Trap and Release of Hydrogen, Deuterium and Tritium by/from Graphite

Graphite is the primary candidate for the first wall of magnetically confined fusion devices. For this application, it is important to know the surface properties and trap/release behavior of hydrogen isotopes to understand fuel recycling/inventory in the graphite first wall. The surface analysis of as-received graphite revealed that the inherent hydrogen content is larger in isotropic compared to the anisotropic graphite. This is due to the presence of non-graphitized carbon atoms in the isotropic graphite which act as the trapping sites of hydrogen atoms. Ion bombardment causes the reduction of the crystallite size of graphite (damage modification), leading to amorphous-like structure. The thermal desorption spectra of hydrogen isotopes consisted of three desorption peaks for the modified graphite. The desorption mechanisms and parameters of three peaks are determined. These parameters were used to estimate the fuel inventory in the graphite.