A new mechanism was proposed for the formation of vacancy voids in irradiated metal as being due to the successive development of two types of instabilities in a system of interacting point defects produced by neutron irradiation. The first stage of the void formation process involves the nucleation of local vacancy clusters possessing a high, relative to the surroundings, concentration of defects; the second state involves lattice instability inside such clusters.

New Mechanism of the Formation of Vacancy Voids. Y.N.Devyatko, O.V.Khomyakov, M.Y.Kagan: Low Temperature Physics, 2010, 36, 313-6