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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

 Times Cited Count:19 Percentile:34.5(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

Development of prototype reactor maintenance, 1; Application to piping system of sodium-cooled reactor prototype

Kotake, Shoji*; Chikazawa, Yoshitaka; Takaya, Shigeru; Otaka, Masahiko; Kubo, Shigenobu; Arai, Masanobu; Kunogi, Kosuke; Ito, Takaya*; Yamaguchi, Akira*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04

A maintenance management required to prototype nuclear power reactors is proposed. Monitoring and control of sodium impurity and thermal transient are extremely important for sodium boundary maintenance for sodium-cooled fast reactors. At the fast stage of the prototype reactor Monju operation, degradation mechanism on the piping should be demonstrated based on operation experiences. Therefore inspection on a representative position for crack indication and pipe thickness is proposed. Due to less experience of SFR plants, early detection of boundary failure is considered. For a matured operation stage, when degradation mechanism is well demonstrated based on inspection data, inspection cycle could be extended. And for commercial reactors, maintenance without inspection will be established based on accumulated operation experiences including those of the prototype reactor Monju.

Journal Articles

Development of prototype reactor maintenance, 2; Application to piping support of sodium-cooled reactor prototype

Arai, Masanobu; Kunogi, Kosuke; Aizawa, Kosuke; Chikazawa, Yoshitaka; Takaya, Shigeru; Kubo, Shigenobu; Kotake, Shoji*; Ito, Takaya*; Yamaguchi, Akira*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04

Applications for maintenance program on piping support of prototype fast breeder reactor Monju are studied. Based on degradation mechanism, snubbers in Monju primary cooling system showed lifetime more than the plant lifetime of 30 years by experiments conservatively. For the first step during construction, visual inspection on accessible all supports could be available. In that visual inspection, mounting conditions and damages of all accessible supports could be monitored. One of major features of the Monju primary piping system is large thermal expansion due to large temperature difference between maintenance and operation conditions. Thanks to that large thermal expansion, integrity of the piping support could be monitored by measuring piping displacement. When technologies of piping displacement monitoring are matured in Monju, visual inspection on piping support could be shifted to piping displacement monitoring. At that stage, the visual inspection could be limited only on representative supports.

Journal Articles

The R&D goal of Monju

Hiroi, Hiroshi*; Arai, Masanobu; Kisohara, Naoyuki

Dai-21-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 3 Pages, 2016/06

The purpose of fast breeder reactors (FBR) and the role of Monju were discussed in Ministry of education, culture, sports science and technology-Japan (MEXT) after the Fukushima NNP accident. The discussion has concluded that FBRs contribute to energy security and reduction of high-level radioactive waste, and that Monju is to be utilized to demonstrate these usefulness and to implement international contributions. This paper addresses anticipated R&D results from Monju on the basis of the enforcement of new nuclear regulation, the energy situations in Japan and the international status of FBR development and collaborations.

Journal Articles

Simultaneous analysis of silicon and boron dissolved in water by combination of electrodialytic salt removal and ion-exclusion chromatography with corona charged aerosol detection

Mori, Masanobu*; Sagara, Katsuya*; Arai, Kaori*; Nakatani, Nobutake*; Ohira, Shinichi*; Toda, Kei*; Itabashi, Hideyuki*; Kozaki, Daisuke*; Sugo, Yumi; Watanabe, Shigeki; et al.

Journal of Chromatography A, 1431, p.131 - 137, 2016/01

 Times Cited Count:7 Percentile:53.49(Biochemical Research Methods)

Journal Articles

Past, present, and future of Monju

Mukai, Kazuo; Arai, Masanobu; Ito, Kazuhiro; Okawachi, Yasushi

Nippon Genshiryoku Gakkai-Shi, 56(9), p.554 - 560, 2014/09

no abstracts in English

Oral presentation

Resumption of system start-up test of prototype FBR Monju

Arai, Masanobu

no journal, , 

no abstracts in English

Oral presentation

The Results obtained from the 20 years of "Monju" plant data, 9; Proposal on data treatment improvement and future vision

Shiotani, Hiroki; Sawazaki, Hiromasa; Nakamura, Yoshihide; Sato, Takeshi; Uchida, Takenobu; Arai, Masanobu

no journal, , 

We are evaluating operating data of about 20 years (Evaluation of "Monju Research Plan") through the collaboration of both older and younger engineers. In this study, we will propose the use of information technologies and/or statistics tools in future evaluation to make the data treatment in an effective and efficient manner. In addition to that, we will also present a vision for supporting and cooperating technical tradition and knowledge discovery, etc. nuclear engineers by machine learning technologies toward the commercialization of fast reactor cycle systems.

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