Recent modelling advances in NDT to improve safety and sustainability for the next generation of nuclear reactor

In the frame of Generation 4 Nuclear Reactor developments, the French LMA Laboratory and the French CEA nuclear institute undertake a joint work for improving monitoring and inspection of future Sodium Fast Reactors.The goal is to properly test and monitor, with non-destructive acoustic methods, structures and materials at different scales (from micrometric to metric) and at different operating states (nominal, partial, shutdown, incidental or even accidental). Indeed, acoustic signatures can be recorded (reflected signals, vibrations, noise), and, after treatment, allow checking the good health or state of components and structures immersed in liquid sodium (detection of displacements, flaws, leaks, bubbles, buckling).This is a real challenge as the media are rather complex, due to their geometry (shapes and access), their physical properties (multiphase, heterogeneous, anisotropic, flowing fluid, thermal gradients), high temperature, irradiation and sodium. This leads to use active acoustic methods (volumetric and guided waves) or passive ones (acoustic emission), and linear and non-linear acoustic methods.A number of experiments are performed at full scale or less, mainly in simulating water fluid (in conventional water test vessels, on water loops, with Schlieren bench) but also in sodium facilities.Numerical simulations are performed with available or tuned codes (multi-physics, ray tracing and finite elements, spectral finite elements ) in order to predict wave propagation within materials and structures. In addition, among other inverse methods used, defect detection can be done with time reversal techniques coupling with adjoint method.The future MISTRAL common lab will allow to ease this joint work between CEA Cadarache and LMA.