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Suzuki, Takashi; Otosaka, Shigeyoshi*; Kuwabara, Jun
no journal, ,
no abstracts in English
Cs discharge from rivers to the ocean near the Fukushima Dai-ichi Nuclear Power Plant using a simple modelSakuma, Kazuyuki; Aoyama, Michio*; Nakanishi, Takahiro; Kurikami, Hiroshi; Machida, Masahiko; Yamada, Susumu; Iwata, Ayako
no journal, ,
MERCURY is one of the models developed to simply predict Cs discharge from rivers to the ocean for understanding of Cs migration from seawater and sediment to the ecosystem and for estimating Cs discharge under heavy rainfall immediately. It is composed of a tank model, relationships between water discharge and suspended solids load, and two-component exponential models for river water Cs concentration. Using the MERCURY, Cs discharge to the ocean from five rivers near the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in 2018 and 2019 was estimated to be 0.23 and 0.81 TBq. Cs discharge in 2019 was larger than in 2018 due to the two huge typhoons in October 2019, Hagibis and Bualoi. Although the model has some limitations such as underestimating the Cs discharge during a heavy rainfall due to lack of modeling dependence of Cs concentration on sediment size, it can quickly evaluate the effect of Cs discharge from rivers to the coastal area near FDNPP.
Nagai, Haruyasu; Terada, Hiroaki
no journal, ,
The Fukushima Daiichi Nuclear Power Station accident in March 2011 released significant amounts of radioactive materials into the atmosphere. In order to evaluate the environmental impacts and resultant radiological doses to the public due to the accident, the source term of radioactive materials discharged into the atmosphere was estimated and updated in a series of research conducted by Japan Atomic Energy Agency (JAEA). In these studies, the source term was reversely estimated from environmental monitoring data with an analysis method using atmospheric dispersion simulations. The atmospheric dispersion model mainly used in these studies was the Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) developed by JAEA. In this report, the estimation method of source term and analysis results are presented.
Cs emitted from Fukushima Daiichi Nuclear Power Plant; MIPs with identical source term and meteorological dataSato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kadowaki, Masanao; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; et al.
no journal, ,
Two Model Intercomparison of Projects (MIPs) of atmospheric dispersion model targeting on Cs released from Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 2011 were conducted. Both MIPs were conducted using an identical source term of Cs, identical meteorological data, and the same horizontal grid resolution (3 km and 1 km) to exclude the uncertainties of the model originated from them. Our analyses indicated that most of the model well simulated the atmospheric Cs obtained from the operational aerosol sampling of the national suspended particle matter network. Our analyses also indicated that meteorological data were most critical for reproducing the atmospheric Cs events, and the extent of the horizontal diffusion and the deposition were critical if the meteorological field was reasonably simulated. The comparison of the results between the two MIPs elucidated that the fine grid resolution is required to simulate atmospheric Cs in the vicinity of FDNPP, but the use of the fine grid resolution does not always improve the performance of the models especially for areas distant from the FDNPP. The results of both MIPs elucidated that the good performance of some models improved the performance of the multimodel, highlighting the advantage of using a multimodel ensemble.