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Sekioka, Yasushi*; Takeda, Seiji; Kimura, Hideo
JAEA-Research 2009-062, 68 Pages, 2010/03
JAEA-Research-2009-062.pdf:3.62MB
In safety assessment for geological disposal, release of radionuclides from vitrified waste is dependent on dissolution rate of glass matrix. It is assumed that the alteration and dissolution of glass in an engineered barrier system proceeds by a mechanism not related by the chemical affinity for dissolution reaction of glass matrix. Recent studies indicate that the glass dissolution rate is likely to decrease as time passed, but scientific basis on the dissolution process has not been necessarily understood. We estimate uncertainty of the glass dissolution rate represented by not only a model of constant dissolution rate but also a model of decreasing dissolution rate. In order to estimate the parameter uncertainty of the glass dissolution rate, we carried out the statistical analysis of the appropriate release rate data of boron for a hypothetical condition of disposal system, based on investigating the relation between published data of glass dissolution and those experimental conditions. As a result of the model of constant dissolution rate, the uncertainty of the glass dissolution rate is estimated to be a variance with about 3 orders and logarithmic mean of 0.004 g/m
/day. The glass dissolution rate by the decreasing model changes in the range of 10
to 10
g/m/day by 1000 years and is lower than the minimum value estimated by the model of constant dissolution rate. The result indicates that the difference of two models may lead to large variance of the glass dissolution rate in safety assessment.
Takeda, Seiji; Yamaguchi, Tetsuji; Nagasawa, Hirokazu; Watanabe, Masatoshi; Sekioka, Yasushi; Kanzaki, Yutaka; Sasaki, Toshihisa; Ochiai, Toru; Munakata, Masahiro; Tanaka, Tadao; et al.
JAEA-Research 2009-034, 239 Pages, 2009/11
JAEA-Research-2009-034.pdf:33.52MB
In safety assessment for geological disposal of high level radioactive waste, it is of consequence to estimate the uncertainties due to the long-term frame associated with long-lived radionuclides and the expanded geological environment. The uncertainties result from heterogeneity intrinsic to engineered and natural barrier materials, insufficient understanding of phenomena occurring in the disposal system, erroneous method of measurement, and incomplete construction. It is possible to quantify or to reduce the uncertainties according to scientific and technological progress. We applied a deterministic and a Monte Carlo-based probabilistic method simulation techniques to the uncertainty analysis for performance of hypothetical geological disposal system for high level radioactive waste. This study provides the method to evaluate the effects of the uncertainties with respect to scenarios, models and parameters in engineering barrier system on radiological consequence. The results also help us to specify prioritized models and parameters to be further studied for long-term safety assessment.
Oe, Toshiaki*; Nagasaki, Shinya*; Kimura, Hideo; Takeda, Seiji; Sekioka, Yasushi; Kato, Hiroyasu*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 7(3), p.194 - 209, 2008/09
Sorption coefficients complied in a database have been checked for the sake of keeping the consistency. Major factors affecting the data scatter were examined by applying the mechanistic sorption models such as ion exchange and/or surface complexation models for the case of bentonite, clay minerals, and rock samples. The results suggested there were few data sets that were enough for the analysis by the later model. The sorption coefficients of neptunium or selenium on quartz and neptunium, tin and uranium on bentonite covers wide pH range and can be applicable for the extended analysis by the surface comlexation model. As for the case of cesium that is the key elements in performance analysis, the experimental condition such as ionic strength, mixture of sand are of great importance. Procedures were examined to speculate the parameters, which are not explicitly indicated in the data base and necessarily used in the ion exchange model, to reduce the variance of the sorption data.
Oe, Toshiaki*; Nagasaki, Shinya*; Kimura, Hideo; Takeda, Seiji; Sekioka, Yasushi; Kato, Hiroyasu*; Akahori, Kuniaki*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 7(3), p.210 - 220, 2008/00
Uncertainty found in the statistical data of Cs sorption coefficients was investigated. Careful data treatment indicated the major reason of data scatter was caused by the differences of the concentrations of co-existing ions and initial Cs concentrations. Analysis of the pH dependence of the data by adopting PHREEQC or MINEQL-TO which enable to treat ion exchange model coupled with the surface complexation model indicated the sorption coefficients could be represented for both cases obtained by batch method and diffusion method. In this analysis the same data set was used even for the extremely different experimental setup and the perturbation of environmental condition such as the Na concentration and pH brought strong influence on the data stability. The results also suggested that the scatter of the Cs sorption coefficient could be understandable and minimized through the analysis adopting mechanistic sorption model.
Takeda, Seiji; Sekioka, Yasushi; Yotsuji, Kenji; Kimura, Hideo; Inagaki, Yaohiro*
no journal, ,
no abstracts in English
Sekioka, Yasushi; Takeda, Seiji; Kimura, Hideo; Yamaguchi, Tetsuji; Oe, Toshiaki*; Nagasaki, Shinya*; Sasaki, Takayuki*; Kozaki, Tamotsu*; Inagaki, Yaohiro*
no journal, ,
no abstracts in English
Oe, Toshiaki*; Nagasaki, Shinya*; Kimura, Hideo; Takeda, Seiji; Sekioka, Yasushi; Kato, Hiroyasu*; Akahori, Kuniaki*
no journal, ,
no abstracts in English
-isosaccharinic acidKitamura, Akira; Sekioka, Yasushi*
no journal, ,
Solubility of palladium and tin has been experimentally investigated in the presence of -isosaccharinic acid (ISA). The obtained solubility increased with increasing concentration of ISA, especially for palladium.
Watanabe, Masatoshi; Takeda, Seiji; Sekioka, Yasushi; Kimura, Hideo
no journal, ,
no abstracts in English
Takeda, Seiji; Sasaki, Toshihisa; Sekioka, Yasushi; Kimura, Hideo
no journal, ,
no abstracts in English
Takeda, Seiji; Sekioka, Yasushi; Kimura, Hideo; Sasaki, Toshihisa
no journal, ,
no abstracts in English
Kimura, Hideo; Takeda, Seiji; Sasaki, Toshihisa; Sekioka, Yasushi
no journal, ,
no abstracts in English
Oe, Toshiaki*; Nagasaki, Shinya*; Kimura, Hideo; Takeda, Seiji; Sekioka, Yasushi; Kato, Hiroyasu*
no journal, ,
no abstracts in English
Sasaki, Toshihisa; Takeda, Seiji; Sekioka, Yasushi; Kimura, Hideo
no journal, ,
no abstracts in English
Sawaguchi, Takuma; Takeda, Seiji; Kozaki, Tamotsu*; Sekioka, Yasushi; Kato, Hiroyasu*; Kimura, Hideo
no journal, ,
no abstracts in English
