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

Abstract

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 4×10 4 to 1×10 5 Pa. For protium and deuterium the properties diffusivity ( D), Sieverts’ constant ( K s), permeability ( Φ), trapping energy ( E t) and the trap sites concentration ( N t) 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 ( m 2 s −1)=4.166×10 −8 exp (−12 027/RT), K s ( 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), E t ( J/ mol)=55 554, and N t ( sites/ m 3)=0.79×10 24 . The dynamics of the hydrogen isotopes transport and the origin of the trapping phenomenon are discussed in connection with the OPTIFER-IVb microstructure.