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Moriguchi, Yuichi*; Sato, Yosuke*; Morino, Yu*; Goto, Daisuke*; Sekiyama, Tsuyoshi*; Terada, Hiroaki; Takigawa, Masayuki*; Tsuruta, Haruo*; Yamazawa, Hiromi*
KEK Proceedings 2021-2, p.21 - 27, 2021/12
no abstracts in English
Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolutionSato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu
rel, A.*; Qulo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.
Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10
The third model intercomparison project for investigating the atmospheric behavior of Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.
Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.
Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10
Times Cited Count：6 Percentile：26.43(Environmental Sciences)The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.
Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input dataSato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; et al.
Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10
Times Cited Count：40 Percentile：85.28(Meteorology & Atmospheric Sciences)A model intercomparison of the atmospheric dispersion of Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed Cs events, and the figure-of-merit in space for the total deposition of Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the Cs concentrations.
Kr concentration in JapanTerada, Hiroaki; Nagai, Haruyasu; Yamazawa, Hiromi*
Journal of Nuclear Science and Technology, 50(12), p.1198 - 1212, 2013/12
Times Cited Count：11 Percentile：64.2(Nuclear Science & Technology)The Lagrangian atmospheric dispersion model of the nuclear emergency response system WSPEEDI-II was validated with the measured Kr concentrations in tens-of- to hundreds-of-km (middle-range) scale area by conducting dispersion simulations with the release rate from the Rokkasho reprocessing plant in Japan. The calculated weekly concentrations of Kr during April and September in 2008 agreed with the measurements within a factor of two. However, the sensitivity analysis to horizontal grid resolution of the meteorological model ranging from 2 to 54 km showed the calculated results had the dependency on the grid resolution. An empirical modification of the horizontal diffusion parameter was attempted based on the sensitivity analysis to reduce the redundant diffusion effect in dispersion simulations with relatively high grid resolution. The modified parameter contributed to reduce the dependency of calculated concentrations on the grid resolution.
I and Cs resulting from the Fukushima Daiichi Nuclear Power Plant accidentChino, Masamichi; Terada, Hiroaki; Katata, Genki; Nagai, Haruyasu; Nakayama, Hiromasa; Yamazawa, Hiromi*; Hirao, Shigekazu*; Ohara, Toshimasa*; Takigawa, Masayuki*; Hayami, Hiroshi*; et al.
NIRS-M-252, p.127 - 135, 2013/03
We estimated the release rates and total amounts of I and Cs discharged into the atmosphere from March 12 to April 5, 2011. The applied method is a reverse estimation by coupling environmental monitoring data with atmospheric dispersion simulations under the assumption of unit release rate (1 Bq/h). It calculates release rates of radionuclides (Bq/h) by dividing measured air concentrations of I and Cs into calculated ones at sampling points. The estimated temporal variation of releases indicates that the significant release, over 10
Bq/h of I, occurred on March 15, following to relatively small releases, 10
10
Bq/h, but the release rates from March 16 are estimated to be rather constant on the order 10 Bq/h until March 24. The release rates have decreased with small day-to-day variations to the order of 10
10
Bq/h of I on the beginning of April. The estimated source term was examined on the point of the time trend, total releases and the ground depositions of Cs by using different atmospheric dispersion models with above source term and compared them with observed Cs deposition distribution. These examinations showed that the estimated source term was reasonably accurate during the period when the plume flowed over land in Japan.
I and Cs accidentally discharged from the Fukushima Daiichi Nuclear Power Plant into the atmosphereChino, Masamichi; Nakayama, Hiromasa; Nagai, Haruyasu; Terada, Hiroaki; Katata, Genki; Yamazawa, Hiromi*
Journal of Nuclear Science and Technology, 48(7), p.1129 - 1134, 2011/07
Times Cited Count：731 Percentile：99.99(Nuclear Science & Technology)The release amounts of I and Cs into the atmosphere due to the Fukushima Daiichi Nuclear Power Plant is preliminary estimated by coupling monitoring data on air concentrations and atmospheric dispersion simulation assuming unit release rate (1 Bq/h). The estimated results show that the large amount of release, the peak value of about 10
Bq/h of I on March 15, continued for a week after the accident, and, after March 23, the release rates have generally been declining to the order of 10 to 10 Bq/h. The total amounts of I and Cs discharged into the atmosphere are estimated about 1.5
10
Bq and 1.210 Bq.
Furuno, Akiko; Terada, Hiroaki; Chino, Masamichi; Yamazawa, Hiromi*
Atmospheric Environment, 38(40), p.6989 - 6998, 2004/12
Times Cited Count：20 Percentile：41.46(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.
accountancy and quality assuranceKikuchi, Masahiro*; Muraoka, Susumu*; Osabe, Takeshi*; Terada, Hiromi; Shimizu, Kenichi; Otani, Tetsuo*; Fujimaki, Kazunori*; Ishikawa, Tadatsugu*; Shinohara, Yoshinori*
Dai-23-Kai Kaku Busshitsu Kanri Gakkai Nihon Shibu Nenji Taikai Rombunshu, p.91 - 98, 2002/12
Nuclear material measurement is an important measure to determine the amount of nuclear material of each stage such as receipt, shipment, inventory and hold-up. The material accountancy based on the material balance among the measurements is a measure to control of nuclear material. The material accountancy, from its technical aspect, can be used as promising measures for purposes from operator's level to state's level such as the nuclear safety, property control and environmental preservation other than safeguards measures only to conclude no diversion of nuclear material. This paper discusses various purposes of nuclear material measurements and clarifies the certain function to be expected at each purpose. Based on the discussion, critical points for the quality assurance of each stage are studied.
Nagai, Haruyasu; Furuno, Akiko; Terada, Hiroaki; Umeyama, Nobuaki; Yamazawa, Hiromi; Chino, Masamichi
JAERI-Research 2001-012, 28 Pages, 2001/03
JAERI-Research-2001-012.pdf:1.77MB
Japan Atomic Energy Research Institute is advancing the study for prediction of material circulation in the environment to cope with environmental pollution, based on SPEEDI (System for Prediction of Environmental Emergency Dose Information) and WSPEEDI (Worldwide version of SPEEDI), which are originally developed aiming at real-time prediction of atmospheric dispersion of radioactive substances accidentally released from nuclear facility. As a part of this study, dispersion simulation of volcanic gas erupted from Miyake Island is put into practice. After the stench incident at the west Kanto District on 28 August 2000 caused by volcanic gas from Miyake Island, simulations dealing with atmospheric dispersion of volcanic gas from Miyake Island have been carried out. This report describes the details of these studies.
Katagiri, Masaki; Kishimoto, Maki; Terada, Hiromi; ; *; ; Ito, Hirokuni; ; Kobayashi, Fumiaki
IEEE Transactions on Nuclear Science, 37(3), p.1400 - 1404, 1990/06
Times Cited Count：3 Percentile：45.11(Engineering, Electrical & Electronic)no abstracts in English
Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Grahn, H.*; Br
nnstr
m, N.*; von Schoenberg, P.*; Kondo, Hiroaki*; Terada, Hiroaki; Nagai, Haruyasu; et al.
no journal, ,
The second intercomparison of atmospheric model targeting on the radionuclide (i.e. Cs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 2011 is conducted. Thirteen atmospheric models, which include both the Lagrangian- and Eulerian-based dispersion models, participate in this model intercomparison project (MIP). The purposes of this MIP are to (1) understand the transport process of the radionuclide in atmosphere, (2) estimate the uncertainties in wet and dry deposition process among the models, (3) reveal the essential key processes to reproduce the plume of Cs, (4) assess the multi-model ensemble mean, and (5) obtain the knowledge for improving the physical processes of the models. To exclude the uncertainties of the model results originated from the emission inventory, all models used the same emission inventory. The meteorological data with fine spatiotemporal resolution, which was calculated by the Japanese operational weather forecast model coupled with the local ensemble transform Kalman Filter data assimilation system, was applied for all models to reduce the uncertainties originated from the difference in the meteorological field. As well as the comparison among the models, the comparison between the models and in-situ measurement from the national suspended particle matter (SPM) sampling network are conducted. The comparisons between the model results and the SPM data indicate that the Cs concentration near the FDNPP transported without precipitation process was relatively well reproduced by using the meteorological data with fine spatiotemporal resolution. On the contrary, Cs concentration accompanied with precipitation has large inter-model spread. In the presentation, we will discuss the more detailed analyses about the physical process to determine the Cs concentration.
Cs from the Fukushima Daiichi Nuclear Power Plant Accident using identical input dataSato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; et al.
no journal, ,
An intercomparison of atmospheric dispersion model targeting on the physical process of Cs released from the Fukushima Daiichi Nuclear Power Plant was conducted. Twelve atmospheric models participated in this project. To exclude the uncertainties of the model result due to the emission inventory and meteorological data, all models used the same emission and meteorological data. Concentration of Cs from the national suspended particle matter monitoring network and the deposition density by the aircraft were used for the comparison between results of the model and observation. Our analyses elucidated the figure of merit in space (FMS) of the model ensemble mean was improved from a previous model intercomparson about the accumulated deposition. The model ensemble mean captured approximately 36% of the observed high concentration. The inter-model spread of the capture rate was from 8% to 38%. It was originated from the difference in deposition and diffusion processes among the models.
Cs from the Fukushima Daiichi Nuclear Power Station Accident using identical meteorological data and source termSato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; et al.
no journal, ,
no abstracts in English
Yamazawa, Hiromi*; Oura, Yasuji*; Moriguchi, Yuichi*; Terada, Hiroaki; Sekiyama, Tsuyoshi*; Goto, Daisuke*; Tsuruta, Haruo*
no journal, ,
no abstracts in English
Cs) from the Fukushima Daiichi Nuclear Power Station Accident using identical meteorological data and source termSato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; et al.
no journal, ,
no abstracts in English
Yamazawa, Hiromi*; Sato, Yosuke*; Adachi, Shinichiro*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; et al.
no journal, ,
Cs-137 released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was conducted by 12 models. The present study focuses on differences in the model results of atmospheric Cs-137 concentration of Plume 2, which traveled southward in the morning of 15 March, 2011, in the area 100 to 200 km downwind from FDNPP by using the concentration data recently evaluated from gamma radiation spectral data at monitoring stations (MS data) and those measured from the suspended particulate matter filters (SPM data). Comparison was made from the following aspects: (1) plume arrival time, (2) concentration level, (3) cross-wind surface concentration profile, (4) vertical concentration profile and (5) mass balance of Cs-137 activity including deposition processes. Additional analyses were made also for Plume 4, which traveled over the same area on 16 March under rainy condition.
Yamazawa, Hiromi*; Sato, Yosuke*; Oura, Yasuji*; Moriguchi, Yuichi*; Terada, Hiroaki; Furuno, Akiko; Tsuzuki, Katsunori; Kadowaki, Masanao; Sekiyama, Tsuyoshi*; Adachi, Koji*; et al.
no journal, ,
no abstracts in English
Yamazawa, Hiromi*; Sato, Yosuke*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Goto, Daisuke*; Morino, Yu*; Kondo, Hiroaki*; Qurel, A.*; Fang, S.*; Takigawa, Masayuki*; et al.
no journal, ,
Following the previous atmospheric transport model intercomparison project (MIP2), a new model intercomparison (MIP3) has been conducted in which, out of 12 models in MIP2, 9 models are participating. The main aim of MIP3 is to examine the effects of using a refined meteorological data with a finer horizontal resolution of 1 km. The horizontal distribution Cs-137 deposition in the eastern part of Honshu Island calculated by the models were compared with the aerial survey results to find that the simple ensemble average of the 9 models was a little worse than that of the 12-model ensemble in MIP2 statistically. However, in the sector in the northwestern direction from the accidental site, the deposition pattern by the MIP3 ensemble is more consistent with the survey result compared with that of MIP2. As for the atmospheric concentrations, although the model performance for the plumes that traveled over wider areas was slightly poorer for MIP3 than MIP2, the MIP3 ensemble generally showed better performance for the plumes that affected the near area in the Hamadori area. This better performance can be attributed to the better representation of topography in the meteorological simulation.
Cs from the Fukushima Daiichi Nuclear Power Station AccidentSato, Yosuke*; Sekiyama, Tsuyoshi*; Sheng, F.*; Kajino, Mizuo*; Qulo, D.*; Qurel, A.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.
no journal, ,
no abstracts in English
