2019 Fiscal Year Final Research Report
Application of adavanced electron microscopy to elucidate Cs-rich microparticles released from Fukushima Daiichi
| Project/Area Number |
16K12585
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Multi-year Fund |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Kyushu University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
大貫 敏彦 東京工業大学, 科学技術創成研究院, 教授 (20354904)
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| Project Period (FY) |
2016-04-01 – 2020-03-31
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| Keywords | 福島第一 / セシウム / 透過型電子顕微鏡 / CsMP / 放射能 |
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| Outline of Final Research Achievements |
We have determined the spatial distribution of the numbers and radioactive fraction (RF) of the CsMPs in surface soil, which is defined as the sum of the CsMP radioactivity (in Bq) divided by the total radioactivity (in Bq) of soil. The number and RF of CsMPs were determined to be 22.1-101 particles/g and 15.4-34.0%, 24.3-64.8 particles/g and 36.7-37.4%, and 0.869-8.00 particles/g and 27.6-80.2%, respectively. These distributions are consistent with the major plume trajectories of released radionuclides on March 14, 2011, in the late afternoon through to the late afternoon of March 15, 2011, indicating that the CsMPs formed only during this short period. It also indicates that Unit 3 is the most plausible source of the CsMPs at the beginning of the release based on an analysis of the sequence of release events. The quantitative map of the distribution of CsMPs provides an important understanding of CsMP dispersion dynamics and can be used to assess risks in inhabited regions
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| Free Research Field |
環境科学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究の一連の成果では、福島第一原発から放出された高濃度放射性セシウム含有微粒子（CsMP）の内部構造を詳細に分析することによって、ウランを含むデブリの構成元素の存在状態とメルトダウン時の挙動を明らかにすることができました。また、簡易定量法を開発し、福島県内の土壌に適用して、CsMPの個数と放射能寄与率（RF）を示しました。原発付近では個数が多く低RF値で、水溶性セシウムの寄与が大きくなることや、プルームの軌跡との比較によって、CsMPの形成時期や、流れを推測することができました。これらの結果は、福島第一原発で起きたこと、その環境影響を正しく考察するうえで重要な知見となっています。
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