Key Issues of Plasma-Wall Interaction

In this section the crucial problems of plasma-wall interaction are discussed, which need to be solved in order to achieve a high availability of a fusion power plant. 

On those areas with net-deposition the deposited particles form layers which may become a problem because 

the layer can fall off as flakes after some time disturbing the plasma and 

tritium can be retained in these layers in amounts which are beyond those 

There are large uncertainties about the tritium retention problem. The most pessimistic extrapolations based on data from co-deposition of tritium with carbon [8] conclude that the allowed maximum of 350 g of T retained in the vessel will be reached after only a few ITER discharges. This is seen as a genuine problem with graphite, whereas other candidate wall materials like W do not show such a strong effect of tritium retention. Therefore, already for ITER it is of paramount importance to clarify this problem and to verify that carbon as a wall material is acceptable at all for tritium operation. 

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