2026
ACL
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Mehdi Nasselahsen, Sarah Thilliez, Jules Delacroix, Sawsen Youssef, Laurent Brissonneau, Jacques Poirier, Pascal Piluso, Emmanuel de Bilbao, 'Iron and 304L-stainless steel oxidation under oxygen and steam atmosphere at high temperature from 1350°C to 1600°C', J. Nucl. Mater. 619 156270 (2026) doi:10.1016/j.jnucmat.2025.156270
At high temperature, corium can form as a mixture of molten materials from the nuclear fuel, the cladding and the vessel of nuclear reactors. The loss of coolant can cause high temperature oxidation in oxidizing atmospheres, leading to heat release and hydrogen production. Within the context of severe nuclear accidents, this study examines the oxidation of iron and 304 L stainless steel in oxygen and steam, as key components of corium. The VITOX experimental facility is used to carry out separate-effect oxidation tests at high temperature under both atmospheres. Post-mortem analyses are performed on oxidized materials using Scanning Electron Microscopy with Energy Dispersive X-ray (SEM/EDS) to understand and analytically model the oxidation mechanisms. The oxidation of liquid iron under both oxygen and steam can be described by linear kinetics. The oxidation of solid 304 L under steam transitions from linear to parabolic regime, similarly to the liquid state kinetics. At 1575 °C ± 25 °C, alloying elements in liquid 304 L stainless steel delay hydrogen release by 1200 s compared to liquid iron. Post-test analyses show that oxidation mechanism of liquid iron under steam is driven by surface interactions with the formation of an outer liquid Fe1-xO layer. For 304 L oxidation under steam, a solid spinel-like Fe2CrO₄ phase is formed in both solid and liquid state, with oxidation rather controlled by diffusion mechanisms.
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