Hydrogen profiles in tokamak fusion reactor first walls

Calculations have been performed to predict the hydrogen isotope profiles in the. first wall of proposed fusion reactors. These profiles are obtained from numerical diffusion calculations which include D-T implant, H production through the (n,p) reaction, and thermal cycling of the wall. It is shown that the use of titanium as a first wall material can lead to steady-state hydrogen isotope concentrations greater than 1000 appm under proposed EPR and NUWMAK operating conditions. Calculations for stainless steel, under the same operating conditions, show hydrogen isotope concentrations of less than 20 appm. Thus, retained hydrogen and the possibility of structural degradation due to hydrogen embrittlement should be important considerations in selection of first wall materials.