This paper presents 3D finite element simulations of the In-Service Inspection of ferromagnetic steam generator tubes of Fast Breeder Reactors. 3D FEM models, resulting in large scale electromagnetic eddy current computations with up to 5,100,000 2nd order tetrahedrons are analyzed using parallel simulations with 1024 CPUs on Fujitsu BX900 and using an in-house developed 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 at various frequencies. ISI of SG tubes using ECT and detection of defects for large SP models are validated trough 3D FEM simulations.