A new empirical model for self-leveling behavior of cylindrical particle beds

Koji Morita, Tatsuya Matsumoto, Shinpei Nishi, Tatsuya Nishikido, Songbai Cheng, Hirotaka Tagami, Tohru Suzuki, Yoshiharu Tobita

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


During the material relocation phase of core disruptive accidents in sodium-cooled fast reactors, the rapid quenching and fragmentation of molten materials discharged from the reactor core into the lower plenum region can lead to the formation of debris beds. Coolant boiling may lead to leveling of the mound-shaped beds, which changes both the beds' coolability with decay heat in the fuel and the neutronic characteristics. In this study, a series of experiments using simulant materials were performed to develop an experimental database of self-leveling processes of particle beds in a cylindrical system. To simulate the coolant boiling in the beds in the experiments, a gas injection method was used to percolate nitrogen gas uniformly through the base of a bed with a conical-shaped mound. Time variations in bed height during the self-leveling process were measured for different particle sizes, densities and sphericities, and gas injection velocities. Using a dimensional analysis approach, a new model was proposed. This model correlates the experimental data on transient bed height with an empirical equation using a characteristic time for self-leveling development and an equilibrium bed height. The proposed model reasonably predicts the self-leveling development of particle beds.

Original languageEnglish
Pages (from-to)713-725
Number of pages13
Journaljournal of nuclear science and technology
Issue number5
Publication statusPublished - May 3 2016

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering


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