Muramatsu Yasuyuki, Matsuzaki Hiroyuki, Toyama Chiaki, Ohno Takeshi
Faculty of Science, Gakushuin University, Mejiro 1-5-1, Toshima-ku, Tokyo 171-8588, Japan.
Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-0032, Japan.
J Environ Radioact. 2015 Jan;139:344-350. doi: 10.1016/j.jenvrad.2014.05.007. Epub 2014 Jun 13.
Iodine-131 is one of the most critical radionuclides to be monitored after release from reactor accidents due to the tendency for this nuclide to accumulate in the human thyroid gland. However, there are not enough data related to the reactor accident in Fukushima, Japan to provide regional information on the deposition of this short-lived nuclide (half-life = 8.02 d). In this study we have focused on the long-lived iodine isotope, (129)I (half-life of 1.57 × 10(7) y), and analyzed it by accelerator mass spectrometry (AMS) for surface soil samples collected at various locations in Fukushima Prefecture. In order to obtain information on the (131)I/(129)I ratio released from the accident, we have determined (129)I concentrations in 82 soil samples in which (131)I concentrations were previously determined. There was a strong correlation (R(2) = 0.84) between the two nuclides, suggesting that the (131)I levels in soil samples following the accident can be estimated through the analysis of (129)I. We have also examined the possible influence from (129m)Te on (129)I, and found no significant effect. In order to construct a deposition map of (131)I, we determined the (129)I concentrations (Bq/kg) in 388 soil samples collected from different locations in Fukushima Prefecture and the deposition densities (Bq/m(2)) of (131)I were reconstructed from the results.
碘 - 131是反应堆事故释放后需要监测的最关键的放射性核素之一，因为这种核素易于在人体甲状腺中积累。然而，关于日本福岛反应堆事故，没有足够的数据来提供该短寿命核素（半衰期 = 8.02天）沉积的区域信息。在本研究中，我们聚焦于长寿命碘同位素碘 - 129（半衰期为1.57×10⁷年），并通过加速器质谱法（AMS）对从福岛县不同地点采集的表层土壤样本进行分析。为了获取事故释放的碘 - 131与碘 - 129的比率信息，我们测定了82个先前已测定碘 - 131浓度的土壤样本中的碘 - 129浓度。两种核素之间存在很强的相关性（R² = 0.84），这表明事故后土壤样本中的碘 - 131水平可通过碘 - 129的分析来估算。我们还研究了碲 - 129m对碘 - 129的可能影响，未发现显著影响。为了构建碘 - 131的沉积图，我们测定了从福岛县不同地点采集的388个土壤样本中的碘 - 129浓度（贝克勒尔/千克），并根据结果重建了碘 - 131的沉积密度（贝克勒尔/平方米）。
