Numerical analysis of ECT signals for bulge and dent type defect on SG tube

초록

Electromagnetic numerical analysis of eddy current non-destructive testing signals for bulge and dent type defect on steam generator tube is presented. The bulge defect can be found near tube sheet and is mainly caused by explosive tube expansion. The dent defect can appear near tube support plate and is mainly caused by thermal expansion of the plate. The INCONEL600 tube which is adopted in Uljin-4 NPP in Korea is used as an analysis model. The bobbin probe is used for obtaining the impedance signals. For the numerical analysis the electromagnetic governing equation for eddy current problem is derived from Maxwell's equation, and by performing the finite element formulation 3-D finite element code with brick element is developed. For the interpretation of simulated results and comparison the numerical results with experimental ones, the numerically simulated signals are adjusted by using the ASME standard 100% through hole defect signal. To see the effect of the defect on the impedance signal, parametric case study is performed and the results are presented in this paper. Also the impedance signals of bulge and dent defect with additional volumetric defect is presented. The results in this paper can be helpful for the analysis and interpretation of the field impedance signals obtained during the examination of the steam generator in NPP.