This paper presents experimental measurements and 3D finite element simulations of the In-Service Inspection (ISI) of ferromagnetic steam generator (SG) tubes covered by a sodium layer. The ISI of SG tubes is using remote field eddy current technique (RF-ECT) and detect defects located near or between tube support plates and SG tube. Large scale electromagnetic eddy current computations are performed using parallel simulations with up to 1024 CPUs on Fujitsu BX900 based on in-house developed/parallelized code 3D-RFECT. Validations of FEM simulations with experimental measurements for helical tubes are conducted for a large model of SG tubes support plate and three SG tubes attached to it.