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ADVanced Inspection of Complex StructurEs

Periodic Reporting for period 1 - ADVISE (ADVanced Inspection of Complex StructurEs)

Reporting period: 2017-09-01 to 2019-02-28

In recent years, there has been increasing concern for safe long-term operation of existing European nuclear power plants. The ultrasonic inspection of corrosion resistant alloys used in these plants, in particular claddings, austenitic welds and cast austenitic steels, is a long-standing issue in the field of nuclear non-destructive testing and evaluation (NDE). For these materials, a complex microstructure is responsible for both structural noise and attenuation, thus degrading the performance of ultrasonic non-destructive testing. At the same time plant owners wish to replace radiographic inspections by ultrasound as a less disruptive, safer and faster technique. To address these issues and thereby keep on improving safety and reliability of Generation II and III reactors, there are still a number of technical breakthroughs to overcome, including the need to improve NDE techniques for complex structured material.
The overall objective of the ADVISE project is to enable the ultrasonic inspection of complex structured materials so as to improve confidence in inspection of Generation II and III European reactors.
In particular:
- The optimisation of the performance of existing ultrasonic inspections, where better signal-to-noise ratio, deeper penetration depth and more reliable diagnostics are required
- The application of ultrasound to cases where it cannot be applied today and where the industry currently must resort to radiography, which is highly disruptive and has certain imminent dangers due to the radiation used.
ADVISE has 4 main technical objectives:
- Increase the comprehension and modelling of complex structures for accurate prediction
- Develop new tools for material characterisation and input data
- Provide advanced inspection methods
- Provide defect evaluation methods and assisted diagnostics.
Besides these technical objectives, ADVISE also has an educational and dissemination objective of improving, harmonising and sharing knowledge about ultrasonic inspection of complex structured materials while ensuring results uptake by the industry.
ADVISE published its first major deliverable, a public State of the art report on ultrasound inspection of complex structured materials and compiled a mock-up inventory containing a comprehensive list of material samples and component mock-ups from industrial partners. Many of these parts have since been made available to academic partners, in particular for the development of a method for bulk material characterisation, which aims to derive information on average grain size and distribution from ultrasonic data.
A significant effort was made in a group exercise on the characterisation of the macrostructure of welds. A weld was manufactured according to realistic specifications, and a series of ultrasonic measurements was taken, from which both the grain orientation map and the average grain size were estimated. As a ‘ground truth’ reference, we used two different approaches to predict weld formation and analysed metallographic images. Preliminary results confirm the viability of the approach for welds with a more or less extruded structure and rather homogeneous grain size, and indicate the need for 3D extensions for more complex welds, as well as more work on structures with a more heterogeneous grain size distribution.
The first generation of an array transducer design optimisation scheme has been developed, which allows the optimal selection of transducer frequency to achieve a desired level of detection, classification or sizing. The CIVA platform has been adapted to the needs of the project with an elaborate plug-in mechanism, which allows the integration of the different algorithms, including a framework for inversion-based diagnostics and optimisation. This platform was made available to partners and training was provided. A new adaptive imaging technique was proposed to optimise images of defects when only approximate information is available about the material characteristics. In order to facilitate rapid prototyping, the UTIS platform was shared, and two algorithms for the improvement of signal to noise ratio in inspections on coarse grained materials were integrated and evaluated. Furthermore, a prototype of an impedance matched transducer was manufactured, which promises a significant increase of signal to noise ratio. Use cases for the demonstration of the project’s achievements also were identified by the industrial partners.
While the scientific activities of the project were progressing, the ADVISE partners also initiated many dissemination activities to raise awareness of the project. A public website was set up and a brochure was produced at the project start. Also, the project was presented during many international events in the field of NDE.
With the development of inspection and signal processing methods, as well as material characterisation, ADVISE specifically addresses the remaining technology gaps: the inspection of cast austenitic stainless steel for large thicknesses and austenitic welds and dissimilar metal welds.
The exploitation of ADVISE findings will lead to the provision of knowledge, processes, methods, tools and equipment that can be both used by the scientific community and the nuclear industry.
The project intends to pave the way for the application of ultrasonic inspection techniques on components which complex structured material represents a performance barrier with today’s available technology. The developed methodology will help overcoming difficulties faced in in-service inspection, manufacturing, and during the erection of plants.
ADVISE will contribute to the EU effort to prevent accidents and thereby avoid radioactive releases, by delivering innovative and efficient solutions for currently operating Generation II and III nuclear reactors. The project results will enable performance increases in terms of inspectable depth, defect detection and characterisation accuracy, and inspection time. Repair needs will be identified in a more efficient, timely and accurate manner.
By providing NDE simulations and analysis tools, ADVISE will contribute to reduce the cost and to enhance the performances of the inspections. Indeed, an increased use of simulation will enable more reliable inspections while also reducing the number of test samples.
The greatest economic impact of ADVISE is expected for plant owners, followed by in service inspection service providers offering inspection techniques to utilities. By far the most important gain is to be expected if ADVISE succeeds in developing a viable alternative inspection technique for specific high value components, such as the radiographic inspection of cast elbow pipes.
Solving issues related to current inspection methods is actually answering a specific need from the European nuclear industry and will enable to maintain and reinforce their leadership in the operation of their existing nuclear fleet. The ADVISE industrial partners will guarantee the adaptability to industrial needs of the tools and methods developed in the project and ensure their implementation in the industrial context.
On the side of design and manufacturing of new plants, the improvement of the quality of new components will definitely place the industrial entities of the European Union among the best and the most credible ones on the nuclear market.
Ultrasonic Inspection of an austenitic stainless steel mockup using angle wedge contact transducer