TRITIUM RETENTION IN NEUTRON-IRRADIATED CARBON-BASED MATERIALS AND BERYLLIUM

The effects of neutron-induced damage on the tritium retention have been studied experimentally for graphite and other carbon-based materials in the damage range ≤4 dpa and for beryllium in the range ≤40 dpa. The results for graphite and other carbon-based materials are in qualitative agreement with previous studies what concerns the increase of tritium retention with neutron damage in the range below about 0.1 dpa. On the other hand the kinetics of tritium transport and adsorption seems to be faster and the estimated number of tritium traps of irradiated material in the asymptotic region above about 0.1 dpa is remarkably lower (~ 1000 appm) than in a previous study (~6000 appm). The studies of tritium retention in neutron-irradiated beryllium are rendered difficult because of the huge amount of neutron-generated tritium, which has to be released before. This requires such high temperatures that probably any reversible neutron-induced traps are annealed. A gradual increase of tritium retention with increasing fast neutron fluence of about a factor ten is observed in the range <40 dpa, which is assumed to be due to irreversible changes in the microstructure of the samples.