Dislocation loops in neutron irradiated vanadium

An electron microscope study has been made on annealing behaviour of dislocation loops in commercial purity vanadium as a function of neutron irradiation conditions. Upon post-irradiation annealing vacancy loops are observed to grow in the specimen irradiated to 8.2 x 1019 n.cm-2 and interstitial loops grow in the specimen irradiated to 4.2 x 1019n.cm-2 or less fluences. In the specimen irradiated to 2.1 x 1018 n.cm-2 at - 1960C, clustering of interstitials to be small dislocation loops is apparent on annealing at 2500C. Extent of the growth of interstitial loops increases with increasing annealing temperature up to about 5000C. On annealing at higher temperature the interstitial loops decrease in both size and density to disappear out of the specimen. The extension in size distribution curve for vacancy loops to larger diameter region is apparent on annealing at temperatures of 40000C and above. The net density of vacancy point defects stored in the loops decrease on annealing at temperature above 5000C, while the average diameter of the loops continue to grow with annealing temperature up to 6300C; segments of dislocation line appear in the specimen annealed at the temperature. (author)