Tritium diffusive transport parameters and trapping effects in the reduced activating martensitic steel OPTIFER-IVb

A time-dependent gas-phase isovolumetric desorption technique has been used to obtain the hydrogen isotopes transport parameters between 423 and 892 K and driving pressures ranging from 4×104 to 1×105 Pa. For protium and deuterium the properties diffusivity (D), Sieverts’ constant (Ks), permeability (Φ), trapping energy (Et) and the trap sites concentration (Nt) are given. On the basis of ideal harmonic vibration of the hydrogen isotope atoms in a unique type of solution site, the values derived for the characteristic protium oscillation temperatures are: θ=1884 K, θ*=2387 K. These values lead to the following extrapolated tritium transport parameters: D (m2 s−1)=4.166×10−8 exp (−12 027/RT), Ks(mol m−3 Pa−1/2)=0.271 exp (−27 905/RT), Φ (mol m−1 Pa−1/2 s−1)=1.127×10−8 exp (−39 933/RT), Et (J/mol)=55 554, and Nt (sites/m3)=0.79×1024. The dynamics of the hydrogen isotopes transport and the origin of the trapping phenomenon are discussed in connection with the OPTIFER-IVb microstructure.