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Journal Articles

Effect of inner wall cracking on the cavitation bubble formation in the mercury spallation target at J-PARC

Ariyoshi, Gen; Saruta, Koichi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Maeno, Koki*; Li, Y.*; Tsutsui, Kihei*

Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.1407 - 1420, 2023/08

Cavitation damage on a target vessel due to proton beam-induced pressure waves is one of the crucial issues for the pulsed neutron source using a mercury spallation target. As a mitigation technique for the damage, the helium microbubble injection into the mercury has been carried out by using a swirl bubbler in order to utilize compressibility of bubbles. Moreover, double-walled structure, which consists of an outer wall and an inner wall, has been applied as the target head structure. In this study, we aim to develop an abnormality diagnostic technology to detect the inner wall cracking, which is caused by such cavitation damage, from the outside of the target vessel. The mercury flow fields in the case with the cracking are evaluated by computational fluid dynamics analysis based on finite element method. And then, effect of the cracking on the flow field is discussed from the point of view of the flow-induced vibration and the acoustic vibration.

Journal Articles

New material exploration to enhance neutron intensity below cold neutrons; Nanosized graphene flower aggregation

Teshigawara, Makoto; Ikeda, Yujiro*; Yan, M.*; Muramatsu, Kazuo*; Sutani, Koichi*; Fukuzumi, Masafumi*; Noda, Yohei*; Koizumi, Satoshi*; Saruta, Koichi; Otake, Yoshie*

Nanomaterials (Internet), 13(1), p.76_1 - 76_9, 2023/01

 Times Cited Count:0 Percentile:59.51(Chemistry, Multidisciplinary)

To enhance neutron intensity below cold neutrons, it is proposed that nanosized graphene aggregation could facilitate neutron coherent scattering under particle size conditions similar to nanodiamond. It might also be possible to use it in high neutron radiation conditions due to graphene's strong sp2 bonds. Using the RIKEN accelerator-driven compact neutron source and iMATERIA at J-PARC, we performed neutron measurement experiments, total neutron cross-section, and small-angle neutron scattering on nanosized graphene aggregation. The measured data revealed, for the first time, that nanosized graphene aggregation increased the total cross-sections and small-angle scattering in the cold neutron energy region, most likely due to coherent scattering, resulting in higher neutron intensities, similar to nanodiamond.

Journal Articles

A Consideration on the use of shear waves to improve the sensitivity of an optical ultrasonic sensor for under-sodium viewers

Saruta, Koichi; Shirahama, Takuma*; Yamaguchi, Toshihiko; Ueda, Masashi

E-Journal of Advanced Maintenance (Internet), 10(2), p.1 - 8, 2018/08

Journal Articles

Journal Articles

Multi-point strain measurement using FBG-OTDR optical fiber sensor

Saruta, Koichi; Kobayashi, Takao*

EUR-26577-EN, p.490 - 496, 2014/07

Journal Articles

Development of a health monitoring system using a thermal-resistant fiber Bragg grating for fast reactor power plants; Performance evaluation of a thermal-resistant FBG for strain measurement

Saruta, Koichi; Tsukimori, Kazuyuki; Shimada, Yukihiro; Nishimura, Akihiko; Kobayashi, Takao*

Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.219 - 222, 2009/08

A thermal-resistant fiber Bragg grating (FBG) fabricated by femtosecond laser processing was examined to evaluate the performance as a strain sensor, compared with a conventional FBG sensor. Each FBG was affixed on a stainless-steel beam along with a strain gauge to measure the Bragg wavelength shift as a function of strain. We used the intensity of the reflection spectra from the FBGs as a weighting factor to determine the Bragg wavelengths. Although the strain sensitivity for the thermal-resistant FBG was found to be 0.34 pm/$$mu$$$$varepsilon$$, a measurement accuracy of $$pm$$3$$mu$$$$varepsilon$$ was able to be achieved by employing the Bragg wavelength determination algorithm, which was comparable to a measurement accuracy of $$pm$$2$$mu$$$$varepsilon$$ for the conventional FBG sensor.

JAEA Reports

Countermeasure to prevent temperature rise of primary upper shield in HTTR; Performance test of countermeasures under actural core configuration

Tachibana, Yukio; Hontani, Koji*; Kojima, Takao; Takeda, Takeshi; Emori, Koichi; Saruta, Toru; Iyoku, Tatsuo; Kunitomi, Kazuhiko

JAERI-Tech 2000-026, p.61 - 0, 2000/03

JAERI-Tech-2000-026.pdf:2.18MB

no abstracts in English

JAEA Reports

Impurity measurement test of HTTR; At the commissioning tests

Sakaba, Nariaki; Emori, Koichi; Saruta, Toru

JAERI-Tech 99-072, p.125 - 0, 1999/10

JAERI-Tech-99-072.pdf:5.85MB

no abstracts in English

Oral presentation

Development of vibration and deformation monitoring techniques for high temperature structures by heat-resistant FBG, 4

Shimada, Yukihiro; Nishimura, Akihiko; Saruta, Koichi; Tsukimori, Kazuyuki; Yoshikawa, Masanari*; Kobayashi, Takao*

no journal, , 

A Fiber Bragg Grating (FBG) sensor is a powerful method of vibration of a structure and the leading methods of carrying out modification monitoring. However, since the FBG sensor which exists now does not have high temperature resistance, use in a high temperature plant is difficult. In recent years, the micro fabrication to high embrittlement materials, such as quartz, became possible by development of ultra fast pulsed laser. We performed the non-heat laser processing to the optical fiber using femto-second pulsed laser.

Oral presentation

Fabrication and performance assessment of FBG sensor with pulse laser processing

Shimada, Yukihiro; Nishimura, Akihiko; Saruta, Koichi; Tsukimori, Kazuyuki; Kobayashi, Takao*

no journal, , 

Fiber Bragg Grating (FBG) is the periodic refractive-index structure in an optical fiber core, where the light of a specific wavelength is reflected. It can be used as temperature or a distorted sensor by measuring change of the reflective wavelength of FBG. We processed FBG using a Chirped Pulse Amplification titanium sapphire laser. As a result, we confirmed produced FBG had the tolerance at the high temperature. The heat-resistant FBG sensor developed using ultra-short pulse laser processing will contribute to the surveillance of power plants.

Oral presentation

Processing of heat-resistant fiber Bragg grating using femto-second pulse laser by point-by-point method

Shimada, Yukihiro; Nishimura, Akihiko; Saruta, Koichi; Tsukimori, Kazuyuki; Kobayashi, Takao*

no journal, , 

Fiber Bragg grating (FBG) sensor system is a powerful method of detecting strain and temperature of a structure, and is put in practical use widely. However, a general FBG sensor system has a fault without tolerance in high temperature. We performed the micro fabrication in the silica fiber by the point by point method using femtosecond pulse laser. As a result, we succeeded in heat-resistant creation of FBG.

Oral presentation

Assignment of monitoring system for high-temperature structure using heat resistant fiber Bragg grating

Shimada, Yukihiro; Nishimura, Akihiko; Saruta, Koichi; Tsukimori, Kazuyuki; Kobayashi, Takao*

no journal, , 

The fiber Bragg grating sensor with heat-resistance in microfabrication that used the ultrafast pulse laser was produced. The sensing system optimized to the characteristic of the produced sensor was designed, produced, and the distortion of piping in a mock plant and the examination of the vibration measurement were done. The result of current development is summarized, and the development task in the future is clarified.

Oral presentation

Fundamental study of acoustic emission in rotating machines by non-contact measurement using laser interferometer

Ota, Yasufumi; Saruta, Koichi; Noguchi, Shotaro; Ueda, Masashi

no journal, , 

no abstracts in English

Oral presentation

FBG-OTDR optical fiber sensor; Application to multi-point strain measurement

Saruta, Koichi

no journal, , 

no abstracts in English

Oral presentation

Sensitivity characteristics of optical ultrasonic sensors using a metallic membrane for under-sodium inspection

Saruta, Koichi; Yamaguchi, Toshihiko; Ueda, Masashi

no journal, , 

no abstracts in English

Oral presentation

R&D program of maintenance technologies for the fast reactors in the sodium engineering research facility

Ueda, Masashi; Yamaguchi, Toshihiko; Saruta, Koichi

no journal, , 

no abstracts in English

Oral presentation

The R&D Programs of Maintenance Technology for FBR Monju Using the Sodium Engineering Research Facility

Saruta, Koichi; Yamaguchi, Toshihiko; Ueda, Masashi

no journal, , 

Oral presentation

Research and development to improve laser cutting process by an adaptive control system; Study on control method for laser cutting using optical signal by dross

Mizutani, Haruki; Saruta, Koichi; Kamei, Naomitsu; Muramatsu, Toshiharu

no journal, , 

no abstracts in English

34 (Records 1-20 displayed on this page)