ADVANCES IN THE THEORY OF SWELLING IN IRRADIATED METALS AND ALLOYS

Recent advances in the theory of swelling are reviewed. These include (1) the development of a cascade diffusion theory to treat quantitatively the fluctuations in point defect concentrations caused by locally inhomogeneous point defect production, (2) the incorporation of mobile helium and its effects on void growth into the theory, and (3) the spatial variation in swelling during charged particle bombardment. Summaries of (1) and (2) are given. A more complete development of (3) is presented. Three phenomena responsible for spatial variation of swelling during heavy-ion bombardment are assessed. Loss of point defects to the free surface results in only a minor perturbation of swelling under the usual conditions considered. Interstitials injected by the bombarding beam may severely deplete the void volume under certain conditions. The effect is extremely sensitive to defect and materials parameters and is largest for low swelling materials. The previously unexplored depletion of swelling resulting from diffusional spreading of point defects out of the region of maximum energy deposition is evaluated and found to be significant. © 1979.