Irradiation of the samples was carried out, at temperatures of up to 1100K, by using α energies of between 5 and 28MeV, rates of between 8 x 1013 and 4 x 1015m2s, and doses of the order of 1017/m2. The He release during irradiation decreased markedly with increasing irradiation depth. The diffusion data could be described by:

D (m2/s) = 1.1 x 10-6 exp[-1.14(eV)/kT]

at temperatures of between 800 and 1050C.

P.Jung: Journal of Nuclear Materials, 1992, 191-194, 377-81