Steel oxidation phenomena during Molten Corium siliceous Concrete Interaction (MCCI)

The VULCANO facility at CEA Cadarache is a Molten Corium Concrete Interaction (MCCI) installation for testing material reactions representative of the late stages of a nuclear reactor severe accident. The objectives of the VBS-U3 test were to study ablation phenomena and oxidation of the metallic phase when two liquid phases are present: oxide phase and metallic phase (steel). In this paper we describe the materials post-test analysis of the VULCANO VBS-U3 test performed at the Institute for Transuranium Elements in Karlsruhe (JRC-ITU) with the focus on the metallic phase oxidation of the corium. Post-test analyses show that the remaining metallic phase of the corium is under two forms: drops discontinuously dispersed in the oxide phase forming an emulsion and a continuous metallic ingot clearly separated from the oxide phase. In average, taking into account or not the metallic phase dispersed in the oxide phase, between 60% and 70% of the steel has been oxidized. The size of the drops and their proportion in the oxide phase is depending on their distance from horizontal and vertical walls of the concrete test section. Oxidation mechanisms are mainly depending on two parameters: nature of the metallic interface and localization in the test section. Calculations at thermodynamic equilibrium show that the only product from steel oxidation is (Fe,Cr)3O4, Cr2 O3 is never formed. Moreover taking into account the two gaseous species coming from the concrete (CO2 and H2O), considered up to now as being the only sources of oxidation of the metallic phase, the steel oxidation proportion is estimated at only 14% at thermodynamic equilibrium meaning that complementary phenomena are involved during MCCI.

SANCHEZ-BRUSSET Mathieu;  PILUSO P.;  BALAT-PICHELIN Marianne;  BOTTOMLEY Paul;  WISS Thierry; 

2015-01-13

ELSEVIER SCIENCE SA

JRC93321

0925-8388,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC93321,   

10.1016/j.jallcom.2014.11.041,