Kurikami, Hiroshi; Sakuma, Kazuyuki; Malins, A.; Sasaki, Yoshito; Niizato, Tadafumi
Journal of Environmental Radioactivity, 208-209, p.106005_1 - 106005_11, 2019/11
To assess the uptake of Cs-137 (Cs) by freshwater fish, we developed a compartment model for the migration of Cs on the catchment scale from forests to river water. We modelled a generic forest catchment with Fukushima-like parameters to ascertain the importance of export pathways of Cs from forests to river water for the uptake of Cs by freshwater fish. The results suggest that the decreasing trend of Cs in river water and freshwater fish was due to combination of the decreasing trend in the forest leaves/needles and litter compartments, and the increasing trend in soil. The Cs concentrations within these forest compartments plateau at around ten years after the fallout due to Cs circulation in forests reaching an equilibrium state.
Onuki, Toshihiko*; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya*; Sasaki, Yoshito; Niizato, Tadafumi
Journal of Nuclear Science and Technology, 56(9-10), p.814 - 821, 2019/09
We used the spent mushroom substrata (SMSs) which are a kind of by-product after growing edible mushrooms for the investigation of radioactive Cs mobility in litter zone in a forest of Fukushima prefecture, Japan. The powder SMS was filled in a plastic net bag of 0.350.55 m, then was placed in a forest for 6 months under three kinds of different conditions without treatment (No treatment), covered with wooden box (With box), and with zeolite placed on upper position of ground surface (With zeolite). We determined the ratio of radioactivity (TF) in the SMS to that of the soil and litter beneath the SMS bags. TFs of "No treatment" and of "With zeolite" were determined between 0.01 and 0.05 for 6 months. On the other hand, TFs of "With box" were lower by one order at 2 and 4 months than those of "No treatment" and of "With zeolite", and nearly the same values as TFs of "No treatment" and "With zeolite" at 6 months. These results clearly indicate that radioactive Cs accumulates in SMS mainly by throughfall. In addition, for a period of several months, fungi contribute to the accumulation of radioactive Cs in the litter zone, even though radioactive Cs was tightly associated with the soil.
Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.
JAEA-Research 2019-002, 235 Pages, 2019/08
The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.
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
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 to 10, 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.
Watanabe, Takayoshi; Oyama, Takuya; Ishii, Yasuo; Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito
KEK Proceedings 2017-6, p.122 - 126, 2017/11
no abstracts in English
Ise, Kotaro; Sasaki, Yoshito; Amano, Yuki; Iwatsuki, Teruki; Nanjo, Isao*; Asano, Takahiro*; Yoshikawa, Hideki
Geomicrobiology Journal, 34(6), p.489 - 499, 2017/07
We investigated the change in bacterial community structure after drilling boreholes, 09-V250-M02 and 09-V250-M03 in the 250 m depth research gallery of Horonobe Underground Research Laboratory (URL). In 09-V250-M02, -Proteobacteria was predominantly detected in the clone library analyses of the groundwater samples conducted immediately after drilling the borehole. All these -Proteobacteria clones are closely related to . which is known as sulfide oxidizing chemoautotrophic bacteria. After four years, the microbial structure was drastically changed and most detected OTUs were uncultured species such as candidate division OP9 and Chloroflexi relatives which are frequently detected in deep-sea sediments.
Sasaki, Yoshito; Ishii, Yasuo; Abe, Hironobu; Mitachi, Katsuaki; Watanabe, Takayoshi; Niizato, Tadafumi
Horticulture Journal, 86(2), p.139 - 144, 2017/04
To examine the translocation of radiocesium (Cs) scattered by the Fukushima Daiichi Nuclear Power Plant accident that occurred in March 2011 to the Japanese chestnut, we investigated the autoradiography and radiocesium concentration in each part of the Japanese chestnut. The Japanese chestnut fruit has a thin skin between the kernel (cotyledons) and shell; the kernel of the fruit is edible. Cs concentration in each part of the fruit was found to be almost the same at about 1.010 Bqkg. Radiocesium concentration in chestnut weevil larvae found on the fruit was approximately one-seventh of that in the kernel.
Sasaki, Yoshito; Abe, Hironobu; Mitachi, Katsuaki; Watanabe, Takayoshi; Ishii, Yasuo; Niizato, Tadafumi
Journal of Environmental Radioactivity, 161, p.58 - 65, 2016/09
We report the behavior of radiocesium on the tree bark and its transfer into the stemflow of chestnut in a forest in Fukushima. The radiocesium concentration is greatest in 2-cm stem, less in 5-mm stem, and least in the leaves. In the 2-cm stem, the radiocesium concentration of the bark was approximately 10 times that of wood. The average Cs-137 concentration of the dissolved fraction of stem flow was about 10 Bq/L; the pH was nearly constant at 5.8. A strong positive correlation was observed between the radiocesium concentration and the electrical conductivity of the dissolved fraction of stemflow; this result suggests that radiocesium and electrolytes have the same elution mechanism from the tree. Some of the particles in the particulate fraction of the stem flow was strongly adsorbed radiocesium.
Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito; Ishii, Yasuo; Watanabe, Takayoshi
Journal of Environmental Radioactivity, 161, p.11 - 21, 2016/09
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.
Onuki, Toshihiko; Aiba, Yukitoshi*; Sakamoto, Fuminori; Kozai, Naofumi; Niizato, Tadafumi; Sasaki, Yoshito
Scientific Reports (Internet), 6, p.29866_1 - 29866_6, 2016/07
We here first report the direct accumulation pathway of radioactive Cs from contaminated wood logs to the fruit-bodies of shiitake mushrooms through the basal portion of the stipe by using spectroscopy, autoradiography, and X-ray micro CT techniques.
Sasaki, Yoshito; Funaki, Hironori; Iri, Shatei; Dohi, Terumi; Hagiwara, Hiroki
Limnology, 17(2), p.111 - 116, 2016/04
The behavior of radiocesium (Cs) in aquatic plants (five species) and algae (three genera) that had been grown in a river (one sampling point) and ponds (four sampling points) in the area around the Fukushima Daiichi Nuclear Power Plant was investigated. The sediment-to-plant transfer factor (TF) was measured. For aquatic plants, the highest value was 5.55 for from the river; the lowest was 3.34 10 for from a pond. There were significant differences in the values for aquatic plants belonging to the same genus. The water-to-plant TF of filamentous algae ( sp.) and cyanobacteria (coexisting sp. and sp.) were 2.39 10 and 1.26 10, respectively. The Cs concentration of cyanobacteria fraction in pond water was 4.87 10 Bq/L, the same order of magnitude as the Cs concentration of pond water. Enrichment of radiocesium in cyanobacteria was not observed.
Katsuyama, Chie*; Nashimoto, Hiroaki*; Nagaosa, Kazuyo*; Ishibashi, Tomotaka*; Furuta, Kazuki*; Kinoshita, Takeshi*; Yoshikawa, Hideki; Aoki, Kazuhiro; Asano, Takahiro*; Sasaki, Yoshito; et al.
FEMS Microbiology Ecology, 86(3), p.532 - 543, 2013/12
Anaerobic microbial activity has a major influence on the subsurface environment, and should be considered in subsurface activities including the construction of radioactive waste repositories. We investigated denitrification and methanogenesis in anoxic groundwater from 140 m depth in two boreholes, where the redox potential fluctuated. The average maximum potential denitrification rates, measured under anaerobic conditions in the two boreholes using an N tracer. Methanogenesis candidates were detected by 16S rRNA gene analysis. Although the stable isotope signatures suggested that some of the dissolved methane was of biogenic origin, no potential for methane production was evident during the incubations. The groundwater at 140 m depth did not contain oxygen, had an Eh ranging from -144 to 6.8 mV, and was found to be a potential field for denitrification.
Amano, Yuki; Nanjo, Isao; Murakami, Hiroaki; Yabuuchi, Satoshi; Yokota, Hideharu; Sasaki, Yoshito; Iwatsuki, Teruki
Chikasui Gakkai-Shi, 54(4), p.207 - 228, 2012/11
We verified the surface-based hydrochemical investigation for deep underground at Horonobe Underground Research Laboratory (URL) at Horonobe, Hokkaido, Japan, and identified the hydrochemical changes during the URL construction. The evaluation of the relationship between the number of borehole and understanding of water chemistry suggests that three basic borehole investigations and additional borehole for high permeable geological structure (fault and fractured zone) are required to illustrate cross-sectional hydrochemical distribution including the uncertainty in kilometers scale survey line. The observation and numerical analysis of hydrochemical variation (salinity, pH, ORP) around URL indicate that the groundwater pressure and the salinity in the vicinity of high permeable geological zone are varying due to groundwater inflow into the drift. The variation was consistent with the prediction reported previously. These results are considered to be referred to the management during surface-based investigation and construction of underground facility at the other sedimentary rock area.
Yoshikawa, Hideki; Kawakita, Masakazu*; Fujiwara, Kazuhiro*; Sato, Tomofumi; Asano, Takahiro*; Sasaki, Yoshito
Materials Research Society Symposium Proceedings, Vol.1475, p.617 - 622, 2012/06
Since it was suggested that the microbes have ability to generate their biofilm in deep underground condition, we examined the effects of biofilm on radionuclide migration scenario. To estimate the effect on matrix diffusion, through diffusion experiment for a biofilm of Desulfovivrio desullfuricans were performed. The effective diffusion coefficient of the biofilm was 10 m/s order which was about ten times smaller than that in free water. It is suggesting that the microbes and biofilm will not interfere with matrix diffusion as a retardation of radionuclide in rock.
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.
Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06
Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.
Asano, Takahiro; Ishii, Kosuke*; Miyasaka, Iku*; Sasaki, Yoshito; Yoshikawa, Hideki; Yui, Mikazu
no journal, ,
no abstracts in English
Sasaki, Yoshito; Asano, Takahiro; Iwatsuki, Teruki; Yoshikawa, Hideki; Yui, Mikazu
no journal, ,
no abstracts in English
Asano, Takahiro; Sasaki, Yoshito; Nagaosa, Kazuyo*; Kato, Kenji*; Yoshikawa, Hideki
no journal, ,
no abstracts in English
Fukunaga, Sakae*; Ishii, Kosuke*; Miyasaka, Iku*; Asano, Takahiro; Sasaki, Yoshito; Yoshikawa, Hideki
no journal, ,
no abstracts in English