Fundamental research on the integrated measurement method using laser and ultrasound for fuel debris investigation

This study hopes to combine LIBS technology and ultrasound technology to quickly obtain the distribution, shape, and surface elemental composition of nuclear fuel debris in PCVs. In this paper, the working principle and the construction of the remote LIBS system are described. The operating principles of ultrasound systems for shape and solid-liquid surface distinction measurements are introduced. Then, the remote LIBS and ultrasound systems are integrated to develop an elemental mapping system. The validation experiment of the elemental mapping system is carried out on the simulated nuclear fuel debris. The elemental mapping system successfully obtained a 3D elemental map containing information on the simulated nuclear fuel debris samples' position, shape, and surface elemental composition. Finally, the shape measurement result from the ultrasound system was optimized using the elemental measurement result from the remote LIBS system. Through the validation experiment, it can be seen that the use of ultrasound measurements helps to obtain information about the shape and position and predict the solid and liquid surfaces of the simulated fuel debris simultaneously. This dramatically improves the efficiency of remote LIBS measurements. The application of the remote LIBS system can effectively measure elemental composition on the surface of simulated nuclear fuel debris. Meanwhile, the microchip LIBS system can optimize the shape measurement results of the ultrasound system. Therefore, integrating the two systems allows for more efficient and accurate measurement of nuclear fuel debris' shape, position, and surface elemental composition.