RD&D-Programme 2004 - SKB

One of SKI’s comments on RD&D 2001 was that coherent documentation of results and experience
obtained from nondestructive testing was lacking. A report presenting results up to and
including 2002 has been compiled /5-10/.
Efforts have been aimed at gathering knowledge and evaluating the potential of these methods.
An important goal is to determine the reliability of the NDT methods. Efforts have been
concentrated on the most critical and largest objects.
Nodular iron inserts
The outer parts of the insert are ultrasonically tested by the suppliers. The testing is carried out
in two stages with different probes designed for this purpose. Through-transmission ultrasonic
testing has been used to test the cast material between the channel tubes. The first tests show
that there are good prospects for developing the method. Figure 5-13 shows the results of a test
performed with this method. The figure is based on the signal obtained from through-transmission
testing through all channel positions at a given length position. The signal has then been
compiled for the six tests and a mean value has been calculated. This gives a picture over the
entire cross-section through this position on the insert. The figure clearly shows that an area
around 270 centimetres from the bottom of the insert had indications of defects between the
channels. On closer examination it turned out that there really was a defect within this area.
Figure 5-14 shows the area when the insert has been cut up about 270 centimetres from the
bottom.
The results of the tests indicate that there are good prospects for detecting defects in different
parts of the insert. It also proved to be possible to detect the areas for the spacer plates with poor
bonding between the plate and the nodular iron.
100.0
Through-transmission testing
Mean value of transmitted signal in %
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
10
30
50
70
0.0
90
110
130
150
170
190
Length of insert (cm)
210
230
250
270
290
310
330
350
370
390
410
430
450
Figure 5-13. Mean value of transmitted signal in percent for a given position.
RD&D-Programme 2004 61