An electrochemical-pulse method was used to study the diffusion of H and D. The surfaces of the Ta specimens were cleaned by out-gassing in ultra-high vacuum at high temperatures, and were protected against new oxide formation by a vapor-deposited thin film of Pd. The H and D diffusivities at 25C were 1.9 x 10-6 and 9.1 x 10-7cm2/s, and the associated activation energies were 3.4 and 3.7kcal/mol, respectively.

Diffusion of Hydrogen and Deuterium in Ta, Nb, and V. N.Boes, H.Züchner: Physica Status Solidi A, 1973, 17[2], K111-4