Ph.D. projects

---

Investigation of ion irradiation induced damage in reactor pressure vessel (RPV) steels

Libang Lai

Dr. Paul Chekhonin (HZDR)

Structural Materials

03/2021-09/2024

This thesis is part of ENTENTE project. The goal of the thesis is to investigate the damage induced by ion irradiation in reactor pressure vessel (RPV) steels. Ion irradiation is a promising tool to emulate neutron-irradiation effects in RPV steels. Although there are some issues of ion irradiation, it provides accelerating study and development of the RPV steels due to much faster dose rate. In present work, two western types of RPV steels and two different doses of ion irradiation for both materials are studied.

First, comprehensive microstructure characterization is implemented applying different electron microscopy techniques, including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX). For unirradiated materials, initial dislocation lines, particles, grain boundaries, grain orientations are characterized and evaluated. For irradiated materials, cross-sectional samples are cut by focus ion beam (FIB) technique. STEM is then applied to characterize dislocation loops induced by irradiation. More details, see: https://doi.org/10.3390/met13081339.

Second, a microstructure-informed model is established to predict the hardness increase induced by irradiation. Nanoindentation is used to measure the hardness of unirradiated and irradiated samples for both materials. The model established is based on dispersed barrier hardening (DBH) model, using the microstructure data obtained and mentioned above. More details, see: https://doi.org/10.3390/met14030257.

Furthermore, other aspects are also covered. For example: transferability of ion and neutron irradiation; post-irradiation annealing to analyze the stability of dislocation loops; issues of performing nanoindentation, etc.

---