Ultrasonic methods for the characterization of materials used in nuclear components to improve diagnosis – MUSCAD

The MUSCAD project falls under the SNR orientation “Sensors and Instrumentation” (orientation 15) and the “materials and processes axis” (Axis 3) attached to the challenge “Stimulate Industrial Renewal” (Challenge 3). This is a Collaborative Research Project - Enterprises (ESRP), which brings together public laboratories of INSA Lyon, Aix-Marseille University (AMU) and CEA, an industrial partner, EDF-R&D and the company EXTENDE.
Non Destructive Testing (NDT) brings together all the techniques, tests, exams, implemented during manufacture or maintenance, to ensure the integrity of a manufactured product or an industrial plant. These techniques aim at detecting the presence of possible defects estimated critical to the safety and / or proper operation of the inspected component. The NDT methods are part of the industrial tools that help to improve productivity and help to ensure product compliance with quality and safety requirements.
NDT techniques based on ultrasonic elastodynamic waves are very widespread in the nuclear industry in particular because they allow control in the component volume. However, complex and heterogeneous structures (coarse grained steels, welding, bimetallic assembling ...) are commonly found in the cooling systems of nuclear reactors pressurized water (PWR) used in all French nuclear power plants. The heterogeneity of these materials degrade performance of controls because of many scattering effects (attenuation, structural noise, dispersion) undergone by the ultrasonic wave. In addition, local variations in their mechanical properties (grain size, crystallographic orientation ...) lead to differences of response according to the inspection position.
To assess the reliability of the inspection techniques used on such components, simulation is increasingly used but requires an accurate knowledge of the inspected structure properties. The MUSCAD project aims to develop new complex media characterization tools, in particular those including a heterogeneous and anisotropic microstructure, by solving inverse problem applied on ultrasonic measurements. The objective of this approach is to evaluate the mechanical properties of these materials directly usable as an input of simulation tools in order to improve diagnosis and the controllability of the components. According to used mechanical parameters, the model sensitivity will be quantified on a case of realistic representative study of a weld control.
This coupled approach including characterization technique and simulation tools should enable us to make progress on understanding of propagation phenomena and ultrasonic scattering in austenitic welds. We seek to quantify more clearly the influence of the weld structure on the performance of non-destructive ultrasonic testing. The key strategic axes of the project are:
- The development of simulation codes dedicated to the modeling of ultrasonic beam propagation in damping and anisotropic materials in order to simulate experimental setup of non-destructive evaluation (NDE) techniques.
- The development of ultrasonic characterization tools developed by INSA to more reliable measurements by determining a confidence interval on identified parameters.
- The study of the sensitivity of an inspection method to mechanical parameters on a realistic case of ultrasonic NDT.

The results of studies conducted in the project will be directly used in the assembly control processes qualification files. The integration of developments in the CIVA software platform opens perennial prospects for new acquisition and inversion strategies . The dissemination of the work will be performed by EXTENDE distributor of the CIVA software.