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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
Times Cited Count：44 Percentile：97.1(Astronomy & Astrophysics)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.
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：262 Percentile：99.73(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.
Nishihata, Yasuo; Tanaka, Hirohisa*; Mitachi, Senshu*; Kasai, Hideaki*
Kogyo Zairyo, 62(5), p.41 - 44, 2014/05
no abstracts in English
*; *; *; *; *
PNC TJ9502 89-001, 100 Pages, 1989/03
Cladding tubes of advanced austenitic stainless steel with more superior creep strength and void swelling resistance than the modified 316 stainless steel are being developed in Power Reactor and Nuclear Fuel Development Corporation. In National Research Institute for Metals, a part of internal-pressurized creep test is conducted as a member of Creep-subgroup in PNC in order to evaluate a creep properties of developed cladding tubes under internal pressure. In the present 18th program, creep rupture tests under internal pressure at 750C and interrupted creep tests under internal pressure at 700C were carried out for two kinds of cladding tubes of advanced austenitic stainless steel which had been domestically trial-manufactured in fiscal year 1987. Two kinds of cladding tubes in this test, 62AS and 62AK, have the same main chemical composition, 15Cr-20Ni-2.5Mo-0.25Ti-0.1Nb, as the cladding tubes examined in the 13th, 14th and 16th programs. Creep rupture strength under internal pressure of 62AK was higher for shorter rupture times than that of 62AS, but for longer rupture time, creep rupture strength of 62AK was nearly equal to that of 62AS. 62AS in this study showed the higher creep rupture strength than 60AS which was trial-manufactured in fiscal year 1985. It was considered that more superior creep rupture strength of the cladding tubes for this study was due to higher temperature solution heat treatment enough to dissolve Nb and higher cold-working. The size of cladding tube (outside diameter and thickness) trial-manufactured in fiscal year 1987 is different from that of fiscal year 1985 cladding tube, but the effect of cladding tube size on creep rupture strength was not recognized. The interrupted creep tests of 62AS and 62AK were conducted under hoop stress of 100 and 81MPa at 700C, and the creep deformation data of cladding tubes were measured. Swelling of tube for 62AS showed transient and steady regions like an ordinary ...
*
PNC TN241 85-02, 105 Pages, 1984/12
The development program for cladding tubes of 316 stainless steel was completed at 12th creep test, and cladding tubes of 316 modified stainless steel which indicated superior creep rupture strength were developed. From now on, hight temperature strength of cladding tubes of solution hardened austenitic stainless steel will be evaluated, according to the development program for the stainless steel which is expected to have better void swelling resistence than 316 modified stainless steel. The program is carried out by Alloy Development Working Group. In the present 13th creep test, tensile test, burst test, creep rupture test under internal pressure and metallurgical observation have been performed for cladding tubes of four kinds of austenitic stainless steel, domestically trial-manufactured in fiscal year 1982, Out of six kinds. The four kinds are 15Cr-15Ni-2.5Mo-0.25Ti(57MSI), 15Cr-20Ni-2.5Mo-0.20Ti(57MK2), 15Cr-20Ni-2.5Mo-0.35Ti(57MK3) and 15Cr-25Ni-2.5Mo-0.25Ti(57MK4). Results obtained are: (1)There are little differences in tensile properties among the four kinds of solution hardened austenitic stainless steel and 316 modified stainless steel. (2)Burst strength of 57MK2 is the highest among those of the four kinds. (3)Creep rupture strength of the four kinds under internal pressure are all higher than that of 316 modified stainless steel at high temperature and long time. That of 57MK2 is the highest among those of the four kinds. The order of calculated creep rupture, strength of the four kinds and 316 modified stainless steel at 675C and 17,760h is 57MK2
57MK457MS357MS1
316 midified stainless steel. Moreover, creep tests under uniaxial tension and internal pressure for the cladding tube 55MK (316 modified stainless steel), domestically trial-manufactured for "MONJU" core in fiscal year 1980, have been performed. By evaluation of creep data for 55MK and 55MS obtained these tests and the previous tests, an equation for creep strain ...
*
PNC TN241 83-19, 93 Pages, 1983/12
In regard to "Joyo" MK-II reload fuel cladding tubes, 56JK and 56JS, which were domestically produced on a large scale with specifications set in fiscal year 1980, many kinds of test such as tensile test, burst test, creep rupture test under internal pressure, as well as metallurgical microstructure observation and hardness test, were conducted. From these test data, the specifications for fuel cladding tubes were evaluated and design data were obtained for "Monju" initial core fuel cladding tubes. In addition, as for "Monju" fuel cladding tube, 55MS, domestically trial-manufactured in fiscal year 1980, high temperature characteristic data were also obtained by conducting creep and creep rupture test under uniaxial tension and internal creep test. Results obtained are: (1)There are little differences in tensile and burst test results between 56JK and 56JS. They show almost same strengths and elongations as 55MK and 55MS. (2)There are little differences in creep rupture test results under internal pressure between 56JK and 56JS. Compared with cladding tube creep rupture test results under internal pressure, which were performed in the first to 11th test, the results of this time have the same level of creep rupture strength (650C 
7,560h, 675C 17,760h) as both 54M and 55M. This result shows that creep rupture strength under internal pressure of cladding tubes in large scale production (56JK and 56JS) is the highest as the one in trial-manufacturing (54M and 55M). (3)There is scattering of data in creep rupture test under internal pressure among each one of the member insitutions. But there is little difference between creep curves obtained from continuous measurement of an outside diameter and creep test method under uniaxial tension. This means that continuous measurement of an outside diameter is better than off-and on-measurement of an outside diameter. (4)Creep rupture strength under uniaxial tension at test ...
*; *; *; Obara, Katsuaki
PNC TN241 72-43, 94 Pages, 1972/11
PNC-TN241-72-43.pdf:4.4MBPNC-TN241-72-43T.pdf:5.5MB
no abstracts in English
; ; ; *; *;
Kagicho Kinzoku Zairyo Gijutsu Kenkyusho To Genken No Kyodo Kenkyu Seika Hokokusho, p.3 - 27, 1972/00
no abstracts in English
*; *; *; Obara, Katsuaki
PNC TN241 71-55, 85 Pages, 1971/11
PNC-TN241-71-55.pdf:3.86MBPNC-TN241-71-55TR.pdf:4.71MB
no abstracts in English
Takir, D.*; Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; et al.
no journal, ,
JAXA spacecraft and sample return mission Hayabusa2 has arrived at the near-Earth asteroid 162173 Ryugu, which is classified a primitive carbonaceous object. Here we report recent results of near-infrared spectrometer (NIRS3) on the Hayabusa2 spacecraft. The observations provide direct measurements of the surface composition of Ryugu and context for the returned samples. NIRS3 has detected a weak and narrow absorption feature centered at 2.72 micrometer across entire observed surface. This absorption feature is attributed to the presence of OH-bearing minerals. The NIRS3 observations also revealed that Ryugu is the darkest object to be observed up-close by a visiting spacecraft. The intensity of the OH feature and low albedo are consistent with thermally-and/or shock-metamorphosed, and/or carbon-rich space-weathered primitive and hydrated carbonaceous chondrites.
