A thermodynamic analysis of H-Be interactions was used as the basis of a new approach to describing the behavior of H in Be. The approach was based upon the assumption that the so-called true solubility of H in Be was extremely low, and that endothermic trapping by impurities and gas-filled bubbles was responsible for the H inventory in Be at temperatures greater than 700K. Thus, H which was implanted into Be at high temperatures was assumed to be retained as H atoms which were trapped at impurities, and as molecular H2 within pores and bubbles. Langmuir-type adsorption and dangling sp2-bond relaxation were suggested to occur in the case of H-graphite interactions. Three types of trap were proposed. These were C interstitial loops with an associated adsorption enthalpy of -4.4eV/H2, graphite network edge atoms with an associated adsorption enthalpy of -2.3eV/H2, and basal plane adsorption sites with an associated enthalpy of 2.43eV/H2. The sorption capacity of each type of graphite could be described by its own unique set of traps. Irradiation with neutrons or energetic C ions increased the number of traps. At a damage level of about 1dpa, under room temperature irradiation, the concentration of the first 2 traps reached levels of 1500 and 500ppm[at], respectively.

S.L.Kanashenko, A.E.Gorodetsky, A.P.Zakharov, W.R.Wampler: Physica Scripta Volume T, 1996, 64, 36-40