Radioactivity study of EAST structural materials based on neutron activation system

The plasma operation in the Experimental Advanced Superconducting Tokamak (EAST) would generate 2.45 MeV neutrons and a small fraction of 14 MeV neutrons. Neutrons react with structural materials, leading to the production of radioactive isotopes. The identification of nuclides and the determination of radioactive activity are of great significance for radiation protection and fusion material applications. In this study, structural materials including stainless steel 316L(SS316L), stainless steel 304L(SS304L), aluminum(Al), tungsten(W) and copper(Cu) were transported to the activation terminal for fusion neutron irradiation. The gamma ray spectra were measured using high-purity germanium (HPGe) detector, and the main radioactive nuclides of SS316L and SS304L are Mn-56, while the main radioactive nuclide of Al is Al-28. For Cu and W, the main radionuclides resulting from neutron reactions are Cu-66 and W-187, respectively. The uncertainty of the radioactivity is 2.27 similar to 7.94 % for W, 1.95 similar to 5.84 % for SS316L, 2.10 similar to 6.07 % for SS304L, 0.68 similar to 1.69 % for Al and 2.59 similar to 6.75 % for Cu. The specific activity of radionuclides is proportional to neutron yield, so the material activation is the main source of radiation dose during irradiation with high-yield neutron. The neutron activation coefficients of SS316L, SS304L, Al, Cu and W are 2.74538 x 10(-14), 3.6411 x 10(-14), 2.50711 x 10(-12), 1.76506 x 10(-12) and 3.51725 x 10(-14), respectively. The coefficient represents the radioactive activity generated by each fusion neutron. In addition, the predicted activity was calculated using FISPACT program and compared with experiments.