Assessment of bearing pad fretting flaws in CANDU Zr-Nb pressure tubes
Conference
·
OSTI ID:403323
- Ontario Hydro Technologies, Toronto, Ontario (Canada)
- Ontario Hydro Nuclear, Toronto, Ontario (Canada)
Flaws due to fretting of the fuel bundle bearing pads on the inside wall of the pressure tubes have been detected in some Ontario Hydro CANDU reactors. The major pressure tube structural integrity consideration with these flaws is delayed hydride cracking initiation. CANDU-specific fitness-for-service evaluation procedures have been developed to evaluate these flaws for pressure tube structural integrity. These procedures are described in this paper, along with an example assessment of actual inservice flaws. Experience to date with bearing pad fretting flaws has been favorable. Crack growth from a flaw has not been detected. Thus far, all bearing pad fretting flaws which have been evaluated have satisfied the acceptance criteria. The example assessment demonstrates that the most limiting factor in terms of reactor operation is the reactor Heatup/Cooldown cycles limit from the delayed hydride cracking initiation evaluation. However, the Heatup/Cooldown cycles limit has not necessitated removal of a pressure tube.
- OSTI ID:
- 403323
- Report Number(s):
- CONF-960706--; ISBN 0-7918-1782-2
- Country of Publication:
- United States
- Language:
- English
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