Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Atomic Energy Research Laboratory, Tokyo City University, Kawasaki, Kanagawa, Japan.
Radiat Prot Dosimetry. 2022 Sep 9;198(13-15):1170-1174. doi: 10.1093/rpd/ncac138.
According to the observed data of the activity concentration of $^{137}$Cs in Lake Onuma on Mount. Akagi, located in Gunma Prefecture, the decrease of the activity concentration slowed down since 2 years after the accident of Fukushima Daiichi Nuclear Power Plant. In the present study, we applied the time fractional diffusion equation to reproduce long-term changes in the time series of the activity concentration. In addition, we also reproduced the vertical distribution of the activity concentration with the parameter values, estimated by the time series data. We found that the model fit the observed data well for both time series and vertical distribution.
根据位于群马县的赤城山湖沼中观测到的 137Cs 活度浓度数据，自福岛第一核电站事故发生后 2 年以来，活度浓度的下降速度已经放缓。在本研究中，我们应用时间分数扩散方程来再现活度浓度时间序列的长期变化。此外，我们还利用时间序列数据估计的参数值再现了活度浓度的垂直分布。我们发现，该模型对时间序列和垂直分布的观测数据拟合得都很好。
