Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, 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, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" 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.

Separation of radiocaesium-bearing micro particle from environmental samples; Application to litter samples

Tagomori, Hisaya; Dohi, Terumi; Ishii, Yasuo; Kanaizuka, Seiichi*; Fujiwara, Kenso; Iijima, Kazuki

JAEA-Technology 2019-001, 37 Pages, 2019/03

JAEA-Technology-2019-001.pdf:26.85MB

An efficient methodology for separating the radiocaesium-bearing micro particles (CsMPs) released by the TEPCO's Fukushima Dai-ichi Nuclear Power Station accident is required to investigate their spatial distribution and physicochemical properties. In this report we developed an efficiency separation method for CsMP from litters since the radiocaesium in litter may affect the radiocaesium cycling in forest ecosystem. One CsMP separation from litter containing lots of soil particles was attained within three days using electron microscopic analysis with digestion treatment of organic matter. This methodology is expected as CsMPs efficient separation method for not only forest floor litter but also barks and leaves of living tree, and other organic materials in the forested environment.

Characterization of NbAl strands subjected to an axial-strain for fusion DEMO reactor

Hemmi, Tsutomu; Koizumi, Norikiyo; Nunoya, Yoshihiko; Okui, Yoshio*; Matsui, Kunihiro; Nabara, Yoshihiro; Isono, Takaaki; Takahashi, Yoshikazu; Okuno, Kiyoshi; Banno, Nobuya*; et al.

IEEE Transactions on Applied Superconductivity, 19(3), p.1540 - 1543, 2009/06

https://doi.org/10.1109/TASC.2009.2018237

NbAl cable-in-conduit (CIC) conductors have been developed as one of candidates for the fusion DEMO reactor. The performances of superconducting strands in the CIC conductor are affected by transverse electromagnetic force and thermal strain at reaction heat treatment. In order to accurately design the conductors for the fusion DEMO reactor, the performance evaluation of the NbAl strands, which is processed by a rapid heating, quenching and transformation (RHQT) method, was performed under various temperature, magnetic field and axial-strain conditions. The measured and parameterized results of the NbAl strands are presented.

Internally Cu-stabilized RHQT NbAl superconductors with Ta matrix

Takeuchi, Takao*; Tagawa, Kohei*; Noda, Tetsuji*; Banno, Nobuya*; Iijima, Yasuo*; Kikuchi, Akihiro*; Kitaguchi, Hitoshi*; Kosuge, Michio*; Tsuchiya, Kiyosumi*; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 16(2), p.1257 - 1260, 2006/06

https://doi.org/10.1109/TASC.2006.870804

Next generation nuclear fusion magnets would require a high-current conductor in fields more than 16 T. A CIC conductor of the rapid RHQT processed NbAl may be a promising candidate. Good deformability of intermediately-formed bcc supersaturated-solid solution indeed allowed fabricating such a CIC conductor, which would be subsequently transformation annealed. Ag has been internally included as a basic constituent of a round strand so far, because Ag is almost non-reactive with Nb matrix during the RHQ. However, both of Ag and Nb are not suitable nuclei from the viewpoint of radioactivity when irradiated with neutrons. Recently, we have succeeded in replacing the Nb matrix with Ta that has the advantage of shorter half-life of radioactivity. In the present study, an attempt has been made to replace the Ag internal stabilizer with Cu, in the aim of further reducing radioactivity, based on anticipation that Ta would be less reactive with Cu than Nb did.

Examination of the isolation method of the radioactive microparticles in the environmental sample

Tagomori, Hisaya; Ishii, Yasuo; Kanaizuka, Seiichi*; Dohi, Terumi; Iijima, Kazuki

no journal, , 

In order to evaluate the chemical form and distribution of radionuclide in soil and litter near the Fukushima Daiichi Nuclear Power Plant, method for isolating radioactive particles were carried out. Main procedures for isolating radioactive particles are as follows; After drying and size classification, samples are decomposed with hydrogen peroxide. And then, IP method is carried out to monitor the distribution of radionuclide. A portion showing high radiation is selected as microscopic analysis which composed of Field Emission-Electron Prove Micro-Analyzer (FE-EPMA) and Energy-Dispersive X-ray Spectroscopy (EDS). As results of above method, several particles with unique elemental compositions such as Ba was identified. Moreover, methods for isolating particles of 100 - 200 um using the Micro Manipulator were established. The isolation of fine particles (less than 50 um), were also applied by the meaning of digging a trench on the carbon tape using Focused Ion Beam (FIB).