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

The effects of neutron-induced damage on the tritium retention have be en studied experimentally for graphite and other carbon-based material s in the damage range less than or equal to 4 dpa and for beryllium in the range less than or equal to 40 dpa. The results for graphite and other carbon-based materials are in qualitative agreement with previou s studies what concerns the increase of tritium retention with neutron damage in the range below about 0.1 dpa. On the other hand the kineti cs of tritium transport and adsorption seems to be faster and the esti mated number of tritium traps of irradiated material in the asymptotic region above about 0.1 dpa is remarkably lower (similar to 1000 appm) than in a previous study (similar to 6000 appm). The studies of triti um retention in neutron-irradiated beryllium are rendered difficult be cause of the huge amount of neutron-generated tritium, which has to be released before. This requires such high temperatures that probably a ny reversible neutron-induced traps are annealed. A gradual increase o f tritium retention with increasing fast neutron fluence of about a fa ctor ten is observed in the range <40 dpa, which is assumed to be due to irreversible changes in the microstructure of the samples.