Tritium sorption and desorption from JET beryllium tiles under temperature, electron radiation and magnetic field

Tritium release at annealing of samples cut from beryllium tiles exposed to D + D, D + T plasma in the Joint European Torus (JET) was investigated under 5 MeV fast-electron radiation at the dose rate 14 MGy h^-1 and in a magnetic field of 1.7 T separately and simultaneously in order to evaluate possible effects of these factors. Abundances of chemical forms of tritium-molecular T₂ (44%), atomic T⁰ (42%), and ionic T⁺ (14%) and their distribution were determined in the plasma-exposed beryllium samples with lyomethods. Fast-electron radiation considerably increased the fractional tritium release at annealing by a factor of approximately 5. The magnetic field increased the fractional tritium release at annealing both without and under electron radiation by approximately 25%. Sorption of tritium in samples cut from an unused beryllium tile was investigated at about 1 Pa of T₂ at 773 K for 3 h both with and without simultaneous electron radiation and/or magnetic field. The amount of the tritium sorbed was found to be 3.3-6.2 kBq cm^-2. Most of the tritium sorbed was localized in subsurface layers up to a depth of 80 μm of the beryllium samples.