Plant aging Steam Generator Corrosion

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Discussion Overview

The discussion revolves around the aging effects and corrosion in steam generators and related components in boiling water reactors (BWRs). Participants explore the factors contributing to these issues, including material properties, environmental conditions, and system design aspects.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires about the susceptibility of steam generators to aging and corrosion, suggesting heat and humidity as potential factors.
  • Another participant emphasizes the importance of feedwater chemistry and the material of steam generator tubes, mentioning Inconel 600 and 690, and references stress corrosion cracking.
  • A participant corrects the initial claim about BWRs having steam generators, noting that BWRs generate steam directly in the vessel and mentioning the role of steam separators and dryers.
  • There is a question about the mechanics of pressure changes in the reactor during a steam line rupture, with a participant expressing confusion about the expected outcomes.
  • A later reply clarifies that a main steam line break would lead to a loss of pressure due to inventory loss, and discusses the susceptibility of stainless steels and Inconels to various forms of stress corrosion cracking.

Areas of Agreement / Disagreement

Participants express differing views on the presence of steam generators in BWRs, with some clarifying that BWRs do not utilize steam generators while others initially suggest otherwise. The discussion includes multiple perspectives on the causes of corrosion and the implications of system design.

Contextual Notes

Participants mention various factors affecting corrosion, including material composition, microstructure, and environmental conditions, but do not resolve the complexities of these interactions or the specific implications for BWR safety and maintenance.

Who May Find This Useful

Individuals interested in nuclear engineering, specifically in the maintenance and safety aspects of boiling water reactors and the effects of aging on reactor components.

koab1mjr
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Hi

I am told that steam generator is an area that is suseptible to aging effects and corrosion. I was wondering if anyone can elaborate on this a bit. Is it just due to the heat and humididty? I am studying BWRs and safety and maintanced aspects and I was thinking of focusing on this area of plant.

Thanks
 
Last edited:
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koab1mjr said:
I am told that steam generator is an area that is suseptible to aging effects and corrosion. I was wondering if anyone can elaborate on this a bit. Is it just due to the heat and humididty?
No, the chemistry of the feedwater is critically important, as is the material of the SG tubes (e.g., Inconel 600 vs. 690). The fabrication method (how the tubes are held in the tubesheet) may also play a role (through the stress in the joint). Google 'stress corrosion cracking'. Look on the NRC site under 'Alloy 600'.

I am studying BWRs and safety and maintanced aspects and I was thinking of focusing on this area of plant.
This doesn't make sense: BWRs do not have steam generators.
 
Thanks for the response. Sorry I misspoke the steam line. Forgot BWR make steam right in the vessel. Is it true that both require separation of water vs steam. Is that where the steam line comes in.

Lastly why would a rupture in the steam line cause pressure in the reactor to decrease i would figure the opposite would occur.

Anyway I am very new to this stuff so sorry if these questions seem obvious or whatever.

I will look up stress corrosion though
 
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Main Steam line break would cause loss of pressure because the system looses inventory.

The primary cooling system is more or less closed (excluding make up and leakage).

BWRs have steam separators and dryers that allow 'dry' steam (as dry at saturated conditions as possible without superheat) to pass to the high pressure turbine. The separators and dryers are stainless steel, which are subject to stress corrosion cracking.

Corrosion is a function of material composition (chemistry), microstructure (which is affected by fabrication processes), and environment (time, temperature, stress and water chemistry, and radation to some extent). There are nickel-bearing materials (Inconels) in some BWR components.

Stainless steels and Inconels are susceptible to Intergranular (IG) stress corrosion cracking (SCC), or Irradiation-Assisted (IA) SCC.
 

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