Radiocesium-bearing microparticles cause a large variation in Cs activity concentration in the aquatic insect (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan

Ishii, Yumiko*; Miura, Hikaru*; Jo, J.*; Tsuji, Hideki*; Saito, Rie; Koarai, Kazuma; Hagiwara, Hiroki; Urushidate, Tadayuki*; Nishikiori, Tatsuhiro*; Wada, Toshihiro*; et al.

PLOS ONE (Internet), 17(5), p.e0268629_1 - e0268629_17, 2022/05

https://doi.org/10.1371/journal.pone.0268629

We investigated the variability in Cs activity concentration in individual aquatic insects in detritivorous caddisfly () and carnivorous dobsonfly () larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity, whereas no such outliers were observed in dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMPs distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.

Evaluation of bioavailable radiocesium in the sediment in forest river and dam reservoir

Takechi, Seiichi*; Tsuji, Hideki*; Koshikawa, Masami*; Ito, Shoko*; Funaki, Hironori; Hayashi, Seiji*

Rikusuigaku Zasshi, 82(1), p.1 - 16, 2021/02

Since the Fukushima Daiichi Nuclear Power Plant accident in 2011, soil minerals and organic matter including radiocesium have been deposited in the dam lakes near the nuclear power plant. There is concern that radiocesium will gradually leach from the lake bottom into the lake water, resulting in prolonged radioactive contamination of the freshwater ecosystems especially in downstream of the dams. In this study, we collected undisturbed sediment core samples at the center of the Yokokawa Dam lake in Fukushima Prefecture and suspended sediment in the inflowing river of the dam for 4 years and evaluated the amount of bioavailable form of radiocesium (exchanged, oxidized, and organic forms) in these samples by sequential extraction tests using the BCR method focusing on the temporal change.

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima; As a part of dissemination of evidence-based information

Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.

JAEA-Review 2017-018, 86 Pages, 2017/10

JAEA-Review-2017-018.pdf:17.58MB

Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.

Fabrication process qualification of TF Insert Coil using real ITER TF conductor

Ozeki, Hidemasa; Isono, Takaaki; Kawano, Katsumi; Saito, Toru; Kawasaki, Tsutomu; Nishino, Katsumi; Okuno, Kiyoshi; Kido, Shuichi*; Semba, Tomoyuki*; Suzuki, Yozo*; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200804_1 - 4200804_4, 2015/06

https://doi.org/10.1109/TASC.2014.2364393

Mizunami Underground Research Laboratory Project, Annual report for fiscal year 2011

Kunimaru, Takanori; Mikake, Shinichiro; Nishio, Kazuhisa; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Ishibashi, Masayuki; Sasao, Eiji; Hikima, Ryoichi; Tanno, Takeo; Sanada, Hiroyuki; et al.

JAEA-Review 2013-018, 169 Pages, 2013/09

JAEA-Review-2013-018.pdf:15.71MB

Japan Atomic Energy Agency (JAEA) at Tono Geoscience Center (TGC) is pursuing a geoscientific research and development project namely the Mizunami Underground Research Laboratory (MIU) Project in crystalline rock environment in order to construct scientific and technological basis for geological disposal of High-level Radioactive Waste (HLW). The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). The MIU Project has been ongoing the Phase II and the Phase III in 2011 fiscal year. This report shows the results of the investigation, construction and collaboration studies in fiscal year 2011, as a part of the Phase II and Phase III based on the MIU Master Plan updated in 2010.

Radio frequency plasma transition caused by gas puffing and/or direct current biasing using multiturn internal antenna

Yamauchi, Toshihiko; Kobayashi, Seiji*; Sugibayashi, Hideyuki*; Tachibana, Toshiyuki*; Naito, Shunya*; Kanno, Yoshinori*; Hiruta, Toshihito

Japanese Journal of Applied Physics, 51(1), p.01AA02_1 - 01AA02_7, 2012/01

https://doi.org/10.1143/JJAP.51.01AA02

In the beginning of this study, the RF (radio frequency) plasma by the internal antenna which is in contrast to that of the external antenna, was considered for the transition from the charged coupled plasma (CCP) to the inductively coupled plasma (ICP) not to be observed. On the contrary, in our plasma experiment by using the internal multi-turn RF antenna, the transition phenomenon was observed at the extent of 40 W in RF power. In this experiment, the relation between the gas pressure and the RF power on the transition from CCP to ICP indicated almost the same characteristic as Paschen's law. But the transition physics, or the absorption mechanism of RF power based on the collision dumping, was strongly complex. We have experimentally represented the CCP-ICP transition to study the physics using the original physical technique. Firstly, we changed the CCP into the ICP by the gas control. It was considered that the increase of the electron temperature caused the transition. Secondly, the decrease of gas pressure displayed the same meaning with the longer period of the self-pulse transition. Thirdly, the self-bias caused by RF power and the external bias applied between the RF antenna and the stage were described for the transition physics.

Low alkaline cement used in the construction of a gallery in the Horonobe Underground Research Laboratory

Nakayama, Masashi; Sato, Haruo; Sugita, Yutaka; Ito, Seiji*; Minamide, Masashi*; Kitagawa, Yoshito*

Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.51 - 56, 2011/01

https://doi.org/10.1115/ICEM2010-40038

In Japan, any high level radioactive waste repository is to be constructed at over 300 m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly fly-ash contained silicafume cement), containing over 60wt% of silica-fume (SF) and fly-ash (FA). HFSC was used experimentally as the shotcrete material in construction of part of the 140 m deep gallery in Horonobe URL. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel using HFSC shotcrete is about 73 m and about 500 m of HFSC was used. The workability of HFSC shotcrete was confirmed in this experimental construction.

Compact DEMO, SlimCS; Design progress and issues

Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.

Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07

https://doi.org/10.1088/0029-5515/49/7/075029

Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).

Dissociation characteristics of light absorbed dioxin analogues calculated by density functional theory

Yamauchi, Toshihiko; Kobayashi, Seiji*; Ito, Shinichi*; Yamazaki, Kazuhiko; Kamei, Yasutaka*; Kanno, Yoshinori*

Kankyo Kagakkai-Shi, 19(6), p.507 - 515, 2006/11

https://doi.org/10.11353/sesj1988.19.507

Using DFT two benzene rings in Co-PCB are found to be twisted on the bond axis, whose angle is 37.8 in Co-PCB(3,3,4,4,5), and it is 90 in PCB(1,1,2,2,3,3,4,4,5,5), and two benzene rings of TCDD or TCDF are in the same plane. Next, the dissociation of chlorine atom from dioxin is realized using the violet light below 318 nm as the bond dissociation energy 3.83.9 eV estimated by the energy difference between the dioxin and the chlorine atom plus dioxin radical. The orbital bond energy is estimated to be 4.15.5 eV, and the zero-point energy is also estimated to be 0.381.65 eV. The bond dissociation energy is inverse proportion to the number of chlorine atoms in dioxins. On the other hand, the dissociation reaction by the extract of chlorine using hydrogen atom is successfully analysed. The reaction times of dechlorination, or the extract reaction of chlorine and the photolytic process, are 2240 fs.

Study on vertical component seismic isolation system with coned disk spring

Kitamura, Seiji; Ito, Kei; Moro, Satoshi

ASME PVP 2004, 486(2), p.61 - 67, 2004/07

The outline of the vertical seismic isolation system for component and a series of model tests with full scale coned disk spring and damper are shown in this paper.