Kristina Lindgren Supervisors: Krystyna Stiller, Mattias Thuvander Vattenfall contact: Pål Efsing
Irradiation induced precipitation in reactor pressure vessel steel welds
Reactor Pressure Vessel Low alloy steel, cladded with stainless steel
https://en.wikipedia.org/wiki/Nuclear_power_plant#/media/File:PressurizedWaterReactor.gif
Welds are most susceptible Radiation and heat
PWR
Ringhals R4 at% Low Cu, high Ni
[Brumovsky 2010]
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Radiation induced precipitation
[Odette, 2009]
• Nanometre precipitates contain Ni, Mn, Si and Cu
• High Ni steels: more Ni, Mn and Si in the precipitates
• Late blooming phases?
• Accelerated embrittlement!?
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• What are the characteristics of the precipitates?
• How do they evolve? • Do we have “late blooming precipitates”,
i. e. an acceleration in embrittlement? • What does the accelerated irradiation tell us
about the actual, low flux, RPV?
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Materials
Name Fluence (1023 n/m2)
Flux (1016 n/(m2s))
Reference 0 - H2.0 2.0 2.31 H6.4 6.4 3.81 S4.6 4.6 0.15
Still high flux compared to actual RPV
Corresponding approx. years in reactor
0 ~20 ~60 ~45
Atom probe tomography
X, Y
X, Y
Field Evaporation
Position Sensitive Detector
3D Reconstruction
+DC
ToF-MS
Atom Probe Tomography Experimental
• Detection efficiency 37% • Typical analyzed volume:
50x50x200 nm3 • Parameters:
- Voltage 20% pulse fraction, 50 K, 200 kHz - Laser 0.3 nJ, 30 K, 200 kHz
• Specimen preparation: FIB/SEM
Photo from Chalmers homepage: https://www.chalmers.se/en/researchinfrastructure/CMAL/instruments/APT/Pages/default.aspx
Results: Clusters
H6.4 ~60 years
(nm)
Orange – Cu atoms
Green isoconcentration surfaces Ni+Mn+Si=8.2%
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Conclusions • Number density and size increase with fluence • No late blooming precipitates • Flux effects: Surveillance material have the same type of
clusters (but less Cu). • Larger clusters (-> larger contribution to embrittlement) • Lower number density (-> smaller contribution to embrittlement)
• The actual RPV...
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Future work
• APT of PIA (post irradiation annealed) material from Ringhals – Halden (collaboration with Magnus Boåsen, KTH)
• APT of samples exposed in the ICEWATER project
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Publications
• Lindgren, K., Stiller, K., Efsing, P., Thuvander, M. On the analysis of clustering in an irradiated low alloy reactor pressure vessel steel weld. Microscopy and Microanalysis, submitted
• Lindgren, K., Boåsen, M., Efsing, P., Stiller, K., Thuvander, M. Evolution of radiation induced precipitates in reactor pressure vessel steel welds (Tentative title). Writing in progress.
Licentiate seminar November 29th 10.00
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“It has long been an axiom of mine that the little things are infinitely the most important” Sherlock Holmes, A Case of Identity, Sir Arthur Conan Doyle
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