The surface rate constants of deuterium in the reduced activating martensitic steel OPTIFER-IVb

A gas permeation technique has been used to obtain the deuterium surface rate constants for adsorption σK1 and recombination σK2 in the martensitic steel OPTIFER-IVb. The measurements were performed over the temperature range 523–723 K with deuterium driving pressures ranging from 5×102 to 5×105 Pa. The deuterium surface rate constants obtained are: σK1 (mol m−2 s−1 Pa−1)=2.998×10−8 exp(−29230/RT), σK2 (mol−1 m4 s−1)=2.838×10−7 exp(−28679/RT), R in J/K mol−1. An intermediate gas transport regime has been accounted for over the experimental range. The transport regime was found close to the surface-limited regime as the deuterium driving pressure is lowered and the temperature increased. Permeability Φ has been derived together with surface rate constants: Φ (mol m−1 Pa−1/2 s−1)=5.311×10−8 exp(−44988/RT). This is in very good agreement with the permeability previously measured using a different gas evolution method, evidencing the consistency of the obtained results.