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 (10(18)/m(2) s) and helium with low energy (30 eV, which cannot produce displacement damage) and high flux (10(22)/m(2) s). 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. (c) 2007 Elsevier B.V. All rights reserved.