Critical Reflections about Doel3 & Tihange2

Integrity reactor vessels Doel 3 and Tihange 2

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3 Identification of the flaws in the reactor vessel

In 2012, flaws have been detected during an ultrasonic inspection. These flaws are located mainly in the lower core shell of the Doel3 reactor vessel. The number of flaws amounts 7205 ( [ 14 ] p32). The distribution in position with respect to the inner wall is presented in figure 3 (figure 4.7 in [ 14 ] p34) and the distribution in size is presented in figure 4 (figure 4.21 in [ 14 ] p55).

Figure 3: Distribution of the flaws with respect to the inner wall distance [ 14 ] p34.

Figure 5 (figure 4.6 on [ 14 ] p33) shows the distribution of the flaws in the lower core shell. The left side shows an actual cross-section measurement, the right side shows the flaws within a sector of 20 o . Figure 6 (figure 4.16 in [ 14 ] p47) presents an image of the flaws in the lower core shell for different sectors. The sectors between 200 o [ 14 ] p47 and 220 o exhibit a high flaw density. Figure 7 presents the distribution of the flaws around the circumference of the lower core shell, measured in 2012 and in 2014. The mean flaw density between the first 100 mm from the inner reactor surface amounts 2.1 / dm 3 and the maximum flaw density is 25.8 / dm 3 ( [ 15 ] p7). The mean flaw distance is 20.4 mm, the maximum distance is 565 mm ( [ 15 ] p7). The smallest flaw distance was not mentioned in these reports. In 2014, a new ultrasonic inspection has been performed. During this inspection, a higher number of flaws has been found, i.e. 11607 instead of 7205 in the lower inner shell. ( [ 16 ] p27). Also the reported flaws appear to be larger, the mean size found in the 2012 inspection was 9.6 × 7.6 mm, in 2014 16.0 × 12.7 mm and the largest flaws in 2012 67.9 × 38.4 mm, in 2014 179.0 × 72.3 mm ( [ 16 ] p29). In figure 8 (4.9 in [ 16 ] p28), the new distribution of the flaw distance to the inner vessel wall is presented and in figure 9 (4.11 in [ 16 ] p30) the distribution of the flaw size. In the reports

R.Boonen & J.Peirs

May 18, 2017