Neutron spectroscopy study on crystalline electric field excitations in NdB

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

https://doi.org/10.7566/JPSJ.94.054705

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

https://doi.org/10.3390/ceramics8010024

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

https://doi.org/10.1080/00223131.2025.2475164

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 400C up to 25 dpa. Post-irradiation ring tensile tests were carried out at strain rates of 3.310, 3.310 and 3.310 s at a test temperature of 350C. 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 3.310 s. 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.

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

https://doi.org/10.1093/rpd/ncae194

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 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 () 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.

Variation analysis of atmospheric 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

https://doi.org/10.1016/j.jenvrad.2024.107432

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 Be activity concentrations. The average concentrations on nonprecipitation and precipitation days were 5.5 and 3.8 mBq/m, respectively. This difference of 31% (1.7 mBq/m) on average, was attributable to the washout effect, which was more significant in the summer. Regarding the association between 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 10 mm/day. Furthermore, when precipitation occurred on two successive days, the Be activity concentrations on the second day significantly decreased regardless of precipitation.

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.

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

https://doi.org/10.1016/j.net.2023.09.001

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

https://doi.org/10.1088/1742-6596/2605/1/012024

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.

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

https://doi.org/10.1380/vss.66.525

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.

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.