Development of coupling FEM-BEM method for steam generator inspection

In Japan, all steam generator tubings in PWR (Pressure Water Reactor) plants have to be inspected regularly using eddy current testing. The primary coolant circulates through thousands of tubes within the steam generator and transfers heat from the reactor core to the secondary coolant. These tubes, which are made of non-magnetic Inconel 600, are strengthened by support plate and tubesheet which are made of magnetic carbon steel. In order to make a simulation of inspection and furtherly to sizing flaw from inspection data in the tubesheet and support plate portion, a conventional FEM-BEM method which is applicable to non-magnetic substance is established to cope with magnetic material including problems. The conducting media are described by FEM, whereas the surrounding space is treated by BEM. The air/conductor interface conditions are ensured by the continuity of the tangential component of magnetic field intensity. A new mutual induction differential four-sensor probe is used and the ECT signals are ob...