A first attempt was made at solving the problem of the growth of a single void in the presence of anisotropically diffusing radiation-induced self-interstitial atom clusters. In order to treat a distribution of voids, ensemble averaging over the positions of centres of voids was performed by using a mean-field approximation. In this way, it was possible to model physical situations in between the standard rate theory treatment of swelling (isotropic diffusion), and the purely 1-dimensional diffusion of clusters in the production bias model. The background absorption by dislocations was instead treated isotropically, with a bias for interstitial cluster absorption which was assumed to be similar to that of individual self-interstitial atoms. It was found that, for moderate anisotropy, unsaturated void growth was characteristic of this anisotropic diffusion of clusters. In addition, a higher initial void-swelling rate was obtained than that predicted by standard rate theory, whenever the diffusion was anisotropic.

Absence of Saturation of Void Growth in Rate Theory with Anisotropic Diffusion. T.S.Hudson, S.L.Dudarev, A.P.Sutton: Journal of Nuclear Materials, 2002, 307-311[2], 976-81