Numerical Analysis of Bi-Directional Hydrogen Isotopes Transport in First Wall of ITER Helium Coolant Ceramic Breeding Testing Blanket Module

Helium-Cooled Ceramic Breeding Blanket Module(HCCB-TBM) will be installed on ITER machine to test its tritium breeding performance and thermal removal ability. The first wall of HCCB TBM is to handle the bombardment of plasma particles and confine the internal functional materials. The co-exist of plasma driven deuterium/tritium particle permeation from vacuum outside surface and hydrogen partial pressure driven permeation from inside surface forms the bi-directional transport of hydrogen isotopes of the first wall. This bi-directional transport would make the surface recycling parameter of outside surface and the purification of tritium from blanket bred zone much difference. A bi-directional hydrogen isotopes transport model is built to investigate the hydrogen transport performances of the first wall in the commercial software COMSOL. The simulation results show that the coolant channels in the first wall act as such an effective hydrogen isotopes removing dwell that the bi-directional transport is decoupled. During each ITER plasma pulse, part of the tritium deeply permeated into the first wall during discharge period will permeate backward to the vacuum side. As a result, the backward permeation during plasma dwell time would make a reduction to the tritium permeation loss to coolant channels.