Eddy current analysis round robin using the NRC steam generator mockup.
This paper discusses round-robin exercises to assess inspection reliability using the NRC steam generator (SG) mock-up at Argonne National Laboratory. The purpose of the round robins is to assess the current reliability of SG tubing inservice inspection, determine the probability of detection (POD) as function of flaw size or severity, and assess the capability for sizing of flaws. The mock-up contains hundreds of cracks and simulations of artifacts such as corrosion deposits and tube support plates that make detection and characterization of cracks more difficult in operating steam generators than in most laboratory situations. Eddy current signals from the laboratory-grown cracks used in the mock-up have been reviewed to ensure that they provide reasonable simulations of those obtained in the field. The mock-up contains 400 tube openings. Each tube contains nine 22.2-mm (7/8-in.) diameter, 30.5-cm (1-ft) long, Alloy 600 test sections. The flaws are located in the tube sheet near the roll transition zone (RTZ), in the tube support plate (TSP), and in the freespan. The flaws are primarily intergranular stress corrosion cracks (axial and circumferential, ID and OD). In addition to the simulated tube sheet and TSP the mock-up has simulated sludge and magnetite deposits. A validated multiparameter eddy current algorithm that provided a detailed isometric plot for every flaw was used to establish the reference state of defects in the mock-up. The detection results for the 11 teams were used to develop POD curves as a function of maximum depth, voltage and the parameter m{sub p}, for the various types of flaws. The 95% one-sided confidence limits (OSL), which include errors in maximum depth estimates, are presented along with the POD curves. For the second round robin a reconfigured mock-up is being used to evaluate the effectiveness of eddy current arrays.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 795043
- Report Number(s):
- ANL/ET/CP-106955
- Country of Publication:
- United States
- Language:
- English
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