Doel 3 & Tihange 2 - Some Peer-reviewed Scientific Papers & Reports

2. Findings in Doel 3 and Tihange 2

Figure 2.11: Estimation of the material susceptibility to hydrogen flaking as function of hydrogen and sulphur concentration in the steel. [23]

since these segregated zones are the last areas to solidify and to do the α to γ transition and therefore contain the largest concentration of impurities. Furthermore, the indications are found to be parallel to the RPV inner surface, a typical orientation for hydrogen flakes. [1, 14] However, some properties of the measured indications do not perfectly correspond to typical hydrogen flakes, i.e. the dimensions. Indeed, the average indication size corresponds to the typical dimensions for hydrogen flakes, 4 to 14 mm, as mentioned by Electrabel. [30] However, the largest indications measured, are more then 10 times larger than the typical hydrogen flake size, up to 179.0 mm for Doel 3 and 154.5 mm for Tihange 2. As mentioned before, it has to be noted that the detection parameters for the MIS-B machine in 2014 are set to measure a conservative size for the indications. However, even during the inspections in 2012, indications up to 67.9 mm for Doel 3 and 38.0 mm for Tihange 2 are measured. These oversized indications may indicate a possibility of growing hydrogen flakes on a long time scale.

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