Yamaguchi, Masaaki; Maekawa, Keisuke; Takeuchi, Shinji*; Kitamura, Akihiro; Onishi, Yasuo*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 20(2), p.53 - 69, 2013/12
We developed a simple novel and fast simulation model to predict a long-term distribution of Cs deposited on the land surface of Fukushima due to the Fukushima Dai-ichi Nuclear Power Plant accident triggered by a magnitude 9.0 earthquake and resulting tsunami on 11 March 2011. The model utilizes the Geographical Information System (GIS) to integrate online open data provided by individual institutes, and simulate mechanisms of soil erosion, transport and sedimentation. A preliminary calculation shows the significant deposition of sediments in lakes and reservoirs and eroded silt and clay tend to be transported downstream to river mouths than eroded sand. These results were found to be qualitatively consistent with existing data.
Yokota, Hideharu; Amano, Kenji; Maekawa, Keisuke; Kunimaru, Takanori; Naemura, Yumi*; Ijiri, Yuji*; Motoshima, Takayuki*; Suzuki, Shunichi*; Teshima, Kazufumi*
JAEA-Research 2013-002, 281 Pages, 2013/06
To evaluate permeable heterogeneity in a fracture and scale effects which are problems to be solved based on the mass transportation data of fractures in hostrock, a number of tracer tests are simulated in a fictitious single plate fracture generated on computer in this study. And the transport parameters, e.g. longitudinal dispersion length, true velocity and dilution rate, are identified by fitting one- and two-dimensional models to the breakthrough curves obtained from the simulations in order to investigate the applicability of these models to the evaluation of tracer test. As a result, one-dimensional model yields larger longitudinal dispersion length than two-dimensional model in the both cases of homogeneous and heterogeneous hydraulic conductivity fields of the fictitious fracture. And, the longitudinal dispersion length identified from a tracer test is smaller and/or larger than the macroscopic longitudinal dispersion length identified from whole fracture. It is clarified that these are occurred by shorter or longer distance between boreholes compare to the correlation length of geostatistical heterogeneity of fictitious fracture.
Komatsu, Mitsuru*; Nishigaki, Makoto*; Seno, Shoji*; Hirata, Yoichi*; Takenobu, Kazuyoshi*; Tagishi, Hirotaka*; Kunimaru, Takanori; Maekawa, Keisuke; Yamamoto, Yoichi; Toida, Masaru*; et al.
JAEA-Research 2012-001, 77 Pages, 2012/09
This research focused on methods of estimating the amounts of groundwater recharge, which are normally required as upper boundary conditions in groundwater flow analyses, based on measurements of infiltrating water in the ground, to systematize the methods and establish systems which are stable and measurable on site over a long time. Regarding developing measurement systems, fiber-optic strain measurement methods that enable multiple-point and long-distance measurement were used for measuring three quantities: suction pressure, soil moisture and volumetric water content rate obtained by applying water absorption swelling material, and each measurement was discussed. The results showed that the fiber-optic soil aquameter has two types of practical application: one for measuring suction pressure (Type I), and the other for measuring volumetric water content rate obtained by applying water absorption swelling material (Type III). Furthermore, by using measurement instruments in actual fields, the validity of the two methods for estimating the rainfall infiltration capacities of shallow-layer soils, that is, estimating the capacities either directly by measurements of soil water or from unsaturated hydraulic conductivities, was confirmed.
Inagaki, Manabu*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Maekawa, Keisuke; Shibata, Masahiro
JAEA-Research 2011-056, 37 Pages, 2012/03
In Japan, a step-wise approach is applied in the site selection process for the geologic disposal site. Preliminary surface-based investigations will be followed by detailed investigations. The basic repository concept, including underground design and layout, will be discussed at the end of surface-based investigations. The repository concept will depend on the spatial extent of the candidate rock formation(s) and their barrier performance. However, information obtained from the surface is limited and includes uncertainties. It is thus important to assess host rock performance considering uncertainties. In this study, methodology for evaluation of geological conditions has been developed that focuses on determining the usable volume of host rock with specific performance characteristics. Initially, multiple performance indices have been discussed and defined from the viewpoint of barrier performance. Then the evaluation procedure is illustrated by using the dataset obtained from the Horonobe Underground Research Laboratory Project. Finally the proposed procedure is reviewed and future challenges are extracted.
Yamamoto, Yoichi; Maekawa, Keisuke; Yokota, Hideharu; Yamazaki, Masanori
JAEA-Research 2011-042, 97 Pages, 2012/02
The surface hydrogeological investigation has been carried out in and around the Horonobe Underground Research Laboratory area as a part of Horonobe URL project. Observations of meteorological, river flux, water quality, soil moisture and groundwater level have been continued in order to understand the groundwater recharge rate and groundwater flow in the shallow part, which are required for the setting of boundary and initial condition of the groundwater flow analysis. This report shows the summary of the surface hydrogeological investigation and results of recharge rates of investigation basins from December 2004 to November 2009 are calculated by using the water budget method. Spatial estimation of hydrological quantities for the groundwater recharge rate is demonstrated by the runoff analysis. As a result, average of the groundwater recharge rate of whole basins is estimated to 131mm/yr. Suggestive observations related to hydraulic properties of the geology and faults are obtained from consideration to the groundwater recharge rate for each basin.
Maekawa, Keisuke; Osada, Masahiko*
Dai-41-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.53 - 58, 2012/01
It has been known that the rock material properties would be different from the condition before excavation due to air-ventilation into the shaft. The phenomena would be significant to assess a long-term geological disposal safety. But any methodologies to understand the effect have not been established yet. This paper shows the results of rock tests for engineering properties including drying-induced deformation experiment as one part of establishing research and assessment methodologies of the sedimentary rock material properties. As a result we show the tendency of drying-induced deformation of diatomaceous mudstone and the significant points of rock tests for engineering properties.
Komagata, Eiichi*; Kawasuso, Atsuo; Yabuuchi, Atsushi*; Maekawa, Masaki; Batchuluun, C.*; Yasuda, Keisuke*; Ishigami, Ryoya*; Kume, Kyo*; Iwase, Akihiro*; Hori, Fuminobu*
Physics Procedia, 35, p.75 - 79, 2012/00
Fe48-at.% Al alloy were implanted with 50 keV H ions to the fluence of 310 and 110 /cm at room temperature. Positron annihilation Doppler broadening and lifetime measurements for these alloys have been carried out using slow positron beam apparatus with an energy range of 0.2 to 30.2 keV. The positron annihilation S-parameter decreased by H ion irradiation. Also the positron lifetimes for hydrogen deposited region in the alloy decreased by the irradiation. These results show that implanted H atoms were trapped by vacancy type defects.
Niizato, Tadafumi; Imai, Hisashi*; Maekawa, Keisuke; Yasue, Kenichi; Kurikami, Hiroshi; Shiozaki, Isao*; Yamashita, Ryo*
Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 10 Pages, 2011/10
A critical issue for building confidence in the long-term safety of geological disposal is to demonstrate the stability of the geosphere, taking into account its likely future evolution. This study aims to establish comprehensive techniques for characterising the overall evolution of coastal sites through studying the palaeohydrogeological evolution in the coastal system around the Horonobe area, Hokkaido, northern Japan. Information on natural events and processes related to the palaeohydrogelogical evolution of the area have been integrated into the conceptual models that indicates the temporal and spatial sequences of the events and processes, such as climatic and sea-level changes, palaeogeography, and geomorphological and geological evolution in the area. The groundwater flow simulation, which is based on the conceputualisation of the long-term geosphere evolution, shows the sensitivities of natural events and processes on groundwater flow properties in a coastal setting.
Yokota, Hideharu; Yamamoto, Yoichi; Maekawa, Keisuke
Chikasui Gakkai-Shi, 53(2), p.193 - 206, 2011/05
It is important for assessing the safety of geological disposal of high-level radioactive waste to understand shallow to deep groundwater flow as the driving force of mass transport. JAEA has been carrying out the surface hydrological investigation in the Horonobe area, Hokkaido. Results of groundwater-level observations, and relationship between distributions of groundwater-level and geological structures suggest that constructions of underground facilities have no effect on shallow groundwater-level fluctuations, and that water infiltrate from ground surface into shallow underground in the snow covered season, and that water infiltrate into deeper underground along faults. In the future, it is necessary to quantitatively assess the water infiltration and recharge based on directly and/or indirectly observed data of evapotranspiration and soil moisture content by weighing lysimeter and ADR method soil moisture meter, and tensiometer.
Itazu, Toru; Kato, Tomoko; Maekawa, Keisuke
Nippon Chikasui Gakkai 2011-Nen Shunki Koenkai Koen Yoshi, p.34 - 39, 2011/05
Biosphere assessment, which is a part of safety assessment for geological disposal of radioactive waste, addresses the migration of radionuclide from underground to near the ground surface. Advection-dispersion calculation for this purpose must take into the consideration the following factors: long-distance migration of solute, a requirement to calculate the inflow of solute into the rivers or sea bed supposed to be the final position, demand to control numerical dispersion in heterogeneous field. In this study, we adopt the Random-Walk Method having functions required to biosphere assessment and developed a program available to groundwater analysis by using MODFLOW. The program is verified by comparison with the analytical solution and studied about application method to biosphere assessment.
Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; Sasamoto, Hiroshi; Yoshikawa, Hideki; Shibata, Masahiro; et al.
JAEA-Research 2011-001, 193 Pages, 2011/03
This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project, of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological conditions obtained from the surface-based investigations in the Horonobe Underground Research Laboratory project as an example of actual geological environment.
Yamamoto, Yoichi; Maekawa, Keisuke; Yabuuchi, Satoshi; Yokota, Hideharu
Nippon Chikasui Gakkai 2010-Nen Shuki Koenkai Koen Yoshi, p.166 - 171, 2010/11
no abstracts in English
Yokota, Hideharu; Yamamoto, Yoichi; Yamazaki, Masanori; Maekawa, Keisuke
Nippon Chikasui Gakkai 2010-Nen Shuki Koenkai Koen Yoshi, p.160 - 165, 2010/11
no abstracts in English
Yamamoto, Yoichi; Maekawa, Keisuke
JAEA-Data/Code 2010-014, 105 Pages, 2010/10
Horonobe Underground Research Center has carried out meteorological observation in Horonobe-cho as a part of the Horonobe URL project. Meteorological observation in Horonobe-cho was started at Kaishin meteorological station on October 1986, and then Toikanbetsu meteorological station, Kamitoikan meteorological station, Horonobe downtown meteorological station, Hokushin meteorological station and Hokushin evapotranspiration tower were established sequentially, meteorological observations were conducted at a total of 6 points in the end. The meteorological observation data in Horonobe-cho from 1986 to 2009 is compiled in this report. Meteorological characteristics of Horonobe-cho are investigated using statistics data. Hourly data, daily data and monthly data are included in the data set, and the data set is recorded on CD-ROM.
Saegusa, Hiromitsu; Takeuchi, Shinji; Maekawa, Keisuke; Osawa, Hideaki; Semba, Takeshi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.133 - 140, 2010/10
Yokota, Hideharu; Yamamoto, Yoichi; Maekawa, Keisuke; Hara, Minoru*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.81 - 86, 2010/10
It is important for assessing the safety of geological disposal of high-level radioactive waste to understand groundwater flow as the driving force of mass transport. In the groundwater-flow simulation, hydraulic boundary conditions are required, including groundwater recharge rates. However, infiltration of water from the surface is difficult to clarify in detail because water near the surface is sensitive to external influence such as climatic variations. In the Horonobe area of northern Hokkaido, the Japan Atomic Energy Agency has been carrying out various hydrological observations to estimate the recharge rate. In the Horonobe area, subsurface temperature and soil moisture content have been observed at HGW-1 site and Hokushin Meteorological Station. These results have revealed the groundwater infiltration and recharge occurring throughout year, the shallow groundwater-infiltration velocity depending on the depth, and the position of Zero Flux Plane. In the future, it is necessary to quantitatively assess the shallow groundwater infiltration and recharge rate, the intermediate runoff, and the evapotranspiration based on the observed data of the weighing lysimeter, the tensiometer, and so on.
Maekawa, Keisuke; Makino, Hitoshi; Kurikami, Hiroshi; Niizato, Tadafumi; Inagaki, Manabu; Kawamura, Makoto*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.71 - 80, 2010/10
It is important for establishing safety assessment techniques of HLW geological disposal to understand groundwater flow and solute transport. We have carried out groundwater flow and solute transport analysis using geological and hydrological information from surface-based investigations in the Horonobe area. From this study, a methodology to integrate activities from site investigations and evaluation to solute transport analysis was tested. We have been also carrying out a simulation of groundwater flow and salinity concentration distribution using information on geological evolution considering the impacts of natural events and processes. From the result, we could outline the impacts of natural events and processes on geological environments. We plan to apply a methodology of groundwater flow and solute transport analysis to the shallow part, the Horonobe coastal area. It must be important techniques in support of generic safety assessment for future geologic disposal in Japan.
Yamamoto, Yoichi; Maekawa, Keisuke; Yokota, Hideharu; Mukai, Kazuyuki*; Ishii, Keiji*
Doboku Gakkai Heisei-22-Nendo Zenkoku Taikai Dai-65-Kai Nenji Gakujutsu Koenkai Koen Gaiyoshu (DVD-ROM), p.525 - 526, 2010/09
no abstracts in English
Maekawa, Keisuke; Saegusa, Hiromitsu; Inaba, Kaoru*; Shimogochi, Takafumi*
JAEA-Research 2010-001, 238 Pages, 2010/07
In the design and safety assessment of the geological disposal system of the high-level radioactive waste (HLW), it is extremely important to improve the reliability of the evaluation of the investigation of the geological environment, which provides technical basis. Especially, the knowhow and the experience of groundwater flow modeling based on the data acquired in deep underground at the coastal area are needed to be enhanced because these are little. Against this background, we have carried out modeling and groundwater flow simulation of the Horonobe coastal area. The knowledge and the knowhow acquired through this work were accumulated and arranged as a knowledge base by executing the following items. (1)The discussion of applicability of the workflow of evaluation of the groundwater flow for the coast region, and extension and update according to need. (2)Understand of groundwater flow based on existing investigation result in Horonobe coastal area, (2-1)Estimation of distribution of salinity in groundwater, (2-2)Extraction and arrangement of knowhow and judgment basis in modeling and simulation works. As a result, the knowledge was expanded concerning the groundwater flow evaluation methodology needed in design and safety assessment of the geological disposal system that is able to correspond to various geological environments in our country.
Yokota, Hideharu; Tomura, Goji; Maekawa, Keisuke
Proceedings of 3rd International Workshop and Conference on Earth Resources Technology 2009 (CD-ROM), p.169 - 178, 2009/12
Japan Atomic Energy Agency has been carrying out Horonobe Underground Research Laboratory Project for understanding of characteristics of the geological environment as a part of research and development programs on geological disposal of high-level radioactive waste. As developing techniques for long-term monitoring of geological environment, we have been measuring the groundwater pressure using boreholes in order to monitor any influences due to the construction of the underground facilities. The results from examination of relations with the data of the long-term monitoring of groundwater pressure, geological characteristics obtained from the drilling cores, logging data and hydraulic characteristics of the boreholes suggest the existing of the continuative hydrogeological structure at the neighborhood of a feature geological boundary, and that the distribution of continuative hydrogeological structures around the underground facilities depends on the geological characteristics not the depth from ground level.