Accumulation of helium in tungsten irradiated by helium and neutrons

Effects of helium on the microstructural evolution in tungsten were investigated using computer simulation based on a rate theory. Two cases were considered: helium with high energy (1 keV) and low flux (1018/m2s) and helium with low energy (30 eV, which cannot produce displacement damage) and high flux (1022/m2s). Neutron irradiation at 10−6 dpa/s and 873 K was used in the calculations as a typical irradiation condition. Helium–vacancy clusters with high concentration were formed near the incident surface during neutron and helium irradiations. The formation of helium–vacancy clusters suppressed the helium diffusion deeper into the specimen. The results show that a helium plasma with low energy and high flux has a greater effect on the accumulation of helium–vacancy clusters near the incident surface than would a helium plasma with high energy and low flux.