Material problems and requirements related to the development of fusion blankets: The designer point of view

Abstract

The structural materials considered for solid and liquid metal breeder blankets are the austenitic and martensitic steels and vanadium alloys. The principal concerns with these materials are: 1. (a) the high-temperature-induced swelling of the austenitic steels, 2. (b) the low temperature irradiation embrittlement of martensitic steels, and 3. (c) the exact specification of the preferred alloy composition(s), properties during and following irradiation, and technological aspects (fabrication and welding) for the vanadium alloys. Solid breeder blankets are based on the use of lithiated ceramics such as Li 2O, LiAlO 2, Li 4SiO 4 and Li 2ZrO 3 and beryllium as a neutron multiplier. The main uncertainty with these materials is their behaviour under irradiation, particularly at higher burnups and fluences than have been achieved hitherto. Liquid metal blankets, utilising pure Li or the LiPb eutectic as the tritium breeding material, can be either self- or separately-cooled; separate coolants include water (with LiPb) and helium. The important materials issues with the LiPb are the development of permeation barriers to contain the tritium and, for the self-cooled option, electrical insulators to reduce the MHD pressure drop to acceptable levels.