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Journal Articles

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

 Times Cited Count:30 Percentile:96.87(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 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$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.

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

JAEA Reports

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.

JAEA Reports

JRR-2 decommissioning activity, 2

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

JAERI-Tech 2005-018, 84 Pages, 2005/03

JAERI-Tech-2005-018.pdf:27.52MB

no abstracts in English

Journal Articles

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

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.

JAEA Reports

JRR-2 decommissioning activity, 1

Nakano, Masahiro; Arigane, Kenji; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki; Sakuraba, Naotoshi; Oba, Nagamitsu

JAERI-Tech 2003-072, 92 Pages, 2003/08

JAERI-Tech-2003-072.pdf:6.99MB

The decommissioning plan of the Japan Research reactor No2(JRR-2), decommissioning activities until the first half of phase-3, radioactive wastes and exposure dose of workers are described in this report. Since the first criticality in October 1960, JRR-2 had been operated about 36 years for various experiments. However, JRR-2 was permanent shutdown in December 1996 based on JAERI's long term plan, and the decommissioning of the JRR-2 was started in August 1997. Decommissioning of the JRR-2 was planed for 11 years from 1997 to 2007 and the program was divided into 4 phases. The decommissioning activities of the phase-1, phase-2 and the first half of phase-3 had already completed as planned in March 1998, February 2000, March 2002, respectively. The decommissioning activities of the later half of Phase-3 (dismantling of the reactor cooling systems) are carrying out at present time with planed 2002 and 2003 fiscal years.

Oral presentation

For discussions with the public for the safety of nuclear power; Risks for judgments

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

no journal, , 

The risk is used for an index to judge. The risk to be considered varies according to the purpose of the judgment. The analysis of the risk needs the knowledge of the nuclear energy system and society.

Oral presentation

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.

Oral presentation

For discussions with the public for the safety of nuclear power; Social risk and nuclear risk

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

no journal, , 

In society, understanding of risk is various. We will show how to understand risk and describe how to face risks in the society. Individual risks are accepted by individuals, but it is necessary for society to construct a structure in society that allows risks to be tolerated by society. For that purpose, we also describe what social risk is and how society and individuals face social risks and how to choose risks to accept. We consider not only the concept of nuclear risk but also how nuclear risk should be accepted from the viewpoint of disaster prevention for the public.

Oral presentation

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.

Oral presentation

For discussions with the public for the safety of nuclear power; Risk assessment for nuclear safety and application to external event

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

no journal, , 

A considering nuclear safety, it is an important task to clarify the relationship with "peace of mind" that is the heart of people. In this paper, a fundamental methodology of risk assessment for nuclear safety is introduced based on a probabilistic risk assessment (PRA) method. Furthermore, an application of the methodology for an external event is also discussed.

Oral presentation

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.

Oral presentation

For discussions with the public for the safety of nuclear power; Various patterns of risk application method and examples

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

no journal, , 

Target of PRA is not calculating PRA to get CDF/CFF, but providing significant and useful information from PRA results for risk-informed activities. Lot of risk applications have been implemented these about 20 years in US. After Fukushima Dai-ichi accidents, Japanese Nuclear Regulation Authority provided new regulatory requirements about external events and beyond design events. And Risk Application faces full-scale implementation. In this report, several methods of risk application are showed with adequate risk indexes. Two examples of risk application, risk-informed shutdown management and RI-ISI, are provided. The explanation about Risk Informed Decision-Making Process is made.

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