The morphology of radiation damage in copper irradiated with neutrons at elevated temperatures.

Abstract

This thesis is an investigation of the radiation damage morphology of high purity copper crystals irradiated with fast neutrons at temperatures in the range of 250C to 4OO C. At these high temperatures neutron damage is found to accumulate into large 3-dimensional rafts up to 100 um in size, and the well known homogeneous distribution of black dot damage which is characteristic of irradiations at lower temperatures is not observed. The characteristics and composition of the rafts of damage 0 at different temperatures in the range 250 C to 400 C have been compared and found to differ to a large extent. It has also been shown that the background areas between rafts contain a rather low density of damage at all temperatures studied. It is therefore concluded that many of the interstitial atoms formed during irradiation migrate over large distances through the crystal lattice to precipitate at the sites of the dislocations forming the large rafts, and so denuded inter-raft areas are left behind. It is proposed that these large rafts originate from grown in dislocations present in the crystals before irradiation