Compression properties of neutron irradiated beryllium pebbles

Compression properties of neutron irradiated beryllium pebbles manufactured by the rotating electrode method and the Mg reduction method were evaluated from compression load tests at 10% deformation. Neutron irradiation was carried out up to a total fast neutron fluence of about 4×1025 n/m2 (E>1 MeV, about 8 dpa) at 400, 500 and 600°C. There was no significant difference for the two kinds of beryllium pebbles. Additionally, it became clear that not only helium concentration, but also dpa value is an important factor which might influence the compression properties, because the compression load at 10% deformation for the present specimens irradiated at high dpa was smaller than that of the specimens, with similar helium concentration, irradiated at low dpa.