Materials Activation Study on the EAST Neutral Beam Injection Port

Neutral beam injection heating system is one of the main heating methods to improve the operating parameters of EAST plasma physics. However, the neutron emission intensity can reach up to 10¹⁴ n/s. Because of the neutral beam injection (NBI) with a larger open size, the neutrons stream along the NBI duct. That may affect the safe and stable operation for NBI. In this paper, by using Monte Carlo program MCNP and activation program FISPACT, the material activation of the NBI key components has been researched based on EAST neutral beam two-dimensional geometric model when the angle between the reverse beam and the coaxial beam is 112.5 degrees. The theoretical simulation results are in good agreement with the experimental measurements. The results show that ⁵¹Cr, ⁵⁸Co and ⁵⁴Mn with medium and long life have obvious peak value of gamma energy spectrum, which indicate that those nucleus are the main active nuclides of SS304 and copper. When EAST stopped operating for 5 min, the shut down dose rate generated by activated gamma photon had been reduced to the dose rate limit designed by International Thermonuclear Experimental Reactor. This work could provide a preliminary exploration for material activation and shutdown dose rate analysis of the fusion reactor neutral beam injection port.