Investigation of influence of liquid surface flow on object shape imaging by air-coupled ultrasonic imaging

Abstract

Fuel debris removal on decommissioning of Fukushima Daiichi nuclear power plants requires the investigation inside Primary Containment Vessel (PCV) to obtain clear status of fuel debris. Although the camera investigation was conducted inside the PCV recently, further high radiation and longtime measurement environment approaching fuel debris may cause camera to malfunction. Therefore, ultrasonic imaging measurement was proposed in this research. In particular, the air-coupled ultrasonic imaging system has been developed for fuel debris investigation in air. However, in case that the fuel debris come out of the water surface, the influence of liquid surface flow should be considered. In this paper, the identification method of liquid surface and debris shape was proposed. The method was validated by analyzing vibration of the liquid surface experimentally. The results showed the method identified frequency of liquid surface vibration using air-coupled ultrasound. In conclusion, the proposed method has possibility to apply for identification of liquid surface and debris shape.