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Journal Articles

Development of the multi-cubic $$gamma$$-ray spectrometer and its performance under intense $$^{137}$$Cs and $$^{60}$$Co radiation fields

Kaburagi, Masaaki; Shimazoe, Kenji*; Kato, Masahiro*; Kurosawa, Tadahiro*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*

Nuclear Instruments and Methods in Physics Research A, 1010, p.165544_1 - 165544_9, 2021/09

 Times Cited Count:0 Percentile:0.03(Instruments & Instrumentation)

The number of nuclear facilities being decommissioned has been increasing worldwide, in particular following the accident of the Tokyo Electric Power Company Holdings' Fukushima Daiichi Nuclear Power Station in 2011. In these nuclear facilities, proper management of radioactive materials is required. Then, A $$gamma$$-ray spectrometer with four segmentations using small volume CeBr$$_{3}$$ scintillators with a dimension of $$5 times 5 times 5$$ $$rm{mm}^3$$ was developed. The four scintillators were coupled to a multi-anode photomultiplier tube specific to intense radiation fields. We performed the $$gamma$$-ray exposure study under $$^{137}$$Cs and $$^{60}$$Co radiation fields. Under the $$^{137}$$Cs radiation field, the relative energy resolution at 1375 mSv/h was the relative energy resolution at 1375 mSv/h was 9.2$$pm$$0.05%, 8.0$$pm$$0.08%, 8.0$$pm$$0.03%, and 9.0$$pm$$0.04% for the four channels, respectively.

Journal Articles

Gamma-ray spectroscopy with a CeBr$$_3$$ scintillator under intense $$gamma$$-ray fields for nuclear decommissioning

Kaburagi, Masaaki; Shimazoe, Kenji*; Kato, Masahiro*; Kurosawa, Tadahiro*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

Nuclear Instruments and Methods in Physics Research A, 988, p.164900_1 - 164900_8, 2021/02

 Times Cited Count:1 Percentile:81.22(Instruments & Instrumentation)

An increasing number of nuclear facilities have been decommissioned worldwide following the 2011 accident of the TEPCO' Fukushima Daiichi Nuclear Power Station. During the decommissioning, radioactive materials have to be retrieved under proper management. In this study, a small cubic CeBr$$_3$$ spectrometer with dimensions of 5 mm $$times$$ 5 mm $$times$$ 5 mm was manufactured to perform $$gamma$$-ray spectroscopy under intense $$gamma$$-ray fields. Furthermore, thanks to a fast digital process unit and a customized photomultiplier, the device could perform $$gamma$$-ray spectroscopy at dose rates of over 1 Sv/h. The energy resolution (FWHM) at 662 keV ranged from 4.4% at 22 mSv/h to 5.2% at 1407 mSv/h for a $$^{137}$$Cs radiation field. Correspondingly, at 1333 keV, it ranged from 3.1% at 26 mSv/h to 4.2% at 2221 mSv/h for a $$^{60}$$Co radiation field, which suggested to realize $$gamma$$-ray assessment of $$^{134}$$Cs, $$^{137}$$Cs, $$^{60}$$Co, and $$^{154}$$Eu at dose rates of over 1 Sv/h.

Journal Articles

A Cubic CeBr$$_{3}$$ gamma-ray spectrometer suitable for the decommissioning of the Fukushima Daiichi Nuclear Power Station

Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

Nuclear Instruments and Methods in Physics Research A, 971, p.164118_1 - 164118_8, 2020/08

 Times Cited Count:3 Percentile:76.41(Instruments & Instrumentation)

Journal Articles

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd$$_{3}$$(Al,Ga)$$_{5}$$O$$_{12}$$ scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

 Times Cited Count:24 Percentile:96.18(Nuclear Science & Technology)

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 4$$times$$4 to 8$$times$$8 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m $$times$$ 60 m and 65 m $$times$$ 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the $$gamma$$-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10$$^{circ}$$).

Journal Articles

JT-60 operation results after its modification for higher plasma current with single null open divertor

; Horiike, Hiroshi; Neyatani, Yuzuru; Matsukawa, Makoto; Ando, Toshiro; Yoshino, Ryuji; Arai, Takashi; Ninomiya, Hiromasa; Yamamoto, Masahiro; ; et al.

Proc. of the 14th Symp. on Fusion Engineering,Vol. 1, p.177 - 180, 1992/00

no abstracts in English

Journal Articles

Current drive and confinement studies during LHRF experiments in JT-60

Imai, Tsuyoshi; Ushigusa, Kenkichi; Sakamoto, Keishi; Ikeda, Yoshitaka; Fujii, Tsuneyuki; Saigusa, Mikio; Yoshino, Ryuji; Uehara, Kazuya; Nagashima, Takashi; Kimura, Haruyuki; et al.

Nuclear Fusion, 28(8), p.1341 - 1350, 1988/00

 Times Cited Count:24 Percentile:65.91(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Development of energy recognizable type gamma camera mounted on the unmanned helicopter, 3; Field test around the Fukushima Daiichi NPP site

Shikaze, Yoshiaki; Torii, Tatsuo; Shimazoe, Kenji*; Jiang, J.*; Takahashi, Hiroyuki*; Kurosawa, Shunsuke*; Kamada, Kei*; Yoshikawa, Akira*; Yoshino, Masao*; Ito, Shigeki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Development of energy recognizable type gamma camera mounted on the unmanned helicopter II, 2; Field test around the Fukushima Daiichi NPP site

Shikaze, Yoshiaki; Torii, Tatsuo; Nishizawa, Yukiyasu; Yoshida, Mami*; Shimazoe, Kenji*; Jiang, J.*; Takahashi, Hiroyuki*; Kurosawa, Shunsuke*; Kamada, Kei*; Yoshikawa, Akira*; et al.

no journal, , 

no abstracts in English

Oral presentation

Feasibility study on a red-emitting-scintillation probe with an optical fiber for a high-rate dose-monitor

Kodama, Shohei*; Kurosawa, Shunsuke*; Morishita, Yuki; Usami, Hiroshi; Hayashi, Masateru*; Tanaka, Hiroki*; Yoshino, Masao*; Kamada, Kei*; Yoshikawa, Akira*; Torii, Tatsuo

no journal, , 

After Fukushima 1st Nuclear Plant accident, a large number of radioactive pollutants or nuclear debris with very high dose of more than a few Sv/h still have existed. To estimate the dose of such pollutants, a Japan Atomic Energy Agency research group has suggested a new technique to use a long optical fiber and a red-emitting scintillator, and the scintillation photons are read outside of high dose area. We tested the gamma-ray detection performance of a ruby (Cr:Al$$_{2}$$O$$_{3}$$) and a newly developed Cs$$_{2}$$HfI$$_{6}$$ scintillators as a scintillating probe coupled with an optical fiber in this study.

Oral presentation

Fundamental study of fast high energy gamma-ray spectrometer

Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Foong, W. S.*; Uenomachi, Mizuki*; Kamada, Kei*; Kin, J. Y.*; Yoshino, Masao*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

no journal, , 

no abstracts in English

Oral presentation

CeBr$${}_3$$ gamma-ray spectrometer toward the decommissioning of the Fukushima Daiichi Nuclear Power Station

Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Foong, W. S.*; Uenomachi, Mizuki*; Kamada, Kei*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Introduction to multi Cubic high energy gamma-ray spectrometer

Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

no journal, , 

Oral presentation

Performance study of multi cubic high energy $$gamma$$-ray spectrometric system for the decommissioning of the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station

Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

no journal, , 

The retrieval of the nuclear fuel debris, which is the substance including melted nuclear fuel and structural materials, will be started from fiscal 2021. Then, as a non-destructive analysis technology of the nuclear fuel debris, a $$gamma$$-ray spectroscopy system is being developed to measure high energy $$gamma$$ rays due to $$^{154}$$Eu and nuclear reactions under high dose rate, which was composed of a CeBr$$_{3}$$ cubic, photomultiplier tube, and fast signal processing unit. This presentation reports that the exposure study of the detector system was performed for a $$_{60}$$Co field at the dose rates of up to 750 mSv/h, and the detector response was investigated at each dose rate.

Oral presentation

Development of $$gamma$$-ray spectrometry system specific to high dose-rate radiation fields for the retrieval of nuclear fuel debris in Tokyo Electrical Power Company Holdings' Fukushima Daiichi Nuclear Power Station

Kaburagi, Masaaki; Shimazoe, Kenji*; Kato, Masahiro*; Kurosawa, Tadahiro*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

no journal, , 

The retrieval of nuclear fuel debris will be started at Tokyo Electrical Power Company Holdings' Fukushima Daiichi Nuclear Power Station. Because of high dose-rate fields on the surface of nuclear fuel debris and these inhomogeneous elements, non-destructive analysis is required during the retrieval. Here, it is presented that a $$gamma$$-ray spectrometry system specific to high dose-rate fields was developed and its performance under intense $$gamma$$-ray fields was evaluated for the retrieval of nuclear fuel debris.

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