Effect of cascade localization induced bias on defect structure evolution

A vacancy dominant atmosphere during neutron irradiation was analyzed with special attention on the initial local distribution of point defects in a cascade, i.e. a vacancy rich region which occupies a volume smaller that that occupied by interstitials. When the diffusion of vacancies starts from this localized volume and there are sinks in the cascade, vacancies have more possibilities to be absorbed by sinks than interstitials which start from an expanded volume. Consequently the contribution of vacancies in modifying the microstructure in the cascade is larger than that of interstitials. The model was applied to experimentally observed interstitial loop shrinkage and void swelling. The importance of the effect of the difference in initial local distributions of two species of point defects in the cascade (Cascade Localization Induced Bias) was emphasized.