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.

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

https://doi.org/10.13182/NT15-15

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 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 consumption reaction previously found in the simulated solution proceeded equally well in the actual solution.

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.

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

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 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, 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.

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

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 300C 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.

Measurement of radiolytically generated hydrogen from HALW and analysis of the inhibitory effect on hydrogen release, 2; Comparison of measured hydrogen concentration and its estimate

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

no journal, , 

no abstracts in English

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.

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.