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Nakanishi, Toshimichi*; Komatsu, Tetsuya; Ogata, Manabu; Kawamura, Makoto; Yasue, Kenichi*
Gekkan Chikyu "Kiso deta Kara Kangaeru Dai Yonkigaku No Shintenkai-I" Gogai No.71, p.148 - 155, 2022/02
The formation process of terrace topography was investigated by observing and analyzing boring core samples collected in the middle reaches of the Kumano River. It was assumed that the older terrace topography was distributed higher than the current riverbed surface. However, since tributary debris flow deposits may be thickly distributed beneath the old gyre river valley, care must be taken when using the surface of the ground as an index of uplift and erosion.
Yamaguchi, Masaaki; Kato, Tomoko; Suzuki, Yuji*; Makino, Hitoshi
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(2), p.72 - 82, 2020/12
An efficient analytical tool to calculate temporal change of topography and repository depth due to uplift and erosion was developed for use in performance assessment of high level radioactive waste geological disposal. The tool was developed as ArcGIS model, incorporating simplified landform development simulation, to enable trial calculation of various conditions such as initial topography, uplift rate and its distributions, and repository location. This tool enables to support decision on which processes, features, and their changes should be taken into account for performance assessment, by calculating topography change and repository depth change under various conditions.
Shimada, Taro; Takeda, Seiji; Mukai, Masayuki; Munakata, Masahiro; Tanaka, Tadao
Materials Research Society Symposium Proceedings, Vol.1744, p.229 - 234, 2015/04
Integrated safety assessment methodology which analyzes radionuclide migration reflecting the spatial and temporal changes of disposal systems was developed for a geological disposal site with uplift and denudation, and then some case analyses for an assumed site with sedimentary rocks were carried out. The combination of uniform uplift and denudation has the most effect on the radionuclide migration because the groundwater flow velocity increases with decreasing the depth from the ground surface. In the case without denudation, tilted uplift has more effect than uniform uplift because flow velocity in tilted uplift increase with increasing hydraulic gradient. The long-term change of the geological structures including the uplift and denudation, the hydraulic conditions, and the recharge and outlet of the groundwater around a candidate site should be carefully investigated to determine the appropriate the place,depth and layout of the repository.
Shimada, Taro; Takubo, Kazuya; Takeda, Seiji; Tanaka, Tadao
no journal, ,
In long-term safety assessment of geological disposal system, it is necessary to evaluate the impact on the nuclides migration where groundwater flow and water composition are changed with decreasing a depth of the repository by uplifts and denudation. Therefore, we developed an integrated safety assessment methodology for uplifts and denudation where nuclides migration was evaluated reflecting temporal and spatial changes of parameters of natural and engineered barriers such as distribution coefficient, porosity and groundwater velocity, which were obtained by calculation of groundwater flow, salt water distribution and long-term transition of engineered barriers. The methodology was applied to an assumed disposal site composed of sedimentary rocks with uplift and denudation. Migration parameters of engineered barrier such as coefficient of water permeability and porosity of buffer material were evaluated considering the interaction between overpack and surrounding bentonite clay under the condition of water composition. Migration parameters of the natural barrier such as distribution coefficient were determined by the combination of the geology section and water composition section on the migration pathway from the repository to the outlet of the natural barrier at the depth of 40m from the surface. The migration fluxes of some radionuclides at the outlet of natural barrier were evaluated and then the impacts on nuclides migration by uplifts and denudation were compared.
Takeda, Seiji; Munakata, Masahiro; Namekawa, Maki; Sakai, Ryutaro; Shimada, Taro; Tanaka, Tadao
no journal, ,
In long-term safety assessment of geological disposal system, it is necessary to evaluate the impact on the radionuclides migration where groundwater flow and water composition are changed with decreasing a depth of the repository by uplifts (two types: uniform and tilted) and denudation. We developed an integrated safety assessment methodology for uplifts and denudation where radionuclides migration analysis was combined with calculation results of groundwater flow and salt concentration distribution in a disposal site and of long-term transition of engineered barriers to estimate their properties and migration parameters. Assuming disposal site composed of sedimentary rocks with uplifts and denudation, we carried out the sensitivity analyses on groundwater velocity and salt concentration and indicated the requirements for future investigation of natural barrier related to uplifts and denudation at a candidate site from the estimation results.
Yamaguchi, Tetsuji
no journal, ,
no abstracts in English
Sakamoto, Michihito*; Wakasugi, Keiichiro*; Kabasawa, Satsuki; Yamaguchi, Masaaki
no journal, ,
no abstracts in English
Kabasawa, Satsuki; Sakamoto, Michihito*; Takahashi, Yuta; Yamaguchi, Masaaki
no journal, ,
no abstracts in English
Kawamura, Makoto; Jia, H.*; Koizumi, Yukiko*; Nishiyama, Nariaki; Umeda, Koji*
no journal, ,
Using topographical analysis with GIS using 10 m DEM, we created 2 km river crossing lines on each side of the three rivers, Abegawa, Oigawa and Kumanogawa, starting from the estuary and going straight to the course of the river every 3 km. In addition, the geological information of the river transverse line was extracted. When the cross-sectional lines of the three rivers are displayed together, it can be seen that the river bed rises and the undulations increase as it goes upstream. A comparison of the cross-sectional shapes of the three rivers reveals similar trends, with peaks of undulations on both sides of the rivers in the middle to upper reaches located approximately 500-1,500 m from the center of the river. The relative height between bed and peak also tends to be around 200-600 m. The difference in elevation between the peaks on both sides of the river and the river bed increased in the upstream direction, that is, the depth of the valley to the river bed increased in the upstream direction. When the riverbed slope of the river longitudinal created from the riverbed elevation was taken, an inflection points where the slope trend rose from the upstream area was seen in all three rivers regardless of the geology and geological structure. Although the trend of elevation of the riverbed and increase in undulations from the relatively flat landform near the mouth of the river upstream is pseudo, it suggests a temporal process of landform formation due to uplift and denudation from the flat lowland. This will be information that contributes to verification of the validity of future predictions and performance evaluation models that incorporate topographical changes, such as topographical change simulations.
Kabasawa, Satsuki; Sakamoto, Michihito*; Takahashi, Yuta; Yamaguchi, Masaaki
no journal, ,
no abstracts in English
