Experimental comparative study of activation of stainless steels by 14 MeV neutrons

The activities induced by D–T fusion neutrons in samples of stainless steels considered as structural materials for perspective fusion devices were experimentally investigated. The total activity of the Russian ferritic steel 10H9VFA, which is one of the candidates for the first wall structural material of the Russian Demo design, is compared with the total activities of two SS316 samples and of the ferritic steels MANET-II (Germany) and F82H (Japan). The experiments were carried out at the high-intensity neutron generator SNEG-13. Samples were simultaneously irradiated at two positions corresponding to mean neutron energies of 14.93 and 14.37 MeV. The measurements have shown that for cooling times up to a few months, the total specific activity of the investigated steels is mainly determined by reactions on Ni, Cr and Fe. The activity of the steels 10H9VFA and F82H is slightly less than that of MANET-II, the activity of which, in turn, is significantly less than that of SS316 and AISI 316 LN. This arises mainly from the lower contents of nickel in 1OH9VFA and F82H. For all of the considered steels the activity is higher at the larger mean neutron energy, indicating the important role of (n,2n) reactions for steel activation at neutron energies of 14–15 MeV. The experimental data are to be used for direct comparison of activation characteristics of structural materials as well as for the validation of activation data.