Modelling the ECT of U-Bend Steam Generator Tubes by the Boundary Element Method

摘要

We are interested in modelling the eddy current testing of U-bend tubes in steam generators that are part of the second barrier containment of radioactive materials in nuclear pressurized water reactors. The bending may cause a variation in thickness and an ovalization of the tube, and sometimes produces a dent at the intrados of the U-bend. It also affects the movement of the probe that can be tilted and shifted. The detection and characterization of defects in this zone requires a signal analysis due to geometric distortions and thus their modelling. Numerical simulation of these phenomena is challenging as the method used must be sufficiently flexible to adjust to small geometric distortions and accurate enough for the digital noise does not disturb their low signal variations. As part of collaboration between CEA LIST and IRSN, that is the French public expert in nuclear and radiological risks, we used an integral formulation resolved by the boundary element method to simulate the effects of bending for eddy current testing. For this a specific adaptation of the integral model developed at CEA LIST has been introduced. We will present the model, this adaptation and the main results obtained of which some will be compared to experimental measurements carried out as part of this study.