Study on water stopping, repair and stabilization of lower PCV by geopolymer, etc. (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

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

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 FY2021, this report summarizes the research results of the "Study on water stopping, repair and stabilization of lower PCV by geopolymer, etc." conducted from FY2021 to FY2023. Since the final year of this proposal was FY2023, the results for 3 fiscal years were summarized. In order to retrieve fuel debris, it is necessary to shut off the water at the bottom of the dry well and repair it in order to control the PCV water level. Therefore, in this study, we evaluated a construction method of stopping the water of the jet deflector with an improved geopolymer and repairing the lower part of the dry well by experiments and simulations. In addition, after understanding the properties of the fuel debris coated with the geopolymer, the long-term life of the waste body was evaluated. As a result, it was predicted that by utilizing geopolymers, it is possible to stop water and repair the lower part of the PCV in consideration of steps from construction to waste management.