HREM OF (C)-TYPE DISLOCATIONS IN HIGH-DOSE NEUTRON-IRRADIATED AND POSTIRRADIATION ANNEALED ZIRCALOY-2

High resolution electron microscopy (HREM) was performed on [c]-type d islocations in annealed Zircaloy-4 which had been neutron irradiated t o 20 dpa at 690 K. Lattice images of the [c]-type dislocations, which lie on the basal plane, reveal unfaulted dislocation structure. Conven tional TEM analysis of these dislocations in postirradiation annealed Zircaloy-2 shows that the [c]-component dislocations have Burgers vect ors of 1/3[1123BAR] and [0001]. Large bends in the [c]-component dislo cation network are associated with multiple [a]-type dislocations. Ini tial results by electron holography of the [c]-type dislocation core r egion produces phase shifts having a length of approximately 3 basal p lanes in isolated regions along the length of the dislocations. The sh ift may occur due to large solute concentrations.