The accumulation of 4He, its diffusion characteristics and the microstructure were studied after irradiation at 70 and 200C with neutrons having an energy of E > 0.1MeV to fluences of 1.0 x 1022 to 1.3 x 1023/cm2. Experimental results on the concentration of radiogenic He, after irradiation and isothermal annealing (700-1200C, 1h), were obtained. The accumulation of He corresponded to a linear dependence up to a fluence of about 6 x 1022/cm2 (E > 0.1MeV). For fluences of 6 x 1022 to 1.3 x 1023/cm2 (E > 0.1MeV), a deviation from the linear dependence and towards a decrease in the rate of accumulation was observed. The diffusion of radiogenic He in Be upon annealing at 70 to 200C was low. Intense diffusion and degassing of He from Be began at an annealing temperature of 700C. Upon annealing at 1100 to 1200C, almost all of the He escaped from the irradiated Be.

Accumulation and Diffusion of Radiogenic Helium in Beryllium. V.P.Chakin, S.V.Belozerov, A.O.Posevin: Physics of Metals and Metallography, 2007, 104[3], 247-51