ABSTRACT A hybrid method for estimation of atmospheric concentrations of multiple radionuclides was developed and applied to NaI(Tl) pulse height records measured in Ibaraki Prefecture in the morning of 15 March 2011 when three radioactive plumes from the Fukushima Dai-Ichi Nuclear Power Plant Accident passed. The method is based on the simple principle for separation from deposited radionuclides’ contribution and the concentration estimation for multiple radionuclides. Difficulty in the concentration estimation due to complexity of surrounding terrains and geometry was overcome to obtain spatiotemporal variations in atmospheric concentrations of Xe-133, Te-132, I-131, I-132 and I-133 in the three plumes at 21 monitoring stations. The plume axis with higher I-131 concentration of 5.40 kBq m-3 than the previous estimations during the second plume was found in the northwestern inland area. A substantially lower Xe-133/I-131 concentration ratio of the first plume than those of the others was again recognized. The details of non-uniform spatial distribution of the radionuclide composition were found for each of the three plumes.

中文翻译：

---

根据茨城县测量的 NaI(Tl) 脉冲高度分布估计福岛第一核电站事故排放的 2011 年 3 月 15 日大气放射性核素浓度空间分布

摘要 2011 年 3 月 15 日上午，当福岛第一核电站事故的三个放射性羽流通过时，开发了一种估算多种放射性核素大气浓度的混合方法，并将其应用于茨城县测量的 NaI(Tl) 脉冲高度记录。 . 该方法基于从沉积的放射性核素的贡献和多种放射性核素的浓度估计中分离的简单原理。克服了由于周围地形和几何形状的复杂性造成的浓度估计困难，获得了 21 个监测站三个羽流中 Xe-133、Te-132、I-131、I-132 和 I-133 的大气浓度时空变化. I-131 浓度较高的羽轴为 5。在西北内陆地区发现了第二次羽流期间比先前估计值高 40 kBq m-3。再次发现第一羽流的 Xe-133/I-131 浓度比明显低于其他羽流。对于三个羽流中的每一个，都发现了放射性核素组成的非均匀空间分布的细节。