Tomiyasu, Keisuke*; Ito, Naoko*; Okazaki, Ryuji*; Takahashi, Yuki*; Onodera, Mitsugi*; Iwasa, Kazuaki*; Nojima, Tsutomu*; Aoyama, Takuya*; Ogushi, Kenya*; Ishikawa, Yoshihisa*; et al.
Advanced Quantum Technologies (Internet), 1(3), p.1800057_1 - 1800057_7, 2018/12
Spin-state transition, also known as spin crossover, plays a key role in diverse systems. In theory, the boundary range between the low- and high-spin states is expected to enrich the transition and give rise to unusual physical states. However, no compound that realizes a nearly degenerate critical range as the ground state without requiring special external conditions has yet been experimentally identified. This study reports that the Sc substitution in LaCoO3 destabilizes its nonmagnetic low-spin state and generates an anomalous paramagnetic state accompanied by the enhancement of transport gap and magneto-lattice-expansion as well as the contraction of Co-O distance with the increase of electron site transfer. These phenomena are not well described by the mixture of conventional low- and high-spin states, but by their quantum superposition occurring on the verge of a spin-state transition.
Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro*; Okochi, Takuo*; Yasui, Akira*; et al.
Applied Physics Letters, 112(2), p.021603_1 - 021603_5, 2018/01
A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, Fe) without charging issues. We found that Cs atoms were likely to be adsorbed evenly over the entire particle. Spatially-resolved X-ray absorption spectra (XAS) of the Cs M-edge region showed Cs to be present in a monocation state (Cs). Further pinpoint XAS measurements were also performed at the Fe L-edge to determine the chemical valence of the Fe atoms. Our results demonstrate the utility of SR-PEEM as a tool for spatially-resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.
Watanabe, Takayoshi; Oyama, Takuya; Ishii, Yasuo; Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito
KEK Proceedings 2017-6, p.122 - 126, 2017/11
no abstracts in English
Nakanishi, Takahiro; Oyama, Takuya; Hagiwara, Hiroki
KEK Proceedings 2017-6, p.107 - 111, 2017/11
At riverbanks in six rivers (Odaka, Ukedo, Takase, Kuma, Tomioka and Kido rivers) of eastern Fukushima, dose rate distribution in the cross section had been observed from January 2013 to December 2016. Dose rates in the flood plain which were flooded periodically were different from the surroundings. In rivers without reservoirs (Odaka, Takase and Kuma rivers), dose rates in the flood plain were affected by average radiocesium inventory in the whole catchments. By contrast, in rivers with reservoirs (Ukedo, Tomioka and Kido rivers), dose rates in the flood plain were affected by those in the downstream area of reservoirs and the erosion effect.
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
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.
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
Saegusa, Hiromitsu; Oyama, Takuya; Iijima, Kazuki; Onoe, Hironori; Takeuchi, Ryuji; Hagiwara, Hiroki
Journal of Environmental Radioactivity, 164, p.36 - 46, 2016/11
The environments of Fukushima have been contaminated due to the Fukushima Daiichi Nuclear Power Plant accidents caused by the Great East Japan Earthquake on March 11, 2011. Released radio-cesium mainly affects radiation dose in the environment of Fukushima. It is concerned that redistribution of the radiation dose due to water discharge will be occurred due to the transportation of radio-cesium. Especially, deposition of the transferred soil particle with radio-cesium at flood plain with downstream area is possible cause of increasing radiation dose. Therefore, it is important to understand the influence of deposition behavior of radio-cesium on radiation dose. The paper discusses the deposition behaviors of radio-cesium at river based on the data obtained from the river investigations.
Hama, Katsuhiro; Sasao, Eiji; Iwatsuki, Teruki; Onoe, Hironori; Sato, Toshinori; Fujita, Tomoo; Sasamoto, Hiroshi; Matsuoka, Toshiyuki; Takeda, Masaki; Aoyagi, Kazuhei; et al.
JAEA-Review 2016-014, 274 Pages, 2016/08
We synthesized the research results from the Mizunami/Horonobe Underground Research Laboratories (URLs) and geo-stability projects in the second midterm research phase. This report can be used as a technical basis for the Nuclear Waste Management Organization of Japan/Regulator at each decision point from siting to beginning of disposal (Principal Investigation to Detailed Investigation Phase).
Hama, Katsuhiro; Mizuno, Takashi; Sasao, Eiji; Iwatsuki, Teruki; Saegusa, Hiromitsu; Sato, Toshinori; Fujita, Tomoo; Sasamoto, Hiroshi; Matsuoka, Toshiyuki; Yokota, Hideharu; et al.
JAEA-Research 2015-007, 269 Pages, 2015/08
We have synthesised the research results from Mizunami/Horonobe URLs and geo-stability projects in the second mid-term research phase. It could be used as technical bases for NUMO/Regulator in each decision point from sitting to beginning of disposal (Principal Investigation to Detailed Investigation Phase). High quality construction techniques and field investigation methods have been developed and implemented and these will be directly applicable to the National Disposal Program (along with general assessments of hazardous natural events and processes). It will be crucial to acquire technical knowledge on decisions of partial backfilling and final closure by actual field experiments in Mizunami/Horonobe URLs as main themes for the next phases.
Yamashita, Takuya*; Shimoyama, Yusuke*; Haga, Yoshinori; Matsuda, Tatsuma*; Yamamoto, Etsuji; Onuki, Yoshichika; Sumiyoshi, Hiroaki*; Fujimoto, Satoshi*; Levchenko, A.*; Shibauchi, Takasada*; et al.
Nature Physics, 11(1), p.17 - 20, 2015/01
Onishi, Takashi; Koyama, Shinichi; Masud, R. S.*; Kawamura, Takuya*; Mimura, Hitoshi*; Niibori, Yuichi*
Nippon Ion Kokan Gakkai-Shi, 25(4), p.220 - 227, 2014/11
no abstracts in English
Misumi, Kazuhiro*; Tsumune, Daisuke*; Tsubono, Takaki*; Tateda, Yutaka*; Aoyama, Michio*; Kobayashi, Takuya; Hirose, Katsumi*
Journal of Environmental Radioactivity, 136, p.218 - 228, 2014/10
Major controls on spatiotemporal variations of Cs activity in seabed sediments derived from the Fukushima Dai-ichi Nuclear Power Plant accident during the first year after the accident were investigated by using numerical simulations. The model successfully reproduced major features of the observed spatiotemporal variations of Cs activity in sediments. The spatial pattern of Cs in sediments, which mainly reflected the history of Cs activity in the bottom water overlying the sediment and the sediment particle size distribution, became established during the first several months after the accident. Taking Cs activities in sediments in the coastal area and in the vicinity of the power plant into account, increased the simulated total inventory of Cs in sediments off the Fukushima coast to a value on the order of 10 Bq.
Kasada, Ryuta*; Goto, Takuya*; Fujioka, Shinsuke*; Hiwatari, Ryoji*; Oyama, Naoyuki; Tanigawa, Hiroyasu; Miyazawa, Junichi*; Young Scientists Special Interest Group on Fusion Reactor Realization*
Purazuma, Kaku Yugo Gakkai-Shi, 89(4), p.193 - 198, 2013/04
Japanese young researchers who have interest in realizing fusion reactor have analyzed Technology Readiness Levels (TRL) in Young Scientists Special Interest Group on Fusion Reactor Realization. In this report, brief introduction to TRL assessment and a view of TRL assessment against fusion reactor projects conducting in Japan.
Shimo, Michito*; Kumamoto, So*; Tsuyuguchi, Koji; Onoe, Hironori; Saegusa, Hiromitsu; Mizuno, Takashi; Oyama, Takuya
JAEA-Research 2012-043, 98 Pages, 2013/03
One of the goals of the Mizunami Underground Research Laboratory (MIU) Project is to develop technical basis for investigation, analysis and evaluation technologies for understanding the deep underground geological environment in various scales. Understanding groundwater flow system is one of the important issues in the project, and to achieve this purpose, technologies for hydrogeological model and groundwater flow simulation technique, have to be established. As a result of this study, the significant hydrogeological structures around the MIU Construction Site were estimated. The inflow rate into the MIU facilities and hydraulic and geochemical impacts around the MIU Construction Site caused by the MIU facilities construction were predicted. The effect of pre-grouting to the MIU facilities was also confirmed.
Nakayama, Masashi; Amano, Kenji; Tokiwa, Tetsuya; Yamamoto, Yoichi; Oyama, Takuya; Amano, Yuki; Murakami, Hiroaki; Inagaki, Daisuke; Tsusaka, Kimikazu; Kondo, Keiji; et al.
JAEA-Review 2012-035, 63 Pages, 2012/09
The Horonobe Underground Research Laboratory Project is planned to extend over a period 20 years. The investigations will be conducted in three phases, namely "Phase 1: Surface-based investigations", "Phase 2: Construction Phase" (investigations during construction of the underground facilities) and "Phase 3: Operation phase"(research in the underground facilities). This report summarizes the results of the investigations for the 2011 fiscal year (2011/2012). The investigations, which are composed of "Geoscientific research" and "R&D on geological disposal technology", were carried out according to "Horonobe Underground Research Laboratory Project Investigation Program for the 2011 Fiscal year". The results of these investigations, along with the results which were obtained in other departments of Japan Atomic Energy Agency (JAEA), are properly offered to the implementations and the safety regulations. For the sake of this, JAEA has proceeded with the project in collaboration with experts from domestic and overseas research organisations.
Shimo, Michito*; Kumamoto, So*; Kosaka, Hiroshi; Onoe, Hironori; Saegusa, Hiromitsu; Mizuno, Takashi; Oyama, Takuya
JAEA-Research 2012-004, 126 Pages, 2012/04
One of the goals of Mizunami Underground Research Laboratory (MIU) Project is to develop technical basis for investigation, analysis and evaluation technologies for understanding deep underground geological environment in various scales. Understanding groundwater flow system is one of the important issues in the project, and to achieve this purpose, technologies for a hydrogeological model and the groundwater flow simulation technique, have to be established. In this study, hydrogeological modeling and groundwater flow simulations have been carried out in order to predict hydraulic and geochemical impacts around the MIU Construction Site and inflow rate into the MIU facilities. As a result of this study, the significant hydrogeological structures could be estimated. The inflow rate into the MIU facilities and hydraulic and geochemical impacts with the MIU facilities construction could be predicted. The effect of pre-grouting to the MIU facilities could be also confirmed.
Iwatsuki, Teruki; Sato, Haruo; Nohara, Tsuyoshi; Tanai, Kenji; Sugita, Yutaka; Amano, Kenji; Yabuuchi, Satoshi; Oyama, Takuya; Amano, Yuki; Yokota, Hideharu; et al.
JAEA-Research 2011-009, 73 Pages, 2011/06
The research and development plan in Horonobe Underground Research Laboratory are summarized according to the 2nd Midterm Plan till 2014 fiscal year of JAEA. In this midterm, galleries and the infrastructures for the research and development up to the depth of 350 m are constructed by Private Financial Initiative (PFI). Additionally Phase 3: Operation phase at the galleries begins in parallel to Phase 2: Construction phase. In these phases various research and development including collaboration with other institutes are conducted at the galleries. Generallic applicable techniques on the subject of the investigation of geological environment, facility construction in deep underground and the reliability of geological deposal are developed during the phase. The feasibility and reliance of various technologies concerning geological disposal is demonstrated by widely opening the outcome to the public in the society.
Kunimaru, Takanori; Mikake, Shinichiro; Nishio, Kazuhisa; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Hayano, Akira; Takeuchi, Ryuji; Saegusa, Hiromitsu; Oyama, Takuya; Mizuno, Takashi; et al.
JAEA-Review 2011-007, 145 Pages, 2011/03
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). Geoscientific research and the MIU Project are planned in three overlapping phases; Surface-based Investigation Phase (Phase 1), Construction Phase (Phase 2) and Operation Phase (Phase 3). Currently, the project is under the Construction Phase. This document introduces the results of the research and development in fiscal year 2009, as a part of the Construction Phase based on the MIU Master Plan updated in 2002, (1) Investigation at the MIU Construction Site and the Shobasama Site, (2) Construction at the MIU Construction Site, (3) Research Collaboration, etc. The goals of the Phase 2 are to develop and revise the models of the geological environment using the investigation results obtained during excavation and determine and assess changes in the geological environment in response to excavation, to evaluate the effectiveness of engineering techniques used for construction, maintenance and management of underground facilities, to establish detailed investigation plans of Phase 3.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Kondo, Shuji; Kanazawa, Shuhei; et al.
Reza Kenkyu, 38(9), p.669 - 675, 2010/09
This paper reviews the temporal contrast and spatial beam quality improvement techniques in a high intensity Ti:sapphire laser system that is based on chirped-pulse amplification (CPA). We describe a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier that uses high energy, clean pulse seeding and is shown to significantly improve the contrast to better than 10-10 relative to the peak of the main femtosecond pulse. We also report the use of a diffractive optical element for beam homogenization of a 100 J level Nd:glass green pump laser, achieving a flat-topped spatial profile with a filling factor near 80 %.
Kosuge, Atsushi; Kiriyama, Hiromitsu; Shimomura, Takuya*; Tanoue, Manabu*; Kanazawa, Shuhei; Ochi, Yoshihiro; Mori, Michiaki; Tanaka, Momoko; Okada, Hajime; Sasao, Hajime*; et al.
Reza Kenkyu, 38(9), p.706 - 710, 2010/09
High conversion efficiency of optical parametric chirped-pulse amplification (OPCPA) is demonstrated with the use of a commercial frequency-doubled Q-Switched Nd:YAG laser. In the high energy seeded OPCPA, we have achieved a pump-to-signal conversion efficiency of 28%. Our result represents, to our knowledge, the most efficient OPCPA to date pumped by a commercial frequency-doubled Q-switched Nd:YAG laser.