Eddy current tomography of deposits in steam generator

Eddy current testing (ECT) using coils is widely practised in in-service inspection of steam generators in nuclear power plants of pressurized water reactor type. In this paper, we consider the shape estimate problem of magnetic deposits given some ECT signals. The non-linearity and the ill-posedness of this inverse problem make it quite challenging. We focus on the axisymmetric case and build a PDE-based direct model with Dirichlet-to-Neumann boundary operators to describe the relationship between observed data and the inspected component. With this direct model, we propose an inverse algorithm of gradient descent shape optimization type involving a regularization technique by boundary differential operators. First numerical experiments are quite encouraging.