Study on Alignment Estimation of Nuclear Fuel Bundle in Spent Fuel Pool with Multi-Ultrasound Signal Analysis

In the Wolsung nuclear power plant, workers move the spent fuel bundles that have been maintained in the water to reduce the radiation level and temperature for several years. Spent fuel bundles under 5m of boron water are moved into a dry container with the naked eye. Therefore, it is not easy to maneuver the spent fuel bundle gripper (hereafter gripper) to the center of the spent fuel bundle with the naked eye. If a spent fuel bundle is hit by approaching the spent fuel bundle, there is a risk that some fuel rods will be separated. This study suggests a technique to prevent the collision of the gripper and a spent fuel bundle. An ultrasound sensor is used for the inspection of high radiation nuclear power plant components such as nuclear reactor pipes, and nuclear fuel rods in light-water nuclear power plants. An ultrasound beam field is calculated to select the frequency of ultrasound performance such as the near-field length and directivity. A test bed is fabricated with a multi-channel ultrasound system. Variation of peak amplitude with the lateral offset is analyzed to obtain the information of lateral offset and the deviation of normalized peak values of four ultrasound sensors used to derive the direction of offset.