Asymmetric Dislocation/Point-Defect Interactions and the Modeling of Void Swelling

Abstract

An internally consistent model has been developed for analyzing void swelling during irradiation. The model employs Wigner-Seitz cells around each type of sink, namely dislocation lines, voids, and grain boundaries. Uniform generation of vacancies and interstitials is accounted for, as is diffusion in response to both concentration and radial interaction field gradients. The cells are coupled by equating concentrations and current flows at their peripheries, for arbitrary densities of the various types of sinks. A procedure has been developed for obtaining the best radial interaction fields to replace the actual angularly dependent ones surrounding dislocations. Analytical theoretical support for the chosen value (-1/4 of the average of the square of the actual field) has been developed. Quantitative accuracy has been assessed by comparison with numerical studies employing full angular dependence. The predicted swelling-rate bias factor of approx. 50% is in excellent agreement with available swelling-rate data when one assumes that approx. 16% of the defects initially generated escape close-pair recombination within the cascade. Reasonable theoretical support exists for this survival fraction.