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Cs discharge from a mountainous forested catchment using reservoir sediments and sinking particlesFunaki, Hironori; Yoshimura, Kazuya; Sakuma, Kazuyuki; Iri, Shatei; Oda, Yoshihiro
Journal of Environmental Radioactivity, 189, p.48 - 56, 2018/09
Times Cited Count：17 Percentile：52.92(Environmental Sciences)Kitamura, Akihiro; Kurikami, Hiroshi; Yamaguchi, Masaaki; Oda, Yoshihiro; Saito, Tatsuo; Kato, Tomoko; Niizato, Tadafumi; Iijima, Kazuki; Sato, Haruo; Yui, Mikazu; et al.
Nuclear Science and Engineering, 179(1), p.104 - 118, 2015/01
Times Cited Count：8 Percentile：56.13(Nuclear Science & Technology)The prediction of the distribution and fate of radioactive materials eventually deposited at surface in the Fukushima area is one of the main objectives and expected to be achieved in an efficient manner. In order to make such prediction, a number of mathematical models of radioactive contaminants, with particular attention on cesium, on the land and in rivers, lakes, and estuaries in the Fukushima area are developed. Simulation results are examined with the field investigations simultaneously implemented. The basic studies of the adsorption/absorption mechanism of cesium and soils have been performed to shed light on estimating distribution coefficient between dissolved contaminant and particulate contaminant.
Cs distribution in Fukushima after the Fukushima Dai-ichi Nuclear Power Plant accident; A Parameter sensitivity analysisYamaguchi, Masaaki; Kitamura, Akihiro; Oda, Yoshihiro; Onishi, Yasuo*
Journal of Environmental Radioactivity, 135, p.135 - 146, 2014/09
Times Cited Count：38 Percentile：72.86(Environmental Sciences)We applied a model, to predict long term cesium distribution on Fukushima area, based on the USLE and simple sediment discharge formulas. Sensitivity analysis was conducted here to narrow the range of the output results due to the uncertainties of parameters. The preliminary calculation indicated significant deposition of sand portion within river basins. On the other hand the most of the eroded silt and clay portions were transported downstream to the river mouths. Annual sediment outflow into the ocean from Abukuma River and its total from the other 13 river basins vary between calculation cases based on the variation of land use, landform or precipitation. On the other hand, contributions of those parameters are relatively small for Cs concentration within transported soil. This indicates the total amount of Cs outflow into the ocean could be controlled by amount of soil erosion and transport, and total amount of Cs remaining within the basin.
Cs distribution on territory of FukushimaKitamura, Akihiro; Yamaguchi, Masaaki; Oda, Yoshihiro; Kurikami, Hiroshi; Onishi, Yasuo*
Transactions of the American Nuclear Society, 109(1), p.153 - 155, 2013/11
Long term Cs transport and its future distribution on the territory of Fukushima were predicted based on the USLE and the GIS. By modeling the soil erosion, transport, and deposition, we simulated the future distributions of air dose rates of Cs in mSv/h for 2, 6 and 21 years after the accident. The predictions made by METI were compared with the present results. The predictions of relatively high air dose rate areas were consistently matched between the two models over time. However, our model seemed to predict the decreasing rate of the Cs concentration with time to be slightly less than that of METI prediction. Some portions of the results obtained in the present study were used to provide influxes of sediments and Cs as boundary conditions and lateral inflows for the hydraulic river model.
Oda, Yoshihiro; Takasu, Tamio*; Sato, Hisashi; Sawada, Atsushi; Watahiki, Takanori*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 67(2), p.186 - 197, 2011/04
Because of the density difference between fresh groundwater and saline groundwater, the groundwater behaves complicated flow. It is well known that the expected barrier functions such as candidate buffer materials and others for high level radioactive waste geological isolation are inhibited by the saline water. The simulations have been required to evaluate the groundwater flow, because the available data by in-situ investigation of the saline and fresh ground water flows is very limited. In the simulation, the complex coupled process of advection-dispersion, seepage flow and density drive flow should be implemented in the simulation codes. The extensive verification studies have been done for modeling and simulation codes until now, but those results were compared only with qualitative experimental data. For the quantitative evaluations, we developed the quantitative measurement technique by optical method for saltwater intrusion, especially for the saltwater concentration distribution in transition zone, on laboratory experiment. We have obtained the quantitative data of the shape of saltwater wedge and saltwater concentration distribution at both transient and steady states.
Shimo, Michito*; Kumamoto, So*; Ito, Akira*; Karasaki, Kenji*; Sawada, Atsushi; Oda, Yoshihiro; Sato, Hisashi
JAEA-Research 2010-040, 57 Pages, 2010/11
JAEA-Research-2010-040.pdf:5.12MB
In safety analysis of geological disposal of the high-level nuclear waste, it is important to evaluate appropriately the mass transport characteristics of the bedrock as the natural barrier. Especially, it has been found that the porosity of the rock matrix is high and fractured zones are developing and therefore the mass transport characteristics will be the mixture of those for porous media and the fractured media. In this work, we conducted, (1) a study on the method to mine out the rock block sample of tens of-centimeter to maximum 1 m scale, (2) a study on a method of the tracer test using a rock block sample and a series of scoping analysis. We also examined the uncertainty associated the hydrogeological model using a method combining a forward and inverse analysis, based on the various type of data sets obtained at Horonobe site, such as the temperature distribution and hydraulic head and salinity distribution.
Oda, Yoshihiro; Watahiki, Takanori*; Sato, Hisashi; Sawada, Atsushi
JAEA-Research 2010-020, 23 Pages, 2010/08
JAEA-Research-2010-020.pdf:2.49MB
For the geological disposal of high level radioactive waste, it is important to know the groundwater flow to evaluate the geological isolation system. Simulation codes are used for the evaluation of the saline groundwater flow and distribution, because various and a lot of investigations and experiments are needed. At in-situ, simulation codes have to solve advection-dispersion flow coupling with density flow which occurs by the density difference between saline and fresh groundwater. But the results of laboratory experiments are qualitative data, then the verification cannot be done in quantitatively. The quantitative data of saltwater intrusion experiment, then we try to simulate saltwater intrusion by Dtransu2D-EL code which can calculate advection-dispersion flow coupled with density flow. Between the results of the simulation and the experiments, the toe point of wedge by the simulation shows good coincidence, but the top point is not good coincidence. As for the transition zone of saltwater intrusion, the band width of the experimental result decrease from the toe to the top, but the simulation result shows countertrend.
Shimo, Michito*; Kumamoto, So*; Ito, Akira*; Karasaki, Kenji*; Sawada, Atsushi; Oda, Yoshihiro; Sato, Hisashi
JAEA-Research 2009-060, 70 Pages, 2010/03
JAEA-Research-2009-060.pdf:14.26MB
It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground appropriately. Though it is considered that the mass transport in sedimentary rock occurs in pores between grains mainly, fractures of sedimentary rock can be main paths. In this study the following three tasks were carried out: (1) laboratory hydraulic and tracer experiments using the rock cores of Wakkanai formation, (2) a study on the tracer test and sampling technique for the larger scale, (3) a study on the reduction technique of uncertainty of the hydrogeological models using data from surface-based investigation. On the block scale tracer test technique, the sampling technique using wire saw and tracer test technique using block samples were suggested. As for the reduction technique of uncertainty of the hydrogeological model, availability of the information other than pressure data, such as the temperature and salinity and all, were presented.
Fujisaki, Kiyoshi; Suzuki, Hideaki*; Fujita, Tomoo; Ito, Akira*; Oda, Yoshihiro
Proceedings of 2nd International Conference on Coupled T-H-M-C Processes in Geo-systems; Fundamentals, Modeling, Experiments and Applications (GeoProc 2006), p.213 - 219, 2006/05
An important part of the safety assessments of near field in a geological disposal system of high-level radioactive waste consists an assessment of the coupled thermal-hydraulic-mechanical and chemical (THMC) phenomena. In order to validate the newly developed THMC model, the engineered scale experimental studies on the coupled THMC processes by COUPLE equipment have been carried out with a simulated engineered barrier surrounded by a mortar block. In this experiment, temperature at heater and side surface of mortar block was controlled at constant temperature, respectively. And high-pH water reacted with mortar infiltrates into the buffer material. This paper presents the results of measured data by various sensors during the experiment and sampling data of pH and leaching cations in buffer material after the experiment, in COUPLE equipment. And also the results of preliminary simulations on coupled T-H processes and chemical process in the experiment are described.
Aoyanagi, Shigeo; Oda, Yoshihiro; Sasamoto, Hiroshi; Shibata, Masahiro; Tanai, Kenji; Taniguchi, Naoki; Nishimura, Mayuka; Fujisaki, Kiyoshi; Kikuchi, Hirohito*; Matsumoto, Kazuhiro*
Hoshasei Haikibutsu Anzen Kenkyu Nenji Keikaku (Heisei-13-Nendo
Heisei-17-Nendo) Kenkyu Seika Hokokushu, p.179 - 203, 2006/03
no abstracts in English
Oda, Yoshihiro; Suzuki, Hideaki*; Kawakami, Susumu; Yui, Mikazu
JNC TN8400 2004-024, 55 Pages, 2005/02
JNC-TN8400-2004-024.pdf:1.29MB
The research for numerical experiments on the coupled Thermo -Hydro -Mechanical and Chemical (THMC) processes in the near-field of a high-level radioactive waste repository has been initiated, in order to increase reality in the near-field environmental condition adopted in the evaluation of engineered barrier design and performance assessment. As a part of this research, experimental studies on the coupled THMC processes by COUPLE equipment have been carried out. The COUPLE equipment simulates the coupled processes in the near-field after emplacement of the engineered barrier. The specimen of COUPLE equipment is composed of heater, buffer material and mortar block. In this experiment, temperature at heater and side surface of mortar block was kept at 100 and 70 Celsius's degree, respectively. And high-pH water reacted with mortar infiltrates into the buffer material. This report presents the results of measured data by Cation Exchange, X-Ray diffraction, and SEM/EDS. From these result, there is no large difference in buffer material between before and after this experiment.
; Oda, Yoshihiro;
Journal of Nuclear Science and Technology, 39(6), p.647 - 654, 2002/06
Times Cited Count：38 Percentile：89.68(Nuclear Science & Technology)None
Oda, Yoshihiro; Funasaka, Hideyuki; Wang, X.*; Obara, Kenji*; Wada, Hitoshi*
JNC TY8400 2000-002, 47 Pages, 2000/03
JNC-TY8400-2000-002.pdf:2.53MB
no abstracts in English
Oda, Yoshihiro; Koyama, Tomozo; Funasaka, Hideyuki
Hoshasei Haikibutsu Shori Shobun To Saishori Ni Kansuru Nicchu Wakushoppu, 0 Pages, 2000/00
None
Oda, Yoshihiro; Funasaka, Hideyuki; *
JNC TY8400 99-006, 30 Pages, 1999/03
no abstracts in English
Shigetome, Yoshiaki; ; Yamanouchi, Takamichi; Oda, Yoshihiro;
PNC TN8410 98-088, 48 Pages, 1998/05
At the fire and explosion incident of Bituminization Demonstration Facility, the fault of cell ventilation system (plugging of the HEPA filter) occurred in a short time. In addition the breakdown of the filter occurred at the explosion which happened ten hours after the extinguishment of the fire. Investigation of filter damage was conducted in order to know the extent of the breakdown, the contamination by radioactivity and soot mass gain of HEPA filter. Scanning electron micrograph (SEM) was also used to observe the appearance of soot adhesion on the filter media. This report shows the result of the investigation.
Oda, Yoshihiro; Funasaka, Hideyuki; *
PNC TY8604 98-001, 23 Pages, 1998/03
no abstracts in English
Oda, Yoshihiro; Funasaka, Hideyuki
Journal of Alloys and Compounds, 255(1-2), p.24 - 30, 1997/06
Times Cited Count：8 Percentile：54.47(Chemistry, Physical)None
Oda, Yoshihiro; Funasaka, Hideyuki
Proceedings of International Conference on Future Nuclear Systems (GLOBAL'97), 0 Pages, 1997/00
None
