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Journal Articles

Characterizing vertical migration of $$^{137}$$Cs in organic layer and mineral soil in Japanese forests; Four-year observation and model analysis

Muto, Kotomi; Atarashi-Andoh, Mariko; Matsunaga, Takeshi*; Koarashi, Jun

Journal of Environmental Radioactivity, 208-209, p.106040_1 - 106040_10, 2019/11

 Times Cited Count:2 Percentile:55.77(Environmental Sciences)

Vertical distributions of $$^{137}$$Cs in the soil profile were observed at five forest sites with different vegetation types for 4.4 years after the Fukushima Dai-ichi Nuclear Power Plant accident, and $$^{137}$$Cs migration in the organic layer and mineral soil was analyzed based on a comparison of models and observations. Cesium-137 migration from the organic layer was faster than that observed in European forests, suggesting that the mobility and bioavailability of $$^{137}$$Cs could be suppressed rapidly in Japanese forests. The diffusion coefficients of $$^{137}$$Cs in the mineral soil were estimated to be 0.042-0.55 cm$$^2$$y$$^{-1}$$, which were roughly comparable with those of European forest soils affected by the Chernobyl Nuclear Power Plant accident. Model predictions indicated $$^{137}$$Cs mainly distributed in the surface mineral soil at 10 years after the accident. It suggest that the $$^{137}$$Cs deposited onto Japanese forest ecosystems will be retained in the surface layers of mineral soil for a long time.

Journal Articles

Role of filamentous fungi in migration of radioactive cesium in the Fukushima forest soil environment

Onuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Namba, Kenji*; Neda, Hitoshi*; Sasaki, Yoshito; Niizato, Tadafumi; Watanabe, Naoko*; Kozaki, Tamotsu*

Environmental Science; Processes & Impacts, 21(7), p.1164 - 1173, 2019/07

 Times Cited Count:2 Percentile:74.04(Chemistry, Analytical)

The fate of radioactive Cs deposited after the Fukushima nuclear power plant accident and its associated radiological impacts are largely dependent on its mobility from surface soils to forest ecosystems. We measured the accumulation of radioactive Cs in the fruit bodies of wild fungi in the forest at Iidate, Fukushima, Japan. The transfer factors (TFs) of radioactive Cs from soil to the fruit bodies of wild fungi were between 10 $$^{-2}$$to 10$$^{2}$$, a range similar to those reported for the fruit bodies collected in Europe after the Chernobyl accident and in parts of Japan contaminated by nuclear bomb test fallout. Comparison of the TFs of the wild mushroom and that of the fungal hyphae of 704 stock strains grown on agar medium containing nutrients and radioactive Cs showed that the TFs of wild mushroom were lower. TF was less than 0.1 after addition of the minerals zeolite, vermiculite, phlogopite, smectite, or illite of 1% weight to the agar medium. These results indicate that the presence of minerals decrease Cs uptake by fungi grown in the agar medium.

Journal Articles

Study on combination hazard curve of forest fire with lightning and strong wind

Okano, Yasushi; Yamano, Hidemasa

Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 3 Pages, 2017/11

Forest fire hazard assessment methodologies using a logic tree have been applied for the evaluation of combination hazard curves of a forest fire with lightning as an initiator of a forest fire and with a strong wind being independent from a forest fire. The complex shape of the combinational hazard curve of forest fire and lighting is due to that both lightning and high velocity wind tend to appear under unstable weather conditions, and there is correlation between two hazards. The evaluated combinational hazard curve of forest fire and strong wind for the instantaneous wind velocity over 80 m/s has extremely small frequency in the range below 10$$^{-14}$$/year.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima; As a part of dissemination of evidence-based information

Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.

JAEA-Review 2017-018, 86 Pages, 2017/10

JAEA-Review-2017-018.pdf:17.58MB

Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.

Journal Articles

Analysis on the effect of forest decontamination on reducing the air dose rate using the three-dimensional transport code MCNP

Hemmi, Ko; Yamaguchi, Tetsuji; Takeda, Seiji; Kimura, Hideo

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.3 - 14, 2017/06

Conditions of contaminated sources and ranges of forest decontamination that significantly reduce the air dose rate in residential areas were investigated by means of a sensitivity analysis related to the decontamination of the forest contaminated by radiocesium deriving from the accident at Fukushima Daiichi Nuclear Power Station. The contaminated sources including $$^{134}$$Cs and $$^{137}$$Cs were assumed to be a layer of sedimented organic matter (the A$$_{0}$$ layer) and surface soils (the A$$_{1}$$ layer). The air dose rates were calculated using the three-dimensional Monte Carlo transport code MCNP. A slope number of the forest, angles, state of contaminant distribution, radiocesium content in the forest soils, decontamination ranges, distance from the forest boundary to an evaluation point, and height at the evaluation point were adopted as the parameters. The decontamination of a litter (A$$_{0}$$) layer within the distance of 20 m from the forest boundary was revealed to be effective in reducing the air dose rate when the source distribution was homogeneous. The air dose rates were significantly reduced by the decontamination of the A$$_{0}$$ layer within a distance of 40 m from the forest boundary on condition that the radiocesium content of the A$$_{0}$$ layer was larger than that of the A$$_{1}$$ layer and the source distribution was non-homogeneous, such as the forest areas beyond 20 m from the forest boundary, which were more heavily contaminated than those within 20 m.

Journal Articles

Input and output budgets of radiocesium concerning the forest floor in the mountain forest of Fukushima released from the TEPCO's Fukushima Dai-ichi Nuclear Power Plant accident

Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito; Ishii, Yasuo; Watanabe, Takayoshi

Journal of Environmental Radioactivity, 161, p.11 - 21, 2016/09

 Times Cited Count:19 Percentile:27.89(Environmental Sciences)

Estimations of radiocesium input and output budgets concerning the forest floor in a mountain forest region have been conducted in the north and central part of the Abukuma Mountains of Fukushima, after 2 to 3 year period following the TEPCO Fukushima Dai-ichi Nuclear Power Plant accident. The radiocesium input and output associated with surface washoff, throughfall, stemflow, and litterfall processes at the experimental plots have been monitored on a forest floor of evergreen Japanese cedar and deciduous Konara oak forests. The results at both monitoring locations show the radiocesium input to be 4-50 times higher than the output during the rainy season in Fukushima. These results indicate that the radiocesium tend to be preserved in the forest ecosystem due to extremely low output ratios. Thus, the associated fluxes throughout the circulation process are key issues for the projecting the environmental fate of the radiocesium levels.

JAEA Reports

Impact assessment of the forest fires on Oarai Research and Development Center Waste Treatment Facility

Shimomura, Yusuke; Hanari, Akira*; Sato, Isamu*; Kitamura, Ryoichi

JAEA-Technology 2015-062, 47 Pages, 2016/03

JAEA-Technology-2015-062.pdf:1.85MB

In response to new standards for regulating waste management facilities, it was carried out impact assessment of forest fires on the waste management facilities existed in Oarai Research and Development Center of Japan Atomic Energy Agency. At first, a fire spread scenario of forest fires was assumed. The intensity of forest fires was evaluated from field surveys, forest fire evaluation models and so on. As models of forest fire intensity evaluation, Rothermel Model and Canadian Forest Fire Behavior Prediction (FBP) System were used. Impact assessment of radiant heat to the facilities was carried out, and temperature change of outer walls for the assumed forest fires was estimated. The outer wall temperature of facilities was estimated around 160$$^{circ}$$C at the maximum, it was revealed that it doesn't reach allowable temperature limit. Consequently, it doesn't influence the strength of concrete. In addition, a probability of fire breach was estimated to be about 20%. This report illustrates an example of evaluation of forest fires for the new regulatory standards through impact assessment of the forest fires on the waste management facilities.

Journal Articles

Development of a hazard curve evaluation method for a forest fire as an external hazard

Okano, Yasushi; Yamano, Hidemasa

Proceedings of International Topical Meeting on Probabilistic Safety Assessment and Analysis (PSA 2015) (USB Flash Drive), p.22 - 31, 2015/04

An external hazard curve of a forest fire is evaluated based on a logic tree. The logic tree consists domains of "forest fire breakout and spread conditions", "weather condition" and "vegetation and topographical conditions". A location nearby a typical nuclear power plant site in Japan was selected, and the frequency of a large forest fire of the location is approximately 1/5 of the average in Japan. Forest fire breakout points were selected considering typical forest fire causes in Japan. The weather conditions are represented by two parameter sets of "temperature-humidity" and "wind direction-wind speed". A number of forest fire simulations were performed to obtain a response surface for a frontal fireline intensity. The hazard curve is therefore evaluated by a Monte Carlo simulation such that the annual exceedance probability is about 1.0$$times$$10$$^{-4}$$ per year for the frontal fireline intensity of 200 kW/m and about 1.3$$times$$10$$^{-5}$$ per year for 300 kW/m.

Journal Articles

Estimation of $$^{14}$$CO$$_{2}$$ flux at soil-atmosphere interface and distribution of $$^{14}$$C in forest ecosystem

Koarashi, Jun; Amano, Hikaru; Atarashi-Andoh, Mariko; Iida, Takao*; Moriizumi, Jun*

Journal of Environmental Radioactivity, 60(3), p.249 - 261, 2002/06

 Times Cited Count:15 Percentile:62.5

no abstracts in English

JAEA Reports

Development of field investigation techniques for study of regional groundwater Flow; Remote sensing; Study of hydrological characteristics of subsurface using topographic and vegetational information; Part 1

Koide, Kaoru; Yanagizawa, Koichi

PNC-TN7410 93-016, 42 Pages, 1993/10

PNC-TN7410-93-016.pdf:3.7MB

The purpose of this study is to develop estimation methods of hydrological characteristics of subsurface using regional data such as remote sensing data and topographical data in order to evaluate regional groundwater flow in Japan. This study consists of following three steps. The first step is to develop methods to extract the ground surface information. The second step is to quantify the relationship between the ground surface conditions and hydrological characteristics. And the final step is to develop estimation methods of hydrological characteristics of subsurface by using ground surface information. This paper describes the development of extraction methods on the ground surface information as the first step in our study. In this paper, topography and vegetation parameters were selected as the ground surface information which is considered relating to water balance which is one of hydrological characteristics. The study site was selected in the area (5km $$times$$ 5km) around the Tono uranium Mine, Central Japan. In order to extract topographic information, we developed a computer program to calculate direction and inclination of hill slopes using digital elevation map (DEM). The program was validated by comparing calculated results with measured slope data which were read from topographic map in the study site. We also examined grid intervals of DEM so that terrain in the study site can be represented appropriately. As a result, it was known that the grid interval of DEM should be less than 30m in the study site. We tried to classify forest types into three classes, a broad-leaved forest, conifer forest and mixed forest, using seasonal change of the normalized vegetation index (NVI) that was calculated from SPOT HRV data. Multi-temporal data (summer, autumn and winter) of SPOT were used to determine seasonal change of NVI of each forest type. As a result, it was definitely shown that each forest type has a different seasonal change of NVI. We ...

Journal Articles

Environmental monitoring of tritium around radioactive waste disposal area; Analysis of tritium movement in a forest

Amano, Hikaru

Proc. of the 5th Int. Seminar for Liquid Scintillation Analysis, p.55 - 76, 1993/00

no abstracts in English

Journal Articles

Seasonal trends in environmental tritium concentrations in a small forest adjacent to a radioactive waste storage area

Amano, Hikaru; C.T.Garten-Jr.*

Fusion Technology, 21, p.700 - 705, 1992/03

no abstracts in English

Oral presentation

Research and development of margin assessment methodology of decay heat removal function against external hazards, 9; Forest fire hazard assessment methodology

Okano, Yasushi; Yamano, Hidemasa

no journal, , 

There has been an increased concern in the safety of NPP for external hazards, one of which is a forest fire. Conventional forest fire assessments have been performed with deterministic and conservative manner, using so-called envelope initial and boundary conditions on forest fire analyses. In this study, the forest fire hazard assessment methodology, which is subject to an external-hazard probabilistic risk assessment (PRA), is being developed in order to quantitatively evaluate frequency and consequence of the forest fire that has a potential impact on a NPP and then to obtain the Core Damage Frequency. The new methodology based on a logic tree is developed in this study, as well as the sensibility analyses on weather conditions.

Oral presentation

Properties and distribution of radioactive caesium of the surface soil of Japanese cedar forest in Fukushima

Ishii, Yasuo; Sasaki, Yoshito; Kikuchi, Naoyuki; Watanabe, Takayoshi; Oda, Yoshihiro; Niizato, Tadafumi

no journal, , 

As part of "Long-Term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima" (F-TRACE project), JAEA have researched to expect the transportation of radioactive caesium from contaminated mountain forests to estuary and coast through dam, pond, river etc. based on survey data in Fukushima prefecture, and to implement technical information and remedial measures to prevent contamination of decontaminated areas and domestic water supply. In the forest area, it is considered that radioactive caesium existed in the tree canopies move to the surface of the ground through litter fall, through fall and stem flow. In this study, we report properties and distribution of radioactive caesium of the surface soils at stem base of Japanese cedar in the Ogi district of Kawauchi-mura to know the influence of the stem flow on soil.

Oral presentation

Research and development of margin assessment methodology of decay heat removal function against external hazards, 12; Forest fire hazard assessment methodology

Okano, Yasushi; Yamano, Hidemasa

no journal, , 

As a part of the development of forest fire hazard assessment method and event sequence analyses method for a sodium-cooled fast reactor, this paper describes the analysis of hazard curves of fireline intensity and reaction intensity as heat and flame effects of a forest fire by a logic tree improvements, response surface evaluations, and Monte Carlo simulations applying importance sampling.

Oral presentation

Oral presentation

Long-term assessment of transport of radioactive contaminant in the environment of Fukushima (F-TRACE Project), 8; Analysis of surface run-off substances

Ishii, Yasuo; Mitachi, Katsuaki; Abe, Hironobu; Niizato, Tadafumi

no journal, , 

As part of "Long-Term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima" (F-TRACE project), JAEA have researched to expect the transportation of radioactive caesium from contaminated mountain forests based on survey data in Fukushima prefecture, and to implement technical information and remedial measures to prevent contamination of decontaminated areas and domestic water supply. In this study, we report characterization and radio assay of the surface run-off substances at forest research plots in Ogi district of Kawauchi-mura and Yamakiya district of Kawamata-machi in 2013-2014, Fukushima.

Oral presentation

Latest situation and future targets of radiation countermeasures around water and woods environments in a priority investigation area on radioactive materials contamination

Iimoto, Takeshi*; Maedera, Ikuhiko*; Nunokawa, Jun*; Matsuzawa, Hajime*; Kurokawa, Sumihiko*; Yanagawa, Yukihide*; Someya, Seiichi*; Hashimoto, Makoto; Seya, Natsumi; Okawa, Yasuhisa; et al.

no journal, , 

no abstracts in English

Oral presentation

New decontamination technique for forests with interpolyelectrolyte complex and bentonite

Nagasu, Ryosuke*; Yoshida, Masafuyu*; Naganawa, Hirochika; Yanase, Nobuyuki; Nagano, Tetsushi; Mitamura, Hisayoshi; Komatsuzaki, Shoichi*; Kumazawa, Noriyuki*

no journal, , 

A new method for easily removing of radioactive cesium from muck soil in forests has been developed. Fine particles of bentonite having negative charge and high adsorbing ability for cesium can effectively adsorb radioactive cesium, and then, the bentonite fine particles can aggregate and being trapped by interaction with interpolyelectrolyte complex having positive charge, which enables an easy removal of radioactive cesium from muck soil in forests.

Oral presentation

Research and development of margin assessment methodology of decay heat removal function against external hazards, 17; Combination hazard curve evaluation of forest fire and thunder

Okano, Yasushi; Yamano, Hidemasa

no journal, , 

For an evaluation of a combination hazard curve of forest fire and thunder, it is necessary to take into account not only the overlap occurrence frequency but also meteorological effect on a forest fire intensity. The logic tree of a forest fire hazard curve evaluation was utilized in this study for quantitative estimation of the hazard curve of the combination event of forest fire and thunder.

41 (Records 1-20 displayed on this page)