Can aluminium or magnesium be a surrogate for beryllium: A critical investigation of their chemistry

The use of beryllium is still an existing question according to the studies concerning the plasma-wall interactions which are expected to occur in ITER. Prediction of erosion and co-deposition processes for ITER is necessary for the design and the material choice of the first wall. In the current configuration, it is expected that co-deposited layers containing Be, tungsten and possibly carbon will be formed. However, the toxicity of Be limits its use in many experimental facilities around the world. Using aluminium or magnesium as Be replacements in laboratory experiments would solve this problem of toxicity and handling of Be mixed materials. A critical question which automatically arises is the relevance to use Al or Mg regarding the physical and chemical properties of both elements in comparison to the co-deposited layers expected in ITER. This work provides a review of the chemical and physical properties of Al and Mg, in the respect of comparing these properties to those of Be. Thanks to the similarity of its electronegativity to Be, Al can successfully resemble Be in terms of formation of compounds, especially the oxides and possibly the hydrides. However, due to the difference in the nature of the bonding, Mg cannot be a replacement for a possible hydride deposit formation.