Chad M. Parish¹, Daniel G Morrall¹, Yutai Katoh¹, Arunodaya Bhattacharya¹, Andrew R Lupini¹, Philip D Edmondson¹; ¹Oak Ridge National Laboratory

Advanced fission—much less fusion—reactors will subject materials to unprecedented neutron irradiation damage and helium transmutation. Most of the current design approaches to advanced radiation-tolerant materials involve highly engineered nanostructures. The question of how radiation will alter, and ultimately degrade, these nanostructures requires we push the boundaries of electron microscopy. Here at ORNL, we are developing new techniques to understand both metallic and ceramic materials' structural changes under neutron and ion irradiation. HREM combined with machine learning has unbiasedly identified defects in neutron-irradiated silicon carbide. Aberration-corrected STEM has identified the structure of the dislocation loops in ion-irradiated refractory diboride ceramics. Transmission Kikuchi diffraction allows us to probe grain boundary character in irradiated tungsten and compare to STEM X-ray analysis of segregation. Overall, modern electron microscopy allows us to probe irradiation-induced defects in heretofore unimagined detail. This talk will review recent applications to irradiated materials.