Identification of the nature of small point defect clusters in neutron irradiated Fe–16Ni–15Cr by means of electron irradiation

Abstract

The nature of very small point defect clusters in Fe–16Ni–15Cr irradiated with fission neutrons was identified from their behavior under electron irradiation with a high voltage electron microscope. In this analysis, the defect clusters which grew during electron irradiation were judged to be of interstitial (I)-type and those which shrank or disappeared to be of vacancy (V)-type. The fraction of the number of I- and V-type defect clusters in a specimen irradiated as a bulk at 353 K were found to be 7% and 93%, respectively. In a specimen irradiated at 623 K as a bulk, most of defect clusters were I-type with a very small fraction of V-type. In a thin foil specimen irradiated at 573 K, the fraction of I-type defect clusters increased from 20% near the thin specimen edge to 70% at a thicker part of 120 nm. These results were consistent with those in the previous judgement from the shape and contrast of transmission electron microscope image.