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Terada, Hiroaki
Ten Hasseigen Karano Mesosukeru Kakusan Shumireshon; Fukushima Daiichi Genshiryoku Hatsudensho Jiko O Fumaete (Kisho Kenkyu Noto Dai-248-Go), p.115 - 121, 2023/09
no abstracts in English
Terada, Hiroaki; Nagai, Haruyasu
Isotope News, (775), p.44 - 48, 2021/06
no abstracts in English
Nakayama, Hiromasa; Takemi, Tetsuya*
Proceedings of 18th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes (HARMO-18) (USB Flash Drive), p.843 - 847, 2017/10
We have attempted to develop a practical and quick local-scale atmospheric dispersion calculation method using an overlapping technique for plume concentration distributions in an emergency response to nuclear accidents. In order to evaluate the overlapping approach, we performed LESs of turbulent flows and plume dispersion under varying mean wind directions using the meteorological data as the model input. When compared with the simulated results under the real meteorological condition, it is shown that the concentration distribution patterns are reasonably simulated by the overlapping method. It can be concluded that the atmospheric dispersion calculation method using the overlapping technique has potential performance for emergency responses to nuclear accidents.
C accumulated in vegetation around a nuclear facility; Application of a sophisticated land surface C model to the Rokkasho reprocessing plant, JapanOta, Masakazu; Katata, Genki; Nagai, Haruyasu; Terada, Hiroaki
Journal of Environmental Radioactivity, 162-163, p.189 - 204, 2016/10
Times Cited Count：7 Percentile：22.17(Environmental Sciences)Impacts of plant C uptake on (C) distributions around a nuclear facility were investigated by a land surface C model (SOLVEG-II). The simulation combined the SOLVEG-II with a mesoscale model and an dispersion model was applied to CO
transfer at test operations of the Rokkasho reprocessing plant (RRP) in 2007. The calculated C-specific activities in rice grains agreed with the observations. Numerical experiment of chronic CO release from the RRP showed that C-specific activities of rice plants at harvest differed from the annual mean ones in the air, which was attributed to seasonal variations in atmospheric CO and plant growth. C accumulation in plant significantly increased when CO releases were limited during daytime, compared with the results observed during nighttime, due to extensive CO uptake by daytime photosynthesis. These results indicated that plant growth and photosynthesis should be considered in predictions of ingestion dose of C for long-term chronic and short-term diurnal releases of CO, respectively.
Nagai, Haruyasu; Terada, Hiroaki; Chino, Masamichi; Katata, Genki; Mikami, Satoshi; Saito, Kimiaki
Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.4044 - 4052, 2015/08
JAEA has estimated the atmospheric releases of radionuclide during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric transport and deposition model (ATDM). To improve our source term, we are trying to develop more sophisticated estimation method and use new information from severe accident analysis and observation data. As the first step of new trial, we used 
Cs/
Cs ratios of inventories in FNPS1 reactors Unit 1 to 3 and those in surface deposition. By considering temporal change in Cs/Cs ratio of released plume and ATDM simulations, spatial distribution of Cs/Cs ratio in surface deposition was explained. This result can be used to specify from which reactor the dominant release occurred for each time period, and consequently provide useful information to severe accident analysis for the FNPS1 case.
*; Kishimoto, Yoichiro; Narita, Osamu; Shinohara, Kunihiko*; *
PNC TN843 77-05, 25 Pages, 1977/06
A computer program has been written to calculate the exposure dose at an arbitrary point in the atmosphere caused by the emission of radioactive materials from a stack. The dispersion of materials in air is expressed by the Gaussian plume model with ground surface and inversion lid reflections. The exposure or absorbed dose in air is calculated by the spatial integration of point-kernels. Several approximate methods, such as homogeneous-infinite-slab approximation, submersion approximation, etc, have been incorporated as well.
Nagai, Haruyasu
no journal, ,
JAEA has estimated the atmospheric releases of radionuclide during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric transport and deposition model WSPEEDI. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has used our source term for estimating levels of radioactive material in the environment and doses to the public. To improve our source term, we recently made detailed source term estimation by using additional monitoring data near the FNPS1 and WSPEEDI including new deposition scheme. The simulation of modified WSPEEDI and the new source term successfully reproduced the local and regional deposition pattern of 
I and Cs.
Nakayama, Hiromasa; Katata, Genki
no journal, ,
Dry deposition is the process by which gaseous materials and aerosol particles deposit on the ground surface by turbulence or gravity settling. In Japan, many forest areas are located over hilly complex surface geometries. It is difficult to accurately estimate dry deposition amounts for such areas. To deal with the problems, we have developed a local-scale high-resolution atmospheric dispersion model using Large-Eddy Simulation at a grid scale less than 10m which can consider the turbulent effects of local terrain, buildings, and trees. In this study, we apply this model to the study forest site in the suburbs of Tokyo and investigate the relationship between the structure of the forest canopy and dry deposition amounts, considering the dry deposition process of PM2.5.
Yamazawa, Hiromi*; Oura, Yasuji*; Moriguchi, Yuichi*; Terada, Hiroaki; Sekiyama, Tsuyoshi*; Goto, Daisuke*; Tsuruta, Haruo*
no journal, ,
no abstracts in English
