Publications by authors named "Kazuma Koarai"

This paper presents a mass-spectrometric method for determining the radionuclide iodine-129 (I) from the significant amount of interference in inductively coupled plasma tandem quadrupole mass spectrometry (ICP-MS/MS) using a dynamic reaction cell passing a mixture gas of O and CO. Thus far, mass spectrometry analysis of trace amounts of I has been hampered by the presence of xenon-129 (Xe) and the formation of polyatomic ions from excess amounts of stable isotope I. In this study, flowing a mixture gas of O and CO into the dynamic reaction cell (Q2) successfully removed both Xe interference and polyatomic interference (IH) in the analysis of I in ICP-MS/MS.

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Electron spin resonance (ESR) dosimetry is one of the most powerful tools for radiation dose reconstruction. The detection limit of this technique using human teeth is reported to be 56 mGy or 67 mGy; however, the absorbed dose of Fukushima residents after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident was estimated to be lower than this detection limit. Our aim is to assess the absorbed radiation dose of children in Fukushima Prefecture after the accident; therefore, it is important to estimate the detection limit for their teeth.

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After the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident in Japan, freshwater ecosystems near the site remained contaminated by radiocesium (RCs). Clarifying RCs concentrations in aquatic insects is crucial because fishes consume these insects that transfer RCs into freshwater ecosystems. As aquatic insects are usually measured for radioactivity in bulk samples of several tens of insects, variation in RCs concentration among individuals is not captured.

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Article Synopsis
  • The researchers successfully measured low levels of radioactive technetium-99 (Tc) in a complex mixture with competing substances like ruthenium-99 (Ru) and molybdenum hydride (MoH), achieving detection within 15 minutes.
  • They employed an advanced system called online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (SPE-ICP-MS-DRC), which minimizes human error and rigorously separates the target analyte from interference.
  • The new method exhibited a significantly lower detection limit of approximately 9.3 pg/L for Tc, proving effective for analyzing even lower concentrations in environmental samples, like seawater, with high accuracy in recovery tests.
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The Fukushima-Daiichi Nuclear Power Plant (FNPP) accident in March of 2011 released substantial amounts of radionuclides into the environment. We collected 4,957 deciduous teeth formed in children before the Fukushima accident to obtain precise control data for teeth formed after the accident. Radioactivity was measured using imaging plates (IP) and epidemiologically assessed using multivariate regression analysis.

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Sr specific activity in the teeth of young cattle that were abandoned in Kawauchi village and Okuma town located in the former evacuation areas of the Fukushima-Daiichi Nuclear Power Plant (FNPP) accident were measured. Additionally, specific activity in contaminated surface soils sampled from the same area was measured. (1) All cattle teeth examined were contaminated with Sr.

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Here we determined the (90)Sr concentrations in the teeth of cattle abandoned in the evacuation area of the Fukushima-Daiichi Nuclear Power Plant (FNPP) accident. (90)Sr activity concentrations in the teeth varied from 6-831 mBq (g Ca)(-1) and exhibited a positive relationship with the degree of radioactive contamination that the cattle experienced. Even within an individual animal, the specific activity of (90)Sr (Bq (g Sr)(-1)) varied depending on the development stage of the teeth during the FNPP accident: teeth that were early in development exhibited high (90)Sr specific activities, while teeth that were late in development exhibited low specific activities.

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