FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

- 182 -
tube, say 0.5-1.0 metre, so in practice only a few percent of the total PT
volume was inspected for hydride blisters. In contrast, CIGAR inspects
nominally 100% of the PT in a similar period of time. The eddy current gap
operation will be described elsewhere in this conference/6/.
3.3 Problems with CIGARette
After the expected teething problems, CIGARette worked pretty well. A total of
66 PTs were inspected in Pickering 1 and 2, of which about one third showed
reflectors. A further six PTs were inspected in Pickering unit 3. Some of the
problem areas that had to be resolved are discussed below.
Drive Rods/Connectors
The drive rods were loaded by operators working in plastics on the FM
bridge. First, they had to be clean so no slippage occurred in CIGARette's
friction drive. Second, they had to be connected slowly so that the connecting
pins would engage without damage. The connecting pins between the drive rods
and end/head connectors were occasionally damaged during loading. Since about
100 pins are used in each drive rod/head assembly, a critical shortage of
these components arose. Occasionally an inspection had to be performed with a
probe not functioning.
End Connectors
This was a major problem in the early stages with individual wires in the
catinery cable becoming tangled in the pulleys and being cut. Also, the
oscillating rotational scan pattern of the ultrasonic inspection fatigued the
cables at a sharp bend where they came out of the end connector. These
problems were solved by 1) binding the loose wires with tape, and 2) by using
a strain relief spring on the end of the connector.
Rotational Slippage
After only a few inspections it was recognized that progressive rotational
slippage between the drive rod and friction drive (containing the position
readout) could occur. This had serious implications for the ultrasonic
inspection. Blisters were expected only about the 6 o'clock position and a
rotation scan of only 45° was performed about this position. Unrecognized
slippage of only 30° would put the inspection out of the range of the
potential defects. The problem was solved by putting mercury switches in the
end connectors to trigger at the 6 o'clock position to indicate if slippage
occurred.
Operator Comfort
Since CIGARette inspections centre round the operator, fatigue was a potential
problem. The first inspection was done inside the vault in plastic suits, at
great effort. Later, containment penetrations were made, and cabins
constructed, which greatly improved operator conditions.