Experimental study and thermodynamic modelling of corium mixtures Application to severe accidents in Pressurized Water Reactors
Résumé
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. In the framework of the development of the TAF-ID thermodynamic database (www.oecd-nea.org/science/taf-id) on nuclear fuel and to predict the high temperature behaviour of the corium+concrete system, new high temperature thermodynamic data are needed. The LM2T at CEA Saclay centre started an experimental campaign of measure of phase equilibria at high temperature (up to 2400 K) on interesting corium sub-systems. Furthermore a new laser heating setup has been conceived. This technique allows very high temperature measures (T>3000 K) limiting the interactions between the sample and the surroundings. New phase equilibria data on the U-Zr-O system and on the U-Zr-Al-Ca-Si-O system will be presented. Moreover original melting temperature data on the PuO2-UO2-ZrO2 system obtained in collaboration with the JRC-ITU, will be also shown.
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