Long-term variations of radiocesium in houses inside the Fukushima evacuation zones

• Project/Area Number: 19K12306
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: The University of Tokyo
• Principal Investigator: Shozugawa Katsumi 東京大学, 大学院総合文化研究科, 助教 (00507923)
• Co-Investigator(Kenkyū-buntansha): 堀 まゆみ 東京大学, 教養学部, 特任助教 (50782869)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2021: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000); Fiscal Year 2020: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2019: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
• Keywords: 放射性セシウム / 家屋内汚染 / 帰還困難区域 / 除染 / マスク / 内部被ばく / ダスト / 避難指示 / 東京オリンピック / 家屋内

Outline of Research at the Start

福島第一原子力発電所事故後、避難指示区域の解除が逐次行われているが、避難指示が解除されて1年が経過した区域での住民の帰還率は約15%である。その理由の一つに、家屋内汚染の情報不足が挙げられる。放射性セシウムを含む土壌粒子が家屋内に混入することが汚染の原因であることは明らかであるが、時系列の情報が欠けていた。本研究では今後避難指示が緩和または解除される予定のエリアを中心に、家屋内で発生する放射性物質混入の程度を時系列で解析することを目的としている。このことは、次々と避難指示が解除される中において喫緊の課題として遂行されるべき研究と考える。

Outline of Final Research Achievements

In order to clarify the state of contamination in houses in Fukushima evacuation zone over time, radioactive cesium trapped on clothes in a house was periodically measured and the degree of contamination in the house was quantitatively evaluated against the time scale. It was found that the factors most affecting the contamination in a house depended on the airtightness of the house itself and the frequency of entry and exit, not on the degree of contamination outside the house.

Academic Significance and Societal Importance of the Research Achievements

本研究によって家屋内の汚染の要因は家の気密性や窓やドアを開ける頻度に依存することが強く推測されました。気密性が高く、かつ出入りがほとんどない家屋の場合には、家屋周りの汚染度が高い場合でも家屋に放射性セシウムが混入してくる割合は低いことになります。一方で破損等で気密性が落ちてしまった家屋の場合、あるいは頻繁に出入りがあった場合には、家屋外の沈着量と差が生じない可能性もあります。この観測結果は中長期的な避難指示解除後の被ばく量を低減させるうえでも重要な基礎的知見になると考えられます。

Research Products

• [Int'l Joint Research] LSCE/SEARS/CEA(フランス)
• [Int'l Joint Research] Univ. of Hannover(ドイツ)
• [Int'l Joint Research] CEA/LSCE/IPSL(フランス)
• [Journal Article] Identification, isolation, and characterization of a novel type of Fukushima-derived microparticle (2022)
  • Author(s): Macsik Zsuzsanna, Hudston Lisa A., Wurth Kimberly N., Meininger Daniel, Jesinghaus Christian, Tenner Travis J., Naes Benjamin E., Boswell Mitzi, Shozugawa Katsumi, LaMont Stephen P., Steiner Robert E., Steinhauser Georg
  • Journal Title: Journal of Radioanalytical and Nuclear Chemistry Volume: 331 Issue: 12 Pages: 5333-5341
  • DOI: 10.1007/s10967-022-08561-1
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Landside tritium leakage over through years from Fukushima Dai-ichi nuclear plant and relationship between countermeasures and contaminated water (2020)
  • Author(s): Katsumi Shozugawa, Mayumi Hori, Thomas. E. Johnson, Naoto Takahata, Yuji Sano, Norbert Kavasi, Sarata K. Sahoo & Motoyuki Matsuo
  • Journal Title: Scientific reports Volume: 10 Issue: 1 Pages: 19925-19925
  • DOI: 10.1038/s41598-020-76964-9
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Radioactive Games? Radiation Hazard Assessment of the Tokyo Olympic Summer Games (2020)
  • Author(s): Rebecca Querfeld, Mayumi Hori, Anica Weller, Detlev Degering, Katsumi Shozugawa, and Georg Steinhauser
  • Journal Title: Environmental Science & Technology Volume: 54(18) Issue: 18 Pages: 11414-11423
  • DOI: 10.1021/acs.est.0c02754
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Why Japan needs radiation measurement? (2022)
  • Author(s): Katsumi Shozugawa
  • Organizer: Mitate Lab Mid-term Review Symposium
  • Int'l Joint Research
• [Presentation] 静岡県伊東市における2021年産の米・茶葉に含まれる放射性セシウム (2022)
  • Author(s): 小豆川勝見、堀まゆみ
  • Organizer: 日本環境化学会 環境化学物質3学会合同大会
• [Presentation] Localization of actinide-bearing particles in sediment samples from the Fukushima restriction zone (2021)
  • Author(s): Aurélie Diacre, Pascal Fichet, Paul Sardini, Jérôme Donnard, Anne‑Laure Fauré, Olivier Marie, Katsumi Shozugawa, Michaël Susset, Mayumi Hori, Takizawa Tsutomu, Fabien Pointurier, Olivier Evrard
  • Organizer: The EGU General Assembly 2021
  • Int'l Joint Research
• [Presentation] Localization of uranium-bearing particles in soil samples from the Fukushima restriction zone (2020)
  • Author(s): A. DIACRE, P. FICHET, P. SARDINI, J. DONNARD, A-L. FAURE, O. MARIE, K. SHOZUGAWA, M. SUSSET, M. HORI, T. TAKIZAWA, F. POINTURIER, O. EVRARD
  • Organizer: Fukushima and the Ocean
  • Int'l Joint Research
• [Presentation] Seasonal deposition of radiocesium in wooden houses from summer to winter seven years after the Fukushima nuclear accident (2019)
  • Author(s): R. Takakura, K. Shozugawa, M. Hori, M. Matsuo
  • Organizer: Japan Geoscience Union Meeting 2019
  • Int'l Joint Research