Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 73(2): 161-171 (2024)


簡易密封した土壌試料中のゲルマニウム半導体検出装置による40K, 232Th及び238Uの定量と実測の空間線量率との比較Determination of 40K, 232Th, and 238U in Easily-Sealed Soil Using a Germanium Detection System and the Comparison with Actually Measured Air Dose Rates

量子科学技術研究開発機構National Institutes for Quantum Science and Technology

受付日:2023年10月13日Received: October 13, 2023
受理日:2024年2月1日Accepted: February 1, 2024
発行日:2024年7月15日Published: July 15, 2024

貴重な土壌試料をガンマ線測定による天然放射性核種定量後も有効に使うために,PTFEシールによるU-8容器簡易密封法を検討した。本法により標準物質中の天然放射性核種を適切に定量できた。量研機構の1970年代のアーカイブ土壌試料222試料に適用し,40K, 232Th系列,238U系列に加え,土壌が現地の自然環境に長期間曝されていたことの判定のために137Cs濃度データを取得した。定量した天然放射性核種濃度から理論的に計算できる空間線量率の結果は,実測値とよく一致した。

For effective use of valuable soil samples after determination of naturally occurring radionuclides by gamma-spectrometry, a simple U-8 container sealing method with PTFE seals was investigated. When the method was applied to measure naturally occurring radionuclides in standard reference materials, it was found that the method could determine radionuclides adequately. Then using the method, 222 archived soil samples at QST collected in the 1970s, were measured to determine 40K, 232Th and 238U series radionuclides, and also measured for 137Cs activity concentrations to identify whether or not the soil samples were well exposed to natural conditions. The calculated air dose rates using the determined naturally occurring radionuclides agreed well with the ambient air dose rates at the time of sampling.

Key words: naturally occurring radionuclide; caesium-137; archived soil sample; global fallout; air-absorbed dose rate

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