Microstructural analysis of beryllium samples irradiated at high temperature

Beryllium is one of the candidate materials to be used as protection of the first wall and as neutron multiplier in the blanket of a fusion reactor. Both sintered blocks and pebbles have been considered and research and evaluations are underway to characterise tritium release, heat transfer, thermal–mechanical and irradiation behaviour of several material grades. The knowledge of the tritium and helium release kinetics as a function of material microstructure, neutron fluence and temperature is relevant for beryllium fusion applications. In this paper results are presented of out-of-pile annealing tests up to 1000 °C of S-65C beryllium grade produced by Brush Wellman and irradiated in the BR2 material testing reactor in Mol (Belgium). Together with the investigation of both tritium and helium release kinetics from the Brush Wellman beryllium, the effect of crack formation is also discussed, which eventually leads to a concurrent release of tritium and helium.