Hafnium oxidation at high temperature in steam

To assess the potential impact of using hafnium as absorber material in LWRs high temperature accidental situations, oxidation behavior was studied up to 1400°C, i.e. at conditions relevant severe accidents. Different sample geometries were tested and oxidized steam/argon mixtures, either a furnace or thermogravimetric analyzer. Metallographic examinations, hydrogen measurements EPMA oxygen profiles then performed. For rods/discs, metallographic examinations showed presence dense protective oxide film after steam oxidation. No little detected metallic part rod/disc specimens. The reaction rate can be described by parabolic law range mid-to-long term, value effective activation energy determined from experimental data is good agreement with ones published literature. diffusion coefficient estimated each fitting profile obtained on rods its dependence derived 700-1400°C. claddings produced for application integral bundle tests exhibited lower resistance than rods/discs. non-protective layer significant amount picked claddings. Above 800°C, follows cubic quartic 800-1100°C. These highlighted influence surface steam. However, remains well below zirconium alloys same range.