Tungsten nitride as tritium permeation barrier

Abstract

• Three kinds of W and WN layers on steel substrates were deposited. • The samples were investigated by deuterium permeation measurements and compared. • WN and WNW layers are very suitable as tritium permeation barrier layers on steel. • The layer permeabilities of the WN and non-cracked W coatings were calculated. • The layer permeability enables a reliable comparison of permeation barriers. • The hydrogen permeation flux through components in fusion reactors can be estimated. The development and application of robust tritium permeation barrier coatings is crucial for a safe and economic fusion reactor operation. Three different tungsten and tungsten nitride layers on Eurofer97 substrates were investigated by deuterium permeation measurements and compared. The microstructure and crystal structure was characterized before and after permeation measurements. The layer permeability is independent of the layer thickness and substrate of the sample. For a reliable comparison of different tritium permeation barrier coatings, the layer permeability of each layer was calculated. With this layer permeability, the permeation flux through potential fusion device components can be estimated. As examples, the permeation flux through a 0.5 cm thick steel component can be reduced by two orders of magnitude by a 2 μ m thick WN layer and nearly four orders of magnitude by a 2 μ m non-cracked tungsten layer.