In-situ WB-STEM observation of dislocation loop behavior in reactor pressure vessel steel during post-irradiation annealing

Research output: Contribution to journalArticle

Authors

  • Yufeng Du
  • Kenta Yoshida
  • Yusuke Shimada
  • Takeshi Toyama
  • Koji Inoue
  • Kazuto Arakawa
  • Tomoaki Suzudo
  • Milan Konstantinovic
  • Robert Gérard
  • Somei Ohnuki

Institutes & Expert groups

  • Tohoku University - Institute for Materials Research
  • Shimane University - Interdisciplinary Faculty of Science an Engineering
  • JAEA - Japan Atomic Energy Agency - CCSE - Center for Computational Science and e-Systems, Tokai, Ibaraki 319-1195 Japan
  • USTB - University of Science and Technology Beijing
  • Tractebel - Engie

Documents & links

Abstract

To better understand the thermal stability of dislocation loops formed by long-term neutron irradiation in reactor pressure vessel (RPV) steels, in-situ scanning transmission electron microscopy (STEM) observation was performed for a surveillance test specimen of a European pressurized water reactor (PWR). The surveillance test specimen was neutron irradiated to a fluence of 8.2 ×10 23 neutrons • m − 2 . A membrane sample from the surveillance test specimen was annealed at 673 K and 723 K for 30 min using a heating holder, and the same area was in- situ observed under STEM. After annealing, dislocation loops with Burgers vectors of 1 2 ⟨111 ⟩and ⟨100 ⟩were quantitatively examined. When annealing temperature increased from 673 K to 723 K, the number of dislocation loops decreases, whereas the size of them becomes larger. Correspondingly, the proportion of ⟨100 ⟩dislocation loops changes from 27% to 45%. The ratio of ⟨100 ⟩to 1 2 ⟨111 ⟩loops increases with annealing temperature rising. The evolution process of dislocation loops during annealing at 723 K was in-situ observed and analyzed to shed light on the transformation mechanism of dislocation loops going from 1 2 ⟨111 ⟩to ⟨100 ⟩. It is the first time to directly observe that two 1 2 ⟨111 ⟩dislocation loops collide with each other and coalesce to form a ⟨100 ⟩dislocation loop. Moreover, small 1 2 ⟨111 ⟩dislocation loops could be absorbed by large ⟨100 ⟩dislocation loops, whereas the Burgers vector of ⟨100 ⟩loops remained unchanged. Dislocation decoration occurs during annealing due to the interaction between dislocations and loops. The dislocations decorated by loops are pretty stable during the continuous annealing process, which is well explained by molecular dynamics simulation.

Details

Original languageEnglish
Article number100778
Pages (from-to)1-11
Number of pages11
JournalMaterialia
Volume12
DOIs
Publication statusPublished - 12 Jun 2020

Keywords

  • RPV steel, Neutron irradiation, Dislocation loops, In-situ observation, WB-STEM

ID: 6851924