Direct observation of neutron irradiation damage in niobium

Abstract
Polycrystalline sheets of pure niobium were irradiated to a dose of 2 × 1013 neutrons/cm2 (E>1 Mev). Defects appearing as black spots, as well as black-white contrasts, were observed by transmission electron microscopy. The density of the black spots was estimated as 5 × 1015/cm3. The defects were identified as small dislocation loops. Slip traces free of black spots were observed after plastic deformation. Attempts are now being made to determine the nature of the loops.