| 1. |
- Hytonen, Noora, et al.
(author)
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Effect of weld microstructure on brittle fracture initiation in the thermally-aged boiling water reactor pressure vessel head weld metal
- 2021
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In: International Journal of Minerals, Metallurgy and Materials. - : Springer Nature. - 1674-4799 .- 1869-103X. ; 28:5, s. 867-876
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Journal article (peer-reviewed)abstract
- Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant. As-welded and reheated regions mainly consist of acicular and polygonal ferrite, respectively. Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions (0.5-2.5 mu m) at the brittle fracture primary initiation sites. High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch. The density, geometry, and chemical composition of the primary initiation inclusions were investigated. A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the de-bonded interfaces between the uncracked inclusions and weld metal matrix. Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.
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| 2. |
- Lindqvist, Sebastian, et al.
(author)
-
Mechanical behavior of high-Ni/high-Mn Barsebäck 2 reactor pressure vessel welds after 28 years of operation
- 2023
-
In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 581, s. 154447-154447
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Journal article (peer-reviewed)abstract
- To assess long-term operation of the reactor pressure vessel (RPV), surveillance programs are applied for periodic monitoring and prediction of the aging of the mechanical properties due to irradiation and thermal embrittlement. In literature, there are limited data sets to compare the results from the surveillance program to the aging of the RPV. In this work, the tensile and impact toughness properties of the high-Ni, high-Mn welds from decommissioned Barsebäck 2 RPV are characterized. The results indicate that the surveillance program describes sufficiently the aging of the RPV welds. Differences in mechanical properties of the welds from various regions are explained by variations in post-weld heat treatment. The synergetic effect of Ni and Mn on embrittlement appears not to result at low fluences in a significant difference in the embrittlement rate when compared to ASTM E900 embrittlement trend curve prediction.
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| 3. |
- Que, Zaiqing, et al.
(author)
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Brittle fracture initiation in decommissioned boiling water reactor pressure vessel head weld
- 2022
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 569
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Journal article (peer-reviewed)abstract
- The brittle fracture initiation behavior and fracture toughness in the ductile-to-brittle transition region for a thermally-aged weld metal of a decommissioned reactor pressure vessel head (in operation at 288 degrees C for 23 effective full power years) and in the non-aged reference condition were investigated. The results show that brittle fracture initiated primarily from non-metallic inclusions. The correlation between frac-ture toughness and brittle fracture initiation type (inclusion debonding or breakage), initiator size, initi-ation location (as-welded or re-heated regions in the weld metal) were analysed. Despite that thermal ageing does not affect significantly the fracture toughness, it could promote the debonding as a brit-tle fracture primary initiation type. The influence of debonded inclusion on the evolution of cumulative damage and brittle fracture initiation was assessed using crystal plasticity modelling.
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