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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.
Nara, Yoshitaka*; Kashiwaya, Koki*; Oketani, Kazuki*; Fujii, Hirokazu*; Zhao, Y.*; Kato, Masaji*; Aoyagi, Kazuhei; Ozaki, Yusuke; Matsui, Hiroya; Kono, Masanori*
Zairyo, 73(3), p.220 - 225, 2024/03
The fractures in the rock are the main pass of groundwater flow and solute transport. The filling of fine-grained particle, such as clay minerals, was confirmed to decrease the permeability of rock by laboratory experiment. This research aimed to verify the occurance of the phoenomena in the fild. The water containing the clay minerals was injected into the rock at the 200m stage of the Mizunami undearground research laboratory. The hydraulic conductivity decreased two order before and after the injection. This result suggested that the decrease of hydraulic conductivity by the filling of fine-grained particle in the fractures occured in the real field.
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.
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.
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
Times Cited Count：43 Percentile：96.93(Astronomy & Astrophysics)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.
Nakano, Masanao; Fujii, Tomoko; Nemoto, Masashi; Tobita, Keiji; Seya, Natsumi; Nishimura, Shusaku; Hosomi, Kenji; Nagaoka, Mika; Yokoyama, Hiroya; Matsubara, Natsumi; et al.
JAEA-Review 2020-069, 163 Pages, 2021/02
JAEA-Review-2020-069.pdf:4.78MB
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 2019 to March 2020. 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.
Ishida, Tsuyoshi*; Fujito, Wataru*; Yamashita, Hiroto*; Naoi, Makoto*; Fujii, Hirokazu*; Suzuki, Kenichiro*; Matsui, Hiroya
Rock Mechanics and Rock Engineering, 52(2), p.543 - 553, 2019/02
Times Cited Count：16 Percentile：67.51(Engineering, Geological)We pressurized and injected water in a hole drilled downward from a floor of the 500 m level gallery in MIU, central Japan. Acoustic emissions (AEs) monitored with 16 sensors in four boreholes located 1 m away from the HF hole exhibited two-dimensional distributions, which likely delineate a crack induced by the fracturing. Expansions of the regions in which AEs occurred were observed only immediately after the first and second BDs. Many AE events in other periods were distributed within the regions where AE events had already occurred. The initial motion polarities of P-waves indicate that tensile-dominant AE events occurred when the regions expanded and they were distributed primarily on the frontiers of the regions where AE events had already occurred. The experimental results suggest that increasing the injection flow rate is effective for generating new cracks in the refracturing, with the new crack expansions being induced by tensile fracturing.
Osaka, Masahiko; Konashi, Kenji*; Hayashi, Hirokazu; Li, D.*; Homma, Yoshiya*; Yamamura, Tomoo*; Sato, Isamu; Miwa, Shuhei; Sekimoto, Shun*; Kubota, Takumi*; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12
Summer schools for future experts have successfully been completed under Japan Actinide Network (J-ACTINET) for the purpose of development of human resources who are expected to be engaged in every areas of actinide-research/engineering. The first summer school was held in Ibaraki-area in August 2009, followed by the second one in Kansai-area in August 2010. Two summer schools have focused on actual experiences of actinides in actinide-research fields for university students and young researchers/engineers as an introductory course of actinide-researches. Several quasi actinide-handling experiences at the actinide-research fields have attracted attentions of participants at the first school in Ibaraki-area. The actual experiments using actinides-containing solutions have been carried out at the second school in Kansai-area. Future summer schools will be held every year for the sustainable human resource development in various actinide-research fields.
)
and CaClFujii, Toshiyuki*; Okude, Genki*; Uehara, Akihiro*; Sekimoto, Shun*; Hayashi, Hirokazu; Akabori, Mitsuo; Minato, Kazuo; Yamana, Hajimu*
Journal of Radioanalytical and Nuclear Chemistry, 288(1), p.181 - 187, 2011/04
Times Cited Count：6 Percentile：44.28(Chemistry, Analytical)Distribution behavior of Ce(III), Am(III), and Cm(III) between tri-n-butyl phosphate solution and molten calcium nitrate hydrate Ca(NO)
HO or molten calcium chloride hydrate CaClHO was studied radiochemically. In Ca(NO)HO systems, maximum separation factors of Ce and Cm to Am were observed to be 12 (Ce/Am) and 1.7 (Cm/Am). The distribution ratios of these elements increased with the decrease of water activity in the hydrates, and the extractabilities at the water deficient region was less sensitive compared to those at the water abundant region. This trend was similar to the coordination circumstance change observed in electronic absorption spectra of Nd(III) in the hydrates.
Tsuji, Hirokazu; Fujii, Hidetoshi*
Proceedings of 10th German-Japanese Workshop on Chemical Information, p.127 - 130, 2002/00
A neural network model within a Bayesian framework was adopted based on the material database constructed by JAERI for prediction of creep rupture properties of irradiated type 304 stainless steel. Stress level was modeled as a function of 18 variables, including rupture life, creep test temperature, chemical compositions; 10 elements, heat treatment temperature, heat treatment duration, neutron irradiation temperature, fast neutron fluence, thermal neutron fluence, irradiation time, based on JAERI material database in which 347 creep rupture data sets of type 304 stainless steels were stored. The Bayesian method puts error bars on the predicted values of the rupture strength and allows the significance of each individual factor to be estimated.
Tsuji, Hirokazu; Fujii, Hidetoshi*
Tahenryo Kaiseki Jitsurei Handobukku, p.107 - 114, 2002/00
no abstracts in English
Akutsu, Kazuhiro; Shiwaku, Hideaki; Okamoto, Yoshihiro; Suzuki, Shinichi; Ikeda, Atsushi; Kobayashi, Toru*; Numakura, Masahiko; Mahara, Saori*; Nakano, Yoshiharu*; Fujii, Yuki*; et al.
no journal, ,
no abstracts in English
Koyama, Tadafumi*; Hayashi, Hirokazu; Fujii, Toshiyuki*
no journal, ,
no abstracts in English
Minato, Kazuo; Konashi, Kenji*; Fujii, Toshiyuki*; Uehara, Akihiro*; Nagasaki, Shinya*; Otori, Norikazu*; Akabori, Mitsuo; Takano, Masahide; Hayashi, Hirokazu; Tokunaga, Yo; et al.
no journal, ,
Basic research in actinide chemistry and physics is indispensable to maintain sustainable development of innovative nuclear technology. Actinides, especially minor actinides (MA) of americium and curium, need to be handled in special facilities with containment and radiation shields. A three-year-program Basic actinide chemistry and physics research in close cooperation with hot laboratories, ACTILAB, was started to form the basis of sustainable development of innovative nuclear technology. For the basic understanding of the properties of MA-bearing fuels, XAFS (X-ray Absorption Fine Structure) measurements on AmO
and 
O-NMR (Nuclear Magnetic Resonance) measurements on (Pu
Am
)O
were carried out. Curium nitride was synthesized by carbothermic reduction method and the lattice parameters and thermal expansion of CmN were measured by high temperature X-ray diffractometry after purification of aged curium oxide.
Fujito, Wataru*; Yamashita, Hiroto*; Ziad, B.*; Naoi, Makoto*; Ishida, Tsuyoshi*; Fujii, Hirokazu*; Suzuki, Kenichiro*; Matsui, Hiroya
no journal, ,
For utilization a geothermal energy and mining of a shale gas, hydrofracturing technology become important. In this study, in-situ hydraulic fracturing experiment and AE measurement at Mizunami URL was carried out to examine a break mechanism by hydraulic fracturing. The results suggested that AE with shear mechanism at first breakdown is dominated and AE with tension mechanism is generated at new fracturing.
Matsui, Hiroya; Ozaki, Yusuke; Uyama, Masao*; Fujii, Hirokazu*
no journal, ,
no abstracts in English
Oketani, Kazuki*; Nara, Yoshitaka*; Matsui, Hiroya; Fujii, Hirokazu*
no journal, ,
For the geological disposal of radioactive wastes, it is important to understand the long-term migration of radionuclides. The network of fractures and pores in a rock mass, which have a role as the pathway of the fluid flow of materials, may change due to sealing of a material in the long term. We measured changes in hydraulic conductivity of crystalline rock mass using water mixed with clays sampled from a fault in the Mizunami Underground Research Laboratory, Japan Atomic Energy Agency. This result indicates that permeability of in-situ rock mass is possible to decrease by fracture filling with a clay material in a fault.
Kamata, Kento*; Nara, Yoshitaka*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
The precipitation of carbonate minerals in rock is expected to close the fracture opening. In Horonobe URL, we perform the carbonated water injection test to heal the EDZ by the carbonate mineral precipitation. We compare the permeability before and after the injection to evaluate the closure of fractures in the EDZ. The significant change in permeability is not recognized at the present due to the short injection period and continuous injection would be required to change the permeability of EDZ by the precipitation.
Kamata, Kento*; Nara, Yoshitaka*; Matsui, Hiroya; Ozaki, Yusuke; Fujii, Hirokazu*; Zhao, Y.*
no journal, ,
In this study, we perform a carbonated water injection experiment into the fractured rock to investigate the reduction of permeability due to the sealing of fractures by the precipitation of carbonated minerals at the 350m stage in Horonobe URL. We drilled a 80cm borehole from the drift wall and injected the carbonated water into the fractures there in the excavated damaged zone. The hydraulic test that we performed regularly during the injection experiment indicates the reduction of hydraulic conductivity slightly. To understand the mechanism of the reduction of permeability, we plan to analyze the core sample collected by overcoring.
Kamata, Kento*; Nara, Yoshitaka*; Kashiwaya, Koki*; Tada, Yohei*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
We conducted a carbonated water injection experiment at 350m stage in Horonobe URL. Two boreholes with 1m were drilled from drift wall and carbonated water was injected. The cement material powder was added one of the boreholes. The hydraulic conductivity around the borehole where only carbonated water was injected slightly decreased. The hydraulic conductivity around the borehole where both cement material powder and carbonated water decreased and increased because of the clogging of fracture by the powder and dissipation of it.
Kuwabara, Shogo*; Nara, Yoshitaka*; Kashiwaya, Koki*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke; Hiroyoshi, Naoki*
no journal, ,
This study aims to develop a healing method of fractured rock by injection of cement powder and carbonated water to form carbonated minerals. The in-situ hydraulic tests were carried out to confirm the effect of their injection into rock. The decrease of hydraulic conductivity was recognized after the injection of both cement powder and carbonated water, whereas the injection of only carbonated water did not induce the decrease of hydraulic conductivity.
