Research on a quantitative analysis system for radioactive waste based on complete gamma-ray visualization technology using an electron-tracking Compton camera, 1; Measurements conducted in the condensate demineralizer room of the prototype advanced thermal reactor Fugen during its decommissioning

Satoh, Daiki   ; Takada, Atsushi*; Koda, Yuya ; Sonoda, Shinya*; Tanimori, Toru*

As part of a KAKENHI project, we are developing applications of complete gamma-ray visualization technology using an Electron-Tracking Compton Camera (ETCC) for the management and analysis of radioactive waste generated during the decommissioning of nuclear facilities. This presentation reports on measurements conducted in the condensate demineralizer room of the Advanced Thermal Reactor prototype "Fugen," which is currently undergoing decommissioning. Prior contamination surveys using conventional survey meters identified a hotspot with a dose rate of approximately 1 Sv/h near the flange at the bent section of ceiling piping. ETCC measurements were performed under two conditions: with and without the hotspot within the measurement field of view. In the measurement including the hotspot, gamma-ray emissions from the vicinity of the flange were successfully visualized, and the dose rate was estimated to be approximately 1 Sv/h, consistent with the survey meter results. In the measurement excluding the hotspot, we successfully visualized contamination distributed across the entire vent filter at background dose rate levels, which could not be detected by the survey meter. These results demonstrate the capability of ETCC technology to visualize low-level contamination distributions that are difficult to detect with conventional instruments.