NUCLEAR CONTAINMENT INSPECTION USING AN ARRAY OF GUIDED WAVE SENSORS FOR DAMAGE LOCALIZATION

Nuclear power plant containments are typically both the last line of defense against the release of radioactivity to the environment and the first line of defense to protect against intrusion from external objects. As such, it is important to be able to locate any damage that would limit the integrity of the containment itself. Typically, a portion of the containment consists of a metallic pressure boundary that encloses the reactor primary circuit. It is made of thick steel plates welded together, lined with concrete and partially buried, limiting areas that can be visually inspected for corrosion damage. This study presents a strategy using low frequency (<50 kHz) guided waves to find corrosion-like damage several meters from the probe in a mock-up of the containment vessel. A magnetostrictive sensor (MsS) is scanned across the width of the vessel, acquiring waveforms at a fixed interval. A beam forming strategy is used to localize the defects. Experimental results arc presented for a variety of damage configurations, demonstrating the efficacy of this technique for detecting damage smaller than the ultrasonic wavelength.