Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2022

Kokubun, Yuji; Nakada, Akira; Seya, Natsumi; Koike, Yuko; Nemoto, Masashi; Tobita, Keiji; Yamada, Ryohei*; Uchiyama, Rei; Yamashita, Daichi; Nagai, Shinji; et al.

JAEA-Review 2023-046, 164 Pages, 2024/03

JAEA-Review-2023-046.pdf:4.2MB

The Nuclear Fuel Cycle Engineering Laboratories conducts environmental radiation monitoring around the reprocessing plant in accordance with the "Safety Regulations for Reprocessing Plant of JAEA, Part IV: Environmental Monitoring". This report summarizes the results of environmental radiation monitoring conducted during the period from April 2022 to March 2023 and the results of dose calculations for the surrounding public due to the release of radioactive materials into the atmosphere and ocean. In the results of the above environmental radiation monitoring, many items were affected by radioactive materials emitted from the accident at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company, Incorporated (changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016), which occurred in March 2011. Also included as appendices are an overview of the environmental monitoring plan, an overview of measurement methods, measurement results and their changes over time, meteorological statistics results, radioactive waste release status, and an evaluation of the data which deviated of the normal range.

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2021

Nakada, Akira; Kanai, Katsuta; Seya, Natsumi; Nishimura, Shusaku; Futagawa, Kazuo; Nemoto, Masashi; Tobita, Keiji; Yamada, Ryohei*; Uchiyama, Rei; Yamashita, Daichi; et al.

JAEA-Review 2022-078, 164 Pages, 2023/03

JAEA-Review-2022-078.pdf:2.64MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2021 to March 2022. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co., Inc. (the trade name was changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016) in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and exceeded the normal range of fluctuation in the monitoring, were evaluated.

Electrical properties and energy band alignment of SiO/GaN metal-oxide-semiconductor structures fabricated on N-polar GaN(000) substrates

Mizobata, Hidetoshi*; Tomigahara, Kazuki*; Nozaki, Mikito*; Kobayashi, Takuma*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*

Applied Physics Letters, 121(6), p.062104_1 - 062104_6, 2022/08

https://doi.org/10.1063/5.0095468

The interface properties and energy band alignment of SiO/GaN metal-oxide-semiconductor (MOS) structures fabricated on N-polar GaN(000) substrates were investigated by electrical measurements and synchrotron-radiation X-ray photoelectron spectroscopy. They were then compared with those of SiO/GaN MOS structures on Ga-polar GaN(0001). Although the SiO/GaN(000) structure was found to be more thermally unstable than that on the GaN(0001) substrate, excellent electrical properties were obtained for the SiO/GaN(000) structure by optimizing conditions for post-deposition annealing. However, the conduction band offset for SiO/GaN(000) was smaller than that for SiO/GaN(0001), leading to increased gate leakage current. Therefore, caution is needed when using N-polar GaN(000) substrates for MOS device fabrication.

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2020

Nakada, Akira; Nakano, Masanao; Kanai, Katsuta; Seya, Natsumi; Nishimura, Shusaku; Nemoto, Masashi; Tobita, Keiji; Futagawa, Kazuo; Yamada, Ryohei; Uchiyama, Rei; et al.

JAEA-Review 2021-062, 163 Pages, 2022/02

JAEA-Review-2021-062.pdf:2.87MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2020 to March 2021. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co., Inc. (the trade name was changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016) in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and exceeded the normal range of fluctuation in the monitoring, were evaluated.

High-spatial-resolution measurement of magnetization distribution using polarized neutron imaging

Sasada, Seiji*; Hiroi, Kosuke; Osanai, Kenta*; Shinohara, Takenao; Watanabe, K.*; Uritani, Akira*

Japanese Journal of Applied Physics, 60(12), p.126003_1 - 126003_6, 2021/12

https://doi.org/10.35848/1347-4065/ac3524

Petrology and mineralogy of an igneous clast in the Northwest Africa 1685 (LL4) chondrite; Comparison with alkali-rich igneous clasts in LL-chondritic breccias

Niihara, Takafumi*; Yokoyama, Tatsunori; Arai, Tomoko*; Misawa, Keiji*

Meteoritics & Planetary Science, 56(8), p.1619 - 1625, 2021/08

https://doi.org/10.1111/maps.13719

We have conducted petrological and mineralogical studies on an igneous clast in the Northwest Africa (NWA) 1685 (LL4) chondrite. In an earlier description, the meteorite contained similar clasts in the LL chondritic breccias Yamato (Y)-74442 (LL4), Bhola (LL3-6), and Kraehenberg (LL5). We carefully compared their textures as well as mineral and matrix compositions with those of alkali-rich clasts in the LL chondritic breccias. Olivine grains are embedded in glassy matrix and have no chemical. Shock melt veins and fractures were observed only in olivine grains and did not continue to matrix. Major and minor element compositions of olivine grains in the clast are homogeneous. Potassium abundance of matrix glasses of the NWA 1685 clast is lower than those of alkali-rich igneous clasts in Y-74442, Bhola, and Kraehenberg, indicating that the igneous clasts in NWA 1685 are different from the alkali-rich clasts previously reported in the LL chondritic breccias and that they could have formed during an impact melting event, quenched on the LL-chondrite parent body, and finally incorporated into breccia.

Hydrogen production using thermochemical water-splitting iodine-sulfur process test facility made of industrial structural materials; Engineering solutions to prevent iodine precipitation

Noguchi, Hiroki; Kamiji, Yu; Tanaka, Nobuyuki; Takegami, Hiroaki; Iwatsuki, Jin; Kasahara, Seiji; Myagmarjav, O.; Imai, Yoshiyuki; Kubo, Shinji

International Journal of Hydrogen Energy, 46(43), p.22328 - 22343, 2021/06

https://doi.org/10.1016/j.ijhydene.2021.02.071

An iodine-sulfur process offers the potential for mass producing hydrogen with high-efficiency, and it uses high-temperature heat sources, including HTGR, solar heat, and waste heat of industries. R&D tasks are essential to confirm the integrity of the components that are made of industrial materials and the stability of hydrogen production in harsh working conditions. A test facility for producing hydrogen was constructed from corrosion-resistant components made of industrial materials. For stable hydrogen production, technical issues for instrumental improvements (i.e., stable pumping of the HIx solution, improving the quality control of glass-lined steel, prevention of I precipitation using a water removal technique in a Bunsen reactor) were solved. The entire process was successfully operated for 150 h at the rate of 30 L/h. The integrity of components and the operational stability of the hydrogen production facility in harsh working conditions were demonstrated.

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

https://doi.org/10.1016/C2018-0-05383-9

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Reliability improvements of corrosion-resistant equipment for thermochemical water splitting hydrogen production iodine-sulfur process

Kamiji, Yu; Noguchi, Hiroki; Takegami, Hiroaki; Tanaka, Nobuyuki; Iwatsuki, Jin; Kasahara, Seiji; Kubo, Shinji

Nuclear Engineering and Design, 361, p.110573_1 - 110573_6, 2020/05

https://doi.org/10.1016/j.nucengdes.2020.110573

JAEA has been conducting R&D on the thermochemical iodine-sulfur (IS) process for nuclear-powered hydrogen production. The IS process is one of the promising candidates of heat application of the high-temperature gas-cooled reactors. The glass-lined steel is one of the candidate materials which has both corrosion resistance and structural strength. This paper reveals technical matters to improve reliability of the glass-lined steel equipment. It found that the improved glass-lined steel showed soundness in the process environment from the results of stress analyses for the glass layer by FEM, tests for heat cycle, bending load and corrosion.