Speaker
Description
Shouxi Gu1, Qiang Qi1,2, Hai-Shan Zhou1,2
1Institute of Plasma Physics, Hefei Institutes of Physical Sciences, Chinese Academy of Sciences, Hefei, 230031, China
2Science Island Branch, Graduate School of USTC, Hefei, 230036, China
The neutron energy spectrum in solid breeder blankets spans from 10−8 to 14 MeV, generating primary knock-on atoms (PKAs) with energies ranging from 10−4 to several MeV within the breeder material. These PKAs induced by neutron irradiation trigger cascade collision processes, producing substantial displacement damage that threatens irradiation stability. 5 MeV Si ion irradiation was adopted to bombard the mixed-phase Li2TiO3-Li4SiO4 pebbles. Electron spin resonance (ESR) analysis revealed irradiation-induced vacancy-type defects, including oxygen vacancy defects (E’-centers) and non-bridging oxygen hole centers (NBOHCs). Raman spectroscopy demonstrated severe damage to the fundamental structural units of the material, resulting in broadened spectral features with no distinct peaks. Annealing experiments at 300°C and 650°C revealed self-healing behavior as the annealing temperature increased. The damaged structural units gradually recovered, with a significant recovery phenomenon observed in Raman spectra after high-temperature annealing. This suggests that thermal treatment effectively mitigates irradiation-induced lattice disorder, highlighting the material’s potential for self-repair under operational conditions in fusion environments.
Neutron irradiation will generate gaseous transmutation products, H and He, through (n, xH) and (n, xHe) reactions in RAFM steel. These energetic gaseous particles will induce radiation defects in steels. Helium ions as insoluble gases will form voids and bubbles in irradiated steels, which will alter the corrosion process of steels. To study the influence of transmutation-produced helium on the corrosion behavior of CLF-1 steel by lithium ceramic tritium breeders, 100 keV helium ion irradiation of CLF-1 steel was conducted. Corrosion experiments in Li4SiO4 powder at 550 ℃ were conducted for helium ion irradiated CLF-1 steel. The GIXRD of the non-irradiated and helium ion irradiated CLF-1 steel samples after 10 h of corrosion in Li4SiO4 powders, reveals that the corrosion product is the Fe3O4 phase. After irradiation, the diffraction peak intensity of the Fe3O4 phase decreased significantly. The post-irradiation TEM image discovers a separation between the corrosion layer interface and the substrate, with abundant helium bubbles observed near the interface on the substrate side, indicating helium aggregation and growth during corrosion. The sizes of helium bubbles in post-irradiated CLF-1 steel before and after corrosion are measured, respectively. After corrosion, the helium bubbles grew to approximately 2–3 nm, significantly larger than those in the uncorroded CLF-1 steel. Based on these findings, the corrosion layer spallation mechanism of helium-irradiated CLF-1 steel has been proposed.
