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Journal Articles

Third international challenge to model the medium- to long-range transport of radioxenon to four Comprehensive Nuclear-Test-Ban Treaty monitoring stations

Maurer, C.*; Galmarini, S.*; Solazzo, E.*; Ku$'s$mierczyk-Michulec, J.*; Bar$'e$, J.*; Kalinowski, M.*; Schoeppner, M.*; Bourgouin, P.*; Crawford, A.*; Stein, A.*; et al.

Journal of Environmental Radioactivity, 255, p.106968_1 - 106968_27, 2022/12

After performing multi-model exercises in 2015 and 2016, a comprehensive Xe-133 atmospheric transport modeling challenge was organized in 2019. For evaluation measured samples for the same time frame were gathered from four International Monitoring System stations located in Europe and North America with overall considerable influence of IRE and/or CNL emissions. As a lesion learnt from the 2nd ATM-Challenge participants were prompted to work with controlled and harmonized model set ups to make runs more comparable, but also to increase diversity. Effects of transport errors, not properly characterized remaining emitters and long IMS sampling times (12 to 24 hours) undoubtedly interfere with the effect of high-quality IRE and CNL stack data. An ensemble based on a few arbitrary submissions is good enough to forecast the Xe-133 background at the stations investigated. The effective ensemble size is below five.

Journal Articles

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 $$^{137}$$Cs

Kadowaki, Masanao; Furuno, Akiko; Nagai, Haruyasu; Kawamura, Hideyuki; Terada, Hiroaki; Tsuzuki, Katsunori; El-Asaad, H.

Journal of Environmental Radioactivity, 237, p.106704_1 - 106704_18, 2021/10

 Times Cited Count:1 Percentile:0(Environmental Sciences)

The source term of $$^{137}$$Cs for the Fukushima Daiichi 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 were used. Compared with the air concentrations of $$^{137}$$Cs measured by the Comprehensive Nuclear-Test-Ban Treaty Organization, overall, the WSPEEDI-DB simulation reproduced the measurements with some overestimation. Furthermore, the deposition amounts of $$^{137}$$Cs was investigated using concentrations of $$^{137}$$Cs in seawater. The simulated seawater concentrations of $$^{137}$$Cs were underestimated regionally in 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 because of the FDNPS accident in both local and large-scale atmospheric dispersion simulations.

Journal Articles

Refinement of source term and atmospheric dispersion simulations of radionuclides during the Fukushima Daiichi Nuclear Power Station accident

Terada, Hiroaki; Nagai, Haruyasu; Tsuzuki, Katsunori; Furuno, Akiko; Kadowaki, Masanao; Kakefuda, Toyokazu*

Journal of Environmental Radioactivity, 213, p.106104_1 - 106104_13, 2020/03

 Times Cited Count:38 Percentile:93.57(Environmental Sciences)

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station accident in Japan, the spatial and temporal distribution of radioactive materials in the environment is necessary to be reconstructed by computer simulations with the atmospheric transport, dispersion and deposition model (ATDM) and source term of radioactive materials discharged into the atmosphere is essential. In this study, we carried out refinement of the source term and improvement of ATDM simulation by using an optimization method based on Bayesian inference with various measurements (air concentration, surface deposition, and fallout). We also constructed the spatiotemporal distribution of some major radionuclides in the air and on the surface (optimized dispersion database) by using the optimized release rates and ATDM simulations which is used for the comprehensive dose assessment by coupling with the behavioral pattern of evacuees from the accident.

Journal Articles

Submesoscale mixing on initial dilution of radionuclides released from the Fukushima Daiichi Nuclear Power Plant

Kamidaira, Yuki; Uchiyama, Yusuke*; Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko

Journal of Geophysical Research; Oceans (Internet), 123(4), p.2808 - 2828, 2018/04

 Times Cited Count:19 Percentile:82.01(Oceanography)

We developed a submesoscale eddy-resolving oceanic dispersal modeling system consisting of a double nested oceanic downscaling model and an offline oceanic radionuclides dispersion model to investigate influences of submesoscale coherent structures (SCSs) and associated ageostrophic secondary circulations (ASCs) on the three-dimensional (3D) dispersal and initial dilution of the dissolved radioactive $$^{137}$$Cs accidentally released from the Fukushima Daiichi Nuclear Power Plant (FNPP1) occurred since March 2011. The extensive model-data comparison demonstrates that the elaborated innermost high-resolution model at a lateral grid resolution of 1 km successfully reproduces transient mesoscale oceanic structures, the Kuroshio path and stratification, and spatiotemporal variations of 3D $$^{137}$$Cs concentrations. These SCSs and ASCs occurred primarily due to shear instability with baroclinic instability as the secondary mechanism, according to energy conversion and spectral analyses. The vertical $$^{137}$$Cs flux analysis was performed with decomposition of the variables into the mean, mesoscale, and submesoscale components using frequency and wavenumber filters. The vertical $$^{137}$$Cs flux analysis explained that 84% of the FNPP1-derived $$^{137}$$Cs was transported downward below the mixed layer by eddies, with the major contributions from ASCs induced by submesoscale eddies.

Journal Articles

Oceanic dispersion of Fukushima-derived Cs-137 simulated by multiple oceanic general circulation models

Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Miyazawa, Yasumasa*; Usui, Norihisa*

Journal of Environmental Radioactivity, 180, p.36 - 58, 2017/12

 Times Cited Count:11 Percentile:40.96(Environmental Sciences)

This study simulates the oceanic dispersion of Fukushima-derived Cs-137 by an oceanic dispersion model and multiple oceanic general circulation models. The models relatively well reproduced the observed Cs-137 concentrations in the coastal, offshore, and open oceans. Multiple simulations in the coastal, offshore, and open oceans consistently suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Quantification of the Cs-137 amounts suggested that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layers in the North Pacific.

Journal Articles

Updating source term and atmospheric dispersion simulations for the dose reconstruction in Fukushima Daiichi Nuclear Power Station accident

Nagai, Haruyasu; Terada, Hiroaki; Tsuzuki, Katsunori; Katata, Genki; Ota, Masakazu; Furuno, Akiko; Akari, Shusaku

EPJ Web of Conferences, 153, p.08012_1 - 08012_7, 2017/09

 Times Cited Count:2 Percentile:80.99

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in Japan, the spatiotemporal distribution of radioactive materials in the environment are reconstructed by computer simulations. In this study, by refining the source term of radioactive materials and modifying the atmospheric dispersion model (ATDM), the atmospheric dispersion simulation of radioactive materials is improved. Then, a database of spatiotemporal distribution of radioactive materials in the air and on the ground surface is developed from the output of the simulation. This database is used in other studies for the dose assessment by coupling with the behavioral pattern of evacuees from the FDNPS accident. The ATDM simulation was improved to use a new meteorological model and sophisticated deposition scheme. Although the improved ATDM simulations reproduced well the $$^{137}$$Cs deposition pattern in the eastern Japan scale, the reproducibility of deposition pattern was decreased in the vicinity of FDNPS. This result indicated the necessity of further refinement of the source term by optimization to the improved ATDM simulations.

Journal Articles

Numerical simulation on the long-term variation of radioactive cesium concentration in the North Pacific due to the Fukushima disaster

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; Usui, Norihisa*; Kamachi, Masafumi*

Journal of Environmental Radioactivity, 136, p.64 - 75, 2014/10

 Times Cited Count:22 Percentile:57.84(Environmental Sciences)

Numerical simulations on oceanic radioactive cesium dispersions in the North Pacific were conducted with a focus on the long-term variation of the radioactive cesium concentration after the Fukushima disaster. It was suggested that the $$^{137}$$Cs concentration had already been reduced to the pre-Fukushima background value in the wide area within the North Pacific 2.5 years after the Fukushima disaster.

Journal Articles

Intercomparison of numerical simulations on oceanic dispersion of the radioactive cesium released because of the Fukushima disaster

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; Usui, Norihisa*; Kamachi, Masafumi*; Nishikawa, Shiro*; Ishikawa, Yoichi*

Proceedings of 19th Pacific Basin Nuclear Conference (PBNC 2014) (USB Flash Drive), 7 Pages, 2014/08

Numerical simulations on oceanic dispersion of the radioactive cesium in the North Pacific from March 2011 to September 2013 were conducted to clarify the concentration of the radioactive cesium released from the Fukushima Daiichi Nuclear Power Plant. We implemented the oceanic dispersion simulations with two independent ocean reanalysis dataset. It was suggested that the $$^{137}$$Cs concentration in the North Pacific was lower than the pre-Fukushima background level about two years after the Fukushima disaster. The intercomparison revealed that meso-scale eddies in the Kuroshio Extension region may have efficiently diluted the radioactive cesium concentration at the sea surface. In addition, it was suggested that the enhanced downward current accompanied by the meso-scale eddies played an important role in transporting the radioactive cesium into the intermediate layer.

JAEA Reports

Risk communication practice after the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant accident; Awareness of Fukushima residents in internal dosimetry

Furuno, Akiko; Takashita, Hirofumi; Tokunaga, Hiroaki*; Horikoshi, Hidehiko*

JAEA-Review 2014-022, 37 Pages, 2014/07


This paper describes an analysis of the opinion survey that is carried out at the internal dosimetry using whole body counters conducted in Japan Atomic Energy Agency. JAEA staffs explained the examination results of WBC to the residents in private booths and provide necessary advice for them. We carried out two opinion surveys at the internal dosimetry. The first survey was carried out before the screening in order to realize the residents' views of the accidents; the second survey was carried out after the personal dialogue in order to receive the evaluation from examinee for our correspondence. The first survey showed that residents' anxiety about radioactive exposure, hereditary influence on next generation, and so on. On the other hand, more than 90% residents answered in the second survey that "uneasiness reduced" as a result of the direct dialogue. Our private dialogue has also considerably effects.

Journal Articles

Numerical experiments on dispersion of radionuclides in the ocean released from the Fukushima Daiichi Nuclear Power Plant

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; In, Teiji*; Ishikawa, Yoichi*; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*

Reports of Research Institute for Applied Mechanics, Kyushu University, (143), p.111 - 117, 2012/09

Because of the Fukushima Dai-ichi Nuclear Power Plant disaster, some radionuclides were released into the ocean from the Fukushima Dai-ichi Nuclear Power Plant. In response to this situation, numerical experiments were carried out at Japan Atomic Energy Agency using an oceanic dispersion model and an ocean general circulation model to estimate an effect of the radionuclides on marine environment. It was suggested that the radionuclides deposited from the atmosphere mainly in the middle of March after the disaster spread over a comparatively wide area of the Pacific Ocean east of Japan. On the other hand the radionuclides directly released into the ocean from the Fukushima Dai-ichi Nuclear Power Plant were carried along the coast and then spread along the Kuroshio extension.

Journal Articles

Preliminary numerical experiments on Oceanic dispersion of $$^{131}$$I and $$^{137}$$Cs discharged into the ocean because of the Fukushima Daiichi Nuclear Power Plant disaster

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; In, Teiji*; Ishikawa, Yoichi*; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*

Journal of Nuclear Science and Technology, 48(11), p.1349 - 1356, 2011/11


 Times Cited Count:164 Percentile:99.79(Nuclear Science & Technology)

Numerical experiments were carried out to predict the spreading of $$^{131}$$I and $$^{137}$$Cs released into the ocean due to the Fukushima Daiichi Nuclear Power Plant incident. Results in the numerical experiments were in good agreement with the concentrations of $$^{131}$$I and $$^{137}$$Cs in the monitoring data. It was suggested that the high $$^{131}$$I concentration detected in the young lancefish caught off Kitaibaraki city was due to the deposition from the atmosphere. The numerical experiments suggest that the deposition of radionuclides released into the atmosphere in the middle March largely effected the concentrations of radionuclides east of Japan in the Pacific Ocean.

JAEA Reports

WSPEEDI-II system user's manual for a nuclear or radiological emergency

Nakanishi, Chika; Sato, Sohei; Furuno, Akiko; Terada, Hiroaki; Nagai, Haruyasu; Muto, Shigeo

JAEA-Technology 2011-005, 141 Pages, 2011/03


Nuclear Emergency Assistance and Training Center (NEAT) has developed the response system to evaluate the radiological consequences of an accident on a nuclear power plant or nuclear weapons testing around Japan and to support prediction of radioactive material distributions by using an atmospheric dispersion model on the framework of the Response Assistance Network (RANET) which is established by the International Atomic Energy Agency (IAEA). For the enhancement of assistance capability to external organizations at a nuclear or radiological emergency, NEAT will introduce a computer-based emergency response system, "Worldwide version of System for Prediction of Environmental Emergency Dose Information: WSPEEDI 2nd version (WSPEEDI-II)" developed by Division of Environmental and Radiation Sciences. This manual covers the overview of the system and configuration parameters as the basic knowledge needed for operating the systems.

Journal Articles

Development of worldwide version of system for prediction of environmental emergency dose information; WSPEEDI 2nd version

Terada, Hiroaki; Nagai, Haruyasu; Furuno, Akiko; Kakefuda, Toyokazu; Harayama, Takaya*; Chino, Masamichi

Nihon Genshiryoku Gakkai Wabun Rombunshi, 7(3), p.257 - 267, 2008/09

The second version of WSPEEDI (WSPEEDI-II) which has functions to predict the radiological impact of nuclear accident abroad on Japan by quick calculations of air concentration, surface deposition and radiological doses is developed. WSPEEDI-II has the following functions for practical use. (1) High performance prediction of atmospheric dispersion of radionuclides from local to regional ranges with appropriate resolutions by introducing non-hydrostatic atmospheric dynamic model. (2) Source term estimation by coupling calculation results and monitoring data for the case that no source information is available from abroad. (3) On-line prediction data exchanges with major emergency response systems in the United States and Europe with the similar functions as WSPEEDI-II. (4) Web-based graphical user interface system for easy operation of WSPEEDI-II. (5) Preset East-Asian database for the quick start against a nuclear accident in Eastern Asia. This paper describes these new functions.

JAEA Reports

Numerical simulation system for environmental studies: SPEEDI-MP

Nagai, Haruyasu; Chino, Masamichi; Terada, Hiroaki; Harayama, Takaya*; Kobayashi, Takuya; Tsuzuki, Katsunori; Kim, K.; Furuno, Akiko

JAEA-Research 2006-057, 67 Pages, 2006/09


A numerical simulation system SPEEDI-MP has been developed to apply for various environmental studies. SPEEDI-MP consists of dynamical models and material transport models for the atmospheric, terrestrial, and oceanic environments, database for model inputs, and system utilities for file management, visualization, etc. As a numerical simulation tool, a model coupling program (model coupler) has been developed. A coupled model system for water circulation has been constructed with atmosphere, ocean, wave, hydrology, and land-surface models using the model coupler. System utility GUIs are based on the Web technology, allowing users to manipulate all the functions on the system using their own PCs via the internet. In this system, the source estimation function in the atmospheric transport model can be executed on the grid computer system. Performance tests of the coupled model system for water circulation were also carried out for the flood and the storm surge events.

Journal Articles

Development of a source term estimation method for nuclear emergency by long-range atmospheric dispersion simulations

Furuno, Akiko; Chino, Masamichi; Yamazawa, Hiromi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 5(3), p.229 - 240, 2006/09

This paper describes a method of estimating source term, i.e., location, period and amount of atmospheric release of radioactive material in real-time during nuclear emergency. This method consists of: (1) trial simulations of atmospheric dispersions on the possible combinations of these parameters and (2) statistical comparison of model predictions with off-site measurements of air concentrations of radionuclides and/or air does rates from monitoring stations, to find a set of release condition providing model predictions that best fit to the measurement. A parallel execution method for efficiently processing many possible initial conditions is also developed. The performance of this method is favorably evaluated by a verification study by using the dataset from European Tracer Experiment.

Journal Articles

A Migration analysis of ${it Sogatella furcifera}$ (Horv$'a$th) (Homoptera: Delphacidae) using hourly catches and a three-dimensional simulation model

Otsuka, Akira*; Watanabe, Tomonari*; Suzuki, Yoshito*; Matsumura, Masaya*; Furuno, Akiko; Chino, Masamichi; Kondo, Tomoya*; Kamimuro, Tsuyoshi*

Agricultural and Forest Entomology, 8(1), p.35 - 47, 2006/02

 Times Cited Count:16 Percentile:57.54(Entomology)

1 Migration of Sogatella furcifera captured in Japan in the 2003 season were analyzed using hourly catches and a simulation model.2. The catch data showed several clear migration peaks, with average durations of 4 h. The peaks were separated from each other by approximately 12 h, corresponding to the observed fact that planthoppers take off at dusk and dawn.3. The simulation model, together with the hourly catches, enabled an estimation of migration source regions.4. Possible migration sources during our hourly observation period were located in the coastal area of Fujian province in China, as well as Taiwan.

Journal Articles

Development of a numerical simulation model for long-range migration of rice planthoppers

Furuno, Akiko; Chino, Masamichi; Otsuka, Akira*; Watanabe, Tomonari*; Matsumura, Masaya*; Suzuki, Yoshito*

Agricultural and Forest Meteorology, 133(1-4), p.197 - 209, 2005/11

 Times Cited Count:18 Percentile:52.37(Agronomy)

Transoceanic migration of rice planthoppers was precisely simulated by incorporating several parameters related to the flight behavior with a high performance atmospheric dispersion model. The model consists of an atmospheric dynamic submodel and a particle random-walk submodel for atmospheric dispersion. The model also functions in specifying the release area of the migration of planthoppers. Using this model, we carried out a case study simulating the migration of planthoppers to western Japan in mid-June 1998. In the simulation, 56 areas each with a width of two degrees of latitude and longitude were set as tentative take-off areas. The calculated density of immigrants was compared with each observed density by rank correlation coefficients. Possible migration release areas which showed a high correlation to observations were distributed around 23-27N, including Fujian and Taiwan. An air temperature that allowed the planthoppers to fly continuously and flight duration were critical parameters for the simulation results.

Journal Articles

A New trajectory analysis method for migratory planthoppers, $$Sogatella furcifera$$ (Horv$'a$th) (Homoptera: Delphacidae) and $$Nilaparvata lugens$$ (St${aa}$l), using an advanced weather forecast model

Otsuka, Akira*; Dudhia, J.*; Watanabe, Tomonari*; Furuno, Akiko

Agricultural and Forest Entomology, 7(1), p.1 - 9, 2005/02

 Times Cited Count:39 Percentile:83(Entomology)

A new method of backward trajectory analysis for planthopper migration is presented. The method consists of two components: an advanced weather forecast model, MM5, for weather simulation, and a migration model for trajectory calculation. Although the landing process is not considered in the modeling, it is shown that the method is able to precisely simulate the migration and accurately estimate various parameters. This study also shows the importance of high quality weather simulation.

Journal Articles

Experimental verification for real-time environmental emergency response system; WSPEEDI by European tracer experiment

Furuno, Akiko; Terada, Hiroaki; Chino, Masamichi; Yamazawa, Hiromi*

Atmospheric Environment, 38(40), p.6989 - 6998, 2004/12

 Times Cited Count:20 Percentile:42.42(Environmental Sciences)

We have been developing the computer-based emergency response system WSPEEDI which predicts long-range atmospheric dispersion of radionuclides discharged into the atmosphere due to a nuclear accident. The first version of WSPEEDI has a shortage that the spatial and temporal variation of the atmospheric boundary layer was very simply parameterized. Therefore we have developed the new version accomplished with the atmospheric dynamic model, in which the turbulent diffusivity in the mixing layer is calculated with a turbulence closure model. This paper describes the results of performance evaluation of the new version of WSPEEDI by comparing the simulation results with the European Tracer Experiment data. As a result of the verification, it was shown that the increase in the horizontal resolution largely improved the accuracy of the model prediction. The use of the turbulence closure model instead of the simple parameterization largely contributed to improve reproducibility of horizontal distribution of plumes.

Journal Articles

Improvement of Worldwide Version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI), 1; New combination of models, atmospheric dynamic model MM5 and particle random walk model GEARN-new

Terada, Hiroaki; Furuno, Akiko; Chino, Masamichi

Journal of Nuclear Science and Technology, 41(5), p.632 - 640, 2004/05

 Times Cited Count:21 Percentile:78.55(Nuclear Science & Technology)

The new version of WSPEEDI (Worldwide version of System for Prediction of Environmental Emergency Dose Information) is developed by introducing the combination of models, the atmospheric dynamic model MM5 and the Lagrangian particle dispersion model GEARN-new to improve the prediction capability. One of the improvements by the new system is that Environmental contaminations in multi domains are predicted simultaneously, and the other is that more precise physical processes are considered by using predicted meteorological conditions with high resolution in time and space. The performance of the system is evaluated for the test calculations of hypothetical nuclear accident in the East Asia region and the Chernobyl accident. The results of test calculation in East Asia seem to be reasonable and the calculated surface air concentrations of $$^{137}$$Cs from Chernobyl show good agreement with measurements.

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