Abstract
An ultrasonic measurement system was development as a method for inspecting inside the primary containment vessel (PCV), especially for identifying leakage points and determining fuel debris distribution in the decommissioning of Fukushima Dai-ichi nuclear power plant. This measurement system has a liner array sensor and enables the obtaining of both 2-D flow map and reconstructed image of echo intensity distributions at once using Ultrasonic Velocity Profiler (UVP) and aperture synthesis method respectively. In other words, the developed system can visualize flow behavior and determine object surface at the same time and therefore has possibility to carry out the inspection efficiently. Additionally, pulse compression method was incorporated to expand the measurement depth. To verify the practicality of the developed system, it was applied to an experimental situation as may be expected inside the PCVs. As a result, the location of a leakage point and shape of mock fuel debris were estimated from a 2-D flow map and reconstructed image using proposed method.
