Analysis of Eddy Current Noise Signals in U-bend Tube using Finite Element Method

The size and shape of a steam generator heat pipe in a nuclear power plant varies based on the row number. Specifically, row 1, which is the innermost row in the steam generator, exhibits the smallest radius of curvature and U-bend shape. The steam generator heat pipe has a low thickness of approximately 1 mm. Hence, this can geometrically change the cross-sectional area owing to the residual stress accumulated during the manufacturing process of the curvature pipe. This change in cross-sectional shape causes the distortion of the pipe. Eddy current testing (ECT) is performed to ensure the integrity and safety of steam generators in nuclear power plants. If the cross-sectional shape of the curved section of the pipe changes, noise signals may be generated. Using the electromagnetic analysis method of COMSOL Multiphysics, a commercial program based on numerical analysis technology, it is possible to obtain various noise signals by simulating cross-sectional variations based on the curvature of the heat pipe. To increase the reliability of the data, actual inspection data and various types of noise signals obtained via simulation are compared and analyzed. This is expected to be useful for removing noise signals at the actual inspection site.