Nucleation of voids and precipitates under cascade damage

Methods of modelling are presented for various component processes in the stage of nucleation of clusters, i.e. the diffusional effects of sub-cascade structure characteristic of high PKA energy cascades on the evolution of void embryo, and the collisional effects of cascade on the resolution of He atoms contained in a void embryo, and of impurity atoms contained in a precipitate. These estimations provide the transfer coefficients for Fokker-Planck equations which describe the evolution of the clusters. Approximate expressions for the nucleation rates of the clusters are presented. (orig.)