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

Miyahara, Kaname; Ohara, Toshimasa*

Nihon Genshiryoku Gakkai-Shi ATOMO, 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.

Reconstruction of the atmospheric releases of I and 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

http://repo.nirs.go.jp/dspace/bitstream/918273645/330/1/nirs_m_252.pdf

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

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.

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

https://doi.org/10.3327/jnst.38.921

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.

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

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

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

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 Cs released from the Fukushima Daiichi Nuclear Power Plant. Model reproducibility was assessed with the observed hourly atmospheric concentrations of 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 Cs concentrations in plumes which widely spread inland of Tohoku or Kanto regions. By contrast, the models largely underestimated the observed 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.