MATERIAL PROBLEMS AND REQUIREMENTS RELATED TO THE DEVELOPMENT OF FUSION BLANKETS - THE DESIGNER POINT-OF-VIEW

The structural materials considered for solid and liquid metal breeder blankets are the austenitic and martensitic steels and vanadium alloy s. The principal concerns with these materials are: (a) the high-tempe rature-induced swelling of the austenitic steels, (b) the low temperat ure irradiation embrittlement of martensitic steels, and (c) the exact specification of the preferred alloy composition(s), properties durin g and following irradiation, and technological aspects (fabrication an d welding) for the vanadium alloys. Solid breeder blankets are based o n the use of lithiated ceramics such as Li2O, LiAlO2, Li4SiO4 and Li2Z rO3 and beryllium as a neutron multiplier. The main uncertainty with t hese materials is their behaviour under irradiation, particularly at h igher burnups and fluences than have been achieved hitherto. Liquid me tal blankets, utilising pure Li or the LiPb eutectic as the tritium br eeding material, can be either self- or separately-cooled; separate co olants include water (with LiPb) and helium. The important materials i ssues with the LiPb are the development of permeation barriers to cont ain the tritium and, for the self-cooled option, electrical insulators to reduce the MHD pressure drop to acceptable levels.