Kinetics of hydrogen permeation through a Ni-base alloy membrane exposed to primary medium of pressurized water reactors

Highlights: • In situ hydrogen permeation measurement through Ni-base alloy in PWR primary medium. • Hydrogen uptake kinetic modelling correlated with oxide scale growth. • High surface hydrogen activities associated with initial oxidation stage. • Hydrogen participation to stress corrosion cracking mechanisms suggested. - Abstract: Hydrogen permeation kinetics through a Ni-base alloy exposed to simulated pressurized water reactors primary medium at 325 °C has been investigated. In situ measurements exhibit a strong decrease of H flux during the first 50 h of exposure; it has been related to the oxide scale growth at the alloy surface. A kinetic model has been proposed to describe this link. Comparing modelling and experimental results indicates that high H transient activities are generated at the alloy surface during the first hours of oxide scale growth, suggesting that H could play a role in stress corrosion cracking of Ni-base alloys.