Research on Two-Dimensional Ultrasonic Contour Imaging Algorithm for Weld between Nozzle to Shell of Reactor Pressure Vessel

The visual display of ultrasonic signal position of complex geometric welds in nuclear power plants has important reference value for defect judgment. The inner surface of the nozzle of reactor pressure vessel (RPV) in nuclear power plant usually has a certain inclination angle. By using the traditional rectangular B-scan imaging algorithm, there are some outstanding problems in ultrasonic B/C scan imaging of welds between nozzle and shell, such as unintuitive display and inaccurate defect location. In this paper, the algorithm of tangent connection between straight line and straight line, arc and elliptical arc through arc is proposed. The library function of drawing straight line and arc is used to draw the contour, and the ultrasonic signal is displayed in the contour to form a B-scan image with contour. A saddle shaped C-scan image is formed by calculating the threshold of the A-scan signal passing through the gate line in the contour. The validity and practicability of the algorithm are verified by the on-site ultrasonic scanning data of the RPV nozzle and shell weld in the nuclear power plant.