Tritium behavior in plasma-facing walls

Models for tritium permeation from and inventory in the plasma-facing walls of fusion devices are reviewed. These models can readily be applied to calculate the steady state permeation rate of tritium or transient tritium inventory in the wall materials. However, the frameworks for these models are formulated based on the knowledge obtained in laboratory experiments characterized by low-incident hydrogen fluxes. Therefore, care should be taken when applying these models to fusion-relevant conditions, where, for instance, the mechanism of recombination may differ from that under low-incident flux. In addition, it is not clearly understood how a high concentration of tritium accompanied by alpha particles and high-flux neutrons will affect the tritium transport in materials different from those observed under laboratory conditions. (author)