Surface breaking and subsurface manufacturing flaws have been detected by in-service ultrasonic examination in a number of CANDU reactor Zr-2.5Nb pressure tubes. The manufacturing flaws are oriented in the circumferential direction in the Zr-2.5Nb pressure tube, and are axially aligned along the pressure tube. Metallographic examination of these flaws in an ex-service Zr-2.5Nb pressure tube revealed a series of parallel circumferentially oriented discontinuous features oriented at an angle of nominally 40 degrees relative to the axial direction in the pressure tube. Since the surface breaking flaws are exposed to the reactor coolant, it was considered prudent to evaluate potential growth of the flaws by an oxide wedging crack growth mechanism. Oxide wedging crack growth is a slow crack growth mechanism that can occur when zirconium oxide forms on the crack faces due to a corrosion reaction with the reactor coolant. An oxide wedging crack growth model was developed to predict crack growth rates and future flaw sizes as a part of the fitness-for-service evaluation of a Zr-2.5Nb pressure tube containing this type of manufacturing flaw. The model was then applied to predict crack growth from manufacturing flaws that were detected in an operating pressure tube, and the evaluation results were used as part of the justification for continued operation.
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ASME 2016 Pressure Vessels and Piping Conference
July 17–21, 2016
Vancouver, British Columbia, Canada
Conference Sponsors:
- Pressure Vessels and Piping Division
ISBN:
978-0-7918-5042-8
PROCEEDINGS PAPER
Development and Application of Oxide Wedging Crack Growth Model for CANDU Zr-2.5Nb Pressure Tubes
Douglas A. Scarth
,
Douglas A. Scarth
Kinectrics, Inc., Toronto, ON, Canada
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Preeti Doddihal
,
Preeti Doddihal
Kinectrics, Inc., Toronto, ON, Canada
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Monique Ip
Monique Ip
Bruce Power, Toronto, ON, Canada
Search for other works by this author on:
Douglas A. Scarth
Kinectrics, Inc., Toronto, ON, Canada
Preeti Doddihal
Kinectrics, Inc., Toronto, ON, Canada
Monique Ip
Bruce Power, Toronto, ON, Canada
Paper No:
PVP2016-63987, V06AT06A035; 12 pages
Published Online:
December 1, 2016
Citation
Scarth, DA, Doddihal, P, & Ip, M. "Development and Application of Oxide Wedging Crack Growth Model for CANDU Zr-2.5Nb Pressure Tubes." Proceedings of the ASME 2016 Pressure Vessels and Piping Conference. Volume 6A: Materials and Fabrication. Vancouver, British Columbia, Canada. July 17–21, 2016. V06AT06A035. ASME. https://doi.org/10.1115/PVP2016-63987
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