IGSCC in a BWR steam line after 30 years of operation

Ulla Ehrnstén, Juha-Matti Autio, Petra Holmström

Research output: Contribution to conferenceConference articleScientific

Abstract

Intergranular stress corrosion cracking was observed in a 406 x 8 mm stainless steel BWR steam pipe line after 30 years of operation. The material is Type 304 with a carbon content of 0.04%. The operating temperature is 170°C. The failure analysis showed that the material was sensitized, and that the cracking had occurred at a location where re-welding due to weld defect removal had been performed during the assembly of the pipe. The crack located at a distance of about 8 - 11 mm from the fusion line. The degree of sensitization, measured next to cracked region, showed clear sensitization, with a maximum Ir/Ia - value of 2.32%. Although IGSCC in sensitized stainless steel is a well-known phenomenon, this failure has characteristics worthwhile reporting, i.e., the failure occurred at a temperature, where low temperature sensitization is not effective, and the crack locates at a higher than typical distance from the fusion line, which is at least partly due to the thinner wall thickness compared to typical primary piping. Factors affecting crack initiation include at least the relatively few transients during especially start-up of the plant after annual outages, showing that although steady plant operation with few transients obviously are beneficial as reducing the risk for events, crack initiation can occur with time in components fulfilling the requirements for SCC, i.e. a susceptible material, an oxidizing environment and a high stress.
Original languageEnglish
Number of pages10
Publication statusPublished - 2015
MoE publication typeNot Eligible
Event17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015 - Ottawa, Canada
Duration: 9 Aug 201512 Aug 2015

Conference

Conference17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015
Abbreviated titleENVDEG 2015
CountryCanada
CityOttawa
Period9/08/1512/08/15

Fingerprint

Steam piping systems
Crack initiation
Fusion reactions
Stainless steel
Pipe
Cracks
Stress corrosion cracking
Outages
Temperature
Failure analysis
Welding
Welds
Steam
Defects
Carbon

Keywords

  • stainless steel
  • Type 304
  • failure
  • IGSCC
  • BWR

Cite this

Ehrnstén, U., Autio, J-M., & Holmström, P. (2015). IGSCC in a BWR steam line after 30 years of operation. Paper presented at 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015, Ottawa, Canada.
Ehrnstén, Ulla ; Autio, Juha-Matti ; Holmström, Petra. / IGSCC in a BWR steam line after 30 years of operation. Paper presented at 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015, Ottawa, Canada.10 p.
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abstract = "Intergranular stress corrosion cracking was observed in a 406 x 8 mm stainless steel BWR steam pipe line after 30 years of operation. The material is Type 304 with a carbon content of 0.04{\%}. The operating temperature is 170°C. The failure analysis showed that the material was sensitized, and that the cracking had occurred at a location where re-welding due to weld defect removal had been performed during the assembly of the pipe. The crack located at a distance of about 8 - 11 mm from the fusion line. The degree of sensitization, measured next to cracked region, showed clear sensitization, with a maximum Ir/Ia - value of 2.32{\%}. Although IGSCC in sensitized stainless steel is a well-known phenomenon, this failure has characteristics worthwhile reporting, i.e., the failure occurred at a temperature, where low temperature sensitization is not effective, and the crack locates at a higher than typical distance from the fusion line, which is at least partly due to the thinner wall thickness compared to typical primary piping. Factors affecting crack initiation include at least the relatively few transients during especially start-up of the plant after annual outages, showing that although steady plant operation with few transients obviously are beneficial as reducing the risk for events, crack initiation can occur with time in components fulfilling the requirements for SCC, i.e. a susceptible material, an oxidizing environment and a high stress.",
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Ehrnstén, U, Autio, J-M & Holmström, P 2015, 'IGSCC in a BWR steam line after 30 years of operation' Paper presented at 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015, Ottawa, Canada, 9/08/15 - 12/08/15, .

IGSCC in a BWR steam line after 30 years of operation. / Ehrnstén, Ulla; Autio, Juha-Matti; Holmström, Petra.

2015. Paper presented at 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015, Ottawa, Canada.

Research output: Contribution to conferenceConference articleScientific

TY - CONF

T1 - IGSCC in a BWR steam line after 30 years of operation

AU - Ehrnstén, Ulla

AU - Autio, Juha-Matti

AU - Holmström, Petra

N1 - Project code: 102621

PY - 2015

Y1 - 2015

N2 - Intergranular stress corrosion cracking was observed in a 406 x 8 mm stainless steel BWR steam pipe line after 30 years of operation. The material is Type 304 with a carbon content of 0.04%. The operating temperature is 170°C. The failure analysis showed that the material was sensitized, and that the cracking had occurred at a location where re-welding due to weld defect removal had been performed during the assembly of the pipe. The crack located at a distance of about 8 - 11 mm from the fusion line. The degree of sensitization, measured next to cracked region, showed clear sensitization, with a maximum Ir/Ia - value of 2.32%. Although IGSCC in sensitized stainless steel is a well-known phenomenon, this failure has characteristics worthwhile reporting, i.e., the failure occurred at a temperature, where low temperature sensitization is not effective, and the crack locates at a higher than typical distance from the fusion line, which is at least partly due to the thinner wall thickness compared to typical primary piping. Factors affecting crack initiation include at least the relatively few transients during especially start-up of the plant after annual outages, showing that although steady plant operation with few transients obviously are beneficial as reducing the risk for events, crack initiation can occur with time in components fulfilling the requirements for SCC, i.e. a susceptible material, an oxidizing environment and a high stress.

AB - Intergranular stress corrosion cracking was observed in a 406 x 8 mm stainless steel BWR steam pipe line after 30 years of operation. The material is Type 304 with a carbon content of 0.04%. The operating temperature is 170°C. The failure analysis showed that the material was sensitized, and that the cracking had occurred at a location where re-welding due to weld defect removal had been performed during the assembly of the pipe. The crack located at a distance of about 8 - 11 mm from the fusion line. The degree of sensitization, measured next to cracked region, showed clear sensitization, with a maximum Ir/Ia - value of 2.32%. Although IGSCC in sensitized stainless steel is a well-known phenomenon, this failure has characteristics worthwhile reporting, i.e., the failure occurred at a temperature, where low temperature sensitization is not effective, and the crack locates at a higher than typical distance from the fusion line, which is at least partly due to the thinner wall thickness compared to typical primary piping. Factors affecting crack initiation include at least the relatively few transients during especially start-up of the plant after annual outages, showing that although steady plant operation with few transients obviously are beneficial as reducing the risk for events, crack initiation can occur with time in components fulfilling the requirements for SCC, i.e. a susceptible material, an oxidizing environment and a high stress.

KW - stainless steel

KW - Type 304

KW - failure

KW - IGSCC

KW - BWR

M3 - Conference article

ER -

Ehrnstén U, Autio J-M, Holmström P. IGSCC in a BWR steam line after 30 years of operation. 2015. Paper presented at 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ENVDEG 2015, Ottawa, Canada.