Characterization for fusion first-wall damage studies of using tailored D-T neutron fields

Changes in the physical properties of materials due to neutron irradiations are an important factor in the design of a fusion reactor. The neutron field present at the first-wall for a magnetically confined fusion device consists of both the directed 14-MeV neutron flux and the backscattered lower energy (< 14-MeV) neutrons returning from the energy absorbing blanket surrounding the plasma. This same neutron environment can be generated by surrounding a physically small but intense D-T source of neutrons with a spherical blanket of concentric shells of lithium, enriched uranium, and beryllium. By varying the geometry of these shells, the spectral distribution may be tailored to match closely the neutron spectra anticipated in fusion reactors. With a 3x1015m/s source strength and the addition of a blanket, the irradiation volume for doses higher than 10 dpa is about 100 cm3. A correlation was established between swelling gas production rate and displacement rate to illustrate the effects of the difference in neutron spectra from different neutrons sources