Miyamoto Yutaka, Yasuda Kenichiro, Magara Masaaki
Research Group for Analytical Chemistry, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
Research Group for Analytical Chemistry, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
J Environ Radioact. 2014 Jun;132:1-7. doi: 10.1016/j.jenvrad.2014.01.010. Epub 2014 Feb 6.
Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17-April 1, 2011, and May 9-13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as (134)Cs and (137)Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of (129m)Te, (140)Ba, (134)Cs, (136)Cs and (137)Cs was 1.5-1.6 μm, while the diameter of (131)I was 0.45 μm. The diameters of (134)Cs and (137)Cs in the second collection were expressed as three peaks at <0.5 μm, 0.94 μm, and 7.8 μm. The (134)Cs/(137)Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of (134)Cs/(137)Cs - (136)Cs/(137)Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions <0.43 μm and the composition in the 1.1-2.1 μm range (including the AMAD of 1.5-1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes.
2011年，日本原子能机构（JAEA）在位于福岛第一核电站（FDNPP）以南114公里处的东海市，使用多级低压冲击器收集了福岛第一核电站事故释放的空气中放射性粒子。在2011年3月17日至4月1日以及2011年5月9日至13日期间，分两次收集了按粒径分级的样本。这些按粒径分级的采样是在距离福岛第一核电站很近的最早几天进行的。测定了短寿命核素（半衰期为几十天）以及¹³⁴Cs和¹³⁷Cs的放射性。还测量了按粒径分级样本的元素组成。在第一次收集时，¹²⁹mTe、¹⁴⁰Ba、¹³⁴Cs、¹³⁶Cs和¹³⁷Cs的活度中值空气动力学直径（AMAD）为1.5 - 1.6μm，而¹³¹I的直径为0.45μm。第二次收集时，¹³⁴Cs和¹³⁷Cs的直径呈现出<0.5μm、0.94μm和7.8μm三个峰值。第一次收集的¹³⁴Cs/¹³⁷Cs总比值为1.02，但细颗粒部分的比值为0.91。¹³⁴Cs/¹³⁷Cs - ¹³⁶Cs/¹³⁷Cs比值分布图有助于了解放射性Cs组成的变化。粒径<0.43μm部分和1.1 - 2.1μm范围（包括AMAD为1.5 - 1.6μm）内的Cs组成，与使用ORIGEN-II代码计算的福岛第一核电站1号和3号反应堆燃料组成相似。2011年5月收集的Cs组成与2号反应堆燃料组成的计算结果相似。Cs组成的变化意味着福岛第一核电站三个反应堆中的放射性Cs是通过不同过程释放的。
