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# High temperature corrosion phenomena during a nuclear severe accident - The corium-concrete interaction

Abstract : During a severe accident in a nuclear reactor, extreme temperatures may be reached (T>2500 K). In these conditions, the nuclear fuel may react with the Zircaloy cladding and then with the steel vessel, forming a mixture of solid-liquid phases called in-vessel corium. In the worst scenario, this mixture may pierce the vessel and reach the concrete underneath the reactor. Many phenomena take place during MCCI (Molten Core Concrete Interaction) high temperature concrete ablation/decomposition, heat transfer due to gas bubbles agitation, formation of several phases, oxidation of metals, etc. Several studies on the interaction between corium and concrete were published starting from the 1980s; in particular numerous large scale experiments were performed on this subject. Although large scale experiments answer to macro-scale phenomena, such as ablation profile, corium flooding behaviour, coolability of the molten core, density and viscosity evolution, etc., the interpretation of the microstructure of the post-experiments sample is rather challenging. In this framework a campaign of small-scale experiments is ongoing on prototypic corium+concrete system U-Zr-Ca-Si-Al-O. These tests provide useful data for the comprehension of the phenomena occurring during a severe accident, when the molten corium reaches the concrete underneath the damaged steel vessel. It has been observed that depending on the composition of the concrete (more of less rich in SiO$_2$), the final configuration of the ex-vessel corium (i.e., after the in-vessel corium/concrete interaction) can be significantly different
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Submitted on : Monday, December 9, 2019 - 2:21:17 PM
Last modification on : Monday, December 13, 2021 - 9:14:39 AM
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201800001680.pdf
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• HAL Id : cea-02400172, version 1

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A. Quaini, C. Guéneau, S. Gossé. High temperature corrosion phenomena during a nuclear severe accident - The corium-concrete interaction. Eurocorr 2018, Sep 2018, Cracovie, Poland. ⟨cea-02400172⟩

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