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Radioactivity and Air Dose Rate

（2020）

ＱHow can radioactive Cs in a solid phase material such as soil be analyzed?

ＡWe analyzed the properties of radioactive Cs using instruments based on different principles, depending on the purpose.

Property Geometry, elemental composition, and elemental distribution on the surface Elemental distribution and isotopic composition on the extreme surface Internal structure and elemental composition
Analytical instrument Electron probe micro analyzer (EPMA) Time-of-flight secondary-ion mass spectrometry (TOF-SIMS) Transmission electron microscope (TEM)
Principle

An electron beam is applied on the surface of the sample to measure the ejected secondary electrons or transmitted X-ray.

EPMA

（Source：JEOL website）

An ion beam is irradiated on the sample to analyze the resulting mass of ions (secondary ions) ejected from the surface of the sample.

TOF-SIMS

(Source : ULVAC-PHI brochure）

An electron beam is irradiated on a thin-sliced sample to detect the transmitted electron beam. (Nanometer-scale objects can be observed.)

TEM

（Source：JEOL website）
Example of analysis result
  • We examined the elemental composition and distribution of soil particles to which Cs was adhered. 1)
  • From those analysis results, we identified the constituent elements of minerals coexisting with Cs at the same location on the soil particles.
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  • We measured the isotopic abundance of Cs (e.g., 133Cs, 137Cs) in environmental samples containing Cs. 2)
  • From the results, we examined radioactive Cs in the environmental samples to determine whether they were derived from nuclear testing in the past or by accident at 1F; if the latter, which unit of 1F.
    		•
  • We observed soil particles and other objects collected at rivers to which Cs was strongly adhered. 3)
  • Based on the results, we confirmed that Cs was strongly adhered to both clay and weathered minerals.
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    References

    1. 田籠久也, 土肥輝美, 石井康雄, 金井塚清一, 藤原健壮, 飯島和毅(2019): 環境試料中からの放射性セシウム微粒子の単離; リターへの適用事例, JAEA-Technology 2019-001, 37p. https://doi.org/10.11484/jaea-technology-2019-001
    2. Dohi, T., Iijima, K., Omura, Y., Fujiwara, K. and Kikuchi, N. (2017): Application of lichens to evaluate the distribution of radionuclides nearby the Fukushima Dai-ichi Nuclear Power Station, 14th International Conference on the Biogeochemistry of Trace Elements (ICOBTE 2017). Zurich.
    3. Hagiwara, H., Konishi, H., Nakanishi, T., Fujiwara, K., Iijima, K. and Kiatamura, A. (2020): Mineral composition characteristics of radiocesium sorbed and transported sediments within the Tomioka river basin in Fukushima Prefecture, Journal of Environmental Radioactivity, vol. 211, 106042_1-106042_10.
      https://doi.org/10.1016/j.jenvrad.2019.106042