New low-activation criteria for fusion reactor materials

eutron-activated structural materials are the main contributors to radioactive inventory in fusion reactors. Neutron-induced radioactivity strongly depends on the type of irradiated material. With a proper selection of materials, therefore, the radioactive inventory in fusion reactors can be effectively controlled. This is not possible for fission reactors, and it is one of the distinctive points for fusion power. One of the main goals of the research on fusion reactor materials is to develop low-activation alloys with good mechanical and physical properties. For this purpose, a clear definition of low activity is mandatory to support the materials researchers with unambiguous indications. Until now, the definition of low activity was based on waste management and disposal problems. Many proposals dealing with the recycling of the materials or their shallow-land burial (SLB) were formulated. In Europe, SLB is not regarded as a possible scenario. The same procedures followed for the disposal of fission wastes will be probably adopted for fusion wastes. This means the burial of highly radioactive wastes in a deep geologic repository (DGR). Steel is the reference material for short- and medium-term machines. It has been shown that recycling of first-wall steel is not feasible because the induced radioactivity is too high. In this paper the authors present their low-activity concepts for fusion reactor materials and some examples of application