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Phenomenology of Hydrogen Flaking in Nuclear Reactor Pressure Vessels*

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Veröffentlicht/Copyright: 28. September 2014
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Materials Testing
Aus der Zeitschrift Materials Testing Band 56 Heft 6

Abstract

Recently, the problem of hydrogen flaking resurfaced, when internal defects were detected in the reactor pressure vessels of two Belgian nuclear power plants. These defects turned out to be hydrogen flakes formed during the fabrication of these pressure vessels. The goal of this publication is to provide important insights into the phenomenon of hydrogen flaking, the different parameters that play a role in the mechanism, as well as the typical morphology and location of these flakes. Therefore an extensive literature study was combined with a detailed metallurgical characterization of a significant number of flakes. Hydrogen flaking is a fabrication problem, which is strongly linked with segregation phenomena. A combination of a sufficient amount of hydrogen, stresses and a sensitive microstructure causes hydrogen flaking. For these reasons hydrogen flakes inside large reactor pressure vessels are found in the so-called ghost lines, which originate from segregation processes during casting.

Kurzfassung

Kürzlich ist das Thema der Wasserstoff-Flockenbildung wieder aufgetreten als interne Defekte in den Reaktordruckgefäßen von zwei belgischen Atomkraftanlagen entdeckt wurden. Es stellte sich heraus, dass es sich bei diesen Defekten um Wasserstoff-Flocken handelte, die sich während der Fertigung dieser Druckgefäße gebildet hatten. Das Ziel des vorliegenden Beitrages ist es, wichtige Erkenntnisse über das Phänomen der Wasserstoff-Flockenbildung zur Verfügung zu stellen, wie auch die verschiedenen Parameter, die für den Mechanismus von Bedeutung sind sowie die typische Morphologie und die Stelle dieser Flocken anzugeben. Aus diesen Gründen wurde eine extensive Literaturrecherche mit der detaillierten metallurgischen Charakterisierung einer signifikanten Flockenanzahl kombiniert. Bei der Wasserstoff-Flockenbildung handelt es sich um einen Fabrikationsfehler, der eng mit Segregationsphänomenen zusammen hängt. Eine Kombination einer ausreichenden Wasserstoffkonzentration, Spannungen und ein sensitives Gefüge verursachen die Flockenbildung. Daher werden Wasserstoff-Flocken in großen Reaktordruckgefäßen innerhalb sogenannter Ghostlines angetroffen, die von Segregationsprozessen während des Gießens herrühren.

Keywords: Materials testing; hydrogen flaking; reactor pressure vessels; segregation; ghost lines
**Correspondence Address, Dr. Ir. Evy De Bruycker, Laborelec, Rodestraat 125, B1630 Linkebeek, Belgium, E-mail:

Evy De Bruycker studied chemical engineering, followed by a PhD in materials science (2005) at Ghent University. She has been working at Laborelec (GDF Suez), a technical competence centre in electrical power and energy technology in Linkebeek, Belgium, since 2006 as materials expert. Her main areas of expertise are metallography, root cause analysis, hydrogen induced cracking, creep testing, materials for ultra super critical power plants, and superalloys.

Séverine De Vroey graduated as civil engineer in materials science (Université Catholique de Louvain, Belgium) in 2007. She joined Laborelec the same year as materials expert. Her main areas of expertise are metallography, fractography, root cause analysis, corrosion testing, and metallic materials. Her main activity domains are related to nuclear power plants and carbon capture applications.

Staf Huysmans studied electro-mechanical engineering (1977), followed by a PhD in management (KUL) and welding engineering (BWI). From 1978 to 2003 he was employed by Fabricom as head of a materials & welding department. He has been working at Laborelec since 2004 as a senior expert in materials technology. His main areas of expertise are root cause analysis, advanced repair and refurbishment, candidate materials for future power plants, and high temperature components.

Jacqueline Stubbe received a degree in chemical engineering from the University of Brussels, Belgium in 1971. She joined Laborelec the same year, where she developed a broad expertise in materials for electrical industry, with a focus on steels for high temperature and for nuclear applications. She held different positions of management in Laborelec and in the headquarters of GDF Suez before coming back to Laborelec as a mentor for metallurgical expertise.

  1. *

    Extended Version of the Contribution to the VDI Annual Failure Analysis Conference

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Published Online: 2014-09-28
Published in Print: 2014-06-01

© 2014, Carl Hanser Verlag, München

Artikel in diesem Heft

  1. Inhalt/Contents
  2. Inhalt
  3. Fachbeiträge/Technical Contributions
  4. Phenomenology of Hydrogen Flaking in Nuclear Reactor Pressure Vessels*
  5. Spannungsmessung an Gashochdruckleitungen*
  6. Failures Caused by Hydrogen Absorption during Heat Treatment Processes*
  7. Microstructure and Compressive Properties of Open-Cell Silver Foams with Different Pore Architectures
  8. Production and Performance of Al-Ti-C Grain Refiners with Addition of K2TiF6 and Elemental Carbon
  9. Effect and Optimization of Resistance Spot Welding Parameters on the Strength of Welded Hot-Stamped Parts
  10. Investigation of Mechanical Properties and Impact Strength Depending on the Number of Fiber Layers in Glass Fiber- reinforced Polyester Matrix Composite Materials
  11. High Pressure Sintering of Al2O3-CNT Nanocomposites
  12. Mechanical Properties of Boron-Treated Ferritic GGG40.3 Ductile Cast Iron
  13. Investigation of the Structural, Mechanical and Electrical Properties of Cu-Al-Zn Shape Memory Alloys
  14. Scattering, Tracking and Seeding Characteristics of TiO2 using Particle Image Velocimetry in Supersonic Flows
  15. Effect of Depreciation Expenses on Profitability of Mineral Processing Plants
  16. Vorschau/Preview
  17. Vorschau
https://doi.org/10.3139/120.110580
Schlagwörter für diesen Artikel
Materials testing; hydrogen flaking; reactor pressure vessels; segregation; ghost lines

Artikel in diesem Heft

  1. Inhalt/Contents
  2. Inhalt
  3. Fachbeiträge/Technical Contributions
  4. Phenomenology of Hydrogen Flaking in Nuclear Reactor Pressure Vessels*
  5. Spannungsmessung an Gashochdruckleitungen*
  6. Failures Caused by Hydrogen Absorption during Heat Treatment Processes*
  7. Microstructure and Compressive Properties of Open-Cell Silver Foams with Different Pore Architectures
  8. Production and Performance of Al-Ti-C Grain Refiners with Addition of K2TiF6 and Elemental Carbon
  9. Effect and Optimization of Resistance Spot Welding Parameters on the Strength of Welded Hot-Stamped Parts
  10. Investigation of Mechanical Properties and Impact Strength Depending on the Number of Fiber Layers in Glass Fiber- reinforced Polyester Matrix Composite Materials
  11. High Pressure Sintering of Al2O3-CNT Nanocomposites
  12. Mechanical Properties of Boron-Treated Ferritic GGG40.3 Ductile Cast Iron
  13. Investigation of the Structural, Mechanical and Electrical Properties of Cu-Al-Zn Shape Memory Alloys
  14. Scattering, Tracking and Seeding Characteristics of TiO2 using Particle Image Velocimetry in Supersonic Flows
  15. Effect of Depreciation Expenses on Profitability of Mineral Processing Plants
  16. Vorschau/Preview
  17. Vorschau
Heruntergeladen am 10.4.2026 von https://www.degruyterbrill.com/document/doi/10.3139/120.110580/html
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