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Journal Articles

Impact of soil erosion potential uncertainties on numerical simulations of the environmental fate of radiocesium in the Abukuma River basin

Ikenoue, Tsubasa; Shimadera, Hikari*; Kondo, Akira*

Journal of Environmental Radioactivity, 225, p.106452_1 - 106452_12, 2020/12

 Times Cited Count:0

This study focused on the uncertainty of the factors of the Universal Soil Loss Equation (USLE) and evaluated its impacts on the environmental fate of $$^{137}$$Cs simulated by a radiocesium transport model in the Abukuma River basin. The USLE has five physically meaningful factors: the rainfall and runoff factor (R), soil erodibility factor (K), topographic factor (LS), cover and management factor (C), and support practice factor (P). The simulation results showed total suspended sediment and $$^{137}$$Cs outflows were the most sensitive to C and P among the all factors. Therefore, land cover and soil erosion prevention act have the great impact on outflow of suspended sediment and $$^{137}$$Cs. Focusing on land use, the outflow rates of $$^{137}$$Cs from the forest areas, croplands, and undisturbed paddy fields were large. This study indicates that land use, especially forest areas, croplands, and undisturbed paddy fields, has a significant impact on the environmental fate of $$^{137}$$Cs.

Journal Articles

Safety demonstration project on disposing of contaminated soil in Tokai-mura

Murata, Chinatsu; Kitahara, Masaru; Tanaka, Kiwamu; Amazawa, Hiroya; Takebe, Shinichi; Yamada, Osamu*; Kameo, Yutaka

Dekomisshoningu Giho, (62), p.20 - 31, 2020/09

On the basis of Act on Special Measures, municipalities stripped surface soil off the playground of park to decontaminate the soil which had been contaminated with radionuclides released from Fukushima Daiichi Nuclear Power Plant. To minimize the exposure dose of the residents, it was essential to decide safe disposal of the contaminated soil which has been stored at temporary storage areas. Therefore, the ministry of the Environment and Tokai-mura office required Japan Atomic Energy Agency (JAEA) to perform demonstration project of burying the contaminated soil generated by decontamination of public facilities in order to provide decision on the enforcement ordinance and guidelines of burying it. In this project, we acquired data of air dose rate and the personal exposure dose during transporting, burying, and storing the contaminated soil. In addition, we measured radioactivity concentration of dust collected from surroundings of the landfill and seepage water through contaminated soil.

JAEA Reports

Dose estimation in recycling of removed soil as seaside protection forest (Contract research)

Sawaguchi, Takuma; Takai, Shizuka; Takeda, Seiji

JAEA-Research 2020-005, 47 Pages, 2020/06

JAEA-Research-2020-005.pdf:5.09MB

After the Fukushima Daiichi Nuclear Power Station accident, large quantities of radiocesium-contaminated soil were generated from decontamination activities in the Fukushima prefecture. The removed soil has been stored in the prefecture until its final disposal. To complete the final disposal outside Fukushima prefecture, reducing the disposal volume through recycling can prove effective. The Ministry of the Environment, Japan (MOE) has presented a policy to recycle low-radioactive removed soil as recycled materials under the management of public authority. The recycling is limited to civil engineering structures in public projects. In this study, to contribute to guideline development for removed soil recycling by MOE, dose estimation in recycling of removed soil as embankment materials of seaside protection forest was conducted. First, additional doses to workers and the public in construction and service scenarios were evaluated. From the result, the radioactive cesium concentration level of recycled materials, where all additional doses meet the radiation criterion of 1 mSv/y, was derived to be 5,000 Bq/kg. Then, construction conditions were reviewed to reduce additional doses to the public in a service scenario. With the derived radioactivity level of 5,000 Bq/kg, the covered soil thickness of 39 cm or more limited the doses to less than 10 $$mu$$Sv/y. Finally, additional doses in a disaster scenario were evaluated. The doses were confirmed to be below 1 mSv/y when the removed soil of 5,000 Bq/kg was used.

Journal Articles

Dose estimation for contaminated soil storage in living environment

Takai, Shizuka; Shimada, Asako; Sawaguchi, Takuma; Takeda, Seiji; Kimura, Hideo

Radiation Protection Dosimetry, 188(1), p.1 - 7, 2020/01

 Times Cited Count:0 Percentile:100(Environmental Sciences)

After the Fukushima Nuclear Power Plant accident, most of radiocesium-contaminated soil generated from decontamination activities outside Fukushima prefecture has been stored at decontamination sites such as schools, parks and residential lands (storage at sites) according to the Decontamination Guidelines. However, additional exposure due to the present storage has not been evaluated. Moreover, entering storage sites, which is not restricted for storage at sites, was not considered in safety assessment conducted in the guidelines. To continue the storage and confirm the effectiveness, understanding of present possible exposures is important. In this study, we evaluated exposure doses for residents and users of storage sites based on the present situation. As a result, annual doses due to residence were 10$$^{-2}$$ to 10$$^{-3}$$ mSv y$$^{-1}$$ and doses due to annual entries were of the order of 10$$^{-3}$$ mSv y$$^{-1}$$. Hence, we confirmed that the exposure due to present storage outside Fukushima is significantly less than 1 mSv y$$^{-1}$$.

Journal Articles

Factors controlling dissolved $$^{137}$$Cs concentrations in east Japanese rivers

Tsuji, Hideki*; Ishii, Yumiko*; Shin, M.*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Kurihara, Momo*; Yasutaka, Tetsuo*; Kuramoto, Takayuki*; Nakanishi, Takahiro; Lee, S*; et al.

Science of the Total Environment, 697, p.134093_1 - 134093_11, 2019/12

 Times Cited Count:6 Percentile:40.05(Environmental Sciences)

To investigate the main factors that control the dissolved radiocesium concentration in river water in the area affected by the Fukushima Daiichi nuclear power plant accident, the correlations between the dissolved $$^{137}$$Cs concentrations at 66 sites normalized to the average $$^{137}$$Cs inventories for the watersheds with the land use, soil components, topography, and water quality factors were assessed. We found that the topographic wetness index is significantly and positively correlated with the normalized dissolved $$^{137}$$Cs concentration. Similar positive correlations have been found for European rivers because wetland areas with boggy organic soils that weakly retain $$^{137}$$Cs are mainly found on plains. However, for small Japanese river watersheds, the building area ratio in the watershed strongly affected the dissolved $$^{137}$$Cs concentration.

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:5 Percentile:62.84(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

Recent status and future issues of molecular modeling studies for clay and fungi adsorbing cesium

Suno, Hiroya; Okumura, Masahiko; Machida, Masahiko

Jiban Kogakkai-Shi, 67(10), p.34 - 35, 2019/10

no abstracts in English

Journal Articles

Time-dependent change of radiation levels in the 80 km zone for five years after the Fukushima accident

Saito, Kimiaki

Environmental Contamination from the Fukushima Nuclear Disaster; Dispersion, Monitoring, Mitigation and Lessons Learned, p.38 - 43, 2019/09

 Times Cited Count:0

no abstracts in English

Journal Articles

Contamination of Fukushima Daiichi Nuclear Power Station with actinide elements

Koma, Yoshikazu; Murakami, Erina

Radiochimica Acta, 107(9-11), p.965 - 977, 2019/09

 Times Cited Count:0 Percentile:100(Chemistry, Inorganic & Nuclear)

Fukushima Daiichi Nuclear Power Station, which is owned by Tokyo Electric Power Company, suffered from the great earthquake and Tsunami on 11 March 2011, and serious contamination with radioactive nuclides occurred. To investigate methodologies of waste management, contaminated materials have been radiochemically analyzed. This paper reviews the analytical data for actinide elements. Actinide nuclides are detected in the contaminated water. The contaminated water is chemically decontaminated, although actinide concentration does not decrease with time. This suggests that actinides come from the damaged fuel with slow dissolution. From the topsoil at the site, Pu, Am and Cm were detected and come from the damaged fuel, whereas U from natural. TRU would slowly move to deeper. Contamination of rubble is nonuniform and actinides are detected as well as fission products. For vegetation, TRU nuclides were found from fallen leaves near the reactor buildings.

Journal Articles

Importance of root uptake of $$^{14}$$CO$$_{2}$$ on $$^{14}$$C transfer to plants impacted by below-ground $$^{14}$$CH$$_{4}$$ release

Ota, Masakazu; Tanaka, Taku*

Journal of Environmental Radioactivity, 201, p.5 - 18, 2019/05

 Times Cited Count:2 Percentile:62.84(Environmental Sciences)

$$^{14}$$CH$$_{4}$$ released from deep underground radioactive waste disposal facilities can be a belowground source of $$^{14}$$CO$$_{2}$$ owing to microbial oxidation of $$^{14}$$CH$$_{4}$$ to $$^{14}$$CO$$_{2}$$ in soils. Environmental $$^{14}$$C models assume that the transfer of $$^{14}$$CO$$_{2}$$ from soil to plant occurs via foliar uptake of $$^{14}$$CO$$_{2}$$. Nevertheless, the importance of $$^{14}$$CO$$_{2}$$ root uptake is not well understood. In the present study, belowground transport and oxidation of $$^{14}$$CH$$_{4}$$ were modeled and incorporated into an existing land surface $$^{14}$$CO$$_{2}$$ model (SOLVEG-II) to assess the importance of root uptake on $$^{14}$$CO$$_{2}$$ transfer to plants. Performance of the model in calculating the belowground dynamics of $$^{14}$$CH$$_{4}$$ was validated by simulating a field experiment of $$^{13}$$CH$$_{4}$$ injection into subsoil. The model was then applied to $$^{14}$$C transfer in a hypothetical ecosystem impacted by continuous $$^{14}$$CH$$_{4}$$ input from the water table (bottom of one-meter thick soil). In a shallowly rooted ecosystem with rooting depth of 11 cm, foliar uptake of $$^{14}$$CO$$_{2}$$ was significant, accounting for 80% of the $$^{14}$$C accumulation in the leaves. In a deeply rooted ecosystem (rooting depth of 97 cm), where the root penetrated to depths close to the water-table, more than half (63%) the $$^{14}$$C accumulated in the leaves was transferred by the root uptake. We found that $$^{14}$$CO$$_{2}$$ root uptake in this ecosystem depended on the distribution of methane oxidation in the soil; all $$^{14}$$C accumulated in the leaves was transferred by the root uptake when methane oxidation occurred at considerable depths (e-folding depths of 20 cm, or 80 cm). These results indicate that $$^{14}$$CO$$_{2}$$ root uptake contributes significantly to $$^{14}$$CO$$_{2}$$ transfer to plants if $$^{14}$$CH$$_{4}$$ oxidation occurs at great depths and roots penetrate deeply into the soil.

Journal Articles

Dose estimation in recycling of decontamination soil from the Fukushima Daiichi NPS accident for land reclamation

Shimada, Asako; Nemoto, Hiromi*; Sawaguchi, Takuma; Takeda, Seiji

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

no abstracts in English

Journal Articles

7.1 Environmental contamination due to radionuclides

Saito, Kimiaki

Genshiryoku No Ima To Ashita, p.148 - 151, 2019/03

no abstracts in English

Journal Articles

Dose estimation in recycling of decontamination soil resulting from the Fukushima NPS accident for road embankments

Takai, Shizuka; Sawaguchi, Takuma; Takeda, Seiji

Health Physics, 115(4), p.439 - 447, 2018/10

 Times Cited Count:2 Percentile:76.51(Environmental Sciences)

After the Fukushima Nuclear Power Station accident, large quantities of radiocesium-contaminated soil generated from decontamination activities have been stored in the Fukushima Prefecture. To reduce the disposal volume, the Ministry of the Environment of Japan has presented a policy to recycle low-radioactive decontamination soil limited to civil engineering structures. However, there has been no practical instance or safety assessment of decontamination soil recycling. In this study, the way of ensuring the safety for decontamination soil recycling for road embankments was discussed. First, based on Japanese construction standards, additional doses to workers and the public in construction and service scenarios were evaluated. From the result, the radioactive cesium concentration level of recycled materials, where all additional doses meet the radiation criterion of 1 mSv y$$^{-1}$$, was derived to be 6,000 Bq kg$$^{-1}$$. To confine additional doses to the public in a service scenario below 0.01 mSv y$$^{-1}$$, soil slope protection of 40 cm or more was needed. Finally, additional doses in a disaster scenario were confirmed to be below 1 mSv y$$^{-1}$$.

Journal Articles

Radiocesium interaction with clay minerals; Theory and simulation advances Post-Fukushima

Okumura, Masahiko; Kerisit, S.*; Bourg, I. C.*; Lammers, L. N.*; Ikeda, Takashi*; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko

Journal of Environmental Radioactivity, 189, p.135 - 145, 2018/09

 Times Cited Count:23 Percentile:9.2(Environmental Sciences)

no abstracts in English

Journal Articles

Dose estimation in recycling of decontamination soil due to Fukushima NPS accident as coastal levees

Takai, Shizuka; Sawaguchi, Takuma; Takeda, Seiji

Proceedings of International Waste Management Symposia 2018 (WM 2018) (Internet), 14 Pages, 2018/03

After the Fukushima Nuclear Power Station accident, large quantities of radiocesium-contaminated soil generated from decontamination activities have been stored in the Fukushima prefecture. To complete the final disposal of decontamination soil, the Ministry of the Environment of Japan presented policy to reduce the disposal volume by using low-level decontamination soil as recycled materials. The use will be limited to civil engineering structures in public projects, such as coastal levee and road embankment. However, there has been no example or safety assessment of recycling of decontamination soil. To contribute to guideline development for the recycling by the Ministry of the Environment, we conducted the safety assessment for recycling of decontamination soil as coastal levee. First, we evaluated additional doses to workers and the public in the case of construction and service of coastal levee. From the result, the radioactive cesium concentration level of recycled materials was derived to be 6,800 Bq/kg. For general designs of coastal levee in Japan, additional doses to the public in the case of service were below 0.01 mSv/y with derived radioactivity level. Finally, we confirmed additional doses in the case of disaster to be below 1 mSv/y.

Journal Articles

Challenges for enhancing Fukushima environment resilience, 6; The Use of the reclaimed materials derived from the removed soil on the basis of the security

Okada, Takashi; Takeda, Seiji; Nakata, Hisakazu

Nippon Genshiryoku Gakkai-Shi, 59(10), p.603 - 607, 2017/10

Because the reclaimed material is used, quantity of disposal of the removal soil can decrease. It is a strategic key to utilize the reclaimed material. As for this report, it is explained to about the fundamentals of the safe use of the reclaimed materials derived from the removed soil.

Journal Articles

Journal Articles

Challenges for enhancing Fukushima environmental resilience, 4; Development of physical and heat treatment methods on aiming at decontamination, volume reduction and reuse of contaminated soil

Yaita, Tsuyoshi; Honda, Mitsunori; Shimoyama, Iwao; Ito, Kenichi*; Mampuku, Yuzo*; Tsuji, Takuya; Matsumura, Daiju

Nippon Genshiryoku Gakkai-Shi, 59(8), p.483 - 487, 2017/08

no abstracts in English

Journal Articles

Volume reduction of cesium contaminated soil by magnetic separation; Pretreatment of organic matters

Horie, Hiroki*; Yukumatsu, Kazuki*; Mishima, Fumihito*; Akiyama, Yoko*; Nishijima, Shigehiro*; Sekiyama, Tomio*; Mitsui, Seiichiro; Kato, Mitsugu

Journal of Physics; Conference Series, 871, p.012102_1 - 012102_7, 2017/07

 Times Cited Count:0 Percentile:100

Journal Articles

Development of cesium-free mineralization for decontamination and reuse of radioactive contaminated soil in Fukushima

Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Baba, Yuji; Hirao, Norie*; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi

Photon Factory News, 35(1), p.17 - 22, 2017/05

We introduce Cs-free mineralization (CFM) for Cs removal and reuse of radioactive-contaminated soil in Fukushima and report recent work conducted in the BL27A beamline in Photon Factory. In this work, we investigated compositional and structural changes of Cs-sorbed weathered biotite (WB) before and after heating treatment with addition of NaCl-CaCl$$_{2}$$ salts under low-pressure condition, to study Cs desorption mechanism from clay minerals. X-ray fluorescence spectroscopy clarified that almost all Cs and K were removed with the salts at 700 $$^{circ}$$C. On the other hand, Ca increased with heating temperature. X-ray diffraction and transmission electron microscopy analysis clarified that phase transitions from WB to some Ca-rich silicate minerals, e.g., augite, were caused by the heating treatment with the salt. Based on these results, CFM is proposed for Cs removal utilizing the mechanism in which large monovalent cations are discharged with accompanying the phase transition. We also discuss the role of Cl in this reaction showing chemical bonding change of Cl observed using X-ray absorption spectroscopy in the early stage of the chemical reaction.

209 (Records 1-20 displayed on this page)