Microstructural Evolution of Welded Stainless Steels on Integrated Effect of Thermal Aging and Low Flux Irradiation
The combined effect of thermal aging and irradiation on cast and welded stainless steel solidification structures is not sufficiently investigated. From theory and consecutive aging and irradiation experiments, the effect of simultaneous low rate irradiation and thermal aging is expected to accelerate and modify the aging processes of the ferrite phase. Here, a detailed analysis of long-term aged material at very low fast neutron flux at LWR operating temperatures using Atom Probe Tomography is presented. Samples of weld material from various positions in the core barrel of the Zorita PWR are examined. The welds have been exposed to 280–285 °C for 38 years at three different neutron fluxes between 1 × 10−5 and 7 × 10−7 dpa/h to a total dose of 0.15–2 dpa. The aging of the ferrite phase occurs by spinodal decomposition, clustering and precipitation of e.g. G-phase. These phenomena are characterized and quantitatively analyzed in order to understand the effect of flux in combination with thermal aging.
KeywordsThermal aging Irradiation Weld ferrite Spinodal decomposition Stainless steel
The authors wish to express their sincere gratitude to Mr. Roger Lundström, who performed specimen extraction and light optical microscopy, and Anders Jenssen for fruitful discussions, both from Studsvik Nuclear AB. EPRI have kindly allowed use of the material. The work was funded by the Swedish Radiation Safety Authority, the Swedish NPPs Materials Group (SUMG) and Studsvik Nuclear AB.
- 4.M. Bjurman, M. Thuvander, F. Liu, P. Efsing, Phase separation study of in-service thermally aged cast stainless steel—Atom probe tomography, in: Proceedings of the 17th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems, CNS 2015Google Scholar
- 5.A. Heinrich, T. Al-Kassab, R. Kirchheim, Investigation of the early stages of decomposition of Cu/0.7 at.% Fe with the tomographic atom probe. Mat. Sci. Eng. A353 (2003) 92_/98Google Scholar
- 7.J.M. Hyde, C.A. English, An analysis of the structure of irradiation induced Cu-enriched clusters in low and high Nickel welds, Materials Research Society Symposium, 2000, pp. R6.6.1–R6.6.12. BostonGoogle Scholar