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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

https://doi.org/10.1126/science.aav7432

Times Cited Count：140 Percentile：99.81(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

An Evaluation method of reflectance spectra to be obtained by Hayabusa2 Near-Infrared Spectrometer (NIRS3) based on laboratory measurements of carbonaceous chondrites

Matsuoka, Moe*; Nakamura, Tomoki*; Osawa, Takahito; Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Nakauchi, Yusuke*; Arai, Takehiko*; Komatsu, Mutsumi*; Hiroi, Takahiro*; et al.

Earth, Planets and Space (Internet), 69(1), p.120_1 - 120_12, 2017/09

AA2017-0327.pdf:1.53MB

https://doi.org/10.1186/s40623-017-0705-4

Times Cited Count：4 Percentile：23(Geosciences, Multidisciplinary)

We have conducted ground-based performance evaluation tests of the Near-Infrared Spectrometer (NIRS3) onboard Hayabusa2 spacecraft and established a method for evaluating its measured reflectance spectra. Reflectance spectra of nine powdered carbonaceous chondrite samples were measured by both NIRS3 and a FT-IR spectrometer. Since raw data obtained by NIRS3 had considerable spectral distortion caused by systematic offsets in sensitivity of individual pixels, we have established two methods for correcting the NIRS3 data by comparing them with the corresponding FT-IR data. In order to characterize the absorption bands in NIRS3 spectra, the depth of each band component D is defined for each wavelength (m). Reflectance spectra of asteroid Ryugu, the target asteroid of Hayabusa2, to be recorded by the NIRS3 are expected to reveal the characteristics of the surface materials by using the evaluation technique.

Journal Articles

NIRS3; The Near Infrared Spectrometer on Hayabusa2

Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Otake, Makiko*; Arai, Takehiko*; Arai, Tomoko*; Hirata, Naru*; Hiroi, Takahiro*; Honda, Chikatoshi*; Imae, Naoya*; et al.

Space Science Reviews, 208(1-4), p.317 - 337, 2017/07

https://doi.org/10.1007/s11214-017-0341-0

Times Cited Count：33 Percentile：72.27(Astronomy & Astrophysics)

NIRS3: The Near Infrared Spectrometer is installed on the Hayabusa2 spacecraft to observe the target C-type asteroid 162173 Ryugu at near infrared wavelengths of 1.8 to 3.2 micrometer. It aims to obtain reflectance spectra in order to detect absorption bands of hydrated and hydroxide minerals in the 3 micrometer-band. We adopted a linear-image sensor with indium arsenide (InAs) photo diodes and a cooling system with a passive radiator to achieve an optics temperature of 188 K, which enables to retaining sufficient sensitivity and noise level in the 3 micrometer wavelength region. We conducted ground performance tests for the NIRS3 flight model (FM) to confirm its baseline specifications. The results imply that the properties such as the signal-to-noise ratio (SNR) conform to scientific requirements to determine the degree of aqueous alteration, such as CM or CI chondrite, and the stage of thermal metamorphism on the asteroid surface.

Journal Articles

Trial synthesis of Li $_{2}$ Be $_{2}$ O $_{3}$ for high-functional tritium breeders

Hoshino, Tsuyoshi; Oikawa, Fumiaki; Natori, Yuri*; Kato, Kenichi*; Sakka, Tomoko*; Nakamura, Mutsumi*; Tatenuma, Katsuyoshi*

Fusion Engineering and Design, 88(9-10), p.2268 - 2271, 2013/10

https://doi.org/10.1016/j.fusengdes.2013.05.013

Times Cited Count：1 Percentile：12.53(Nuclear Science & Technology)

Lithium titanate with additional Li (Li $_{2+x}$ TiO $_{3+y}$ ) and lithium orthosilicate (Li $_{4}$ SiO $_{4}$ ) is one of the most promising candidates for use in a tritium breeder because of its good chemical and mechanical stabilities. Currently, mixtures of tritium breeder pebble and neutron multiplier (Be or Be $_{12}$ Ti) pebble are being considered for use in increasing the tritium breeding ratio in a breeding blanket. However, lithium and beryllium are gradually reacted under practical operating conditions, and therefore a high-functional tritium breeder such as lithium beryllium oxide (Li $_{2}$ Be $_{2}$ O $_{3}$ ) needs to be developed to compensate for this reactive characteristic under high temperature use. In this study, methods of synthesizing Li $_{2}$ Be $_{2}$ O $_{3}$ have been extensively investigated by means of solid-phase reaction. The solid-phase reaction of LiOH(H $_{2}$ O) and BeO is a suitable synthesis method for lithium beryllium oxide (Li $_{2}$ Be $_{2}$ O $_{3}$ ). It is expected that single-phase Li $_{2}$ Be $_{2}$ O $_{3}$ will be stable under the mixture conditions of a tritium breeder and neutron multiplier in the blanket region at high temperatures.

Journal Articles

Development of advanced tritium breeding material with added lithium for ITER-TBM

Hoshino, Tsuyoshi; Kato, Kenichi*; Natori, Yuri*; Oikawa, Fumiaki; Nakano, Natsuko*; Nakamura, Mutsumi*; Sasaki, Kazuya*; Suzuki, Akihiro*; Terai, Takayuki*; Tatenuma, Katsuyoshi*

Journal of Nuclear Materials, 417(1-3), p.684 - 687, 2011/10

https://doi.org/10.1016/j.jnucmat.2010.12.128

Times Cited Count：39 Percentile：95.49(Materials Science, Multidisciplinary)

Lithium titanate (Li $_{2}$ TiO $_{3}$ ) is one of the most promising candidates among tritium breeding materials because of its good tritium release. Addition of H $_{2}$ to inert sweep gas has been proposed for enhancing the tritium release from tritium breeding materials. However, the mass of Li $_{2}$ TiO $_{3}$ was decreased with time in the hydrogen atmosphere. It is assumed that the mass decrease indicates the loss of the oxygen contained in the sample caused by the change from Ti $^{4+}$ to Ti $^{3+}$ , and that the partial pressures of Li-containing species were increased in the hydrogen atmosphere. In order to decrease the mass-change at high temperature, advanced tritium breeding material with added Li should be developed to improve the physical and chemical stability in hydrogen atmosphere. In the case of the Li $_{2+x}$ TiO $_{3+y}$ samples used by the present study, LiOHH $_{2}$ O and H $_{2}$ TiO $_{3}$ were proportionally mixed with the molar ratio Li/Ti of either 2.0 and 2.2. These samples are designated as L20 (Li/Ti = 2.0) and L22 (Li/Ti = 2.2), respectively. The results of XRD measurement showed that the phases in advanced tritium breeding material were as follows. L22 existed as non-stoichiometric compound Li $_{2+x}$ TiO $_{3+y}$ .

Journal Articles

New synthesis method of advanced lithium titanate with Li $_{4}$ TiO $_{4}$ additives for ITER-TBM

Hoshino, Tsuyoshi; Kato, Kenichi*; Natori, Yuri*; Nakamura, Mutsumi*; Sasaki, Kazuya*; Hayashi, Kimio; Terai, Takayuki*; Tatenuma, Katsuyoshi*

Fusion Engineering and Design, 84(2-6), p.956 - 959, 2009/06

https://doi.org/10.1016/j.fusengdes.2008.12.049

Times Cited Count：39 Percentile：93.81(Nuclear Science & Technology)

Li $_{2}$ TiO $_{3}$ is one of the most promising candidates among the proposed solid breeder materials for fusion reactors. Addition of H $_{2}$ to inert sweep gas has been proposed for enhancing the release of bred tritium from breeder material. However, the mass of Li $_{2}$ TiO $_{3}$ was found to decrease with time in the hydrogen atmosphere. This mass change indicates that the oxygen content of the sample decreased, suggesting the change from Ti $^{4+}$ to Ti $^{3+}$ . In order to control the mass change at the time of high temperature use, the development of lithium titanate which has Li $_{4}$ TiO $_{4}$ additive is expected to be effective.

Journal Articles

Preliminary test for reprocessing technology development of tritium breeders

Hoshino, Tsuyoshi; Tsuchiya, Kunihiko; Hayashi, Kimio; Nakamura, Mutsumi*; Terunuma, Hitoshi*; Tatenuma, Katsuyoshi*

Journal of Nuclear Materials, 386-388, p.1107 - 1110, 2009/04

https://doi.org/10.1016/j.jnucmat.2008.12.297

Times Cited Count：9 Percentile：56.98(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Design and trial fabrication of a dismantling apparatus for irradiation capsules of solid tritium breeder materials

Hayashi, Kimio; Nakagawa, Tetsuya; Onose, Shoji; Ishida, Takuya; Nakamichi, Masaru; Takatsu, Hideyuki; Nakamura, Mutsumi*; Noguchi, Tsuneyuki*

Journal of Nuclear Materials, 386-388, p.1083 - 1086, 2009/04

https://doi.org/10.1016/j.jnucmat.2008.12.290

Times Cited Count：0 Percentile：0.01(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Investigation and design of the dismantling process of irradiation capsules containing tritium, 2; Detailed design and trial fabrication of capsule dismantling apparatus and investigation of glove box facility

Hayashi, Kimio; Nakagawa, Tetsuya; Onose, Shoji; Ishida, Takuya; Nakamichi, Masaru; Katsuyama, Kozo; Iwamatsu, Shigemi; Hasegawa, Teiji; Kodaka, Hideo; Takatsu, Hideyuki; et al.

JAEA-Technology 2009-007, 168 Pages, 2009/03

JAEA-Technology-2009-007.pdf:31.88MB

In-pile functional tests of breeding blankets have been planned by Japan Atomic Energy Agency (JAEA), using a test blanket module (TBM) which will be loaded in the International Thermonuclear Experimental Reactor (ITER). In preparation for the in-pile functional tests, JAEA has been being performed irradiation experiments of lithium titanate (Li $_{2}$ TiO $_{3}$ ), which is the first candidate of solid breeder materials for the blanket of the demonstration reactor (DEMO) under designing in Japan. The present report describes (1) results of a detailed design and trial fabrication tests of a dismantling apparatus for irradiation capsules which were used in irradiation experiments by the Japan Materials Testing Reactor (JMTR) of JAEA, and (2) results of a preliminary investigation of a glove box facility for post-irradiation examinations (PIEs). In the detailed design of the dismantling apparatus, datailed specifications and the installation methods were examined, based on results of a conceptual design and basic design. In the trial fabrication, cutting tests were curried out by making a mockup of a cutting component. Furthermore, a preliminary investigation of a glove box facility was carried out in order to secure a facility for PIE work after the capsule dismantling, which revealed a technical feasibility.

JAEA Reports

Investigation and design of the dismantling process of irradiation capsules containing tritium, 1; Conceptual investigation and basic design

Hayashi, Kimio; Nakagawa, Tetsuya; Onose, Shoji; Ishida, Takuya; Kodaka, Hideo; Katsuyama, Kozo; Kitajima, Toshio; Takahashi, Kozo; Tsuchiya, Kunihiko; Nakamichi, Masaru; et al.

JAEA-Technology 2008-010, 68 Pages, 2008/03

JAEA-Technology-2008-010.pdf:11.31MB

In-pile functional tests of breeding blankets for fusion reactors have been planned by Japan Atomic Energy Agency (JAEA), using a test blanket module (TBM) which will be loaded in ITER. The present report describes a conceptual investigation and a basic design of the dismantling process for irradiation capsules which were used in irradiation experiments by the Japan Materials Testing Reactor (JMTR) of JAEA. In the present design, the irradiation capsule is cut by a band saw; the released tritium is recovered safely by a purge-gas system, and is consolidated into a radioactive waste form. Furthermore, adoption of the inner-box enclosing the dismantling apparatus has brought a prospect to be able to utilize an existing hot cell (beta- cell) equipped with usual wall material permeable to tritium, without extensive refurbishing of the cell. Thus, the present study has indicated the feasibility of the present dismantling process for the irradiated JMTR capsules containing tritium.