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| NKS Programme Area: | NKS-R | | Research Area: | Severe accidents | | Report Number: | NKS-374 | | Report Title: | A summary of studies on debris bed coolability and multi-dimensional flooding | | Activity Acronym: | DECOSE | | Authors: | Eveliina Takasuo, | | Abstract: | A summary of the results of the experimental debris bed coolability studies in the COOLOCE programme at VTT is presented in this report. The experiments addressed the effects of the debris bed geometrical shape, which is a result of the melt jet fragmentation and solidification in a water pool. Six variations of the debris bed geometry with different flooding modes were examined in the experiments, including a top-flooded cylinder and five beds with more complex, heap-like geometries. Dryout heat fluxes of the different geometries and flooding modes were compared. In addition, the key question of transferring the experimental results and the small-scale simulations onto a reactor scale is briefly considered. A simulation case modelling a conically-shaped debris bed of 200 tonnes of corium in a generic containment geometry is presented. The large-scale simulation shows dryout characteristics similar to those of the earlier small-scale simulations of the experimental beds. The post-dryout behaviour of a multi-dimensionally flooded bed, which may reach steady-states even when local dryout has occurred, is clearly illustrated in the simulation. | | Keywords: | nuclear reactor, severe accident, dryout heat flux, test facility, core debris, numerical simulation | | Publication date: | 20 Oct 2016 | | ISBN: | ISBN 978-87-7893-459-8 | | Number of downloads: | 2511 | | Download: |  NKS-374.pdf |
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