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Journal Articles

Soil microbial community responding to moderately elevated nitrogen deposition in a Japanese cool temperate forest surrounded by fertilized grasslands

Nagano, Hirohiko; Nakayama, Masataka*; Katata, Genki*; Fukushima, Keitaro*; Yamaguchi, Takashi*; Watanabe, Makoto*; Kondo, Toshiaki*; Atarashi-Andoh, Mariko; Kubota, Tomohiro*; Tateno, Ryunosuke*; et al.

Soil Science and Plant Nutrition, 67(5), p.606 - 616, 2021/10

 Times Cited Count:0 Percentile:0.02(Plant Sciences)

We analyzed the relationships between nitrogen deposition (deposition of nitrate and ammonium ions) and soil microbial properties in a cool temperate forest surrounded by normally fertilized pasture grasslands in northern Japan. The aim of the present study was to gain the primary information on soil microbial response to moderately elevated nitrogen deposition ($$<$$ 10 kg N ha$$^{-1}$$ y$$^{-1}$$). We established three experimental plots in the forest edge adjacent to grasslands and other three plots in the forest interior at least 700 m away from the grasslands. During May to November 2018, nitrogen deposition in each plot was measured. In August 2018, litter and soil (0-5 cm depth) samples were collected from all plots to measure net nitrogen mineralization and nitrification rates as indicators of microbial activity, and microbial biomass carbon and nitrogen and various gene abundances (i.e. bacterial 16S rRNA, fungal ITS, bacterial amoA, and archaeal amoA genes) as indicators of microbial abundance and structure. Nitrogen deposition in the forest edge was 1.4-fold greater than that in the forest interior, even while the maximum deposition was 3.7 kg N ha$$^{-1}$$. Nitrogen deposition was significantly correlated to the net nitrogen mineralization and nitrification rates and the 16S rRNA and bacterial amoA gene abundances. Microbial community structures were different between litter and soil samples but were similar between the forest edge and interior. Significant correlations of nitrogen deposition to the soil carbon to nitrogen ratio, and the nitrate and ammonium contents were also observed. Thus, our results show that moderately elevated nitrogen deposition in nitrogen-limited forest edges can stimulate microbial activities and abundances in soils.

Journal Articles

Reconstruction of the atmospheric releases of $$^{131}$$I and $$^{137}$$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

We estimated the release rates and total amounts of $$^{131}$$I and $$^{137}$$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 $$^{131}$$I and $$^{137}$$Cs into calculated ones at sampling points. The estimated temporal variation of releases indicates that the significant release, over 10$$^{15}$$ Bq/h of $$^{131}$$I, occurred on March 15, following to relatively small releases, 10$$^{13}$$ $$sim$$ 10$$^{14}$$ Bq/h, but the release rates from March 16 are estimated to be rather constant on the order 10$$^{14}$$ Bq/h until March 24. The release rates have decreased with small day-to-day variations to the order of 10$$^{11}$$ $$sim$$ 10$$^{12}$$ Bq/h of $$^{131}$$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 $$^{137}$$Cs by using different atmospheric dispersion models with above source term and compared them with observed $$^{137}$$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.

Journal Articles

Application of numerical simulation to predict the environmental transport of radioactive materials discharged from Fukushima Daiichi Nuclear Power Plant due to accident

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

Proceedings of International Symposium on Disaster Simulation & Structural Safety in the Next Generation (DS '11), p.369 - 374, 2011/09

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Plant accident, the spatial and temporal distribution of radioactive materials in the environment have been and are planning to be analyzed by SPEEDI, WSPEEDI-II, and the numerical simulation system for material transport in the atmospheric, terrestrial, and oceanic environments, SPEEDI-MP. As the first step, the source term of radioactive materials discharged into the atmosphere has been estimated by coupling environmental monitoring data with atmospheric dispersion simulations by SPEEDI and WSPEEDI-II. As the next step, detailed analysis on the local dispersion around the plant by using WSPEEDI-II revealed the mechanism for the formation of high dose rate zone around north-west direction from the plant. Then, we are planning to apply SPEEDI-MP to provide more information on the distribution of radioactive materials in the whole environment.

Journal Articles

Preliminary estimation of release amounts of $$^{131}$$I and $$^{137}$$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

 Times Cited Count:644 Percentile:99.99(Nuclear Science & Technology)

The release amounts of $$^{131}$$I and $$^{137}$$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$$^{16}$$ Bq/h of $$^{131}$$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$$^{11}$$ to 10$$^{12}$$ Bq/h. The total amounts of $$^{131}$$I and $$^{137}$$Cs discharged into the atmosphere are estimated about 1.5$$times$$10$$^{17}$$ Bq and 1.2$$times$$10$$^{16}$$ Bq.

JAEA Reports

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2009 (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 2010-060, 50 Pages, 2011/02

JAEA-Research-2010-060.pdf:6.7MB

Japan Atomic Energy Agency (JAEA) and Radioactive Waste Management Funding and Research Center (RWMC) concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work described above based on the agreement. JAEA have been carrying out the Horonobe Underground Research Laboratory (URL) Project which is intended for sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, the government (the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry) has been promoting construction of equipments for the full-scale demonstration of engineered barrier system and operation technology for high-level radioactive waste (HLW) disposal since 2008, to enhance publics understanding to the geological disposal of HLW, using underground facility, etc. RWMC received an order of the project in fiscal year 2009 (2009/2010) continuing in fiscal year 2008 (2008/2009). Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing in fiscal year 2008. This report summarizes the results of engineering technology carried out in this collaboration work in fiscal year 2009. In fiscal year 2009, a part of the equipments for equipment of buffer material and visualization test apparatus for water penetration in buffer material were produced and house for the equipments and apparatus was constructed.

JAEA Reports

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.

JAEA Reports

Development and management of the knowledge base for the geological disposal technology; Annual report 2006

Umeda, Koji; Oi, Takao; Osawa, Hideaki; Oyama, Takuya; Oda, Chie; Kamei, Gento; Kuji, Masayoshi*; Kurosawa, Hideki; Kobayashi, Yasushi; Sasaki, Yasuo; et al.

JAEA-Review 2007-050, 82 Pages, 2007/12

JAEA-Review-2007-050.pdf:28.56MB

This report shows the annual report which shows the summarized results and topic outline of each project on geological disposal technology in the fiscal year of 2006.

Oral presentation

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

Oral presentation

Local-scale atmospheric dispersion simulation of radionuclides discharged from Fukushima Daiichi Nuclear Power Plant by WSPEEDI-II

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

no journal, , 

no abstracts in English

Oral presentation

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.

Oral presentation

Overview of dispersion analysis by JAEA for radionuclides discharged from the Fukushima Daiichi Nuclear Power Plant into the environment

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

no journal, , 

no abstracts in English

Oral presentation

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).

Oral presentation

Analysis on the atmospheric dispersion of radionuclides discharged from the TEPCO's Fukushima Daiichi Nuclear Power Plant

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

no journal, , 

no abstracts in English

Oral presentation

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.

Oral presentation

Analysis on the atmospheric dispersion processes

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

no journal, , 

no abstracts in English

Oral presentation

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.

Oral presentation

High-resolution numerical simulation of turbulent flows and dry deposition in mountainous forest

Nakayama, Hiromasa; Katata, Genki*

no journal, , 

Dry deposition is important process of chemical material input of gaseous and particulate forms from the atmosphere into the terrestrial ecosystem near the ground surface in the planetary boundary layer. It is difficult to accurately estimate dry deposition amounts for such areas. First, we incorporate our particle dry deposition scheme into the loca-scale high-resolution atmospheric dispersion model and perform test simulations in comparison to indoor experiments. Next, we apply to the hilly-terrain forest in a field-site to analyze the impact of topography and forest structure to dry deposition. It is found that the model successfully simulated the maximum values at the edge of the forest and exponential decrease with a downwind distance from the edge as well as the experiments. Furthermore, for the field-site, the distribution of dry deposition shows a peak at the forest edge, rapidly decreases with a downwind distance from the edge. Although the local decrease is observed at the forest gap, that shows nearly constant within the canopy.

Oral presentation

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.

Oral presentation

Relationship between nitrogen deposition and soil microbial property in a deciduous broad-leaved forest

Nagano, Hirohiko; Atarashi-Andoh, Mariko; Fukushima, Keitaro*; Nakayama, Masataka*; Katata, Genki*; Yamaguchi, Takashi*; Watanabe, Makoto*; Kondo, Toshiaki*; Tateno, Ryunosuke*; Koarashi, Jun

no journal, , 

no abstracts in English

Oral presentation

Does spatially heterogeneous nitrogen deposition affect nitrogen and carbon dynamics in a decidous broad-leaved forest?

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

no journal, , 

no abstracts in English

23 (Records 1-20 displayed on this page)