Tungsten nitride as tritium permeation barrier

Abstract

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 μm thick WN layer and nearly four orders of magnitude by a 2 μm non-cracked tungsten layer.

Keywords

• Deuterium gas driven permeation
• Tritium permeation barriers
• RAFM steel/Eurofer97
• Tungsten nitride
• Layer permeability calculation