Isotopic ratios of uranium and caesium in spherical radioactive caesium-bearing microparticles derived from the Fukushima Dai-ichi Nuclear Power Plant
書誌事項
- 公開日
- 2020-02-24
- 資源種別
- journal article
- 権利情報
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- https://creativecommons.org/licenses/by/4.0
- https://creativecommons.org/licenses/by/4.0
- DOI
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- 10.1038/s41598-020-59933-0
- 公開者
- Springer Science and Business Media LLC
説明
<jats:title>Abstract</jats:title><jats:p>Spherical radioactive caesium (Cs)-bearing microparticles (CsMPs) were emitted during the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March, 2011. The emission source (timing) and formation process of these particles remain unclear. In this study, the isotopic ratios of uranium (<jats:sup>235</jats:sup>U and <jats:sup>238</jats:sup>U) and caesium (<jats:sup>133</jats:sup>Cs, <jats:sup>134</jats:sup>Cs, <jats:sup>135</jats:sup>Cs, and <jats:sup>137</jats:sup>Cs) isotopes in the five spherical CsMPs (ca. 2 μm in size) sampled at 50 km west of the FDNPP were determined using secondary ion mass spectrometry and laser ablation-ICPMS, respectively. Results showed that the <jats:sup>235</jats:sup>U/<jats:sup>238</jats:sup>U ratios of CsMPs were homogeneous (1.93 ± 0.03, <jats:italic>N</jats:italic> = 4) and close to those estimated for the fuel cores in units 2 and 3, and that the Cs isotopic ratios of CsMP were identical to those of units 2 and 3. These results indicated that U and Cs in the spherical CsMPs originated exclusively from the fuel melt in the reactors. Based on a thorough review of literatures related to the detailed atmospheric releases of radionuclides, the flow of plumes from the FDNPP reactor units during the accident and the U and Cs isotopic ratio results in this study, we hereby suggest that the spherical CsMPs originate only from the fuel in unit 2 on the night of 14 March to the morning of 15 March. The variation range of the analysed <jats:sup>235</jats:sup>U/<jats:sup>238</jats:sup>U isotopic ratios for the four spherical particles was extremely narrow. Thus, U may have been homogenised in the source through the formation of fuel melt, which ultimately evaporating and taken into CsMPs in the reactor and was released from the unit 2.</jats:p>
収録刊行物
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- Scientific Reports
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Scientific Reports 10 (1), 3281-, 2020-02-24
Springer Science and Business Media LLC