In this paper, the ECT inversion strategy developed for cracks in a SG tube of a Nuclear Power Plant (NNP) is applied to the shape reconstruction of a natural Stress Corrosion Crack (SCC) in a coolant tube of the NNP. The reconstruction of cracks in the coolant tube is more difficult than the SG tube problem because of a large tube thickness. Two crack models, a planar EDM notch model and a planar notch one with contacting edge area are applied in the reconstruction. Comparing with the true crack profile, the model considering the crack closure gives a better result of reconstruction. The numerical results show that the proposed inverse method is capable to predict the profile of a natural SCC even for a tube of relative large thickness.
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