Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions

Hannu Hänninen, Pertti Aaltonen, Anssi Brederholm, Ulla Ehrnstén, Hans Gripenberg, Aki Toivonen, Pitkänen Jorma, Iikka Virkkunen

Research output: Book/ReportReportProfessional

10 Citations (Scopus)

Abstract

The operating experience of major nuclear power plant (NPP) pressure boundary components has recently shown that dissimilar metal weld joints can jeopardize the plant availability and safety because of increased incidences of environment-assisted cracking (EAC, PWSCC) of Alloy 600 and corresponding weld metals (Alloys 182/82). Alloy 690 and associated weld metals (Alloys 152/52) are widely used for repair and replacement of the affected thick-section components. The selection of new materials relies mainly on excellent laboratory results and short-term service experience. The long-term behavior of these materials and their performance in the plant has still to be demonstrated. Weldability of the studied nickel-base materials is evaluated based on the results obtained with weld metals of different chromium contents. The susceptibility to hot cracking is examined as well as the PWSCC susceptibility in the reactor primary water based on the metallurgical properties of the nickel-base alloys. The microstructure and microchemistry in the multi-pass nickel-base alloy welds is very different than in the wrought and recrystallized nickel-base materials. Additionally, the thermal ageing experience of various nickel-base weld metals is discussed. Weld residual stresses and their role in PWSCC as well as surface stress improvement techniques for PWSCC mitigation are also reviewed. Finally the application, improvements and qualification of NDE for nickel-base weld locations are evaluated concerning the probes, techniques and scanning devices. The need for representative mock-ups for technique development and qualification is discussed. The technical basis for development of inspection requirements for dissimilar metal welds and efforts to qualify inspection procedures and personnel are also emphasized. Maintaining the structural integrity of the NPP and oil refinery main components throughout the service life in spite of the several possible ageing mechanisms related to the dissimilar metal welds is essential for plant safety and availability.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages212
ISBN (Electronic)951-38-6806-0
ISBN (Print)951-38-6805-2
Publication statusPublished - 2006
MoE publication typeNot Eligible

Publication series

NameVTT Tiedotteita - Research Notes
PublisherVTT
No.2347
ISSN (Print)1235-0605
ISSN (Electronic)1455-0865

Fingerprint

Dissimilar metals
Nuclear power plants
Welds
Nickel
Metals
Inspection
Oils
Availability
Mockups
Thermal aging
Weldability
Structural integrity
Service life
Residual stresses
Chromium
Repair
Aging of materials
Personnel
Scanning

Keywords

  • nuclear power plants
  • refineries
  • steel structures
  • welded joints
  • dissimilar metals
  • welding
  • Ni-base alloys
  • residual stress
  • environment-assisted cracking
  • hot cracking
  • non-destructive testing

Cite this

Hänninen, H., Aaltonen, P., Brederholm, A., Ehrnstén, U., Gripenberg, H., Toivonen, A., ... Virkkunen, I. (2006). Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Meddelanden - Research Notes, No. 2347
Hänninen, Hannu ; Aaltonen, Pertti ; Brederholm, Anssi ; Ehrnstén, Ulla ; Gripenberg, Hans ; Toivonen, Aki ; Jorma, Pitkänen ; Virkkunen, Iikka. / Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions. Espoo : VTT Technical Research Centre of Finland, 2006. 212 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2347).
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Hänninen, H, Aaltonen, P, Brederholm, A, Ehrnstén, U, Gripenberg, H, Toivonen, A, Jorma, P & Virkkunen, I 2006, Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions. VTT Tiedotteita - Meddelanden - Research Notes, no. 2347, VTT Technical Research Centre of Finland, Espoo.

Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions. / Hänninen, Hannu; Aaltonen, Pertti; Brederholm, Anssi; Ehrnstén, Ulla; Gripenberg, Hans; Toivonen, Aki; Jorma, Pitkänen; Virkkunen, Iikka.

Espoo : VTT Technical Research Centre of Finland, 2006. 212 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2347).

Research output: Book/ReportReportProfessional

TY - BOOK

T1 - Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions

AU - Hänninen, Hannu

AU - Aaltonen, Pertti

AU - Brederholm, Anssi

AU - Ehrnstén, Ulla

AU - Gripenberg, Hans

AU - Toivonen, Aki

AU - Jorma, Pitkänen

AU - Virkkunen, Iikka

N1 - Project code: 631

PY - 2006

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N2 - The operating experience of major nuclear power plant (NPP) pressure boundary components has recently shown that dissimilar metal weld joints can jeopardize the plant availability and safety because of increased incidences of environment-assisted cracking (EAC, PWSCC) of Alloy 600 and corresponding weld metals (Alloys 182/82). Alloy 690 and associated weld metals (Alloys 152/52) are widely used for repair and replacement of the affected thick-section components. The selection of new materials relies mainly on excellent laboratory results and short-term service experience. The long-term behavior of these materials and their performance in the plant has still to be demonstrated. Weldability of the studied nickel-base materials is evaluated based on the results obtained with weld metals of different chromium contents. The susceptibility to hot cracking is examined as well as the PWSCC susceptibility in the reactor primary water based on the metallurgical properties of the nickel-base alloys. The microstructure and microchemistry in the multi-pass nickel-base alloy welds is very different than in the wrought and recrystallized nickel-base materials. Additionally, the thermal ageing experience of various nickel-base weld metals is discussed. Weld residual stresses and their role in PWSCC as well as surface stress improvement techniques for PWSCC mitigation are also reviewed. Finally the application, improvements and qualification of NDE for nickel-base weld locations are evaluated concerning the probes, techniques and scanning devices. The need for representative mock-ups for technique development and qualification is discussed. The technical basis for development of inspection requirements for dissimilar metal welds and efforts to qualify inspection procedures and personnel are also emphasized. Maintaining the structural integrity of the NPP and oil refinery main components throughout the service life in spite of the several possible ageing mechanisms related to the dissimilar metal welds is essential for plant safety and availability.

AB - The operating experience of major nuclear power plant (NPP) pressure boundary components has recently shown that dissimilar metal weld joints can jeopardize the plant availability and safety because of increased incidences of environment-assisted cracking (EAC, PWSCC) of Alloy 600 and corresponding weld metals (Alloys 182/82). Alloy 690 and associated weld metals (Alloys 152/52) are widely used for repair and replacement of the affected thick-section components. The selection of new materials relies mainly on excellent laboratory results and short-term service experience. The long-term behavior of these materials and their performance in the plant has still to be demonstrated. Weldability of the studied nickel-base materials is evaluated based on the results obtained with weld metals of different chromium contents. The susceptibility to hot cracking is examined as well as the PWSCC susceptibility in the reactor primary water based on the metallurgical properties of the nickel-base alloys. The microstructure and microchemistry in the multi-pass nickel-base alloy welds is very different than in the wrought and recrystallized nickel-base materials. Additionally, the thermal ageing experience of various nickel-base weld metals is discussed. Weld residual stresses and their role in PWSCC as well as surface stress improvement techniques for PWSCC mitigation are also reviewed. Finally the application, improvements and qualification of NDE for nickel-base weld locations are evaluated concerning the probes, techniques and scanning devices. The need for representative mock-ups for technique development and qualification is discussed. The technical basis for development of inspection requirements for dissimilar metal welds and efforts to qualify inspection procedures and personnel are also emphasized. Maintaining the structural integrity of the NPP and oil refinery main components throughout the service life in spite of the several possible ageing mechanisms related to the dissimilar metal welds is essential for plant safety and availability.

KW - nuclear power plants

KW - refineries

KW - steel structures

KW - welded joints

KW - dissimilar metals

KW - welding

KW - Ni-base alloys

KW - residual stress

KW - environment-assisted cracking

KW - hot cracking

KW - non-destructive testing

M3 - Report

SN - 951-38-6805-2

T3 - VTT Tiedotteita - Research Notes

BT - Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Hänninen H, Aaltonen P, Brederholm A, Ehrnstén U, Gripenberg H, Toivonen A et al. Dissimilar metal weld joints and their performance in nuclear power plant and oil refinery conditions. Espoo: VTT Technical Research Centre of Finland, 2006. 212 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2347).