0
research-article

The Effect of Alkali Metal and Alkaline Earth Metal Impurities on the Stress Corrosion Cracking of CANDU Fuel Sheathing

[+] Author and Article Information
G.A. Ferrier

Royal Military College of Canada, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4
graham.ferrier@rmc.ca

David Kerr

Queen's University, Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada, K7L 3N6
david.kerr@queensu.ca

Joseph Metzler

Royal Military College of Canada, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4
joseph.metzler@rmc.ca

Evan Veryard

Royal Military College of Canada, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4
evan.veryard@mail.mcgill.ca

M. Farahani

Royal Military College of Canada, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4
farahani-m@rmc.ca

P.K. Chan

Royal Military College of Canada, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4
paul.chan@rmc.ca

Mark R. Daymond

Queen's University, Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada, K7L 3N6
mark.daymond@queensu.ca

E.C. Corcoran

Royal Military College of Canada, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4
emily.corcoran@rmc.ca

1Corresponding author.

ASME doi:10.1115/1.4037115 History: Received March 31, 2016; Revised June 15, 2017

Abstract

During normal operation in CANDU® reactors, the Stress Corrosion Cracking (SCC) of fuel sheathing is mitigated effectively, in part, using a thin graphite-based coating known as CANLUB. Mechanisms typically proposed for the demonstrated SCC mitigation offered by CANLUB include lubrication and/or chemical interactions. An additional possibility, that was recently suggested, involves the sequestering of iodine through its interaction with alkali metal and/or alkaline earth metal impurities in the CANLUB coating. This possibility is supported by the systematic analysis and testing in this paper wherein three prevalent impurities (Na, Ca, and Mg) found in CANLUB were incorporated into SCC slotted ring experiments as metal oxides. When the molar concentration of metal oxide (Na2O, CaO, or MgO) matched or exceeded the molar concentration of iodine (6 mmol = 16 mg/cm3), Na2O and CaO protected the rings from corrosion whereas MgO enhanced their corrosion. When Zircaloy-4 sheathing is subjected to mechanical stress, high temperature, and high concentrations of iodine vapour, it is better protected by siloxane coatings than by graphite-CANLUB coatings. Consequently, since metal impurities (Na, Ca, and Mg) are found more abundantly in siloxane coatings than in graphite-CANLUB coatings, Zircaloy-4 slotted rings were coated with graphite-CANLUB containing Na, Ca, and/or Mg at those more abundant concentrations. Since these concentrations remain below 6 mmol, SCC test results suggest that the siloxane's superior adhesion is an essential first step in preventing corrosion induced by 6 mmol of iodine.

Copyright (c) 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In