FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

Problems with Eddy Current Systems
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These are described in more detail in/6/. The garter spring location system
coil went through several development stages before a satisfactory reliability
and signal-to-noise ratio was achieved. The gap measurement system, which had
been under development before the hydride blistering problem/4/, saw its first
active service during these inspections and required considerable procedural
modifications before satisfactory results were obtained.
Problems with Ultrasonics
The CIGAR heads and flaw detection (volumetric inspection) worked well,
largely because they had been tested extensively in the laboratory. The probes
lasted longer than expected in the reactor radiation fields. Most of the
problems involved failed connectors and radiation decay of cables. Problems
with standing signals were solved by modifying the ultrasonic modules.
We had some problems selecting a recording threshold since hydride blisters
were a new problem. This was solved in practice by using a 'grass-level plus 1
approach. Probe power checks were performed in each PT using a transmit—
receive method between opposite probes, then the gain increased till grass was
observed on the inside surface gate. All signals a certain level above grass
were noted.
Initially there were problems playing hack the data from the 14 channel analog
tape. Videotaping the flaw detector CRT was useful, but a composite print-out
was also required. Eventually the CIGAR computer play back system was modified
to provide an off line isometric playback facility. Figure 9 shows a typical
computer generated plot of a blistered area, produced from the composite data
of four shearwave probes.
The ultrasonic gauging system in CIGARette was not a great success. The
digital thickness gauges selected for this joh, could not be made to operate
in a stable manner with the long cables used. Consequently discrete
measurements were made on the CRT of the flaw detectors. This was very time
consuming and did not provide as high a precision as desired for gap
measurement correction.
4. CLOSING COMMENTS
The CIGAR system will be used for active channel pressure tube inspection in
1985. It will provide the capability to perform a wide range of inspections
on a number of tubes quickly, with minimal manrem expenditure and with
comprehensive data analysis and presentation either on-line or immediately
after the inspection. The CIGARette system that was improvised for the
Pickering 1 and 2 inspections filled the gap adequately and is now operating
well. CIGARette may he used for quick inspections and for special purposes
such as carrying video cameras. Many of the problems experienced with
CIGARette, such as those due to instrumentation cables and connectors, have
not been experienced with CIGAR due to the different delivery methods. From an
NDE viewpoint, the modular CIGAR head worked well, and in the future, one can
predict that new inspection modules will be developed and used for a variety
of different applications.