As hydrogen becomes central to global clean energy strategies, ensuring the safety of storage containers and pipelines is essential. Hydrogen-induced defects (HID)—including embrittlement, blistering, hydrogen-induced cracking (HIC), and high-temperature hydrogen attack (HTHA)—often exhibit irregular, branched geometries that challenge both modelling and ultrasonic detection. In this work, a random-walk method is used to accurately model HID geometries by incorporating statistical features extracted from several realistic HIDs. The simulated crack profiles are implemented in finite element models to evaluate their acoustic backscattering behaviour and generate full matrix capture datasets. Ultrasound images reconstructed using the total focusing method (TFM) show a strong correlation between image amplitude, spatial spread, and the underlying statistical parameters. This work provides a link between measurable defect morphology and ultrasonic image response, supporting more reliable monitoring of HID in hydrogen pipelines and containers.

Aim at characterizing the adhesive-interfacial stiffness, defects of thin coatings with unknown thickness, we propose an ultrasonic pressure reflection coefficient phase spectrum (URCPS) for identification of the interfacial stiffness and defects utilizing material-oriented regularization. The URCPS is derived as a function of interfacial stiffness and thickness based on the phase screen approximation theory and springs model. A new objective function of least-squares coupled cross-correlation algorithm based on URCPS is developed to simultaneously inverse the defects, thickness, and interfacial stiffness of specimens. The effective detection range and detection accuracy of interfacial stiffness are analyzed through finite element method (FEM). A series of simulations were implemented on Cr-coated zirconium cladding specimens with thickness about 7~30 μm, various interfacial stiffness. Ultrasonic experiments achieved the debonding size detection of Cr-coated Zr cadding with relative error of 5.7% compared with the SEM observed size 176 μm, and achieved the integrated identification of thickness and interface stiffness for Cr coated Zr-cladding. It can accurately measure the thickness of Cr coating samples with thickness about 7 μm.

This presentation reports on the development of an ultra-high temperature thin-film ultrasonic thickness (UT) sensor capable of continuous monitoring at temperatures up to 450°C. The sensor, developed by Mitsubishi Heavy Industries, builds upon existing thin-film UT sensor technology for environments below 200°C and addresses the growing need for thickness monitoring in higher temperature ranges. The newly developed BIT thin-film UT sensor demonstrates stable operation under continuous high-temperature exposure, confirmed through thermal cycle and extended heating tests. Additionally, temperature-dependent sound velocity correction techniques were established to enable accurate thickness evaluation at elevated temperatures. This technology enables reliable continuous thickness monitoring of piping and vessels in harsh high-temperature industrial environments, particularly in nuclear power plants , contributing to improved plant maintenance, operational safety, and cost reduction.