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Tsumune, Daisuke*; Tsubono, Takaki*; Misumi, Kazuhiro*; Sakuma, Kazuyuki; Onda, Yuichi*
Pure and Applied Chemistry, 16 Pages, 2024/00
Times Cited Count:0Twelve years after the Fukushima Daiichi Nuclear Power Station (F1NPS) accident, Cs activity concentrations have not yet decreased to pre-accident levels because of direct release from the site and fluvial discharges of Cs deposited on land. It is necessary to consider dispersion processes in the coastal area to understand the impact of multiple river discharges and direct release. To achieve this goal, we carried out oceanic dispersion simulations that considered direct release and fluvial discharges and compared the results with the annual averages of observed data. We assumed that particulate Cs discharged from rivers to the ocean quickly resuspended and re-leached after coagulation and precipitation and that all of the Cs were dispersed. The reproducibility of results was improved by considering fluvial discharges of particulate Cs at all sites between 2013 and 2016, except near the F1NPS. In other words, particulate Cs discharged from rivers was found to influence the results of ocean surface activity concentrations within a relatively short period of time. The impact of direct release was dominant for the observed Cs activity concentrations adjacent to the F1NPS, which was used to estimate direct releases.
Miyakawa, Kazuya; Hayano, Akira; Sato, Naomi; Nakata, Kotaro*; Hasegawa, Takuma*
JAEA-Data/Code 2023-009, 103 Pages, 2023/09
This borehole investigation was carried out to confirm the validity of the distribution of low flow areas deep underground estimated based on the geophysical survey in FY 2020, as a part of an R&D supporting program titled "Research and development on Groundwater Flow Evaluation Technology in Bedrock" under contract to the Ministry of Economy, Trade and Industry (2021, 2022 FY, Grant Number: JPJ007597). The borehole name is Horonobe Fossil seawater Boring-1 and is referred to as HFB-1 borehole. HFB-1 is a vertical borehole drilled adjacent to the Horonobe Underground Research Laboratory (URL), which was drilled from the surface to a depth of 200 m in FY2021 and from a depth of 200 m to 500 m in FY2022. This report summarizes information related to the drilling of HFB-1 and various data (rock core description, geophysical logging, chemical analysis, etc.) obtained from the borehole investigation.
Miyakawa, Kazuya; Nakata, Kotaro*
JAEA-Data/Code 2022-013, 19 Pages, 2023/03
In the Horonobe Underground Research Laboratory (URL) project, groundwater chemistry was analyzed to investigate changes due to the excavation of the underground facility and to review geochemical models until the fiscal year 2019. From the fiscal year 2020, to proceed remaining important issues deduced from the conclusion of the investigations during the fiscal year 2015-2019, primary data such as groundwater chemistry need to be successively acquired. Here, the chemical analysis of 54 groundwater samples in 2022 from boreholes drilled in the 140 m, 250 m, 350 m gallery in the Horonobe URL, and water rings settled in three vertical shafts is presented. Analytical results include groundwater chemistry such as pH, electrical conductivity, dissolved components (Na, K, Ca, Mg, Li, NH, F, Cl, Br, NO, NO, PO, SO, Total-Mn, Total-Fe, Al, B, Sr, Ba, I, alkalinity, dissolved organic carbon, dissolved inorganic carbon, CO, HCO, Fe, sulfide), and O, D along with a detailed description of analytical methods.
Miyakawa, Kazuya; Kashiwaya, Koki*; Komura, Yuto*; Nakata, Kotaro*
Geochemical Journal, 57(5), p.155 - 175, 2023/00
Times Cited Count:0 Percentile:0.01(Geochemistry & Geophysics)In the thick marine sediments, groundwater altered from seawater during the burial diagenesis may exist. Such altered ancient seawater will be called fossil seawater. In such a field, groundwater flow is considered extremely slow because it is not affected by the seepage of meteoric water even after the uplift. During diagenesis, dehydration from silicates causes changes such as a decrease in the salinity of the porewater. However, dehydration reactions alone cannot quantitatively explain water chemistry changes. In this study, we developed an analytical model that considers the dehydration reaction from silicates during the burial process and the upward migration of porewater due to compaction and examined the possible evolution of porewater chemistry. The results showed that the water chemistry, which was strongly influenced by the dehydration reaction from opal-A to quartz and from smectite, was similar to the observations from boring surveys. The results suggest that the fossil seawater formed during the diagenesis may have been preserved since the uplift and strongly supports the slow groundwater flow in the area where the fossil seawater exists.
Ohgama, Kazuya; Hara, Toshiharu*; Ota, Hirokazu*; Naganuma, Masayuki; Oki, Shigeo; Iizuka, Masatoshi*
Journal of Nuclear Science and Technology, 59(6), p.735 - 747, 2022/06
Times Cited Count:1 Percentile:31.61(Nuclear Science & Technology)Hirano, Shinichi*; Ihara, Sota*; Wakai, Satoshi*; Dotsuta, Yuma; Otani, Kyohei; Kitagaki, Toru; Ueno, Fumiyoshi; Okamoto, Akihiro*
Microorganisms (Internet), 10(2), p.270_1 - 270_12, 2022/02
Times Cited Count:7 Percentile:84.82(Microbiology)To understand the role of methanogens in corrosion under anoxic conditions in freshwater, we investigated the corrosion activities of methanogens in samples collected from groundwater and rivers. We enriched microorganisms that can grow with CO/NaHCO and Fe as the sole carbon source and electron donor, respectively, in ground fresh water. Electrochemical analysis revealed that strain can uptake electrons from the cathode at lower than -0.61 V vs SHE and has a redox-active component with electrochemical potential different from those of other previously reported methanogens with extracellular electron transfer ability. This study indicated the corrosion risk by methanogens capable of taking up electrons from Fe in anoxic freshwater environments and the necessity of understanding the corrosion mechanism to contribute to risk diagnosis.
Sugiyama, Daisuke*; Nakabayashi, Ryo*; Tanaka, Shingo*; Koma, Yoshikazu; Takahatake, Yoko
Journal of Nuclear Science and Technology, 58(4), p.493 - 506, 2021/04
Times Cited Count:2 Percentile:31.78(Nuclear Science & Technology)Li, Y.; Hirota, Takatoshi*; Itabashi, Yu*; Yamamoto, Masato*; Kanto, Yasuhiro*; Suzuki, Masahide*; Miyamoto, Yuhei*
JAEA-Review 2020-011, 130 Pages, 2020/09
For the improvement of the structural integrity assessment methodology on reactor pressure vessels (RPVs), the probabilistic fracture mechanics (PFM) analysis code PASCAL has been developed and improved in Japan Atomic Energy Agency based on the latest knowledge. The PASCAL code evaluates the failure probabilities and frequencies of Japanese RPVs under transient events such as pressure thermal shock considering neutron irradiation embrittlement. In order to confirm the reliability of the PASCAL as a domestic standard code and to promote the application of PFM on the domestic structural integrity assessments of RPVs, it is important to perform verification activities, and summarize the verification processes and results as a document. On the basis of these backgrounds, we established a working group, composed of experts on this field besides the developers, on the verification of the PASCAL module and the source program of PASCAL was released to the members of working group. This report summarizes the activities of the working group on the verification of PASCAL in FY2016 and FY2017.
Lu, K.; Katsuyama, Jinya; Li, Y.; Miyamoto, Yuhei*; Hirota, Takatoshi*; Itabashi, Yu*; Nagai, Masaki*; Suzuki, Masahide*; Kanto, Yasuhiro*
Mechanical Engineering Journal (Internet), 7(3), p.19-00573_1 - 19-00573_14, 2020/06
Saito, Yoshimoto*; Hirano, Shinichi*; Nagaoka, Toru*; Amano, Yuki
Ecological Genetics and Genomics, 12, p.100042_1 - 100042_9, 2019/10
Culture-independent molecular techniques enable us to analyze microflora in various environments. Many uncultured prokaryotes have been detected by the molecular methods from extreme environments, including anaerobic, no light, high-pressure, and high temperature. Recently, microbial eukaryotes were also detected in deep-sea environments, suggesting that microbial eukaryotes can adapt to a wider range of environments than previously thought. Here, we performed a culture-independent analysis of eukaryotes from approximately -250 m depth in the Horonobe Underground Research Laboratory at Horonobe, Japan. Our results indicate that fungi are the dominant eukaryotic flora in deep sedimentary rocks of Horonobe. We detected a wide range of species, including Zygomycete, Basidiomycete, and Ascomycete fungi from the rocks. This study is the first report of eukaryotic diversity in deep subsurface sedimentary rocks.
Sugiyama, Daisuke*; Nakabayashi, Ryo*; Koma, Yoshikazu; Takahatake, Yoko; Tsukamoto, Masaki*
Journal of Nuclear Science and Technology, 56(9-10), p.881 - 890, 2019/09
Times Cited Count:4 Percentile:41.24(Nuclear Science & Technology)Ota, Hirokazu*; Ohgama, Kazuya; Yamano, Hidemasa
Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.30 - 39, 2019/09
Nakata, Kotaro*; Hasegawa, Takuma*; Solomon, D. K.*; Miyakawa, Kazuya; Tomioka, Yuichi*; Ota, Tomoko*; Matsumoto, Takuya*; Hama, Katsuhiro; Iwatsuki, Teruki; Ono, Masahiko*; et al.
Applied Geochemistry, 104, p.60 - 70, 2019/05
Times Cited Count:9 Percentile:38.79(Geochemistry & Geophysics)no abstracts in English
Ohgama, Kazuya; Ota, Hirokazu*; Oki, Shigeo; Iizuka, Masatoshi*
Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 9 Pages, 2019/05
Kubota, Kenji*; Aoyagi, Kazuhei; Sugita, Yutaka
Proceedings of 2019 Rock Dynamics Summit in Okinawa (USB Flash Drive), p.729 - 733, 2019/05
During the excavation of shafts and galleries in the deep subsurface for disposing of high-level radioactive waste, an excavation disturbed zone (EdZ) or excavation damaged zone (EDZ) is developed around the shafts and galleries. Such zones could influence the transfer behavior of radioactive nuclides, and it is therefore important to understand the behavior of the EdZ or EDZ. We performed in situ experiments before, during, and after gallery excavation in galleries of 140 and 250 m in depth in an area of soft sedimentary rock in Japan. The results demonstrate that the extent of fractures induced by the gallery excavation related with EDZ was confined to about 0.45 m from the gallery wall in the 140 m gallery and to about 1 m from the gallery wall in the 250 m gallery. The extent of the unsaturated zone related with EdZ was about 1 m in the 140 m gallery, but an unsaturated zone did not appear in the 250 m gallery.
Sugita, Yutaka; Aoyagi, Kazuhei; Kubota, Kenji*; Nakata, Eiji*; Oyama, Takahiro*
JAEA-Research 2018-002, 72 Pages, 2018/06
In a excavation of shafts and galleries in the deep underground for disposing radioactive waste, an excavation damaged zone (EDZ) is developed around the galleries and shafts owing to the stress redistribution. Since the characteristic changes of the rock mass in the EDZ affects the radionuclides migration behavior, it is important to understand the long-term behavior of the EDZ. Thus, we performed the in situ experiment to investigate the long-term behavior of EDZ as part of the collaborative research between Japan Atomic Energy Agency and Central Research Institute of Electric Power Industry in the 140m gallery in the Horonobe Underground Research Laboratory. In this research, we investigated the extent, mechanism of the change of hydro-mechanical characteristic, and long-term behavior of the EDZ on the basis of the comprehensive estimation of the results of the observation of the drift wall and the various investigations using boreholes such as geological investigation, the seismic and resistivity tomography, hydraulic test, water content monitoring, borehole loading test, convergence measurement, and so on. In addition, we clarified applicability and future tasks of the testing method used in this research for the investigation of the long-term behavior of the EDZ.
Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Miyakawa, Kazuya
Journal of Hydrology, 561, p.547 - 556, 2018/06
Times Cited Count:5 Percentile:26.43(Engineering, Civil)no abstracts in English
Kubota, Kenji*; Aoyagi, Kazuhei; Sugita, Yutaka
Koeki Shadan Hojin Butsuri Tansa Gakkai Dai-138-Kai (Heisei-30-Nendo Shuki) Gakujutsu Koenkai Koen Rombunshu, p.51 - 54, 2018/05
In an excavation of shafts and galleries in the deep underground for disposing high level radioactive waste, an excavation disturbed zone (EdZ) or excavation damaged zone (EDZ) is developed around the shafts and galleries owing to the stress redistribution. It is important to understand the behavior of the EdZ or EDZ because these zone could have an effect on the transfer behavior of radioactive nuclide. Therefore, the authors performed the in situ experiment to investigate the behavior of EdZ or EDZ in the 140m and 250m gallery in the Horonobe Underground Research Laboratory. From the result of the experiments, the authors compared the characteristics of EdZ or EDZ between those in 140m and 250m gallery. The extent of the fractures induced by the gallery excavation, i.e., EDZ was about 0.45m in the 140m gallery and about 1m in the 250m gallery. The extent of the unsaturated zones related with EdZ was about 1m in the 140m gallery, however, unsaturated zone was not appeared in the 250m gallery.
Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Ishii, Eiichi; Miyakawa, Kazuya; Sasamoto, Hiroshi
Geofluids, 2018, p.7823195_1 - 7823195_21, 2018/01
Times Cited Count:9 Percentile:57.47(Geochemistry & Geophysics)A groundwater scenario is one of the scenario for safety assessment of geological disposal of high-level radioactive waste. In the safety assessment for groundwater scenario, the slow groundwater flow for a long-term should be an important factor. In the present study, study on stability of groundwater in the Koetoi and Wakkanai formations of Neogene marine based sedimentary rock at the Horonobe area, Hokkaido was performed by investigating the isotopes of chlorine and helium, and the stable isotopes of water. As the results, the stability of groundwater in deeper part of the Wakkanai formation was suggested due to no direct evidence of meteoric water intrusion during the uplift since ca. 1 Ma. Contrary, the groundwater both in the Koetoi formation and the upper Wakkanai formation would be unstable because the meteoric water intrusion was suggested by paleohydrogeological condition and the results of groundwater dating. Likely the Horonobe area, the accurate dating of groundwater would be difficult due to the complex effects of upward and mixing water derived from diagenesis in the thick sediment formation. However, a comparative procedure using both the results of groundwater dating and paleohydrogeological information would be useful for general evaluation of groundwater flow conditions for the long-term (i.e., check the possibility for long-term stability of groundwater).
Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Maeda, Makoto; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.
Energy Procedia, 131, p.258 - 263, 2017/12
Times Cited Count:10 Percentile:98.3(Energy & Fuels)