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Sueoka, Shigeru; Ikeda, Yasutaka*; Kano, Kenichi*; Tsutsumi, Hiroyuki*; Tagami, Takahiro*; Kohn, B. P.*; Hasebe, Noriko*; Tamura, Akihiro*; Arai, Shoji*; Shibata, Kenji*
no journal, ,
no abstracts in English
Hayashida, Kazuki; Kato, Toshihiro; Kubota, Mitsuru; Iwatsuki, Teruki
no journal, ,
This study aims to understand the hydrogeochemical condition and dominant process after the drift closure. To this aim the drift closure experiment was conducted in the granitic rock of 500 m below ground level of Mizunami Underground Research Laboratory. The groundwater chemistry such as major chemical component, pH and redox condition has been monitored in closed drift for 1 year. Dominant processes on chemical evolution of isolated groundwater in the closed drift were identified as follows; continuous replacement by surround rock water, microbial reduction, water-mineral interactions with evaporite, shotcrete and granite.
Sasao, Eiji
no journal, ,
Science Council of Japan mentioned importance of establishment of technology to search rock body with minor fractures. It is significant to understand the fracture frequency in many rock bodies in Japan. The data widely obtained such as by borehole investigation should be available to characterise the fracture frequency. In this study, the speaker discussed the relationship between RQD (Rock Quality Designation) and fracture frequency focused on the Toki granite, central Japan. Fracture data were obtained by investigations in the boreholes drilled from the ground surface and the underground research galleries. There is a significant correlation between RQD value and fracture frequency. The data are then divided into 100 meters length and those RQD values are compared with fracture frequency. The RQD value is also associated with fracture frequency. This result indicates that the method proposed in this study can be ubiquitously applied to various lengths of borehole.
Murakami, Hiroaki; Watanabe, Takahiro; Iwatsuki, Teruki
no journal, ,
Long-term evolution of granitic-groundwater chemistry was calculated by thermodynamics analysis. This analysis is taking into account the actually-observed mineral assemble and residence time of groundwater. The result of this analysis suggest that long-term evolution of pH would be alkaline in case meteoric water remain a major part of recharge source of granitic-groundwater.
Sueoka, Shigeru
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no abstracts in English
Asamori, Koichi; Hama, Yuki; Umeda, Koji*; Tanaka, Hidemi*
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no abstracts in English
Shimizu, Mayuko; Sano, Naomi; Ueki, Tadamasa; Yasue, Kenichi; Niwa, Masakazu; Suzuki, Kazuhiro
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no abstracts in English
Niwa, Masakazu; Shimada, Koji
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In this study, we examined the relationship between development of quartz hydration and fault activity using secondary ion mass spectrometry (SIMS) analysis. This study shows that the SIMS analysis could be applicable for the estimation of hydration thickness of quartz along faults as well as the measurement of obsidian hydration thickness. The tests for still more samples should be further studies to examine geochronological application for fault activity.
Watanabe, Tsuyoshi; Asamori, Koichi
no journal, ,
no abstracts in English
He/
He ratios in the San-in shear zone, southwest JapanUmeda, Koji*; Asamori, Koichi; Saiga, Atsushi; Nishimura, Takuya*
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no abstracts in English
Ozaki, Yusuke; Onoe, Hironori; Takayama, Yusuke; Takayasu, Kentaro; Takeuchi, Ryuji
no journal, ,
The purpose of this study is to identify factors that dominate the saturation in bentonite mixture material during drift closure test. The bentonite mixture buried in two pits in the test drift is monitored to evaluate its hydro-mechanical behavior during the test. To clear the factors effective to the saturation in the mixture, we perform numerical simulation focusing on the effect of swelling, hydraulic conductivity and unsaturated characteristics in the mixture. Our simulation results show that the unsaturated characteristics of the mixture have the greatest effect on the saturation in the mixture. For accurate estimation of saturation change in the mixture, unsaturated characteristics data is key information.
Martin, A.*; Asamori, Koichi; Ishimaru, Tsuneari
no journal, ,
Assessing the stability of the geological environment including the spatio-temporal distribution of active faulting is of particular concern in the context of site selection of critical facilities such as nuclear power plants, spent fuel reprocessing facities as well as geological repositories or surface storage facilities of radioactive waste etc. Understanding the spatial distribution of active faulting is a particular challenge for geologists in that not all active faults have surface expressions. We present here a probabilistic approach based on Bayesian statistics that can be used to combine multiple datasets (in this case historic seismic data and helium isotopes sampled from wells) to produce hazard maps showing the likelihood of active faults existing or not.
Sato, Tatsuhiko; Kataoka, Ryuho*; Yasuda, Hiroshi*; Kubo, Yuki*; Ishii, Mamoru*; Miyake, Shoko*; Park, I.*; Miyoshi, Yoshizumi*
no journal, ,
Estimation of radiation doses for astronauts as well as aircrews due to the exposure to solar energetic particles (SEP) is one of the greatest challenges in space weather research. We are therefore developing a WArning System for AVIation Exposure to Solar energetic particle (WASAVIES), under the framework of Project for Solar-Terrestrial Environment Prediction (PSTEP). In the system, the SEP fluxes incident to the atmosphere are calculated by physics-based models. Thus, WASAVIES can estimate not only the current value but also time variation of the aircrew doses after a GLE event occurs. A brief outline of WASAVIES together with the status of on-going research subjects such as development of the automatic calculation algorithm will be presented at the meeting.
Kurikami, Hiroshi; Malins, A.
no journal, ,
Despite its affinity for binding to soil, radiocesium gradually migrates deeper into the ground over time. This results in a faster rate of reduction of air dose rates than would be expected by radioactive decay. Using radiation transport methods, this study calculated the trajectory of air dose rates over time given the evolution in the depth profile predicted by the model based on an advection-dispersion equation coupled with kinetic models of reversible/irreversible sorption. The results indicate a faster reduction in dose rates than the rate of radioactive decay in the first ten years following fallout, as there is a gradual migration of radiocesium in soil over this period. The rate of reduction of dose rates over the following years is then set by the rate of radioactive decay alone as the majority of the radiocesium has become fixed to the soil matrix.
King, G.*; Sueoka, Shigeru; Ahadi, F.*; Gautheron, C.*; Herman, F.*; Tagami, Takahiro*; Tsukamoto, Sumiko*
no journal, ,
no abstracts in English
Takayasu, Kentaro; Takeuchi, Ryuji; Onoe, Hironori
no journal, ,
The Groundwater REcovery Experiment in Tunnel (GREET) is conducted by making the Closure Test Drift (CTD) recovered with water at the depth of 500m. Backfilling test is conducted as a part of GREET to acquire physical property change of the backfill material. Bentonite mixture was constructed into two pits excavated 1m in depth on the floor of the CTD. Hydraulic pressure, soil pressure and moisture content were measured to grasp the groundwater saturation process and the swelling process of backfill material. The moisture content in the pits got almost fully saturated till one month after. During water filling event, both hydraulic pressure and soil pressure reached 3.1 MPa at maximum. The swelling pressure of the backfill was calculated as 0.03-0.09 MPa. Observation inside the pit will be continued, and characteristics of backfill material will be investigated again. Changes of hydraulic pressure and soil pressure will be simulated and the construction method will be validated.
Fukuda, Shoma*; Sueoka, Shigeru; Hasebe, Noriko*; Tamura, Akihiro*; Arai, Shoji*; Tagami, Takahiro*
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no abstracts in English
Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.
no journal, ,
For the evaluation of the validity and variability of atmospheric transport model results, we compared results of seven models submitted for the model inter-comparison project of Science Council of Japan to simulate 
Cs released from the Fukushima Daiichi Nuclear Power Plant. Model reproducibility was assessed with the observed hourly atmospheric concentrations of Cs in Tohoku and Kanto regions. Among nine plumes from 12 to 21 in March 2011, performance of the models was the best for the plume which dispersed over the Kanto region in 15 March. The models generally reproduced the observed Cs concentrations in plumes which widely spread inland of Tohoku or Kanto regions. By contrast, the models largely underestimated the observed Cs concentrations for the case which passed coastal areas of Japan. Ensemble average of seven models showed reasonable performance for most of plumes, and no individual models reproduced better than the ensemble average.
Komatsu, Tetsuya; Izumida, Atsuto*; Oka, Takahiro*; Takahashi, Takayuki*; Nomura, Katsuhiro; Yasue, Kenichi; Sugai, Toshihiko*
no journal, ,
no abstracts in English
-montmorilloniteKawakita, Ryohei*; Saito, Akito*; Sakuma, Hiroshi*; Anraku, Sohtaro; Oda, Chie; Mihara, Morihiro; Sato, Tsutomu*
no journal, ,
no abstracts in English