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Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji
JAEA-Data/Code 2020-007, 174 Pages, 2020/09
JAEA-Data-Code-2020-007.pdf:4.23MB
The MIG2DF computer code is a computer program that simulates groundwater flow and radionuclide transport in porous media for the safety assessment of radioactive waste disposal. The original version of MIG2DF was released in 1992. The original code employs a two-dimensional (vertical or horizontal cross-section, or an axisymmetric configuration) finite-element method to approximate the governing equations for density-dependent saturated-unsaturated groundwater flow and radionuclide transport. Meanwhile, for geological disposal of radioactive wastes, landscape evolution such as uplift and erosion needs to be assessed as a long-term geological and climate events, considering site conditions. In coastal areas, the impact to groundwater flow by change of salinity distribution to sea level change also needs to be considered. To deal with these events in the assessment, we have revised the original version of MIG2DF and developed the external program which enables MIG2DF to consider unsteady landscape evolution. In these developments, this report describes an upgrade of MIG2DF (Version 2) and presents the configuration, equations, methods, and verification. This reports also give the explanation external programs of MIG2DF: PASS-TRAC (the particle tracking code), PASS-PRE (the code for dataset preparation), and PASS-POST (the post-processing visualization system).
Onoe, Hironori; Kosaka, Hiroshi*; Matsuoka, Toshiyuki; Komatsu, Tetsuya; Takeuchi, Ryuji; Iwatsuki, Teruki; Yasue, Kenichi
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(1), p.3 - 14, 2019/06
In this study, it is focused on topographic changes due to uplift and denudation, also climate perturbations, a method which is able to assess the long-term variability of groundwater flow conditions using the coefficient variation based on some steady-state groundwater flow simulation results was developed. Spatial distribution of long residence time area which is not much influenced due to long-term topographic change and recharge rate change during the past one million years was able to estimate through the case study of the Tono area, Central Japan. By applying this evaluation method, it is possible to identify the local area that has low variability of groundwater flow conditions due to topographic changes and climate perturbations from the regional area quantitatively and spatially.
Takeuchi, Ryuji; Onoe, Hironori; Yasue, Kenichi
no journal, ,
In geological disposal for high-level radioactive waste, time scale for assessment is equal to or more than several hundreds of thousand years. During this time, the surface hydrological environment might change. Especially, changes of precipitation, evapotranspiration and runoff volume might cause a change of groundwater recharge rate (GRR), which is upper boundary condition of groundwater flow for deep underground. This study shows the method to estimate GRR considering the influence of changes for climate condition and landform condition as an example in Tono area. The GRRs of 0.45 Ma are estimated 118% to 237% of the current GRR, and the GRRs of 0.14 Ma are estimated 81% to 196% of the current GRR. In the result of current topography in the glacial period, the recharge rate is estimated 58% to 72% of the current GRR. However it's not possible to estimate the runoff volume based on the topography of 1.0 Ma, which is estimated poor undulations and flat terrains.
Shimada, Taro; Uchikoshi, Emiko*; Takai, Shizuka; Takeda, Seiji
no journal, ,
Long-term topographic change due to uplift, denudation and eustasy may change the field of groundwater flow and nuclide migration when radioactive wastes are disposed at the repository near the sea. In this report, we constructed the frame work for evaluating uncertainties of future topograophic changes. Using the evaluation code under developing at JAEA, we tried evaluating the future topographic change until 0.125k years after for catchment basin near the sea.
Takeda, Seiji
no journal, ,
no abstracts in English
