Atmospheric ammonia deposition and its role in a cool-temperate fragmented deciduous broad-leaved forest

Katata, Genki*; Yamaguchi, Takashi*; Watanabe, Makoto*; Fukushima, Keitaro*; Nakayama, Masataka*; Nagano, Hirohiko*; Koarashi, Jun; Tateno, Ryunosuke*; Kubota, Tomohiro

Atmospheric Environment, 298, p.119640_1 - 119640_12, 2023/04

https://doi.org/10.1016/j.atmosenv.2023.119640

Reconstruction of the atmospheric releases of I and Cs resulting from the Fukushima Daiichi Nuclear Power Plant accident

Chino, 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

http://repo.nirs.go.jp/dspace/bitstream/918273645/330/1/nirs_m_252.pdf

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.

Preliminary estimation of release amounts of I and Cs accidentally discharged from the Fukushima Daiichi Nuclear Power Plant into the atmosphere

Chino, Masamichi; Nakayama, Hiromasa; Nagai, Haruyasu; Terada, Hiroaki; Katata, Genki; Yamazawa, Hiromi*

Journal of Nuclear Science and Technology, 48(7), p.1129 - 1134, 2011/07

https://doi.org/10.3327/jnst.48.1129

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 1.510 Bq and 1.210 Bq.

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2008 (Joint research)

Nakatsuka, Noboru; Hatanaka, Koichiro; Sato, Haruo; Sugita, Yutaka; Nakayama, Masashi; Miyahara, Shigenori; Asano, Hidekazu*; Saito, Masahiko*; Suyama, Yasuhiro*; Hayashi, Hidero*; et al.

JAEA-Research 2009-044, 53 Pages, 2010/01

JAEA-Research-2009-044.pdf:9.03MB

Japan Atomic Energy Agency (JAEA) and Radioactive Waste Management Funding and Research Center (RWMC) effect an agreement about research and development of high level radioactive waste (HLW) disposal and carried out research and technological development about geological disposal technology. JAEA has been carried out the Horonobe Underground Research Laboratory (URL) Project which is intended for sedimentary rock and the Project includes geoscientific research and geological disposal technology. RWMC carried out an investigation about full-scale demonstration of engineered barrier system (EBS) and operation technology for HLW disposal, under the contract with the Natural Resources and Energy Agency, Ministry of Economy, the Trade and Industry. The investigation aims to obtain the citizens' understanding of the geological disposal. This work includes the full-scale demonstration of operation technology in the Horonobe URL. This joint research is about engineering technology concerned with the work. In 2008 fiscal year (2008/2009), the master plan of the work was made, and a part of the device for transportation of engineered barrier was made, and it has begun the exhibition of full-scale bentonite block and overpack.

Analyses of minor elements distribution on SUS316(LC) thermally aged under the stress loading condition

Kondo, Keietsu; Nemoto, Yoshiyuki; Miwa, Yukio; Kaji, Yoshiyuki; Tsukada, Takashi; Yoneyama, Natsuki*; Nakayama, Gen*

no journal, , 

no abstracts in English

Application of numerical simulation system of JAEA to predict the environmental transport of radioactive materials discharged from the Fukushima Nuclear Power Plant

Nagai, Haruyasu; Chino, Masamichi; Terada, Hiroaki; Katata, Genki; Nakayama, Hiromasa

no journal, , 

Japan Atomic Energy Agency has been applying its numerical simulation system to predict the environmental transport of radioactive materials discharged from Fukushima Daiichi Nuclear Power Plant. As the first step, the source term of radioactive materials discharged from the plant into the atmosphere has been estimated by coupling environmental monitoring data with atmospheric dispersion simulations by SPEEDI and WSPEEDI under the assumption of unit release rate (1 Bq/h). As the next step, we are planning to apply our numerical simulation system for material transport in the atmospheric, terrestrial, and oceanic environments, SPEEDI-MP. The method and preliminary results of source estimation and our future plan will be presented.

Atmospheric dispersion simulation of radionuclides in the Eastern Japan region discharged from the Fukushima Daiichi Nuclear Power Plant by WSPEEDI-II

Terada, Hiroaki; Nagai, Haruyasu; Katata, Genki; Furuno, Akiko; Nakayama, Hiromasa; Chino, Masamichi

no journal, , 

To make a contribution to dose assessment of residents and understanding of the formation mechanism of contamination distribution due to the Fukushima Daiichi nuclear accident, we conducted an atmospheric dispersion analysis by using Worldwide version of System for Prediction of Environmental Emergency Dose Information, WSPEEDI-II. The source conditions of released radionuclides we used in our model calculations were based on the tentative values which had been announced by the Nuclear Safety Commission (NSC) of Japan on April 12 and published in Chino et al. (2011). We examined the validity of estimated release rates of radionuclides and model reproducibility for environmental monitoring data such as air dose rate and daily fallout which was measured throughout Japan and announced by the Ministry of Education, Culture, Sports, Science and Technology (MEXT).

Source term estimation and atmospheric dispersion simulations of radioactive materials discharged from the Fukushima Daiichi Nuclear Power Plant due to accident

Nagai, Haruyasu; Chino, Masamichi; Terada, Hiroaki; Katata, Genki; Nakayama, Hiromasa; Ota, Masakazu

no journal, , 

Japan Atomic Energy Agency (JAEA) has been undertaking the task to reconstruct the atmospheric dispersion of radioactive materials discharged from the Fukushima Daiichi Nuclear Power Plant by using computer simulation. As the first step, the source term of radioactive materials discharged into the atmosphere was estimated by coupling environmental monitoring data with atmospheric dispersion simulations under the assumption of unit release rate (1 Bq/h). By using the estimated source term, detailed analysis on the local dispersion around the plant and regional scale dispersion over the eastern Japan area were carried out by WSPEEDI-II simulations. The formation processes of high dose rate zone around north-west direction from the plant and deposition over the eastern Japan area were well reproduced.

Development of a method to estimate dry deposition distributions in forest canopy using a local-scale high-resolution atmospheric dispersion model

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.

Corrosion behavior of weld joint of carbon steel overpack under geological environment, 2; Corrosion behavior of engineering scale testing

Yamazaki, Kazutoshi*; Takao, Hajime*; Kikuchi, Takahiro*; Kuriki, Yoshiro*; Kobayashi, Masato*; Kawakubo, Masahiro*; Shirase, Mitsuyasu*; Iwata, Yumiko*; Tochigi, Yoshikatsu*; Nakayama, Gen*; et al.

no journal, , 

Among factors affecting the corrosion behavior of carbon steel overpack, in order to consider materials (size) and realistic environmental factors which are difficult to reproduce in the laboratory scale test, engineering scale tests in the underground environment were carried out. A mock-up test of the same scale was also carried out on the ground with the aim of controlling and evaluating factors that govern the corrosion phenomenon. As a result of the test for about 3 years, there was no big difference between the average corrosion amount and the maximum corrosion amount of the simulated overpack base metal and the welded part. On the other hand, unlike the laboratory scale test, localization of corrosion due to the adhesion between the buffer material and the simulated overpack was also confirmed during the initial transient period.