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Laboratory Analysis of a Leaking Letdown Cooler from Oconee Unit 3

  • James HyresEmail author
  • Rocky Thompson
  • Jim Batton
Conference paper
Part of the The Minerals, Metals & Materials Series book series (MMMS)

Abstract

This paper covers the results of laboratory examinations performed on a leaking letdown cooler from Oconee Unit 3. The laboratory scope included dewatering, pressure testing, visual inspections, metallography, Vickers micro-hardness, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-Ray Diffraction (XRD), and Optical Emission Spectroscopy (OES). The laboratory examinations identified one tube containing a through-wall crack. The most likely cause of the crack appeared to be OD-initiated caustic stress corrosion cracking (SCC). The presence of heavy deposits on the tube OD surface and heat tinting on the primary and secondary flow seals indicated boiling occurred near the tight radius region of the bundle. Once boiling occurred, caustic-forming species such as calcium phosphate deposited and concentrated on the tube OD surface. The literature indicates as caustic concentrations approach ~20%, the conditions become favorable for caustic SCC to occur in austenitic stainless steels such as Type 316L.

Keywords

Letdown cooler Type 316L stainless steel tubing Intergranular stress corrosion cracking Caustic stress corrosion cracking 

References

  1. 1.
    C.R. Frye, Examination of Letdown Coolers A and B from Crystal River Unit 3, Babcock & Wilcox Report No. RDD:88:5105–01:01, 9 Oct 1987Google Scholar
  2. 2.
    C.R. Frye, Laboratory Comparison of Material from Two Failed Let Down Coolers. Babcock & Wilcox Report No. RDD:88:5178-01:02, 16 Oct 1987Google Scholar
  3. 3.
    R.B. Camper, A B&W Review of Graham Letdown Coolers. B&W No. 47-1170720-00, Jan 1998Google Scholar
  4. 4.
    BAW-1385, Water Chemistry Manual for 177FA Plants, Rev. 6, B&W Nuclear Technologies, Dec 1992Google Scholar
  5. 5.
    EPRI Report 1007820, Closed Cooling Water Chemistry Guideline—Revision 1, Apr 2004Google Scholar
  6. 6.
    R.B. Rebak, Industrial Experience on the Caustic Cracking of Stainless Steels and Nickel Alloys—A Review. UCRL-PROC-216072, Corrosion/2006, 11 Oct 2005Google Scholar
  7. 7.
    K.A. Esaklul (ed.), Handbook of Case Histories in Failure Analysis, vol. 2 (ASM International, 1993)Google Scholar
  8. 8.
    R.H. Jones, Stress Corrosion Cracking. (ASM International, 1992), pp. 102, 114, 352Google Scholar
  9. 9.
    T. Couvant, et al. Investigations on the Mechanisms of PWSCC of Strain Hardened Austenitic Stainless Steels, in Proceeds of the 13th International Conference on Environmental Degradation of Materials in Nuclear Power Systems (2007)Google Scholar
  10. 10.
    R. Thompson, Evaluation of ONS-3 Component Cooling System Water Chemistry, August 2015Google Scholar
  11. 11.
    ASM Handbook, Corrosion, vol. 13, 1987, p. 353Google Scholar
  12. 12.
    D.R. McIntyre, MTI Publication No. 27, Experience Survey—Stress Corrosion Cracking of Austenitic Stainless Steels in Water (1987)Google Scholar

Copyright information

© The Minerals, Metals & Materials Society 2019

Authors and Affiliations

  1. 1.BWX Technologies, Inc.LynchburgUSA
  2. 2.Duke EnergyCharlotteUSA
  3. 3.Duke Energy, Oconee Nuclear StationSenecaUSA

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