Hydrogen isotope retention and recycling in fusion reactor plasma-facing components

The proper design of a fusion reactor is not possible unless there is an understanding of the hydrogen isotope retention and recycling for the plasma-facing components. From the tritium inventory point of view, it is absolutely necessary to understand the short-term and long-term hydrogen isotopes retention characteristics of the individual materials used for the first wall and divertor. From the plasma density and fueling point of view, it is necessary to understand the recycling characteristics of these materials. This report is an overview of the available data on hydrogen isotope retention and recycling for beryllium, tungsten, carbon, and selected liquid metals. For each material discussed, recommendations are made as to the most appropriate values to use for parameters such as diffusivity, solubility, recombination rate coefficient, and trapping.