Post-irradiation annealing of high flux irradiated and surveillance material reactor pressure vessel weld metal

Kristina Lindgren (Corresponding Author), Magnus Boåsen, Zaiqing Que, Krystyna Stiller, Pål Efsing, Mattias Thuvander

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2 Citations (Scopus)


In this study, high flux irradiated and surveillance high Ni and Mn and low Cu welds identical to those of the belt-line region of Ringhals R4 were subjected to annealing at temperatures between 390 and 455 °C for 24–30 h, in order to study the dissolution of irradiation induced clusters and possible matrix defects using hardness testing and atom probe tomography. It was found that the cluster characteristics did not change during annealing at 390 °C, meaning that the size, number density and composition of the clusters, which mainly consist of Ni and Mn, did not change. Thus, the observed decrease in hardness during annealing of the high flux irradiated material is believed to be due to dissolution of matrix defects that were stable at the operating temperature. Cluster dissolution was observed after annealing at 410 °C in the high flux irradiated material, leaving around 10% of the original clusters. These clusters contained more Cu and less Ni and Mn than before annealing. The cluster dissolution at temperatures above 400 °C correlated with the decrease in hardness. The larger clusters of the surveillance material required a higher temperature or longer time to be dissolved compared to the clusters of the high flux material.

Original languageEnglish
Article number153586
Number of pages10
JournalJournal of Nuclear Materials
Publication statusPublished - 15 Apr 2022
MoE publication typeA1 Journal article-refereed


This investigation has been funded by the Swedish Radiation Safety Authority (SSM), as well as by the Swedish Centre for Nuclear Technology (SKC), and Nordic Nuclear Safety Research (NKS). Contribution to the funding also comes from the EU project ENTENTE (No 900018).


  • Atom probe tomography
  • Clusters
  • Embrittlement
  • High flux
  • Irradiation hardening
  • Matrix defects
  • Post irradiation annealing


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