Validity of the source term for the Fukushima Dai-ichi Nuclear Power Station accident estimated using local-scale atmospheric dispersion simulations to reproduce the large-scale atmospheric dispersion of 137Cs. (October 2021)

• Record Type: Journal Article
• Authors: Kadowaki, Masanao; Furuno, Akiko; Nagai, Haruyasu; Kawamura, Hideyuki; Terada, Hiroaki; Tsuduki, Katsunori; El-Assad, Hamza
• Is Part Of: Journal of environmental radioactivity. Volume 237(2021)
• Publication Date: 2021-10
• Subjects: Hemispheric-scale atmospheric dispersion -- Fukushima Dai-ichi nuclear power station accident -- 137Cs -- WSPEEDI-DB -- Source term; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2021.106704
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: The source term of 137 Cs from the Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident was estimated from the results of local-scale atmospheric dispersion simulations and measurements. To confirm the source term's validity for reproducing the large-scale atmospheric dispersion of 137 Cs, this study conducted hemispheric-scale atmospheric and oceanic dispersion simulations. In the dispersion simulations, the atmospheric-dispersion database system Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI)-DB and oceanic dispersion model SEA-GEARN-FDM that were developed by the Japan Atomic Energy Agency were used. Compared with the air concentrations of 137 Cs measured by the Comprehensive Nuclear-Test-Ban Treaty Organization, overall, the WSPEEDI-DB simulations well reproduced the measurements, whereas the simulation results partly overestimated some measurements. Furthermore, the validity of the deposition of 137 Cs by WSPEEDI-DB was investigated using SEA-GEARN-FDM and concentrations of 137 Cs in seawater sampled from the North Pacific. Seawater concentrations of 137 Cs by the oceanic dispersion simulation, in which the deposition flux of 137 Cs by WSPEEDI-DB was used as input from the atmosphere to oceans, were statistically consistent to the measurement. However, the simulated seawater concentrations of 137 Cs were underestimated regionally in the North Pacific. Both the overestimation of air concentrations and underestimation of seawater concentrations could be attributed to the less amounts of 137 Cs deposition by less precipitation over the North Pacific. The overestimation and underestimation could be improved without contradiction between the air and seawater concentrations of 137 Cs using more realistic precipitation in atmospheric dispersion simulations. This shows that the source term validated in this study could reproduce the spatiotemporal distribution of 137 Cs from the FDNPS accident in both local and large-scale atmospheric dispersion simulations. Highlights: The source term of 137 Cs by Terada et al. (2020a) was validated using WSPEEDI-DB. Air concentrations of 137 Cs in the Northern Hemisphere were well simulated. Concentrations of 137 Cs in seawater of the North Pacific were demonstrated. The source term is valid in both local and large-scale atmospheric dispersion. WSPEEDI-DB can address multi-scale atmospheric dispersion of 137 Cs.