FRACTURE-BEHAVIOR OF NEUTRON-IRRADIATED BERYLLIUM

Beryllium might be used as a neutron multiplier in blankets for thermo nuclear fusion machines. Beryllium is irradiated in the BR2 materials testing reactor at SCK.CEN at approximately 200, 400 and 600 degrees C up to a neutron fluence of 2.1 x 10(25) n m(-2) (E-n > 1 MeV). Four b eryllium grades were irradiated and evaluated: S-200-F (vacuum hot pre ssed, 1.2 wt% BeO), S-200-FH (hot isostatic pressed, 0.9 wt% BeO), S-6 5 (vacuum hot pressed, 0.6 wt% BeO) and S-65-H (hot isostatic pressed, 0.5 wt% BeO). The main conclusions that can be drawn from a prelimina ry fracture toughness investigation can be summarised as follows: (1) All beryllium grades exhibit approximately the same behaviour from the fracture toughness point of view, although, small differences are obs erved in the initial tensile properties. (2) The ageing treatment does not significantly affect the tensile properties or the fracture tough ness. (3) Irradiation results in strengthening of the material, loss o f ductility and a decrease in the fracture toughness. However, the irr adiation damage saturates after a specific neutron fluence. (4) Irradi ation at higher temperature increases fracture toughness. (C) 1998 Pub lished by Elsevier Science S.A. All rights reserved.