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Journal Articles

Measurement and analysis of long-term variation of atmospheric $$^{7}$$Be activity concentrations in Dazaifu (western Japan)

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 284, p.107612_1 - 107612_7, 2025/04

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Atmospheric $$^{7}$$Be activity concentration was continuously measured in Dazaifu, western Japan, from 1999 to 2020, and its variation was analyzed. Daily $$^{7}$$Be data analysis, encompassing an analysis for 22 years, revealed a concentration range of not detected - 18 mBq/m$$^{3}$$, characterized by substantial monthly variation and smoothed annual variation. An average daily $$^{7}$$Be activity concentration of 5.0 $$pm$$ 2.6 mBq/m$$^{3}$$ was considered to be representative at the ground-surface-level in 30-40$$^{circ}$$N. Results from a two-way Analysis of variance (ANOVA) indicated statistical significance in monthly and annual $$^{7}$$Be variabilities. The monthly variability of $$^{7}$$Be activity concentration was approximately four times greater than the annual variability. Frequency analysis revealed that the monthly variability comprised major 12-month and minor 6-month periodicities. The substantial decrease in $$^{7}$$Be activity concentration during summer, a primary driver of monthly variation, was also observed at other locations in Japan, attributed to a stable high-pressure system in the Pacific Ocean that stalled over Japan's southern seas, followed by the inflow of air masses containing low $$^{7}$$Be activity concentrations. The annual variation was primarily influenced by the 11-year solar activity cycle, which affects the intensity of cosmic rays that produce $$^{7}$$Be.

Journal Articles

Neutron spectroscopy study on crystalline electric field excitations in NdB$$_4$$

Yamauchi, Hiroki; Metoki, Naoto; Watanuki, Ryuta*; Hong, T.*; Fernandez-Baca, J. A.*; Hagihara, Masato; Masuda, Takatsugu*; Yoshizawa, Hideki*; Ito, Shinichi*

Journal of the Physical Society of Japan, 94(5), p.054705_1 - 054705_8, 2025/04

Journal Articles

Mechanical multiplexer of nuclear spin states

Chudo, Hiroyuki; Yokoi, Naoto*; Matsuo, Mamoru; Harii, Kazuya*; Suzuki, Jun*; Imai, Masaki; Sato, Masahiro*; Maekawa, Sadamichi*; Saito, Eiji*

Physical Review Letters, 134(13), p.130603_1 - 130603_5, 2025/04

 Times Cited Count:0 Percentile:0.00(Physics, Multidisciplinary)

Journal Articles

Reduction and phase transformation of Ce-doped zirconolites

Hayashizaki, Kohei; Hirooka, Shun; Yamada, Tadahisa*; Sunaoshi, Takeo*; Murakami, Tatsutoshi; Saito, Kosuke

Ceramics (Internet), 8(1), p.24_1 - 24_12, 2025/03

Journal Articles

Direct measurement of lattice behavior during femtosecond laser-driven shock front formation in copper

Egashira, Naoya*; Matsuda, Tomoki*; Okuchi, Takuo*; Seto, Yusuke*; Ito, Yusuke*; Shobu, Takahisa; Nakanii, Nobuhiko*; Sano, Tomokazu*; 4 of others*

Journal of Applied Physics, 137(10), p.105903_1 - 105903_8, 2025/03

 Times Cited Count:1 Percentile:0.00(Physics, Applied)

Journal Articles

Tensile properties of irradiated modified 316 stainless steel (PNC316) at slow strain rates

Yano, Yasuhide; Miyazawa, Takeshi; Tanno, Takashi; Akasaka, Naoaki; Yoshitake, Tsunemitsu; Kaito, Takeji; Otsuka, Satoshi

Journal of Nuclear Science and Technology, 8 Pages, 2025/00

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

The effects of strain rate on tensile properties of irradiated modified 316 stainless steel (PNC316) claddings were investigated. PNC316 claddings were irradiated at the experimental fast reactor Joyo using CRT402 control rod assembly at 400$$^{circ}$$C up to 25 dpa. Post-irradiation ring tensile tests were carried out at strain rates of 3.3$$times$$10$$^{-6}$$, 3.3$$times$$10$$^{-7}$$ and 3.3$$times$$10$$^{-8}$$ s$$^{-1}$$ at a test temperature of 350$$^{circ}$$C. The results showed no obvious dependence of all strain rates on tensile properties, although a slight decrease in total elongation was observed at the slowest strain rate of 3.3$$times$$10$$^{-8}$$ s$$^{-1}$$. In addition, only a part of fracture surface at the slowest strain rate showed intergranular type region in the inner surface area, although the grain boundary separation occurred on inner surfaces near the fracture region at all strain rates. It is suggested that presence of a high content of helium near the inner surfaces would be related to the fracture behavior.

Journal Articles

ESR measurement of carbonated hydroxyapatite for dosemeter

Seito, Hajime*; Yokozuka, Eri*; Oka, Toshitaka; Kitatsuji, Yoshihiro; Nagasawa, Naotsugu*

Radiation Protection Dosimetry, 200(16-18), p.1656 - 1659, 2024/11

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

We have examined dosimetric characteristics of bio-inspired carbonated hydroxyapatite (CO$$_{3}$$HAp), which is a main component of calcified tissues like tooth enamel. CO$$_{3}$$HAp powder samples were exposed to gamma-ray with radiation doses ranging from 1 Gy to 1000 Gy at room temperature, and ESR spectra were measured immediately after irradiation and subsequently measured each 1 day during 90 days. The post-irradiation fading resulted in significant 20% decay of the signal amplitude, which stabilised within 7 days after irradiation, and the intensity approached a constant. The sample has good linear dose response in the experiment range of 10 Gy - 1000 Gy. Our results indicate that the CO$$_{3}$$HAp materials is suitable for chemical dosimetry.

Journal Articles

Evaluation of materials for developing a new individual dosemeter using electron spin resonance spectroscopy

Kitamura, Yoshimasa; Oka, Toshitaka; Seito, Hajime*; Yokozuka, Eri*; Nagasawa, Naotsugu*; Kitatsuji, Yoshihiro

Radiation Protection Dosimetry, 200(16-18), p.1660 - 1665, 2024/11

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

In this work, we evaluated the applicability of hydroxyapatite, which is a main component of tooth enamel, as individual dosimeters that can detect from less than 1 Gy to several tens Gy. Commercially available hydroxyapatite was irradiated by $$^{60}$$Co gamma-ray up to 75 Gy and ESR spectrum of the irradiated sample was observed. The relationship between the intensity of produced carbonated radical and the absorbed dose shows a good linearity ($$mathrm{R}^{2}=1$$) from 0 to 75 Gy. The detection limit of this samples was estimated to be 99.7 mGy, and the radical intensity do not change for eight month from the irradiation. These results suggest that this sample can be used as a candidate of the individual dosimeter.

Journal Articles

Polarized and unpolarized neutron scattering for magnetic materials at the triple-axis spectrometer PONTA in JRR-3

Nakajima, Taro*; Saito, Hiraku*; Kobayashi, Naoki*; Kawasaki, Takuro; Nakamura, Tatsuya; Furukawa, Hazuki*; Asai, Shinichiro*; Masuda, Takatsugu*

Journal of the Physical Society of Japan, 93(9), p.091002_1 - 091002_5, 2024/09

 Times Cited Count:2 Percentile:68.78(Physics, Multidisciplinary)

Journal Articles

Variation analysis of atmospheric $$^{7}$$Be activity concentrations with respect to precipitation

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 277, p.107432_1 - 107432_7, 2024/07

Beryllium-7 activity concentrations in the atmosphere and precipitation were continuously measured every day between April 2011 and December 2015 in Dazaifu, western Japan. The measured data were quantitatively analyzed to determine the precipitation-induced variation in $$^{7}$$Be activity concentrations. The average concentrations on nonprecipitation and precipitation days were 5.5 and 3.8 mBq/m$$^{3}$$, respectively. This difference of 31% (1.7 mBq/m$$^{3}$$) on average, was attributable to the washout effect, which was more significant in the summer. Regarding the association between $$^{7}$$Be activity concentration and precipitation, the concentration remained at a similar level for the small precipitation amount of $$<$$5.0 mm/day and showed a decreasing trend (but was insignificant) for the precipitation of 5.0-10.0 mm/day. A significant decrease in the concentration was observed for $$geqq$$10 mm/day. Furthermore, when precipitation occurred on two successive days, the $$^{7}$$Be activity concentrations on the second day significantly decreased regardless of precipitation.

Journal Articles

Lattice dynamics of CH(NH$$_{2}$$)$$_{2}$$PbI$$_{3}$$ and CH(NH$$_{2}$$)$$_{2}$$SnI$$_{3}$$ investigated by inelastic X-ray scattering and comparison of their elastic properties

Tamatsukuri, Hiromu; Murakami, Yoichi*; Saito, Noriko*; Ohashi, Naoki*; Tsutsui, Satoshi*

Physical Review B, 110(2), p.024301_1 - 024301_8, 2024/07

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

JAEA Reports

Differential pressure rise event for filters of HTTR primary helium gas circulators, 2; Investigation of filter deposits and recurrence prevention measures

Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.

JAEA-Technology 2024-003, 17 Pages, 2024/06

JAEA-Technology-2024-003.pdf:1.91MB

In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.

Journal Articles

Persistent magnetic coherence in magnets

Makiuchi, Takahiko*; Hioki, Tomosato*; Shimizu, Hiroki*; Hoshi, Kojiro*; Elyasi, M.*; Yamamoto, Kei; Yokoi, Naoto*; Serga, A. A.*; Hillebrands, B.*; Bauer, G. E. W.*; et al.

Nature Materials, 23(5), p.627 - 632, 2024/05

 Times Cited Count:10 Percentile:94.22(Chemistry, Physical)

Journal Articles

Adsorption behavior of platinum-group metals and Co-existing metal ions from simulated high-level liquid waste using HONTA and Crea impregnated adsorbent

Osawa, Naoki*; Kim, S.-Y.*; Kubota, Masahiko*; Wu, H.*; Watanabe, So; Ito, Tatsuya; Nagaishi, Ryuji

Nuclear Engineering and Technology, 56(3), p.812 - 818, 2024/03

 Times Cited Count:2 Percentile:57.00(Nuclear Science & Technology)

Journal Articles

Introduction to Neutron Radiography Facilities at the Japan Research Reactor-3

Kurita, Keisuke; Iikura, Hiroshi; Tsuchikawa, Yusuke; Kai, Tetsuya; Shinohara, Takenao; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*; Matsubayashi, Masahito

Journal of Physics; Conference Series, 2605, p.012005_1 - 012005_6, 2023/10

The Japan Research Ractor-3 (JRR-3) is operation resumed on February 26, 2021, and the shared use was also restarted in July, 2021. With the resumption of JRR-3 operation, two imaging facilities called TNRF and CNRF have also resumed their utilization. In this presentation, we report the details of these two neutron facilities.

Journal Articles

Measurements of gas-liquid two-phase flow dynamics using high-speed neutron imaging

Ito, Daisuke*; Odaira, Naoya*; Ito, Kei*; Saito, Yasushi*; Kurita, Keisuke; Iikura, Hiroshi

Journal of Physics; Conference Series, 2605, p.012024_1 - 012024_6, 2023/10

Gas-liquid two-phase flow appears in many heat-exchanging devices. To understand the phenomena in such devices, the two-phase flow dynamics should be clarified. In this study, high-speed neutron imaging is applied to the measurements of two-phase flow dynamics, and the accuracy of the void fraction measurement is investigated.

Journal Articles

Development of tracer particles for thermal hydraulic experiment by neutron imaging

Saito, Yasushi*; Ito, Daisuke*; Odaira, Naoya*; Kurita, Keisuke; Iikura, Hiroshi

Journal of Physics; Conference Series, 2605, p.012028_1 - 012028_6, 2023/10

To observe flow velocity distributions by Neutron Imaging, suitable tracer is necessary. The requirements are its density, its visibility, and its wettability (if applied to liquid metal). Gold cadmium tracers have been developed for the Pb-Bi two-phase flow, however, the visibility have not been verified depending on the particle size and the measurement system. As the candidates of tracer particles, Ag, Cd, Au-Cd, and Ag-Cd have been tested by varying its compositions and its diameters. Results show enough visibility if the particles size is larger than 1mm. In addition, Cd tracer particles were applied to the fluidized bed, where the bed materials are metallic particle made of stainless steel, with 1mm diameter. The diameter of Cd trace is about 1.5 mm. From the neutron imaging, the visibility of the tracers is enough to measure the velocity distributions in the fluidized bed.

Journal Articles

Band gap formation in graphene by hybridization with Hex-Au(001) reconstructed surface

Terasawa, Tomoo; Matsunaga, Kazuya*; Hayashi, Naoki*; Ito, Takahiro*; Tanaka, Shinichiro*; Yasuda, Satoshi; Asaoka, Hidehito

Vacuum and Surface Science, 66(9), p.525 - 530, 2023/09

As Au (001) surfaces exhibit a quasi-one-dimensional corrugated structure, Hex-Au(001), its periodicity was predicted to change the electronic structure of graphene when graphene was grown on this surface. Furthermore, the hybridization between graphene and Au is known to introduce bandgap and spin polarization into graphene. Here, we report angle-resolved photoemission spectroscopy and density functional theory calculation of graphene on a Hex-Au(001) surface. A bandgap of 0.2 eV in the graphene Dirac cone was observed at the crossing point of the graphene Dirac cone and Au 6sp bands, indicating that the origin of the bandgap formation was the hybridization between the graphene Dirac cone and Au 6sp band. We discussed the hybridization mechanism and anticipated spin injection into the graphene Dirac cone.

Journal Articles

First observation of $$^{28}$$O

Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.

Nature, 620(7976), p.965 - 970, 2023/08

 Times Cited Count:27 Percentile:94.86(Multidisciplinary Sciences)

no abstracts in English

JAEA Reports

Differential pressure rise event for filters of HTTR primary helium gas circulators, 1; Investigation of differential pressure rise event

Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.

JAEA-Technology 2023-005, 33 Pages, 2023/05

JAEA-Technology-2023-005.pdf:5.25MB

During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.

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