INFLUENCE OF RADIATION-DAMAGE IN GRAPHITE AND BERYLLIUM MATERIALS ON HYDROGEN RETENTION

In the present work, based on a thermodynamic analysis of hydrogen-ber yllium interaction, a new approach for hydrogen behaviour in beryllium is presented. This approach is based on the assumption that ''true'' solubility of hydrogen in beryllium is extremely low and endothermic t rapping in impurities and gas filled bubbles is responsible for hydrog en inventory in beryllium at temperatures higher than 700 K. Hydrogen implanted into beryllium at elevated temperatures is assumed to be ret ained as H-atoms trapped at impurities and as molecular H-2 inside por es and bubbles. The Langmuir type adsorption and dangling sp(2)-bonds relaxation are proposed for the hydrogen-graphite interaction. Three k inds of traps are proposed: carbon interstitial loops with an adsorpti on enthalpy of -4.4 eV/H-2 (Trap 1); graphite network edge atoms with an adsorption enthalpy of -2.3 eV/H-2 (Trap 2); basal planes adsorptio n sites with enthalpy +2.43 eV/H-2 (Trap 3). The sorption capacity of every kind of graphite could be described with its own unique set of t raps. The irradiation with neutrons or energetic carbon ions increases the number of traps. At damage level of similar to 1 dpa under room t emperature irradiation the concentration of traps 1 and 2 reaches 1500 and 500 appm respectively. Estimations of hydrogen inventory for ITER conditions for both beryllium and graphite are provided.