Analysis of transmutation nuclide production in a spallation neutron source

The spallation neutron source (SNS) is considered an excellent tool for simulating the neutron radiation environment of the first wall of future fusion reactors and the test materials used for it. Because of the presence of a high-energy tail in the spallation neutron spectrum, some new transmutation products are generated that are not produced by fusion spectra. To establish the technical feasibility of SNS as a tool for such a simulation, one needs a detailed study of the buildup and decay characteristics of transmutation nuclides. One also needs to show that the buildup of the undesired transmutation products is small enough so that they do not influence the mechanical properties of the test samples towards one end of the material's life. The effect of the high energy component of the SNS neutron spectrum on hydrogen and helium generation also needs to be studied. The authors discuss in this paper a method of performing activation calculations for samples irradiated by the SNS. They have shown that the hydrogen-to-helium ratio for iron (FE) samples irradiated in SNS is comparable to that in the fusion reactor's first wall