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Model of terminal debris bed formation after a CANDU core collapse

  • Robert David EMAIL logo
From the journal Kerntechnik


A CANDU reactor core comprises several hundred horizontal fuel channels spanning a calandria vessel. Loss of sufficient cooling during a severe accident could result in collapse of the core to the bottom of the calandria. A simple computational tool for simulating, in two dimensions, the resulting build-up of a terminal debris bed is described. The tool is used to model a variety of core collapse scenarios. Computed debris beds are generally lower in the middle, ∼10 fuel channels deep, and have higher decay power in their interiors. The initial debris bed porosity is estimated to be 0.65 ± 0.15. High porosity could augment in-vessel hydrogen generation and fission product release during subsequent debris bed heat-up.

Corresponding author: Robert David, Canadian Nuclear Laboratories, Chalk River, Canada, E-mail:

Award Identifier / Grant number: Federal Nuclear Science & Technology Program


I thank M.J. Brown, J.H. Spencer, and R.C. Bowden for review of the manuscript, and Z. Liang for review of the code.

  1. Author contributions: The author has accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: This work was supported by Atomic Energy of Canada Ltd. under the Federal Nuclear Science and Technology program.

  3. Conflict of interest statement: The author declares no conflicts of interest regarding this article.


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Received: 2022-10-19
Published Online: 2023-02-08
Published in Print: 2023-04-25

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