Detailed visualization of radioactive hotspots inside the Unit 1 reactor building of the Fukushima Daiichi Nuclear Power Station using an integrated Radiation Imaging System mounted on a Mecanum wheel robot

統合型放射線イメージングシステムを搭載したメカナムホイールロボットによる福島第一原子力発電所1号機原子炉建屋内の放射性ホットスポットの詳細な可視化

佐藤 優樹  ; 寺阪 祐太   ; 大浦 正利*

Sato, Yuki; Terasaka, Yuta; Oura, Masatoshi*

In the decommissioning of the Fukushima Daiichi Nuclear Power Station, understanding the distribution of radioactive substances and dose-equivalent rates is crucial to develop detailed decontamination plans and minimize worker exposure. In this study, we remotely visualized radioactive hotspots and dose-equivalent rate distribution in Unit 1 reactor building of the station using a Mecanum wheel robot equipped with a Compton camera, simultaneous localization and mapping device, and survey meter. We successfully visualized high-concentration radiation hotspots on the U-shaped piping of the drywell humidity control system and the atmospheric control piping in the ceiling in front of the transverse in-core probe room. Furthermore, the hotspot location was identified in three dimensions using the Compton camera used to analyze the atmospheric control piping. By simultaneously analyzing the dose-equivalent rate data acquired by the survey meter and the hotspot locations visualized by the Compton camera, it was confirmed that the hotspots caused elevated dose-equivalent rates in the surrounding area. Using this robot system in unexplored areas, such as the higher floors of reactor buildings, in future will enable us to obtain information on radiation hotspot locations and dose-equivalent rate distribution.