Hydrogen and deuterium permeation measurements on the double-wall tubes material for the water-cooled Pb–17Li DEMO blanket

The aim of this study is to measure the hydrogen/deuterium transport and inventory parameters in the double-wall tubes (DWT) material for the water-cooled Pb–17Li DEMO blanket. Measurements are conducted using a time dependent permeation method over the temperature range 473–723 K, with hydrogen and deuterium driving pressures in the range 1–105 Pa (0.01–1000 mbar). The samples are also characterised using optical microscopy, SEM, microhardness measurements and mechanical tests. An effective permeability of about 12 times lower than 2.1 mm of bare F82H steel at 573 K and three times lower than 2.1 mm of bare F82H steel at 723 K have been measured. This result is close to the theoretical prevision (multi-layer model).