Ferritic/martensitic steels considered as first-wall candidate materials for fusion reactors experience significant radiation hardening below about 400C. Experimental evidence suggested that the observed defects were large interstitial dislocation loops with Burgers vector b = <100> and b = ½<111>. The atomic characters of <100> and ½<111> loops were investigated here using molecular dynamics simulations, and the atomic configurations were used to calculate the defect image contrast via direct simulation of transmission electron microscopic images. The simulated images were subsequently compared with actual transmission electron micrographs of irradiated ferritic materials and were in very good qualitative agreement, providing strong indication that the observed b = <100> loops were interstitial in nature.

<100>-Loop Characterization in α-Fe - Comparison between Experiments and Modeling. J.Marian, B.D.Wirth, R.Schäublin, J.M.Perlado, T.Díaz de la Rubia: Journal of Nuclear Materials, 2002, 307-311[2], 871-5