Hydrogen isotope diffusive transport parameters in pure polycrystalline tungsten

An experimental time-dependent isovolumetric gas-phase desorption technique has been used to obtain the diffusive transport parameters diffusivity (D) , Sieverts' constant (K-s) and permeability (Phi) as well as the trapping p arameters trap site concentration (N-t) and trapping energy (E-t) of hydrog en isotopes (protium and deuterium) in tungsten. The study was performed in the 673 to 1073 K temperature range and with driving pressures from 1.3 x 10(4) to 10(5) Pa. The characteristic protium oscillation temperatures in t he ground state theta = 893 K and in the excited state theta* = 2467 K were calculated using the approximation of the ideal harmonic vibration of hydr ogen isotope atoms in a unique type of solution site. The extrapolated trit ium transport parameters obtained using these oscillation temperatures were : D (m(2) s(-1)) = 5.34 x 10(=10)exp(-11.2/RT), K-s (mol m(-3) Pa-1/2) = 2. 25 x 10(-2)exp(-27.8/RT), Phi (mol m(-1) Pa-1/2 s(-1)) = 1.20 x 10(-11)exp( -3.9/RT), E-t (kJ mol(-1)) = 100.5, N-t (sites m(-3)) = 2.3 x 10(23). (C) 2 001 Elsevier Science B.V. All rights reserved.