Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 67(7): 329-338 (2018)


市販パーツによる溜め池底質用放射性セシウム鉛直分布測定器An Apparatus for Vertical Distribution Measurement of Radiocaesium in Pond Sediment Using Commercially Available Parts

1産業技術総合研究所機能材料コンピュテーショナルデザイン研究センターResearch Center for Computational Design of Advanced Functional Materials, National Institute of Advanced Industrial Science and Technology (AIST) ◇ 305–8568 茨城県つくば市梅園1–1–1 中央第2 ◇ 1–1–1 Umezono, Tsukuba-shi, Ibaraki Pref. 305–8568, Japan

2産業技術総合研究所ナノ材料研究部門Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) ◇ 305–8565 茨城県つくば市東1–1–1 中央第5 ◇ 1–1–1 Higashi, Tsukuba-shi, Ibaraki Pref. 305–8565, Japan

3東京パワーテクノロジー株式会社環境事業部分析センターAnalysis Center, Environmental Affairs Division, Tokyo Power Technology Ltd. ◇ 267–0056 千葉県千葉市緑区大野台2–3–6 ◇ 2–3–6 Onodai, Midori-ku, Chiba-shi, Chiba Pref. 267–0056, Japan

受付日:2017年12月11日Received: December 11, 2017
受理日:2018年3月22日Accepted: March 22, 2018
発行日:2018年7月15日Published: July 15, 2018


An apparatus for on-site measurement of radiocaesium in pond sediment was developed by assembling commercially available parts. It gives vertical radiocaesium distribution in sediment from γ-ray count data measured by an array of PIN photodiode sensors. Successful conversion from γ-ray count rates to radiocaesium concentration in Bq/kg-wet was attained by an inversion code based on the maximum-entropy method. On-site tests at three ponds in Fukushima prefecture revealed that the apparatus gives vertical distributions close to those of core sampling method by 10 min measurement. It works about 5 h by a small mobile battery. The total cost for the apparatus is about 100,000 Japanese Yen which may not be unacceptable to individuals. The present method measures vertical distribution directly and is superior to other methods which assume empirical profile such as exponential distribution. Experimental error and application to other target such as soil or containers were also discussed.

Key words: radiocaesium; measurement; sediment; vertical distribution; maximum entropy method

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