ML22301A172

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Inspector Training on Corrosion Under Insulation
ML22301A172
Person / Time
Issue date: 10/13/2022
From: Nik Floyd, Kenneth Kolaczyk
NRC/RGN-I/DORS, NRC/NRR/DRO/IRAB
To:
References
Download: ML22301A172 (23)
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Inspector Training on Corrosion Under Insulation NRC Weekly Knowledge Management Presented by Nik Floyd, RI/DORS/EB1 October 13, 2022

Disclaimer This training session is being recorded for future use in the NRCs knowledge management program. The recorded contents of the session, including any questions posted by audience members, will be preserved in accordance with the NRCs record management program and are subject to FOIA disclosure. Please refrain from including any sensitive information (i.e., SUNSI) in any questions that you may ask.

Please leave your chat box open to view all questions and answers posed during the session.

Overview

  • Background
  • Contributors and effects
  • Operating experience
  • How to Spot Corrosion Under Insulation
  • Limitations
  • Inspector best practices
  • Scoping in Licensee Programs
  • Applicable NRC requirements
  • Standards for renewed operating licenses
  • Plant procedures

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Background===

What is corrosion under insulation?

  • The external corrosion of a metal component where the corrosion is either masked and/or exacerbated by the insulation.
  • Most issues have been observed to occur on uncoated carbon steel.

Jacketing Insulation Metal Component

Background - Cause Cause: Moisture intrusion and contact with the exterior surface of the component over time.

Contributors Effects

  • Coated vs uncoated
  • General corrosion
  • Insulation configuration
  • Pitting corrosion
  • Insulation material
  • Environmental conditions
  • Rupture o Indoor versus Outdoor o Marine environment o Operating temperature

Background - Operating Experience

  • Salem Unit 1 (2017, ML18039A899) - Degraded containment liner.
  • Clinton (2016, ML16130A710) - Degraded structural support for control room ventilation.
  • Waterford Unit 3 (2009, OE28818) - Pitting on condensate make-up water piping to wet cooling tower.

Background - Operating Experience Salem Unit 1 Diablo Canyon Unit 2

How to Spot Corrosion Under Insulation Quiz: Can you tell the condition of the component underneath?

How to Spot Corrosion Under Insulation Limitations

  • In most cases, you CANNOT conclude there is corrosion under insulation until a through-wall leak develops.
  • However, there are some indirect visual indications that you may use:

Debris and deposits Discoloration and staining Displacement

How to Spot Corrosion Under Insulation Staining Damaged and Displaced Caution These are indirect visual indications only. The insulation must be removed to confirm. The requirements for removal vary.

How to Spot Corrosion Under Insulation Staining Deposits Deposits and Discoloration Caution These are indirect visual indications only. The insulation must be removed to confirm. The requirements for removal vary.

How to Spot Corrosion Under Insulation This is one component from the previous slide.

Conclusion:

The licensee discovered corrosion and a small, through-wall leak after the insulation was removed.

Leakage was evident from the seam of the insulation and on the floor below.

How to Spot Corrosion Under Insulation Inspector Best Practices

  • Check for debris on and around the component. This could be corrosion products or displaced insulation.
  • Check the surrounding area for evidence of leakage, including the floor, equipment surfaces, and other areas where leakage may be channeled. This could be in the form of deposits or staining.
  • Check for longstanding moisture from above that may cause a wetting and re-wetting cycle of the insulation surrounding uncoated piping.
  • Check for loose fitting insulation (visual, non-intrusive check only).

How to Spot Corrosion Under Insulation Inspector Best Practices Contd

  • Consider the operating environment and insulation configuration. For example:
  • Water source (condensation, rain, etc.) and open pathway.
  • Corrosion on the adjacent, non-insulated portion of the component.
  • Consider digging into the design and licensing basis for the plant with respect to what piping systems are insulated and why.
  • Keep your eyes open for opportunity underneath (perhaps sections of insulation removed to support maintenance activities or plant mods)

Scoping in Licensee Programs Applicable NRC Requirements

  • ASME BPV Section XI IWA-5000, System Pressure Tests
  • Class 1 - No hold time.
  • Class 2/3 - No hold time required if the system has been in operation for:
  • > 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (insulated components)
  • > 10 min (non-insulated components)
  • When examining insulated components, the examination of the surrounding area for evidence of leakage shall be required.
  • For borated systems, insulation shall be removed from pressure retaining bolted connections for VT-2* visual examination.
  • VT-2: Detect evidence of leakage

Scoping in Licensee Programs Standards for Renewed Operating Licenses

  • Generic Aging Lessons Learned (GALL) Report
  • LR-ISG-2012-02, Interim Staff Guidance - Aging management of Internal Surfaces, Fire Water Systems, Atmospheric Storage Tanks, and Corrosion Under Insulation.
  • GALL Report AMPs XI.M29 and XI.M36 were revised to recommend periodic inspections during each 10-year period of the period of extended operation.
  • AMP XI.M29, Aboveground Metallic Tanks
  • AMP XI.M36, External Surfaces Monitoring of Mechanical Components
  • NRC Safety Evaluation Report
  • There may be plant-specific commitments to remove and inspect under insulation.
  • Verify what the NRC required at the time of license renewal, especially for those plants before 2012.

Scoping in Licensee Programs Plant Procedures

  • Visual examination of piping to meet ASME Code requirements.
  • Self-imposed examinations from operating experience.

Reference Slides OpE Operating Experience

  • Issue: Licensee failed to appropriately screen relevant operating experience, received in 2009 and 2010, relating to corrosion of carbon steel piping under insulation.
  • Cause: Located in an outside environment susceptible to the general conditions of the maritime location.
  • CA: Permanently removed piping insulation from the affected piping.

OpE Operating Experience

  • Salem Unit 1 (2017, ML18039A899) - Degraded containment liner
  • Issue: Licensee failed to identify and correct a non-conformance with the Unit 1 containment thermal insulation system.
  • Cause: Configuration did not provide a watertight seal between the containment liner and the insulation cover, and as a result, periodic service water leakage seeped behind the insulation and caused corrosion of the containment liner.
  • CA: Modified top of the insulation panels to prevent water intrusion.

OpE Operating Experience

  • Clinton (2016, ML16130A710) - Degraded structural support for control room ventilation
  • Issue: Licensee failed to identify that a structural support associated with control room ventilation B was degraded to the point it no longer conformed to the seismic analysis.
  • Cause: Condensation and configuration of insulation allowed moisture contact and corrosion of the supports.
  • CA: Re-apply a coating to the supports as well as research and install insulation that was more breathable to minimize moisture accumulation and preclude any further degradation.

OpE Operating Experience

  • Issue: Three gallon per hour through-wall leak was discovered during normal plant operation on outdoor cooling water piping for feedwater booster pumps.
  • Cause: Degradation of aluminum jacketing allowed rainwater to enter the calcium silicate insulation (insulated for freeze protection). Construction specifications did not require coating insulated piping.
  • CA: All the piping was coated before insulation is reapplied. Isolation valves are being added to minimize the amount of common piping.

OpE Operating Experience

  • Waterford Unit 3 (2009, OE28818) - Pitting on condensate make-up water piping to wet cooling tower.
  • Issue: Discovered during routine inspection and painting of piping under insulation. Waterford Unit 3's external corrosion program systematically performs routine inspections and painting of piping under insulation.
  • CA: Expanded inspection scope under current plant program.
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