Analytical Sciences

Abstract − Analytical Sciences, 29(10), 941 (2013).

Aging Effect of 137Cs Obtained from 137Cs in the Kanto Loam Layer from the Fukushima Nuclear Power Plant Accident and in the Nishiyama Loam Layer from the Nagasaki A-bomb Explosion
Tomoko OHTA,* Yasunori MAHARA,*,** Takumi KUBOTA,*** and Toshifumi IGARASHI*
*Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, N13W8, Sapporo, Hokkaido 060-8628, Japan
**Professor Emeritus, Kyoto University, Kyoto, Kyoto 606-8501, Japan
***Research Reactor Institute, Kyoto University, Sennangun, Osaka 590-0494, Japan
We measured 134Cs and 137Cs in the surface soil of the Kanto loam in the eastern Tokyo metropolitan area and the Nishiyama loam in Nagasaki, Japan. The observed 137Cs deposition in the Kanto loam from the Fukushima nuclear power plant (NPP) accident ranged from 4.0 to 77 kBq m−2, which corresponds to 0.3 – 5 times of that in the Nishiyama loam. The 137Cs retardation factor in the Kanto loam obtained seven months after the Fukusima NPP accident and in the Nishiyama loam after 36 and 38 years from the detonation of the Pu atomic bomb (A-bomb) ranged from 180 to 260 and 2000 to 10000, respectively. This difference in the retardation factors is attributed to an aging effect that corresponds to seven months and 36 to 38 years after the deposition of 137Cs occurred on the soil minerals.