Structural displacement is a critical physical quantity for monitoring civil infrastructure. The importance of this measurement has driven the development of numerous dedicated sensors and sensing technologies.

This study presents a novel, cost-effective, and high-accuracy displacement sensor. Its architecture comprises an integrated frequency-modulated continuous-wave (FMCW) radar, a microelectromechanical systems (MEMS) accelerometer, a microcontroller unit (MCU), a wireless data transmission module, and a power supply unit. Through the synergistic fusion of data from the FMCW radar and MEMS accelerometer, the sensor attains exceptional displacement measurement performance with an accuracy better than 0.1 mm. Significant cost reduction was realized by leveraging a readily available FMCW radar chip, prevalent in autonomous vehicle systems, alongside an off-the-shelf MEMS accelerometer, projecting a unit cost under $1,000. Acquired and processed data are wirelessly disseminated to a range of client devices, such as mobile phones, laptops, and desktop computers, via diverse wireless protocols including Wi-Fi, LTE, and LoRa. The sensor operation is facilitated by a flexible power system, drawing energy from either a rechargeable lithium battery or an integrated solar panel, enabling fully self-contained and autonomous operation.

The utility of this sensor spans multiple critical applications, encompassing: (1) continuous monitoring of road and rail bridges for early warning of collapses and impending hazards, (2) automated in-situ evaluations for bridge rating, (3) spatio-temporal displacement characterization utilizing distributed and non-dedicated telecommunication cables, and (4) structural integrity testing of a real nuclear power plant.

SHM is being developed to assess aeroplane structural integrity and obtain maintenance credit. For EU airworthiness, using SHM on Principal Structural Elements (PSE) requires showing compliance with CS-25.571, CS-25.611, CS-25.1529 (large aeroplanes) and CS-23.2240 (GA), with safety at least equivalent to conventional inspections. This talk compares SHM and traditional methods; reviews guidance/standards; and explains how to substantiate SHM performance (POD, false-alarm rate, reliability) via test and analysis at appropriate assembly/functional levels. We cover metallic vs composite specifics; fatigue, accidental and environmental damage; sources of variability and sensitivity to them; failure cases and mitigations (redundancy, checks, qualification commensurate with risk). We discuss flight with known damage and the manufacturer–operator–authority process to update certification assumptions from service experience. Stronger coordination between research and industry—informed by certification awareness—offers significant potential to improve safety through innovation.

Most operators of Nuclear Power Plants (NPPs) and nuclear fuel cycle facility have expressed interest to pursue their operation beyond their initial design lifetime, a strategy known as Long-Term Operation (LTO). To do so in compliance with the European directive on safety, they must not only prove the conformity of their installations, but also continuously improve their safety. Ensuring the integrity of structural materials is a major concern, since some components are extremely complex of even impossible to replace. Conventional In-Service Inspection (ISI) is not only costly but exposes operators to irradiation as well. In addition, retrofitting safety improvements in ageing installations comes with technical, practical (lack of space) and economic challenges.

SHM (Structural Health Monitoring) comes as an appealing solution to better monitor the degradation of materials and act before they become a threat for safety, in complementarity with current methods. The known benefits of SHM for predictive maintenance and the low intrusiveness of modern instrumentation makes it economically sound as well, serving operational performance alongside safety. However, the nuclear industry comes with technical constraints (heat, radiations...), that may require deep adaptations of technologies deployed in other sectors. To advance the state of the art, ASNR has gathered innovative technology providers and industrial end-users in the Euratom-funded research project FIND (Future Instrumentation and coNtrol based on innovative methods and Disruptive technologies for higher safety level), started in 2024.

The nuclear industry is pushing Small Modular Reactors (SMR), characterised by a reduced power output, a compact design and, for some of them, innovative heat transfer fluids (like liquid metals or salts). Their designers want to natively integrate SHM to control inaccessible components and compensate for the limited operational experience regarding innovative materials. Regulators must assess the strategy they propose, based on relevant scientific knowledge, including the experience of other industrial sectors.

Finally, technological bricks of SHM may be applied to monitor safety systems in accidental and post-accidental conditions, during which they would degrade rapidly due to the harsh conditions, while being still necessary to mitigate the consequences of the accident.