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Journal Articles

Atmospheric modeling of $$^{137}$$Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07

 Times Cited Count:12 Percentile:24.72(Meteorology & Atmospheric Sciences)

We compared seven atmospheric transport model results for $$^{137}$$Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of $$^{137}$$Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for $$^{137}$$Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated $$^{137}$$Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated $$^{137}$$Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced $$^{137}$$Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

Journal Articles

Challenges for enhancing Fukushima environmental resilience, 1; Status and lessons

Miyahara, Kaname; Ohara, Toshimasa*

Nippon Genshiryoku Gakkai-Shi, 59(5), p.282 - 286, 2017/05

This review highlights JAEA and NIES's challenges for enhancing Fukushima environmental resilience based on carrying out multifaceted research working with many public and private sector organizations and academia.

Journal Articles

An Overview of progress in environmental research on radioactive materials derived from the Fukushima Nuclear accident

Ohara, Toshimasa*; Miyahara, Kaname

Global Environmental Research (Internet), 20(1&2), p.3 - 13, 2017/03

Toward the environmental regeneration in Fukushima Prefecture and other areas after the Fukushima Daiichi Nuclear Power Station accidents, JAEA and NIES working with many public and private sector organizations and academia have carried out multifaceted research that will help to restore the environment of affected areas. These challenging efforts need to be further strengthened.

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

Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type

Kajino, Mizuo*; Inomata, Yayoi*; Sato, Keiichi*; Ueda, Hiromasa*; Han, Z.*; An, J.*; Katata, Genki; Deushi, Makoto*; Maki, Takashi*; Oshima, Naga*; et al.

Atmospheric Chemistry and Physics, 12(24), p.11833 - 11856, 2012/12

 Times Cited Count:39 Percentile:21.26(Environmental Sciences)

A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2), was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model and achieved completely dynamic solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super micro m. To consider a variety of atmospheric aerosol properties, a category approach is utilized: aerosols are distributed into 4 categories, Aitken, accumulation, soot aggregates, and coarse mode. A regional-scale simulation was performed for the entire year of 2006, covering Northeast Asian region. Statistical analysis showed the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. Modeled size distributions of total weight and chemical components were consistent with the observations, indicating simulations of aerosol mixing types were successful.

JAEA Reports

Conceptual design of solid breeder blanket system cooled by supercritical water

Enoeda, Mikio; Ohara, Yoshihiro; Akiba, Masato; Sato, Satoshi; Hatano, Toshihisa; Kosaku, Yasuo; Kuroda, Toshimasa*; Kikuchi, Shigeto*; Yanagi, Yoshihiko*; Konishi, Satoshi; et al.

JAERI-Tech 2001-078, 120 Pages, 2001/12

JAERI-Tech-2001-078.pdf:8.3MB

This report is a summary of the design works, which was discussed in the design workshop held in 2000 for the demonstration (DEMO) blanket aimed to strengthen the commercial competitiveness and technical feasibility simultaneously. The DEMO blanket must supply the feasibility and experience of the total design of the power plant and the materials. This conceptual design study was performed to determine the updated strategy and goal of the R&D of the DEMO blanket which applies the supercritical water cooling proposed in A-SSTR, taking into account the recent progress of the plasma research and reactor engineering technology.

Journal Articles

Characteristic evaluation of HIP bonded SS/DSCu joints for surface roughness

Sato, Satoshi; Enoeda, Mikio; Kuroda, Toshimasa*; Ohara, Yoshihiro; Mori, Kensuke*; Cardella, A.*

Fusion Engineering and Design, 58-59(1-4), p.749 - 754, 2001/11

 Times Cited Count:2 Percentile:79.29(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Safety analysis of ITER test blanket module for water cooled blanket with pebble bed breeder

Enoeda, Mikio; Kuroda, Toshimasa*; Moriyama, Koichi*; Ohara, Yoshihiro

Journal of Nuclear Science and Technology, 38(11), p.921 - 929, 2001/11

 Times Cited Count:2 Percentile:79.29(Nuclear Science & Technology)

Test module testing in ITER is one of the most important mile-stone for development of the DEMO blanket. In the design of test modules in ITER, it is very important to show that test modules do not cause additional safety concern to ITER. This work has been performed for the evaluation of the substantial safety of Test Module of Water Cooled Solid Blanket, which is the current candidate blanket for the DEMO blanket in Japan. Major issues of the evaluation were establishment of post accident cooling in TM, hydrogen gas generation by Be-steam reaction, and pressure increase and spilled water amount by Loss of Coolant Accident (LOCA) event. The evaluation was performed to derive the upper bound of consequences in significant events, of which scenario can be assumed by the similarity of the safety analysis of Shielding Blanket.

Journal Articles

Nuclear and thermal analyses of supercritical-water-cooled solid breeder blanket for fusion DEMO reactor

Yanagi, Yoshihiko*; Sato, Satoshi; Enoeda, Mikio; Hatano, Toshihisa; Kikuchi, Shigeto*; Kuroda, Toshimasa*; Kosaku, Yasuo; Ohara, Yoshihiro

Journal of Nuclear Science and Technology, 38(11), p.1014 - 1018, 2001/11

 Times Cited Count:23 Percentile:16(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Development of ITER shielding blanket prototype mockup by HIP bonding

Sato, Satoshi; Furuya, Kazuyuki; Hatano, Toshihisa; Kuroda, Toshimasa*; Enoeda, Mikio; Takatsu, Hideyuki; Ohara, Yoshihiro

JAERI-Tech 2000-042, 121 Pages, 2000/07

JAERI-Tech-2000-042.pdf:58.33MB

no abstracts in English

JAEA Reports

Heating facility for brlanket and performance test

Furuya, Kazuyuki; *; Kuroda, Toshimasa*; Enoeda, Mikio; Sato, Satoshi; Hatano, Toshihisa; Takatsu, Hideyuki; Ohara, Yoshihiro

JAERI-Tech 99-025, 45 Pages, 1999/03

JAERI-Tech-99-025.pdf:3.46MB

no abstracts in English

JAEA Reports

Fabrication and testing of small scale mock-ups of ITER shielding blanket

Hatano, Toshihisa; Sato, Satoshi; ; ; Furuya, Kazuyuki; Kuroda, Toshimasa*; Enoeda, Mikio; Takatsu, Hideyuki; Ohara, Yoshihiro

JAERI-Tech 98-058, 77 Pages, 1998/12

JAERI-Tech-98-058.pdf:6.08MB

no abstracts in English

JAEA Reports

Design & analysis of ITER shield blanket

*; Hatano, Toshihisa; *; *; Miura, H.*; Kuroda, Toshimasa*; Furuya, Kazuyuki; Sato, Satoshi; Enoeda, Mikio; Takatsu, Hideyuki; et al.

JAERI-Tech 98-055, 97 Pages, 1998/12

JAERI-Tech-98-055.pdf:3.16MB

no abstracts in English

Journal Articles

Fabrication of an ITER shielding blanket prototype

Sato, Satoshi; Takatsu, Hideyuki; Enoeda, Mikio; Furuya, Kazuyuki; Hatano, Toshihisa; Kuroda, Toshimasa*; Osaki, Toshio*; *; Sato, Shinichi*; Ohara, Yoshihiro

Fusion Technology, 34(3), p.892 - 897, 1998/11

no abstracts in English

Oral presentation

Environmental dynamics analysis of $$^{137}$$Cs due to the Fukushima Daiichi Nuclear Power Station accident based on the intercomparison of atmospheric dispersion models

Morino, Yu*; Kitayama, Kyo*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

no journal, , 

For the evaluation of the validity and variability of atmospheric transport model results, we compared results of seven models submitted for the model inter-comparison project of Science Council of Japan to simulate $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant. Model reproducibility was assessed with the observed hourly atmospheric concentrations of $$^{137}$$Cs in Tohoku and Kanto regions. Among nine plumes from 12 to 21 in March 2011, performance of the models was the best for the plume which dispersed over the Kanto region in 15 March. The models generally reproduced the observed $$^{137}$$Cs concentrations in plumes which widely spread inland of Tohoku or Kanto regions. By contrast, the models largely underestimated the observed $$^{137}$$Cs concentrations for the case which passed coastal areas of Japan. Ensemble average of seven models showed reasonable performance for most of plumes, and no individual models reproduced better than the ensemble average.

Oral presentation

Model inter-comparison of atmospheric Cs-137 from the Fukushima Daiichi Nuclear Power Plant accident

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

no journal, , 

For the evaluation of the validity and variability of atmospheric transport model results, we compared results of seven models submitted for the model inter-comparison project of Science Council of Japan to simulate $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant. Model reproducibility was assessed with the observed hourly atmospheric concentrations of $$^{137}$$Cs in Tohoku and Kanto regions. Among nine plumes from 12 to 21 in March 2011, performance of the models was the best for the plume which dispersed over the Kanto region in 15 March. The models generally reproduced the observed $$^{137}$$Cs concentrations in plumes which widely spread inland of Tohoku or Kanto regions. By contrast, the models largely underestimated the observed $$^{137}$$Cs concentrations for the case which passed coastal areas of Japan. Ensemble average of seven models showed reasonable performance for most of plumes, and no individual models reproduced better than the ensemble average.

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