core-disruptive accident of a sodium-cooled fast breeder reactor, core debris may settle on the coresupport structure and/or in the lower inlet plenum of the reactor vessel because of rapid quenching and fragmentation of molten core materials in the subcooled sodium plenum. Coolant boiling is the mechanism driving the self-leveling of a debris bed that causes significant changes in the heat-removal capability of the beds. In the present study, we develop criteria establishing the onset of this self-leveling behavior that we base on a force balance model assuming a debris bed with a single-sized spherical particle. The model considers drag, buoyancy, and gravity acting on each particle. A series of experiments with simulant materials verified the applicability of this description of self-leveling. Particle size (between 0.5–6 mm), shape (spherical and nonspherical), density (namely of alumina, zirconia, lead, and stainless steel), along with boiling intensity, bed volume, and even experimental methods were taken into consideration to obtain general characteristics of the self-leveling process. We decided to use depressurization boiling to simulate an axially increasing void distribution in the debris bed, although bottom heating was also used to validate the use of the depressurization method. On the self-leveling onset issues, we obtained good agreement between model predictions and experimental results. Extrapolation of our model to actual reactor conditions is discussed.

ジャーナルjournal of nuclear science and technology
出版ステータス出版済み - 4 2010

All Science Journal Classification (ASJC) codes

  • 核物理学および高エネルギー物理学
  • 原子力エネルギーおよび原子力工学


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