Gas-driven permeation of H through Ta was investigated at 900K and 50 to 5000Pa. The permeation rate as a function of time has a peaked shape: after initial rise, it decreased for several hours, remaining approximately proportional to the gas pressure, which was the feature of the surface-limited regime. Computations using an surface-limited regime model were performed. It was concluded that the Ta membrane became asymmetrical due to the contamination of the inlet surface. The solubility of 9.3 x 1018H/cm3Pa1/2 was in good agreement with data available from literature. The recombination and absorption coefficients, K and Ka, were obtained in the ranges K = (6–500) x 10-26/at.cm-4s and Ka = (3–200) x 1012at/cm2sPa, respectively. The values of Ka were very low. It was concluded that long permeation experiments required special measures for the purification of the working gas.

Permeation of Hydrogen through Tantalum - Influence of Surface Effects. A.Pisarev, K.Miyasaka, T.Tanabe: Journal of Nuclear Materials, 2003, 317[2-3], 195-203