RECOIL ENERGY EFFECTS AND DEFECT PROCESSES IN NEUTRON-IRRADIATED METALS

Subdivision of primary recoil energy into sub-cascades in 14 Mev neutron irradiated fcc metals is analyzed in reference to the primary recoil energy spectrum, 10-20 kev per sub-cascade depending on the kind of metals. Shape and size of sub-cascade groups are also related to the recoil energy, including the anisotropy with reference to the incident neutron direction. The extent of the overlapping of sub-cascades to produce vacancy clustered defects are classified from the spacing between sub-cascades, significant overlapping for narrow spacing less than 5 nm in Ag and Au, and no overlapping for wide separation more than 10 nm in Ni and Cu. A discussion is presented on the irradiation rate dependence from the defect cluster formation mechanism and from the degree of cascade-overlap.