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• Hydrogen (H) and deuterium (D) permeation fluxes for tungsten (W) by H-D mixed plasma were studied to clarify the hydrogen isotope effect on permeation by newly designed plasma driven permeation (PDP) device. • When single species of h or d was irradiated, the h permeation rate showed approximately 1.6 times as high as that of d. • H and d permeation fluxes were clearly reduced by seeding he in H-D mixed plasma. At lower temperature (∼723 K), the ratio of steady permeation fluxes of h and d was about 75 : 25, confirming the high permeation flux of h. • H and d permeation fluxes were reached almost unity at 923 K. Hydrogen (H) and deuterium (D) permeation fluxes for tungsten (W) by H-D mixed plasma were studied to clarify the hydrogen isotope effect on permeation by a newly designed plasma driven permeation (PDP) device at Shizuoka University. A mixed H-D plasma was produced by introducing H and D gasses with various ratios. The atomic ratio and permeation flux in the plasma were measured during the experiments. It was found that the H:D atomic ratio in the plasma was almost proportional to the introduced H:D gas ratio. When single species of H or D was irradiated, the H permeation rate showed approximately 1.6 times as high as that of D. Under H-D mixed plasma irradiation, the highest HD permeation rate was observed when the atomic ratio of H:D in the plasma was 50:50. In addition, the effect of He seeding on H-D mixed plasma driven permeation behavior was also evaluated. The recycling of hydrogen isotopes on the upstream side was enhanced due to the formation of He bubbles near the surface, which would prevent the dissolution of hydrogen isotopes into bulk W and enhance the reflection process during plasma exposure. H and D permeation fluxes were clearly reduced by seeding He in H-D mixed plasma. At lower temperature (∼723 K), the ratio of steady permeation fluxes of H and D was about 75 : 25, confirming the high permeation flux of H. These results have demonstrated a significant hydrogen isotope effect, even if He was seeded or not. As the temperature increased, H and D permeation fluxes approached unity at 923 K. This indicates that the hydrogen isotope effect was determined by the combination of recycling / reflection at or beneath the surface, which will be controlled by the temperature during plasma exposure. [ABSTRACT FROM AUTHOR]

• Deuterium plasma driven permeation experiments were performed for W rod sample. • Deuterium recombination coefficient on W surface is obtained by combing the PDP and GDP results. • Deuterium permeation rate through a 8 mm thick W under ITER divertor relevant conditions are estimated by HIDT simulation code. Deuterium (D) plasma driven permeation (PDP) experiments for tungsten (W) samples were conducted by a linear radio frequency (RF) plasma device. In the PDP experiment, the W sample surface is perpendicular to the grain elongation direction. The D ion flux is in the order of 1021 m−2 s−1 determined by a double Langmuir probe. The results show that bias had a limited effect on the D plasma driven permeation behavior. The D recombination coefficient on W surface is obtained at the temperature ranging from 740 K to 1031 K. The experimentally measured recombination coefficient for a pristine W surface is lower than that for a clean W surface. The effect of recombination coefficient on the D permeation and retention behaviors in W are studied by Hydrogen Isotope Diffusion and Trapping (HIDT) simulation code. The low recombination coefficient leads to a high D concentration in W and a high permeation rate at the back surface. The D permeation rate through a 8 mm thick W with a pristine surface is estimated to be 8.1 × 1018 D m s−1 under the incident ion flux of 1 × 1024 m−2 s−1 and temperature of 1173 K. [ABSTRACT FROM AUTHOR]