The simultaneous clustering of point defects during irradiation

The simultaneous clustering of irradiation produced vacancies and interstitials in metals is investigated using the rate theory approach. Rate equations are used to describe the time-dependent concentrations of point defect clusters. Size-dependent bias factors and self-consistent reaction rate constants are used to evaluate the feed-back effects between the evolving vacancy cluster and interstitial loop populations. It is found that the concurrent presence of vacancy clusters depletes the free vacancy population and thereby reduces mutual point defect recombination. This has the effect of enhancing interstitial loop formation; increasing loop concentration, nucleation rate, average size, and growth speed of the average size. In 316 stainless steel, a diinterstitial binding energy of 1.19 eV results in a substantial decrease in loop concentrations at high temperatures, which is in qualitative agreement with experimental data. (author)