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Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:170 Percentile:99.77(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Study on the behavior of radiolytically produced hydrogen in a high-level liquid waste tank of a reprocessing plant; Comparison between actual and simulated solutions

Kinuhata, Hiroshi*; Yamamoto, Masahiko; Taguchi, Shigeo; Surugaya, Naoki; Sato, Soichi; Kodama, Takashi*; Tamauchi, Yoshikazu*; Shibata, Yuki*; Anzai, Kiyoshi*; Matsuoka, Shingo*

Nuclear Technology, 192(2), p.155 - 159, 2015/11

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Experiments using a small-scale apparatus with 30 ml actual high-level liquid waste from the Tokai Reprocessing Plant were carried out to show that the hydrogen concentration in the gas phase reaches a steady-state value of much less than 4% (lower explosive limit) in the absence of sweeping-air. The H$$_{2}$$ concentration reached a steady-state value as was expected and it was compared with a value predicted from an equation with parameters which had been obtained using the simulated solution. Satisfactory agreement showed that the Pd-ion catalytic H$$_{2}$$ consumption reaction previously found in the simulated solution proceeded equally well in the actual solution.

JAEA Reports

Mizunami Underground Research Laboratory Project, Annual report for fiscal year 2010

Kunimaru, Takanori; Mikake, Shinichiro; Nishio, Kazuhisa; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Ishibashi, Masayuki; Ueno, Takashi; Tokuyasu, Shingo; Daimaru, Shuji; Takeuchi, Ryuji; et al.

JAEA-Review 2012-020, 178 Pages, 2012/06

JAEA-Review-2012-020.pdf:33.16MB

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 Phase III started in 2010 fiscal year. This report shows the results of the investigation, construction and collaboration studies in fiscal year 2010, as a part of the Phase II based on the MIU Master Plan updated in 2002.

JAEA Reports

Studies on estimation of hydrogeological structure using self-potential monitoring around Mizunami Underground Research Laboratory (MIU)

Tokuyasu, Shingo; Matsuoka, Toshiyuki; Hodotsuka, Yasuyuki*

JAEA-Research 2012-007, 55 Pages, 2012/06

JAEA-Research-2012-007.pdf:35.8MB
JAEA-Research-2012-007-appendix(DVD-ROM).zip:951.94MB

During drilling the pilot boring in October 2008 before construction of -300 m Access/Research Gallery, groundwater inflow more than 1,000 L/min is induced, and original signals of SP monitoring are observed. First of all in this study, we thus assess the method of data processing to extract the applicable signal from SP monitoring, and the hydrogeological structure is estimated using the treated data. Secondly, the signals of SP monitoring observed between March and April in 2006 when pumping of groundwater from the shafts are applied to the same method of data processing mentioned above. In addition, the treated data is used to estimate the hydrogeological structures more in detail. Considering all results together, the applicability of SP monitoring for estimating the distributions of major water-conducting features and faults with low permeability is discussed. As the result of this study, we conclude that it is likely that the hydrogeological structures would be estimated using the SP monitoring.

JAEA Reports

Mizunami Underground Research Laboratory Project; Results of the borehole investigations to understand the geological environment in and around the Main-shaft fault

Tsuruta, Tadahiko; Takeda, Masaki; Ueno, Takashi; Daimaru, Shuji; Tokuyasu, Shingo; Onoe, Hironori; Shingu, Shinya; Ishibashi, Masayuki; Takeuchi, Ryuji; Matsuoka, Toshiyuki; et al.

JAEA-Technology 2012-001, 134 Pages, 2012/03

JAEA-Technology-2012-001.pdf:41.2MB
JAEA-Technology-2012-001(errata).pdf:0.44MB
JAEA-Technology-2012-001-appendix(CD-ROM).pdf:6.37MB

Tono Geoscientific Research Unit of Japan Atomic Energy Agency (JAEA) is performing the Mizunami Underground Research Laboratory (MIU) project in order to establish comprehensive techniques for the investigation, analysis and assessment of the deep geological environment in fractured crystalline rock. The borehole investigations (two boreholes; 10MI22 borehole and 10MI23 borehole) have been carried out to obtain information on geological, hydrological and hydrochemical characteristics in and around the Main-shaft fault. These investigations provided that features of fracture and alteration on rock mass in and around the Main-shaft fault. Hydrological and hydrochemical properties based on the geological features were also obtained.

Oral presentation

Probabilistic safety analysis on the reprocessing plant at Rokkashomura, 12; Experimental study on the effect suppressing hydrogen emission from concentrated high level liquid waste, 1

Kodama, Takashi*; Nakano, Masamichi*; Matsuoka, Shingo*; Matsuura, Chihiro*; Ito, Yasuo*; Kurosu, Katsuya*; Shiraishi, Hirotsugu; Katsumura, Yosuke*

no journal, , 

It has been known that although a considerable amount of hydrogen is produced radiolytically in the high level liquid waste, only small part is emitted into the gas phase when the liquid depth is large. We report here the results of an experimental study which shows that the liquid-depth effect is caused not by the reaction between hydrogen and radicals, as has been previously suggested, but by Pd-catalyzed reaction between hydrogen and nitric acid. The method for evaluating the magnitute of the effect is also proposed.

Oral presentation

The Inhibitory effect of hydrogen release from high active liquid waste, 2; Mechanism of solution depth effect

Kodama, Takashi*; Nakano, Masanao*; Hayashi, Yoshiaki*; Matsuoka, Shingo*; Ito, Yasuo*; Matsuura, Chihiro*; Shiraishi, Hirotsugu; Katsumura, Yosuke*

no journal, , 

We have reported in the previous meeting that the accumulation of radiolytically produced hydrogen in high-level liquid waste is suppressed owing to some oxidation reaction catalyzed by Pd in the solution. In this report, we present the results of a hydrogen bubbling experiment with mock high-level liquid waste, made to clarify the species involved in the reaction. Analysis was made on nitrous acid and nitric acid in the solution, and also on nitrogen oxide in the outlet gas. It was found that although the concentration of nitrous acid present in the solution is small, nitrogen oxide, consisting mostly of NO, is detected in the gas at concentration corresponding to the decrease of nitric acid in the solution. The amount of the produced nitrogen oxide matched roughly with an estimated amount of reacted hydrogen, confirming that nitric acid is the oxidant.

Oral presentation

The Inhibitory effect of hydrogen release from high active liquid waste, 3; Estimation of the hydrogen concentration of upper space of tank

Kodama, Takashi*; Nakano, Masanao*; Hayashi, Yoshiaki*; Matsuoka, Shingo*; Ito, Yasuo*; Matsuura, Chihiro*; Shiraishi, Hirotsugu; Katsumura, Yosuke*

no journal, , 

We report here an evaluation for hydrogen concentration that may be attained in the upper space of the high-level liquid waste tank when the gas sweeping function happens to be lost. The parameters are the rate of radiolytic production of hydrogen, the rate of Pd-catalyzed hydrogen consuming reaction, and the solubility of hydrogen. For the first, a literature value on nitric acid solution was used, while for the second and third, experimental estimate was made in the present study with mock high-level liquid waste. All data have been taken at ambient temperature. For simplicity, it was assumed that both the gas and the liquid are homogeneous, and that the two phases are in equilibrium regarding hydrogen concentration. These led to an estimate of 0.6% for the hydrogen concentration in the gas phase, a value smaller than the lower limit of explosion.

Oral presentation

Application of seismic interferometry using the vibration caused by the shafts excavation in the granite

Hodotsuka, Yasuyuki; Matsuoka, Toshiyuki; Tokuyasu, Shingo

no journal, , 

Seismic interferometry is an investigation method used to deduce geological structures in the subsurface, by performing cross-correlations between the traces of each record and synthesizing similar data obtained by reflection seismic surveying on surface. In this study, Seismic interferometry using the vibration under the construction works, such as borehole drilling and mucking, etc. at the horizontal tunnel in the Mizunami Underground Research Laboratory, had been carried out to develop the method that obtain seismic image. The reflection image obtained from seismic interferometry using deconvolution has a high signal to noise (S/N) ratio compared to reflection images from normal seismic interferometry.

Oral presentation

Mizunami Underground Laboratory project; Investigation of geology

Kurihara, Arata; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Hayano, Akira; Hayakawa, Masashi; Tagami, Masahiko; Hodotsuka, Yasuyuki; Yuguchi, Takashi; Ochi, Minoru; Tokuyasu, Shingo

no journal, , 

no abstracts in English

Oral presentation

Current status of Mizunami Underground Research Laboratory Project, 1; Geological investigations

Tokuyasu, Shingo; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Tagami, Masahiko; Kurihara, Arata

no journal, , 

no abstracts in English

Oral presentation

Study on hydrogeological structure around the Mizunami Underground Research Laboratory (MIU) site using self-potential method

Tokuyasu, Shingo; Matsuoka, Toshiyuki; Mizunaga, Hideki*; Sugimoto, Yoshihiro*

no journal, , 

no abstracts in English

Oral presentation

Mizunami Underground Research Laboratory project; Geological investigations

Matsuoka, Toshiyuki; Tsuruta, Tadahiko; Tagami, Masahiko; Ishibashi, Masayuki; Tokuyasu, Shingo; Ueno, Takashi; Yuguchi, Takashi

no journal, , 

Current status of geological investigations of the MIU Project Phase II are summarized. Geological mapping, reverse VSP, Analog model simulation and so on, were conducted as Phase II investigations. As results of these investigations, the methodology for the evaluation of geological model constructed in Phase I could be presented.

Oral presentation

Mizunami Underground Research Laboratory Project; Geological investigations

Ishibashi, Masayuki; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Tokuyasu, Shingo; Ueno, Takashi; Kawamoto, Koji; Kuboshima, Koji; Sasao, Eiji

no journal, , 

no abstracts in English

Oral presentation

Mizunami Underground Research Laboratory Project; Results of the borehole investigations to assess the geological environment in and around the Main-shaft fault

Takeuchi, Ryuji; Takeda, Masaki; Ueno, Takashi; Daimaru, Shuji; Tokuyasu, Shingo; Onoe, Hironori; Shingu, Shinya; Ishibashi, Masayuki; Matsuoka, Toshiyuki; Mizuno, Takashi; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on release and transport of aerial radioactive materials in reprocessing plant, 4; Cold test (Part 1) ARF test using mocked fuel reprocessing liquid waste

Tashiro, Shinsuke; Matsumoto, Tetsuya; Kataoka, Osamu; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun; Uchiyama, Gunzo; Ueda, Yoshinori*; et al.

no journal, , 

Measurements on the release ratios of aerial radioactive materials from mocked fuel reprocessing liquid waste under its boiling to dryness process were performed using labo-scaled experiments. Test sample, dissolved 27 elements into nitric acid and arranged to 2M acidity, was heated up to 300 $$^{circ}$$C under the constant air ventilation. Steam, gaseous and airborne materials were collected or absorbed at the condenser, the air filter and the washing bottles. The accumulated release ratios of mocked FP elements from samples were determined using ICP-MS. From the accumulated release ratios determined from the condensed samples, the major release of Cs and Ru could be involved the release of mist and gaseous RuO$$_{4}$$, respectively. Besides, accumulated release ratios of Ru was about 10 to 1000 times higher than Cs, differed from the literature using fuel reprocessing liquid waste. Its differences could be influenced the nitrous acid, which was reduced the generation of RuO$$_{4}$$.

Oral presentation

Measurement and analysis of radiolytically generated hydrogen from HALW, 1; Measurement and evaluation of the hydrogen concentration in the vessel off-gas

Tomiyama, Masahiro; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Shirato, Yoji; Nakamura, Yoshinobu; Kinuhata, Hiroshi*; Kodama, Takashi*; Nakano, Masanao*; Tamauchi, Yoshikazu*; et al.

no journal, , 

no abstracts in English

Oral presentation

Measurement and analysis of radiolytically generated hydrogen from HALW, 2; Comparison of measured hydrogen concentration and its estimation

Kinuhata, Hiroshi*; Kodama, Takashi*; Nakano, Masanao*; Tamauchi, Yoshikazu*; Matsuoka, Shingo*; Tomiyama, Masahiro; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Shirato, Yoji; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on release and transport of aerial radioactive materials in reprocessing plant, 6; Cold test (Part 3) Effect of FP concentration in mocked HLLW to ARF

Tashiro, Shinsuke; Matsumoto, Tetsuya; Kataoka, Osamu; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun; Uchiyama, Gunzo; Ueda, Yoshinori*; et al.

no journal, , 

The release behavior of radioactive materials from high-level radioactive liquid wastes (HLW) from reprocessing plants under an accidents of boiling to dryness of HLW condition has been studied. The influences of FP concentration in the simulated HLW on the release ratio of FP from the waste were measured in the laboratory-scaled experiments using non-radioactive simulated HLW which was prepared by dissolving 27 FP elements into nitric acid and adjusted to 2 M acidity. The simulated HLW was heated up to 300$$^{circ}$$C under the constant air ventilation condition. The accumulated release ratios of FP elements from samples were determined using ICP-MS analysis. It was found that the accumulated release ratio of Ru was decreased with the increase of the initial Ru concentration in the simulated HLW. However, those of Cs and Nd were not influenced by the initial concentrations of them.

Oral presentation

Reverse vertical seismic profiling using the research gallery in granite

Yamada, Nobuto; Matsuoka, Toshiyuki; Ishigaki, Koichi*; Kanazawa, Yohei*; Tokuyasu, Shingo*; Nakahara, Junichi*

no journal, , 

Evaluation on the geological discontinuity is one of the important issues for safety assessment of high-level radioactive waste disposal. A Reverse Vertical Seismic Profiling (RVSP) investigation using blasting vibration for excavation of the research gallery and survey lines placed in the -300m research galleries of the Mizunami Underground Research Laboratory has been carried out to obtain three-dimensional information on the geological discontinuity such as faults and fracture zones in granite during the research galleries excavation works. In this study, results of RVSP are compared with existing information such as sonic logging to estimate spatial distribution of faults and fracture zones, and the applicability of this method to estimate geological structure in the granite is discussed.

24 (Records 1-20 displayed on this page)