Summary
Ultrasonic inspection becomes least reliable in exactly the environments where asset owners most need data. Conventional UT sensors depend on gel-based couplants that degrade over time and break down quickly at elevated temperature, which rules them out for sustained structural health monitoring. Conventional transducers are also difficult to seat against complex geometry, limiting where trustworthy measurements can be taken. Structural Integrity Associates (SIA) has developed thick-film ultrasonic sensors to close that gap, extending its nondestructive examination capabilities into long-term, high-temperature monitoring applications.
Thick-film UT sensors are built from a piezoelectric powder combined with an aqueous binding agent and applied directly to the component surface through aerosol deposition, forming a mechanically robust bond that eliminates the couplant entirely. Films are layered to control thickness precisely, allowing resonance frequencies to be tuned to a specific inspection task. Electrode design adds further flexibility. A single-element configuration supports precise thickness monitoring, while electrodes patterned into customizable arrays steer and focus the ultrasonic beam for detailed internal imaging, defect characterization, and crack tracking, carrying ultrasonic testing well beyond basic wall-thickness measurement.
Because the sensor is bonded rather than coupled, it conforms to demanding geometries such as reactor vessel internals, piping elbows, and bolted connections, and it endures conditions that defeat conventional probes. SIA has tested thick-film sensors for long-term use to 740°F and demonstrated operation up to 1250°F under test conditions. Once installed, the sensors return continuous data during component operation, delivering improved repeatability, precise trending of wall-thickness reduction and crack propagation rates, and better predictive estimates of remaining component life. That is the same real-time asset intelligence behind SIA’s SIIQ™ online monitoring solutions.
The result is a practical path into advanced reactor programs, built on extensive deployment in high-temperature fossil applications. As a conventional ultrasonic method, thick-film UT is already Code-compliant under ASME BPVC Section V, Article 14 examination system qualification, and it falls within the MANDE framework established in Section XI, Division 2 for sodium fast reactors, high-temperature gas reactors, and molten salt reactors. Applied to critical SSCs such as reactor vessels, core barrel supports, and piping, the couplant-free design produces more repeatable measurements and more accurate trending than traditional UT, aligning the technology with RIM program monitoring and MANDE qualification methods IV-3, IV-4, and Appendix V. Application-specific testing for temperature and radiation dose remains necessary to qualify any given deployment, and SIA’s nuclear power team supports that qualification work from evaluation through field implementation.