Weakened oxygen adsorbing the Pt-O bond of the Pt catalyst induced by vacancy introduction into carbon support

Okazaki, Hiroyuki*; Idesaki, Akira*; Koshikawa, Hiroshi*; Matsumura, Daiju; Ikeda, Takashi*; Yamamoto, Shunya*; Yamaki, Tetsuya*

Journal of Physical Chemistry C, 127(49), p.23628 - 23633, 2023/12

https://doi.org/10.1021/acs.jpcc.3c04117

Development of an continuous air monitor for the measurement of highly radioactive alpha-emitting particulates (-aerosols) under high humidity environment

Tsubota, Yoichi; Honda, Fumiya; Tokonami, Shinji*; Tamakuma, Yuki*; Nakagawa, Takahiro; Ikeda, Atsushi

Nuclear Instruments and Methods in Physics Research A, 1030, p.166475_1 - 166475_7, 2022/05

https://doi.org/10.1016/j.nima.2022.166475

In the long-lasting decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), the dismantling of nuclear fuel debris (NFD) remaining in the damaged reactors is an unavoidable but significant issue with many technical difficulties. The dismantling is presumed to involve mechanical cutting, generating significant concentrations of particulates containing -radionuclides (-aerosols) that pose significant health risk upon inhalation. In order to minimize the radiation exposure of workers with -aerosols during the dismantling/decommissioning process at 1F, it is essential to monitor the concentration of -aerosols at the point of initial generation, i.e. inside the primary containment vessels (PCV) of the damaged reactors. Toward this end, an monitoring system for -aerosols ( alpha air monitor: IAAM) was developed and its technical performance was investigated under the conditions expected for the actual environments at 1F. IAAM was confirmed to fulfill four technical requirements: (1) steady operation under high humidity, (2) operation without using filters, (3) capability of measuring a high counting rate of -radiation, and (4) selective measurement of -radiation even under high radiation background with /-rays. IAAM is capable of selectively measuring -aerosols with a concentration of 3.3 10 Bq/cm or higher without saturation under a high humid environment (100%-relative humidity) and under high background with /-radiation (up to 100 mSv/h of -radiation). These results demonstrate promising potential of IAAM to be utilized as a reliable monitoring system for -aerosols during the dismantling of NFD, as well as the whole long-lasting decommissioning of 1F.

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Mizunami Underground Research Laboratory Project, Annual report for fiscal year 2017

Takeuchi, Ryuji; Iwatsuki, Teruki; Matsui, Hiroya; Nohara, Tsuyoshi; Onoe, Hironori; Ikeda, Koki; Mikake, Shinichiro; Hama, Katsuhiro; Iyatomi, Yosuke; Sasao, Eiji

JAEA-Review 2019-005, 76 Pages, 2019/06

JAEA-Review-2019-005.pdf:24.91MB

The Mizunami Underground Research Laboratory (MIU) project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of geological disposal technologies through investigations of the deep geological environment in the crystalline rock (granite) at Mizunami City, Gifu Prefecture, central Japan. On the occasion of the research program and management system revision of the entire JAEA organization in 2014, JAEA identified three remaining important issues on the geoscientific research program based on the latest results of the synthesizing research and development: "Development of countermeasure technologies for reducing groundwater inflow", "Development of modeling technologies for mass transport" and "Development of drift backfilling technologies". The research and development on three remaining important issues have been carrying out on the MIU project. In this report, the current status of the research and development activities and construction in fiscal year 2017 is summarized.

In situ observations reveal how spectral reflectance responds to growing season phenology of an open evergreen forest in Alaska

Kobayashi, Hideki*; Nagai, Shin*; Kim, Y.*; Yan, W.*; Ikeda, Kyoko*; Ikawa, Hiroki*; Nagano, Hirohiko; Suzuki, Rikie*

Remote Sensing, 10(7), p.1071_1 - 1071_19, 2018/07

https://doi.org/10.3390/rs10071071

Plant phenology timings, such as spring green-up and autumn senescence, are essential state information characterizing biological responses and terrestrial carbon cycles. Current efforts for the in situ reflectance measurements are not enough to obtain the exact interpretation of how seasonal spectral signature responds to phenological stages in boreal evergreen needleleaf forests. This study shows the first in situ continuous measurements of canopy scale (overstory + understory) and understory spectral reflectance and vegetation index in an open boreal forest in interior Alaska. Two visible and near infrared spectroradiometer systems were installed at the top of the observation tower and the forest understory, and spectral reflectance measurements were performed in 10 min intervals from early spring to late autumn. We found that canopy scale normalized difference vegetation index (NDVI) varied with the solar zenith angle. On the other hand, NDVI of understory plants was less sensitive to the solar zenith angle. Due to the influence of the solar geometry, the annual maximum canopy NDVI observed in the morning satellite overpass time (10-11 am) shifted to the spring direction compared with the standardized NDVI by the fixed solar zenith angle range (60-70 degree). We also found that the in situ NDVI time-series had a month-long high NDVI plateau in autumn, which was completely out of photosynthetically active periods when compared with eddy covariance net ecosystem exchange measurements. The result suggests that the onset of an autumn high NDVI plateau is likely to be the end of the growing season. In this way, our spectral measurements can serve as baseline information for the development and validation of satellite-based phenology algorithms in the northern high latitudes.

Mizunami Underground Research Laboratory Project, Annual report for fiscal year 2016

Ishibashi, Masayuki; Hama, Katsuhiro; Iwatsuki, Teruki; Matsui, Hiroya; Takeuchi, Ryuji; Nohara, Tsuyoshi; Onoe, Hironori; Ikeda, Koki; Mikake, Shinichiro; Iyatomi, Yosuke; et al.

JAEA-Review 2017-026, 72 Pages, 2018/01

JAEA-Review-2017-026.pdf:18.23MB

The Mizunami Underground Research Laboratory (MIU) project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of geological disposal technologies through investigations of the deep geological environment in the crystalline host rock (granite) at Mizunami, Gifu Prefecture, central Japan. On the occasion of the research program and management system revision of the entire JAEA organization in 2014, JAEA identified three important issues on the geoscientific research program: "Development of countermeasure technologies for reducing groundwater inflow", "Development of modeling technologies for mass transport" and "Development of drift backfilling technologies", based on the latest results of the synthesizing research and development (R&D). The R&D on three important issues have been carrying out on the MIU project. In this report, the current status of R&D activities and construction in 2016 is summarized.

Probabilistic risk assessment method development for high temperature gas-cooled reactors, 2; Development of accident sequence analysis methodology

Matsuda, Kosuke*; Muramatsu, Ken*; Muta, Hitoshi*; Sato, Hiroyuki; Nishida, Akemi; Ohashi, Hirofumi; Itoi, Tatsuya*; Takada, Tsuyoshi*; Hida, Takenori*; Tanabe, Masayuki*; et al.

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

This paper proposes a set of procedures for accident sequence analysis in seismic PRAs of HTGRs that can consider the unique accident progression characteristics of HTGRs. Main features of our proposed procedure are as follows: (1) Systematic analysis techniques including Master Logic Diagrams are used to ensure reasonable completeness in identification of initiating events and classification of accident sequences, (2) Information on factors that govern the accident progression and source terms are effectively reflected to the construction of event trees for delineation of accident sequences, and (3) Frequency quantification of seismically-initiated accident sequence frequencies that involve multiplepipe ruptures are made with the use of the Direct Quantification of Fault Trees by Monte Carlo (DQFM) method by a computer code SECOM-DQFM.

Mizunami Underground Research Laboratory Project, Annual report for fiscal year 2015

Hama, Katsuhiro; Iwatsuki, Teruki; Matsui, Hiroya; Mikake, Shinichiro; Ishibashi, Masayuki; Onoe, Hironori; Takeuchi, Ryuji; Nohara, Tsuyoshi; Sasao, Eiji; Ikeda, Koki; et al.

JAEA-Review 2016-023, 65 Pages, 2016/12

JAEA-Review-2016-023.pdf:47.32MB

The Mizunami Underground Research Laboratory (MIU) project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of geological disposal technologies through investigations of the deep geological environment in the crystalline host rock (granite) at Mizunami City in Gifu Prefecture, central Japan. On the occasion of the reform of the entire JAEA organization in 2014, JAEA identified three important issues on the geoscientific research program: "Development of countermeasure technologies for reducing groundwater inflow", "Development of modelling technologies for mass transport" and "Development of drift backfilling technologies", based on the latest results of the synthesizing research and development (R&D). These R&D on three important issues have been carrying out on the MIU project. In this report, the current status of R&D activities and construction in 2015 is summarized.

Measurement of ion species in high current ECR H/D ion source for IFMIF (International Fusion Materials Irradiation Facility)

Shinto, Katsuhiro; Sene, F.*; Ayala, J.-M.*; Bolzon, B.*; Chauvin, N.*; Gobin, R.*; Ichimiya, Ryo; Ihara, Akira; Ikeda, Yukiharu; Kasugai, Atsushi; et al.

Review of Scientific Instruments, 87(2), p.02A727_1 - 02A727_3, 2016/02

https://doi.org/10.1063/1.4933342

Mizunami Underground Research Laboratory Project, Plan for fiscal year 2015

Hama, Katsuhiro; Takeuchi, Ryuji; Saegusa, Hiromitsu; Iwatsuki, Teruki; Sasao, Eiji; Mikake, Shinichiro; Ikeda, Koki; Sato, Toshinori; Osawa, Hideaki; Koide, Kaoru

JAEA-Review 2015-021, 27 Pages, 2015/10

JAEA-Review-2015-021.pdf:4.35MB

The Mizunami Underground Research Laboratory (MIU) project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of geological disposal technologies through investigations of the deep geological environment in the crystalline host rock (granite rock) at Mizunami City in Gifu Prefecture, central Japan. This report summarizes the research and development activities planned for fiscal year 2015 based on the MIU Master Plan updated in 2015 and so on. On the occasion of the reform of the entire JAEA organization in 2014, JAEA identified the critical issues on the geoscientific research program: "Development of modelling technologies for mass transport", "Development of drift backfilling technologies" and "Development of technologies for reducing groundwater inflow", based on the latest results of the synthesizing R&D. Investigations on those critical issues will be performed at the MIU in fiscal year 2015.