Tritium diffusive transport parameters and trapping effects in the reducedactivating 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 x 10(4) to 1 x 10(5) Pa. For protium and deuterium the properties diffusivity (D), Sieverts' constant (K-s), per meability (Phi), trapping energy (E-t) and the trap sites concentration (N- t) are given. On the basis of ideal harmonic vibration of the hydrogen isot ope atoms in a unique type of solution site, the values derived for the cha racteristic protium oscillation temperatures are: theta = 1884 K, theta(+) = 2387 K. These values lead to the following extrapolated tritium transport parameters: D (m(2)s(-1)) = 4.166 x 10(-8) exp (-12027/RT), K-s(mol m(-3) Pa-1/2) = 0.271 exp (-27 905/RT), Phi (mol m(-1) Pa-1/2 s(-1)) = 1.127 x 10 (-8) exp(-39 933/RT), E-t (J/mol) = 55 554. and N-t (sites/m(3)) = 0.79 x 1 0(24). The dynamics of the hydrogen isotopes transport and the origin of th e trapping phenomenon are discussed in connection with the OPTIFER-IVb micr ostructure. (C) 2000 Elsevier Science B.V. All rights reserved.