Structural materials  

• Definition of structural materials with reduced activation

• Activities of the EURATOM-CEA Association

Definition of structural materials with reduced activation 

The viability of fusion as a future source of energy will be in part determined by factors linked to safety and the environment. Fusion has intrinsic advantages such as the impossibility of runaway reaction and the absence of long-life radioactive waste from fusion reactions. These arguments can be further reinforced by appropriate management of activated materials. Fusion benefits also from its relative early development, to include as early as possible in design, the solutions offered by the use of low activation structural materials . These materials have the advantage of offering a rapid drop in activation.
Note that a low activation material should be able to be handled without complex precautions after a period of 100 years. Besides low activation properties, the materials chosen should have thermo-mechanical properties appropriate for use as internal component structural materials.

The two main design processes of this type of materials consist of :

• replacing in currently existing steels the elements that are penalising from the point of view of activation (nickel and molybdene for example) with more advantageous elements, but also compatible from a metallurgical point of view (manganese or tungsten for example). The main difficulty consists in defining an alloy that is not subject to the effects of expansion under irradiation, nor deterioration in its thermo-mechanical properties. Excellent results are obtained on structures of rapid neutron reactor fuel assemblies. For the moment it mainly concerns enhancing composition to give preference to low activation ingredient elements while preserving qualities under irradiation. This is the path of research favoured  by the European Union, which is developing a low activation martensitic steel called EUROFER.

• not using steels, but other families of materials, such as vanadium alloys or silicon carbide composites offering fast deactivation properties while at the same time holding certain advantages as regards thermal properties (refracting materials). The knowledge base on these materials is smaller due to their relatively recent use. Europe is carrying out exploratory research on the subject.

Activities of the EURATOM-CEA Association

The Association actively participates in the European programme of development of low activation martensitic steel EUROFER, as well as in studies devoted to silicon carbide composites. We quote here some research subjects carried out by the Association :

  
 For further information :

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