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Tracing the Fukushima nuclear accident released Pu and radiocesium isotopes in the environment: the role of isotope ratio analysis
https://repo.qst.go.jp/records/54527
https://repo.qst.go.jp/records/5452773642d2d-6b15-4cab-9366-85a9642cc622
| Item type | 会議発表論文 / Conference Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2014-12-11 | |||||
| タイトル | ||||||
| タイトル | Tracing the Fukushima nuclear accident released Pu and radiocesium isotopes in the environment: the role of isotope ratio analysis | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_5794 | |||||
| 資源タイプ | conference paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
鄭, 建
× 鄭, 建× 田上, 恵子× ト, 文庭× 楊, 国勝× 内田, 滋夫× 鄭 建× 田上 恵子× ト 文庭× 楊 国勝× 内田 滋夫 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident led to the release of large amounts of radionuclides into the environment. In addition to the atmospheric releases, the direct discharges of highly contaminated water from the damaged reactor buildings resulted in contamination of radionuclides in the sea. It has been estimated that the total amount of 137Cs released from the FDNPP accident ranged from 15-35 PBq, while for the refractory actinides, in particular, Pu isotopes, tiny amount (239+240Pu/137Cs activity ratio of ca. 10-7-10-8 in heavily contaminated environmental samples) was released into the environment. The released radioactive materials posed radiation threat to human society. Thus, source identification of radioactive contamination and long-term environmental behaviour of released radioactive materials are important issues of study after the FDNPP accident. For Pu isotopes, it is difficult to estimate the contamination caused by the FDNPP accident if only Pu activity measurement is conducted due to the fact that only tiny amount of core Pu was released. Experience obtained from studies on Pu contamination in the Chernobyl accident and other global and/or regional Pu contamination events indicated that accurate determination of Pu isotopic composition (in particular 240Pu/239Pu and 241Pu/239Pu atom ratios) is essential for reliable source identification. As the major radiation dose contributor, the released amounts of radiocesium, 134Cs and 137Cs have been estimated, and 134Cs/137Cs activity ratio was immediately used to identify radioactive contamination in the environment. However, due largely to the difficulty of 135Cs analysis (because of its long half-life and low-energy β-decay of 76 keV), the amount of 135Cs released and the isotopic fingerprint of 135Cs/137Cs ratio of FDNPP accident have not been studied after the accident. Considering the short half-life of 134Cs, the 134Cs/137Cs activity ratio will become unavailable in the future for identification of FDNPP contamination, and for long-term estimation of the FDNPP accident related fission products mobility in the environment. Therefore, there is a strong scientific need to study the release of 135Cs and to obtain the isotopic fingerprint of 135Cs/137Cs of the FDNPP accident. In this work, we developed novel ICP-MS based analytical methods for accurate determination of radioactive Cs isotopes (135Cs/137Cs atom ratio) and Pu isotopes (240Pu/239Pu and 241Pu/239Pu atom ratios) in environmental samples (litter, soil, sediment and seawater) collected in Fukushima Prefecture before and after the FDNPP accident. We identified the isotopic compositions of radioactive Cs and Pu isotopes released from the FDNPP accident, and estimated the released amounts of 135Cs and Pu isotopes. We demonstrated that radiocesium in the terrestrial environment was mainly released from the Unit 2 reactor. The potential applications of the obtained FDNPP-sourced Cs and Pu fingerprints in the study of long-term environmental behaviour of the released radioactive materials will also be discussed. |
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| 書誌情報 |
Proceedings of the 15th Workshop on Environmental Radioactivity 巻 2014-7, p. 1-12, 発行日 2014-11 |
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