Transmit-receive eddy current probes for defect detection and sizing in steam generator tubes
- Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)
Inspection of steam generator tubes in aging Nuclear Generating Stations is increasingly important. Defect detection and sizing, especially in defect prone areas such as the tubesheet, support plates and U-bend regions, are required to assess the fitness-for-service of the steam generators. Information about defect morphology is required to address operational integrity issues, i.e., risk of tube rupture, number of tubes at risk, consequential leakage. A major challenge continues to be the detection and sizing of circumferential cracks. Utilities around the world have experienced this type of tube failure. Conventional in-service inspection, performed with eddy current bobbin probes, is ineffectual in detecting circumferential cracks in tubing. It has been demonstrated in CANDU steam generators, with deformation, magnetite and copper deposits that multi-channel probes with transmit-receive eddy current coils are superior to those using surface impedance coils. Transmit-receive probes have strong directional properties, permitting probe optimization according to crack orientation. They are less sensitive to lift-off noise and magnetite deposits and possess good discrimination to internal defects. A single pass C3 array transmit-receive probe developed by AECL can detect and size circumferential stress corrosion cracks as shallow as 40% through-wall. Since its first trial in 1992, it has been used routinely for steam generator in-service inspection of four CANDU plants, preventing unscheduled shutdowns due to leaking steam generator tubes. More recently, a need has surfaced for simultaneous detection of both circumferential and axial cracks. The C5 probe was designed to address this concern. It combines transmit-receive array probe technology for equal sensitivity to axial and circumferential cracks with a bobbin probe for historical reference. This paper will discuss the operating principles of transmit-receive probes, along with inspection results.
- Research Organization:
- CH2M Hill, Gainesville, FL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
- OSTI ID:
- 467901
- Report Number(s):
- NUREG/CP-0154; ANL-96/14; NEA/CNRA/R-(96)1; CONF-9510423-; ON: TI97004312; TRN: 97:008367
- Resource Relation:
- Conference: CNRA/CSNI workshop on steam generator tube integrity in nuclear power plants, Oak Brook, IL (United States), 30 Oct - 2 Nov 1995; Other Information: PBD: Feb 1997; Related Information: Is Part Of Proceedings of the CNRA/CSNI workshop on steam generator tube integrity in nuclear power plants; Diercks, D.R. [Argonne National Lab., IL (United States)]; PB: 621 p.
- Country of Publication:
- United States
- Language:
- English
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