Criteria for defining low activation materials in fusion reactor applications

Criteria are proposed for defining low-activation materials. These criteria take into account the three fundamental characteristics of the reactor which will be affected by the neutron-induced radioactivity: radioactive emissions in routine and off-normal conditions, maintenance operations after a shutdown, and finally waste management and disposal aspects. The activation of some typical candidate fusion reactor structural materials (reference steels, reduced activation steels and non-ferrous low-activation alloys) has been simulated in power reactor-relevant conditions. The compliance of the candidate materials with the proposed criteria has been examined. It turns out that only non-ferrous materials can fulfil all the proposed low-activation requirements.