Inversion analysis on vertical radiocesium distribution in pond sediment from γ-ray count measurement

• Published in: Journal of environmental radioactivity Vol. 175-176; pp. 158 - 163
• Main Authors: Ogawa, Hiroshi, Minami, Kimitaka, Kawamoto, Tohru, Kanai, Ramon, Ishikawa, Kohei, Kamimura, Ryuichi
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2017
• Subjects: Cesium Radioisotopes - analysis; Fukushima Nuclear Accident; Gamma Rays; Geologic Sediments - chemistry; Inversion; Maximum entropy method; Ponds; Radiation Monitoring; Radiocesium; Sediment; Soil Pollutants, Radioactive - analysis; Vertical profile; Water Pollutants, Radioactive - analysis; Inversion; Sediment; Maximum entropy method; Vertical profile; Radiocesium
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2017.05.011

Evaluation of vertical distribution of radiocesium in bottom sediment by measuring vertical γ-ray count profile was discussed. A stable inversion formula was derived based on the maximum entropy method. Efficiency of the formula was confirmed by using a low-cost apparatus composed of an array of PIN photodiodes and a single board computer with real-time inversion code. In-door experiment by using five model sediment disks showed good reproducibility of vertical radiocesium profile. On-site experiment was also carried out at a pond in Fukushima to confirm the efficiency. It was suggested that combination of the simple apparatus and MEM inversion formula gave reasonable estimates on vertical radiocesium distribution in bottom sediment of 1 kBq/kg-wet level within about 10 min. •A low-cost apparatus for monitoring radio-Cs in bottom sediment is developed.•Inversion code based on maximum entropy method gives Cs depth profile in real time.•Efficiency of the method is confirmed by in-door and on-site measurements.•Depth profile of radio-Cs concentration was measured in about 10 min.