Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking

Pertti Aaltonen, Martin Bojinov, Mika Helin, Petri Kinnunen, Timo Laitinen, Erkki Muttilainen, Kari Mäkelä, Anneli Reinvall, Timo Saario, Aki Toivonen

Research output: Book/ReportReportProfessional

Abstract

The aim of this literature study has been to evaluate the level of understanding of the role of anionic impurities in environmentally assisted cracking (EAC) of iron- and nickel-based alloys in the coolant conditions of a boiling water reactor (BWR) - type nuclear power plant, mainly under normal water chemistry (NWC). The study has been motivated by a need to find the most relevant experimental approaches that can be applied when looking for correlations between crack growth rate and measurable electrochemical and chemical parameters. Special crack tip chemistry conditions are established, when trace amounts are present in the BWR coolant and become enriched within a crack. Anions may influence both the conductivity and the pH of the coolant within the crack. In addition, they may influence the composition, structure and properties of the oxide films formed on crack walls either directly via adsorption or incorporation or indirectly via the effect of changes in pH within the crack. Based on the proposed mechanisms for EAC, oxide films formed on crack wall surfaces are likely to play a key role in determing the crack growth rate of structural materials. The prediction of the influence of anionic impurities is thus likely to be facilitated by means of understanding their effect on the films on crack walls. One of the most promising approaches to experimentally clarify this influence is based on investigating the electrochemical behaviour of oxide films Fe- and Ni-based materials in high-temperature conditions simulating the special chemistry within a stress corrosion crack. Results from such studies should be compared and combined with ex situ analytical results obtained using modern electron microscopic techniques. In addition to crack growth, currently available electro-chemical techniques should also be applied to find out whether crack initiation can be explained and modelled on the basis of the electrochmical behaviour of oxide films.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages92
ISBN (Electronic)951-38-6052-3
ISBN (Print)951-38-6051-5
Publication statusPublished - 2002
MoE publication typeNot Eligible

Publication series

NameVTT Tiedotteita - Research Notes
PublisherVTT
No.2148
ISSN (Print)1235-0605
ISSN (Electronic)1455-0865

Fingerprint

Crack tips
Oxide films
Impurities
Cracks
Coolants
Crack propagation
Boiling water reactors
Nickel
Crack initiation
Nuclear power plants
Anions
Iron
Corrosion
Adsorption
Electrons
Water
Chemical analysis

Keywords

  • nuclear power plants
  • water chemistry
  • material properties
  • reliability
  • service life
  • management
  • environmentally assisted cracking
  • surface properties
  • oxide films
  • stress corrosion cracking

Cite this

Aaltonen, P., Bojinov, M., Helin, M., Kinnunen, P., Laitinen, T., Muttilainen, E., ... Toivonen, A. (2002). Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Research Notes, No. 2148
Aaltonen, Pertti ; Bojinov, Martin ; Helin, Mika ; Kinnunen, Petri ; Laitinen, Timo ; Muttilainen, Erkki ; Mäkelä, Kari ; Reinvall, Anneli ; Saario, Timo ; Toivonen, Aki. / Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking. Espoo : VTT Technical Research Centre of Finland, 2002. 92 p. (VTT Tiedotteita - Research Notes; No. 2148).
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Aaltonen, P, Bojinov, M, Helin, M, Kinnunen, P, Laitinen, T, Muttilainen, E, Mäkelä, K, Reinvall, A, Saario, T & Toivonen, A 2002, Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking. VTT Tiedotteita - Research Notes, no. 2148, VTT Technical Research Centre of Finland, Espoo.

Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking. / Aaltonen, Pertti; Bojinov, Martin; Helin, Mika; Kinnunen, Petri; Laitinen, Timo; Muttilainen, Erkki; Mäkelä, Kari; Reinvall, Anneli; Saario, Timo; Toivonen, Aki.

Espoo : VTT Technical Research Centre of Finland, 2002. 92 p. (VTT Tiedotteita - Research Notes; No. 2148).

Research output: Book/ReportReportProfessional

TY - BOOK

T1 - Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking

AU - Aaltonen, Pertti

AU - Bojinov, Martin

AU - Helin, Mika

AU - Kinnunen, Petri

AU - Laitinen, Timo

AU - Muttilainen, Erkki

AU - Mäkelä, Kari

AU - Reinvall, Anneli

AU - Saario, Timo

AU - Toivonen, Aki

N1 - Project code: V1SU00351

PY - 2002

Y1 - 2002

N2 - The aim of this literature study has been to evaluate the level of understanding of the role of anionic impurities in environmentally assisted cracking (EAC) of iron- and nickel-based alloys in the coolant conditions of a boiling water reactor (BWR) - type nuclear power plant, mainly under normal water chemistry (NWC). The study has been motivated by a need to find the most relevant experimental approaches that can be applied when looking for correlations between crack growth rate and measurable electrochemical and chemical parameters. Special crack tip chemistry conditions are established, when trace amounts are present in the BWR coolant and become enriched within a crack. Anions may influence both the conductivity and the pH of the coolant within the crack. In addition, they may influence the composition, structure and properties of the oxide films formed on crack walls either directly via adsorption or incorporation or indirectly via the effect of changes in pH within the crack. Based on the proposed mechanisms for EAC, oxide films formed on crack wall surfaces are likely to play a key role in determing the crack growth rate of structural materials. The prediction of the influence of anionic impurities is thus likely to be facilitated by means of understanding their effect on the films on crack walls. One of the most promising approaches to experimentally clarify this influence is based on investigating the electrochemical behaviour of oxide films Fe- and Ni-based materials in high-temperature conditions simulating the special chemistry within a stress corrosion crack. Results from such studies should be compared and combined with ex situ analytical results obtained using modern electron microscopic techniques. In addition to crack growth, currently available electro-chemical techniques should also be applied to find out whether crack initiation can be explained and modelled on the basis of the electrochmical behaviour of oxide films.

AB - The aim of this literature study has been to evaluate the level of understanding of the role of anionic impurities in environmentally assisted cracking (EAC) of iron- and nickel-based alloys in the coolant conditions of a boiling water reactor (BWR) - type nuclear power plant, mainly under normal water chemistry (NWC). The study has been motivated by a need to find the most relevant experimental approaches that can be applied when looking for correlations between crack growth rate and measurable electrochemical and chemical parameters. Special crack tip chemistry conditions are established, when trace amounts are present in the BWR coolant and become enriched within a crack. Anions may influence both the conductivity and the pH of the coolant within the crack. In addition, they may influence the composition, structure and properties of the oxide films formed on crack walls either directly via adsorption or incorporation or indirectly via the effect of changes in pH within the crack. Based on the proposed mechanisms for EAC, oxide films formed on crack wall surfaces are likely to play a key role in determing the crack growth rate of structural materials. The prediction of the influence of anionic impurities is thus likely to be facilitated by means of understanding their effect on the films on crack walls. One of the most promising approaches to experimentally clarify this influence is based on investigating the electrochemical behaviour of oxide films Fe- and Ni-based materials in high-temperature conditions simulating the special chemistry within a stress corrosion crack. Results from such studies should be compared and combined with ex situ analytical results obtained using modern electron microscopic techniques. In addition to crack growth, currently available electro-chemical techniques should also be applied to find out whether crack initiation can be explained and modelled on the basis of the electrochmical behaviour of oxide films.

KW - nuclear power plants

KW - water chemistry

KW - material properties

KW - reliability

KW - service life

KW - management

KW - environmentally assisted cracking

KW - surface properties

KW - oxide films

KW - stress corrosion cracking

M3 - Report

SN - 951-38-6051-5

T3 - VTT Tiedotteita - Research Notes

BT - Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Aaltonen P, Bojinov M, Helin M, Kinnunen P, Laitinen T, Muttilainen E et al. Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking. Espoo: VTT Technical Research Centre of Finland, 2002. 92 p. (VTT Tiedotteita - Research Notes; No. 2148).