The Effect of Microstructure and Temperature Gradient on Radiation-Induced Swelling of Austenitic Steel

Radiation porosity through-thickness of the fuel pin cladding, made of 16Cr-19Ni-2Mo-2Mn-Nb-Ti-V-P-B steel, has been studied with scanning electron microscopy using backscattered electron (BSE) detector. The examined sample was irradiated at a temperature around 480 °С up to an integral damage dose of 87 dpa. It was shown that, due to the temperature gradient through the cladding thickness, the average size of radiation voids reduces, and their concentration increases from internal to external surface. Local nonuniformity of radiation porosity is observed in regions close to internal and external surfaces. It was shown that, non-uniformity of radiation porosity is determined by the material structure, microtwin density and high concentration of low-angle inter-granular boundaries, in particular.