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Masuda, Kenta; Oda, Chie; Nakanishi, Hiroshi*; Sasaki, Ryoichi*; Takase, Toshio*; Akagi, Yosuke*; Fujita, Hideki*; Negishi, Kumi*; Honda, Akira
JAEA-Research 2008-104, 194 Pages, 2009/03
JAEA-Research-2008-104.pdf:9.43MB
Saline groundwater contains high concentrations of chloride ions, which possibly elevate the pH of cement pore water by reacting with hydrogarnet and producing Friedel's salt. Calcium aluminate hydrates and portlandite, which can be found in hydrated ordinary Portland cement (OPC), were immersed in a sodium chloride solution, which had concentrations similar to those found in seawater.
Ishitoya, Kimihide; Nakatani, Takayoshi; Funabashi, Hideyuki; Sasaki, Ryoichi*; Takase, Toshio*; Kurosawa, Mitsuru*
JAEA-Research 2008-092, 64 Pages, 2008/12
JAEA-Research-2008-092.pdf:6.33MBJAEA-Research-2008-092(errata).pdf:0.23MB
In this study, some scenarios for safety assessments were developed. According to each developed scenario, the parameters were set up for dose calculation. Calculated results were analyzed and summarized from the viewpoints of effects of radionuclide migration parameters such as release coefficient, distribution coefficient, ground water velocity and migration distance. Dose more than 10 
Sv/y was calculated in some cases. Increase of ground water velocity or decrease of distribution coefficient caused by sea water inflow into migration path influenced slightly on the dose excess. In case of rapid change of the parameters, severe influences on the dose excess were observed. But, it wasn't thought that this rapid change would happen actually. On the other hand, in case of linear assumption of parameter change from 10,000 y to 100,000 y, dose less than 10 Sv/y was calculated.
Tsujimura, Seiichi; Funabashi, Hideyuki; Ishibashi, Makoto*; Takase, Toshio*; Kurosawa, Mitsuru*
JAEA-Research 2007-030, 105 Pages, 2007/03
JAEA-Research-2007-030.pdf:7.72MB
Uranium waste has characteristics that it is rarely expected to decay its radioactivity and it is not almost recessary to consider external exposure to radiation from waste package. We studied resonable sub-surface disposal concepts for uranium waste considering the characteristics. It showed feasibility of this system. In 2006, the study was done to evaluate the correlation between dose to the public and the parameter in consideration of the uncertainty of the parameter by comprehensive sensitivity analysis calculating repeatedly dose with the data sets by random sampling in parameter ranges given adequately, because last year's study was an evaluation intended for a limited site. The result was that two parameters, "flow velocity of underground water of repository neighborhood" and "distribution coefficient of uranium in natural barrier", had correlation with dose to the public.
Tsujimura, Seiichi; Funabashi, Hideyuki; Ishibashi, Makoto*; Takase, Toshio*; Kurosawa, Mitsuru*
JAEA-Research 2006-029, 96 Pages, 2006/07
JAEA-Research-2006-029.pdf:3.97MB
Uranium waste has characteristics that it is rarely expected to decay its radioactivities and it is not almost necessary to consider external exposure to radiation from waste package. We studied reasonable sub-surface disposal concepts for uranium waste in 2004 and 2005 considering the characteristics. In 2005, we studied necessity of engineered barrier for the disposal of uranium waste, considering change of chemical condition around disposal facilities over long periods of time. Safety assessment was made to analyze effect of difference in sorption parameters at reduction and oxidation conditions. The assessment showed that change from reduction to oxidation around disposal facilities did not lead to increase dose to the public. The assessment with realistic sorption parameters showed that dose to the public was not more than 10 Sv/y. The results proved that it was not necessary to keep reduction conditions around disposal facilities. This two-year- study showed that there was possibility of sub-surface disposal system without engineered barrier for uranium waste.
Seki, Yasushi; Kurihara, Ryoichi; Nishio, Satoshi; Ueda, Shuzo; Aoki, Isao; Ajima, Toshio*; Kunugi, Tomoaki; Takase, Kazuyuki; Shibata, Mitsuhiko
Fusion Engineering and Design, 42(1-4), p.37 - 44, 1998/09
Times Cited Count：1 Percentile：15.03(Nuclear Science & Technology)no abstracts in English
Kurihara, Ryoichi; Ajima, Toshio*; Kunugi, Tomoaki; Takase, Kazuyuki; Shibata, Mitsuhiko; Seki, Yasushi; *; Yamauchi, Michinori*; *; *
Fusion Engineering and Design, 42, p.61 - 66, 1998/00
Times Cited Count：7 Percentile：53.8(Nuclear Science & Technology)no abstracts in English
Kurihara, Ryoichi; Seki, Yasushi; Ueda, Shuzo; Aoki, Isao; Nishio, Satoshi; Ajima, Toshio*; Kunugi, Tomoaki; Takase, Kazuyuki; Yamauchi, Michinori*; *; et al.
Journal of Fusion Energy, 16(3), p.225 - 230, 1997/00
Times Cited Count：3 Percentile：30.37(Nuclear Science & Technology)no abstracts in English
Shirai, Hiroshi; Hirayama, Toshio; Shimizu, Katsuhiro; Tani, Keiji; Azumi, Masafumi; Hirai, Kenichiro*; Konno, Satoshi*; Takase, Keizo*
JAERI-M 93-026, 97 Pages, 1993/02
no abstracts in English
Nakanishi, Hiroshi; Honda, Akira; Oda, Chie; Sasaki, Ryoichi; Fujita, Hideki*; Negishi, Kumi*; Takase, Toshio*; Akagi, Yosuke*
no journal, ,
no abstracts in English
Yamaguchi, Kohei; Oda, Chie; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Takase, Toshio*
no journal, ,
In this research, the batch immersion experiment and the flow-through column experiment of granite and the artificial highperalkaline pore water were conducted, and the main geochemistry reaction was examined. A change with the lapse of time of the saturation index was calculated by the chemical equilibrium computation based on the batch immersion experiment result. The secondary mineral with the possibility of precipitation in the liquid phase based on the calculation result was extracted, and the combination was examined. In addition, the combination of these secondary minerals was applied to the flow-through column experiment result, and the liquid phase composition after the flow-through and the secondary mineral's spatial distribution were compared with geochemistry calculation (PHREEQC) result. As a result, it has been understood to have to understand the main geochemistry reaction paying attention at the precipitation rate of the secondary mineral in the future.
Yamaguchi, Kohei; Oda, Chie; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Takase, Toshio*
no journal, ,
High alkaline pore water runs out from a large amount of cementitious material used for the TRU waste disposal to the host rock, and there is a possibility that the migration characteristic of the nuclide. Here, the applicability of a chemical model in the environment with water flow was evaluated by the viewpoint of the solution composition and the precipitation composition by conducting the experiment that passed high alkaline solution to the column. As a result, a change with the lapse of time of the concentration was able to be reproduced almost for the solution composition. Moreover, the precipitation of Al was not able to be reproduced though Ca and Si were able to be wide in the column. The thermodynamics data of the secondary mineral including Al, the maintenance of the precipitation rate, and the applicability examination to the experiment result etc. are profitable as future tasks.
Nakatani, Takayoshi; Funabashi, Hideyuki; Ishitoya, Kimihide; Sasaki, Ryoichi*; Takase, Toshio*; Kurosawa, Mitsuru*
no journal, ,
no abstracts in English
Shimoda, Satoko*; Saito, Hironori*; Takase, Toshio*; Yamaguchi, Kohei; Oda, Chie; Honda, Akira
no journal, ,
The unstable primary mineral is dissolved and the precipitation of a steadier secondary mineral happens thermodynamically when a high alkaline groundwater of the cement system material origin is infiltrated from the radioactive waste geological disposal facilities to a peripheral bedrock. Therefore, the pore structure of the hostrock changes by the precipitation and dissolution, and the material transportation characteristic of the bedrock changes. It is necessary to decide the chemical reaction scheme for the analysis. However, the combination of the secondary minerals exists innumerably. Therefore, granite was assumed to be an example by summarizing the chemical reaction scheme in the mineral alteration scenario, and the mineral alteration scenario concerning the reaction with a high pH groundwater was presented. It dealt with the uncertainty concerning the mineral alteration by preparing two or more scenarios with a different alteration route.
