Hydrogen transport parameters in the low activation martensitic steel LA12TaLC

This paper describes the results of a gas evolution method to study the interaction of hydrogen with the low activation martensitic steel (LAMS), LA12TaLC. The study was performed in the temperature range between 600 and 900 K and at a loading pressure of 105 Pa. The results obtained for the hydrogen transport parameters in this LAMS are of the same order of magnitude than that for the DEMO reference structural and FW material i.e. DIN 1.4914 MANET (MArtensitic for NET). As in MANET, a reduction of the diffusivity (and hence the permeability) was found after heat treatment in presence of hydrogen, at temperatures over about 740 K. This behaviour is linked to the growth of the pre-existing oxide layer. Due to the temperature, the oxidising impurities present in the gas phase (H2O, CO, CO2, etc.) are able to increase the layer thickness of the samples, creating a permeation barrier. (orig.)