Hydrogen isotope diffusive transport parameters in pure polycrystalline tungsten

Abstract An experimental time-dependent isovolumetric gas-phase desorption technique has been used to obtain the diffusive transport parameters diffusivity (D), Sieverts' constant (Ks) and permeability (Φ) as well as the trapping parameters trap site concentration (Nt) and trapping energy (Et) of hydrogen isotopes (protium and deuterium) in tungsten. The study was performed in the 673 to 1073 K temperature range and with driving pressures from 1.3×104 to 105 Pa. The characteristic protium oscillation temperatures in the ground state θ=893 K and in the excited state θ ∗ =2467 K were calculated using the approximation of the ideal harmonic vibration of hydrogen isotope atoms in a unique type of solution site. The extrapolated tritium transport parameters obtained using these oscillation temperatures were: D ( m 2 s −1 )=5.34×10 −10 exp (−11.2/RT) , K s ( mol m −3 Pa −1/2 )=2.25×10 −2 exp (−27.8/RT) , Φ ( mol m −1 Pa −1/2 s −1 )=1.20×10 −11 exp (−3.9/RT) , E t ( kJ mol −1 )=100.5 , N t ( sites m −3 )=2.3×10 23 .