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.

Construction, management and operation on advanced volume reduction facilities

Higuchi, Hidekazu; Osugi, Takeshi; Nakashio, Nobuyuki; Momma, Toshiyuki; Tohei, Toshio; Ishikawa, Joji; Iseda, Hirokatsu; Mitsuda, Motoyuki; Ishihara, Keisuke; Sudo, Tomoyuki; et al.

JAEA-Technology 2007-038, 189 Pages, 2007/07

JAEA-Technology-2007-038-01.pdf:15.13MB
JAEA-Technology-2007-038-02.pdf:38.95MB
JAEA-Technology-2007-038-03.pdf:48.42MB
JAEA-Technology-2007-038-04.pdf:20.53MB
JAEA-Technology-2007-038-05.pdf:10.44MB

The Advanced Volume Reduction Facilities (AVRF) is constructed to manufacture the waste packages of radioactive waste for disposal in the Nuclear Science Research Institute of the Japan Atomic Energy Agency. The AVRF is constituted from two facilities. The one is the Waste Size Reduction and Storage Facility (WSRSF) which is for reducing waste size, sorting into each material and storing the waste package. The other is the Waste Volume Reduction Facility (WVRF) which is for manufacturing the waste package by volume reducing treatment and stabilizing treatment. WVRF has an induction melting furnace, a plasma melting furnace, an incinerator, and a super compactor for treatment. In this report, we summarized about the basic concept of constructing AVRF, the constitution of facilities, the specifications of machineries and the state of trial operation until March of 2006.

Present status of JRR-2 decommissioning

Nakano, Masahiro; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki

Dekomisshoningu Giho, (30), p.11 - 24, 2004/09

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_30.pdf

Japan Research Reactor No.2(JRR-2), heavy water moderated and cooled tank type research reactor with maximum thermal power of 10MW,was operated for over 36 years, and was permanently shut down in December, 1996. In 1997, decommissioning plan was submitted to the STA, and dismantling was begun. Decommissioning program of JRR-2 is divided into 4 phases. Phase 1, 2 had already been completely finished without any trouble. Furthermore, the phase 3 was also finished in February, 2004 as planned. On exposure of worker in phase 1, 2 and 3, it was achieved to control lower than the estimate. On exposure of worker in phase 1, 2 and 3, it was achieved to control lower than the estimate. Reactor will be removed in phase 4 by one piece removal technique. The reactor building is planned to use effectively as a hot experimental facilities after decommissioning. The decommissioning plan was changed that the reactor would be kept in safety storage.

For discussions with the public for the safety of nuclear power; Their trust on safety

Miyano, Hiroshi*; Muramatsu, Ken*; Noguchi, Kazuhiko*; Narumiya, Yoshiyuki*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsumoto, Masaaki*; Matsunaga, Yoko*; Sugiyama, Kenichiro*

no journal, , 

In considering nuclear safety, it is an important task to clarify the relationship with "peace of mind" that is the heart of people. What is the state that scientific safety is something that people feel safe? We considered the relationship between quantified risk and safety, and ways to acquire peace of mind. We analyzed the thresholds of safety risks as a social common, showed a safe condition, and showed the importance of forming a consensus to obtain peace of mind.

For discussions with the public for the safety of nuclear power; Discussion with the public

Matsunaga, Yoko*; Miyano, Hiroshi*; Noguchi, Kazuhiko*; Muramatsu, Ken*; Narumiya, Yoshiyuki*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsumoto, Masaaki*; Sugiyama, Kenichiro*

no journal, , 

After Fukushima Daiichi nuclear accident, it becomes more important risk communication with the public. In discussions with the public in nuclear safety, communication and discussions on risks that not only nuclear risks also social risks are important. Differences in viewpoints, understanding, and thought about risks become communication difficult. We need to discuss risks fairly, appropriately with the public and reduce total social risks.

For discussions with the public for the safety of nuclear power; Applying risk information to prevention/mitigation of SA

Narumiya, Yoshiyuki*; Miyano, Hiroshi*; Noguchi, Kazuhiko*; Muramatsu, Ken*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsumoto, Masaaki*; Matsunaga, Yoko*

no journal, , 

In order to grasp efficiency of risk information, we tried to apply an insight of PRA to considering of severe accidents; TMI, Chernobyl, and Fukushima Dai-ichi. Based on this analysis, three points are disclosed. At first, PRA can product adequate countermeasures for low-likelihood events; huge earthquake or Tsunami. Next, PRA can prove weak points in design or operation reasonably. Third point is safety culture. PRA and safety culture are seemed to be connected deeply. These analyses revealed PRA is one of the most efficient and systematic risk analysis methods to prevent/mitigate severe accidents.

Direct energy conversion using Perovskite solar cell in synchrotron X-ray region

Fukuda, Tatsuo; Fukada, Yukimasa; Yoshii, Kenji; Shobu, Takahisa; Tominaga, Aki; Kobata, Masaaki; Ieda, Junichi; Shirai, Yasuhiro*; Yanagida, Masatoshi*; Miyano, Kenjiro*; et al.

no journal, , 

Direct energy conversion has been investigated so far using Ni/SiC or Pt/ GaO Schottky junctions with the irradiation of monochromatized synchrotron X-rays. From current-voltage measurements, the energy conversion efficiencies reached up to ~1.6%. Recently we have started measurements using Perovskite solar cell, which contains relatively heavy lead atom to absorb X-rays and is easier to cover wide area. In this talk we would like to discuss the results comparing with the Ni/SiC or Pt/GaO case.