Permeability coefficients and effective diffusivities were measured at 49 to 506C by using an ultra-high vacuum monopole gas analyzer technique. The permeation activation energies for H and D were almost equal, at 8.52 and 8.78kcal/mol respectively, and the corresponding activation energies for diffusion were 1.69 and 1.93kcal/mol. An analysis of the permeability coefficients and effective diffusivities revealed an isotope effect that was slightly greater than the classical ratio (1.41) at low temperatures, but gradually decreased - with increasing temperature - to a value which was just less than 1.41. The effective diffusivities were described by:

H:     D (cm2/s) = 1.61 x 10-3 exp[-1.69(kcal/mol)/RT]

D:     D (cm2/s) = 1.52 x 10-3 exp[-1.93(kcal/mol)/RT]

N.R.Quick, H.H.Johnson: Acta Metallurgica, 1978, 26[6], 903-7