A Thin Alumina Film as a Tritium Adsorption Inhibitor for Stainless Steel 316

The effect of a thin alumina coating on stainless steel 316 (SS316) samples on tritium adsorption and transport are reported. Compact films of alumina were produced on the surfaces of pristine SS316 samples using an atomic layer deposition (ALD) technique. Subsequently, these samples were exposed for 24 h to a deuterium-tritium gas mixture (P-T = 0.5 atm, 25 degrees C). A combination of methods including selective etching and programmed thermal desorption were employed to assess both the depth profile of the tritium concentration in the sample and the total quantity of tritium absorbed, respectively. Tritium was quantitatively determined through the measurement of beta radioactivity using liquid-scintillation counting techniques. Data suggest that SS316 with a thin film of alumina reduces the total tritium uptake by 25% relative to uncoated samples. Importantly, such films appear to reduce, by a factor of 200, tritium diffusion into SS316 and therefore constitute an effective barrier against tritium transport. This observation is of practical importance for tritium and, generally, reactive gas handling.