Challenge for screening of nuclear fuel debris by innovative spectral imaging and its verification by LIBS mapping (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; The University of Osaka*

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2023, this report summarizes the research results of the "Challenge for screening of nuclear fuel debris by innovative spectral imaging and its verification by LIBS mapping" conducted in FY2023. The present study aims to develop a remote-sensing technique to identify the in-reactor materials by a combination of Hyper Spectral Imaging (HSI) and Laser Induced Breakdown Spectroscopy (LIBS). HSI analyzes spectral information of more than 100 colors, and is being applied to classify various materials. On the other hand, material composition cannot be directly evaluated by HSI. Therefore, we thought that the combination of HSI and LIBS could be an accurate and wide-ranging visualization technique. In order to demonstrate the HSI and LIBS, it is necessary to prepare standard materials that simulate in-reactor materials, and to acquire and accumulate training data on them. In this study, the University of Osaka is in charge of the preparation of standard materials and HSI data analysis, Nuclear Fuel Development (NFD) is in charge of the preparation of uranium bearing materials and HSI/LIBS measurements, and JAEA is in charge of LIBS development. On the UK side, the Univ. of Strathclyde, National Nuclear Laboratory (NNL), and Lancaster University participate in the joint research project. The compositions of the standard samples were determined from past experiments and thermodynamic calculation results. Several samples such as UO based composites and concrete were prepared. The HSI data were obtained using a hyperspectral camera installed in the NFD. For LIBS, we worked on the automatic optimization of focal distance as part of the development of remote operation technology.