ORIGIN OF UNBALANCED REACTION OF VACANCIES AND INTERSTITIALS DURING IRRADIATION WITH CASCADES AND INFLUENCE ON MICROSTRUCTURAL EVOLUTION

Based upon the underlying premise that all the microstructure evolution during irradiation results from the assymetrical reaction between vacancies and interstitials, the origin of the assymetry is sought and categorized, and the mechanism of defect structure evolution for each source of assymetry is investigated. The role of neutral sinks and the influence of dislocations are examined for the cases of irradiation with and without cascade damage. Vacancy cluster formation directly from cascades is found to favor the generation of freely migrating interstitials. Stochastic fluctuations of the point defect reactions under the balanced condition of vacancy and interstitial is experimentally detected, and the important role of the fluctuations is found in the determination of the fate of small interstitial cluster embryos produced by cascade damage. The influence of the unbalanced point defect reaction starting from difference in spacial distribution between vacancies and interstitials formed by cascade collisions is discussed as one of the important origins of vacancy dominant reactions.