Post-irradiation annealing of high flux irradiated and surveillance material reactor pressure vessel weld metal
Journal article, 2022

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.

High flux

Atom probe tomography


Irradiation hardening

Post irradiation annealing


Matrix defects


Kristina Lindgren

Chalmers, Physics, Microstructure Physics

M. Boasen

Royal Institute of Technology (KTH)

Zaiqing Que

Technical Research Centre of Finland (VTT)

Marta Krystyna Stiller

Chalmers, Physics, Microstructure Physics

P. Efsing

Royal Institute of Technology (KTH)


Mattias Thuvander

Chalmers, Physics, Microstructure Physics

Journal of Nuclear Materials

0022-3115 (ISSN)

Vol. 562 153586

Subject Categories

Astronomy, Astrophysics and Cosmology

Other Materials Engineering

Condensed Matter Physics

Areas of Advance


Materials Science


Chalmers Materials Analysis Laboratory



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