EXAFS studies for atomic structural change induced by ion irradiation of a reactor pressure vessel steel

Abstract Irradiation embrittlement is one of the most important phenomena in the structural integrity assessment for long-term operated reactor pressure vessels (RPVs). The causes of the irradiation embrittlement of RPVs are the formation of solute clusters and matrix defects. To investigate these embrittlement mechanisms, it is necessary to complementarily apply multiple microstructure analyses such as atom probe tomography and transmission electron microscopy. The extended X-ray absorption fine structure (EXAFS) technique can detect changes in the atomic structure by irradiation around selected atoms. In this study, we performed an EXAFS examination for RPV steels subjected to ion irradiation. We investigated microstructures of the crystal structure around specific element such as Cu, Mn, and Ni. The results indicated that the solute atoms cluster is thought to aggregate in the Fe matrix while maintaining the body-centered cubic structure and that a dumbbell pair could be located around both Cu and Ni atoms.