Bobbin Eddy Current Signal Analysis of Alloy 600 TT Steam Generator Tube Scale Thickness Based on Electromagnetic Characteristics

A steam generator is the major component of a nuclear power plant and its integrity is crucial for the nuclear safety. Steam generator tube eddy current bobbin inspections are periodically performed for utility to detect tube degradation. Scaled deposits on the steam generator tubes cause the performance degradation problem and the thickness of the outer diameter tube surface can be measured using the low frequency absolute bobbin data. In this paper, a tube mock-up with the various thicknesses of the scaled deposit has been manufactured using the mixture of magnetite powder and adhesive material with the spraying method that can improve the density of scaled deposits. The experiment with this scaled deposit standard and the analysis results verify that scaled deposit thickness accumulated on the outer surface of steam generator tubes can be measured quantitatively using eddy current bobbin data.