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*; Nakazawa, Toshiyuki*; Ueta, Shinzo*; Shibata, Masahiro
JNC TN8400 99-069, 41 Pages, 1999/11
As a part of the evaluation for the sorption phenomena of nuclides in compacted bentonite, apparent diffusivities for uranium, neptunium and technetium that are redox-sensitive elements, were measured under reducing conditions. Bentonite used was a sodium bentonite, Kunigel V1. Apparent diffusivities were measured by using in-diffusion method (concentration profile method), under the conditions with varying dry densities of compacted bentonite and sorts of the solution used for water saturation of bentonite in diffusion experiments. As a result of the measurements, following ranges of values for apparent diffusivities were acquired. ...
Sato, Haruo
JNC TN8400 99-065, 379 Pages, 1999/10
A database for diffusivity for a data setting of effective diffusion coefficients in rock matrices in the second progress report, was developed. In this database, 3 kinds of diffusion coefficients: effective diffusion coefficient (De), apparent diffusion coefficient (Da) and free water diffusion coefficient (Do) were treated. The database, based on literatures published between 1980 and 1998, was developed considering the following points. (1)Since Japanese geological environment is focused in the second progress report, data for diffusion are collected focused on Japanese major rocks. (2)Although 22 elements are considered to be important in performance assessment for geological disposal, all elements and aquatic tracers are treated in this database development considering general purpose. (3)Since limestone, which belongs to sedimentary rock, can become one of the natural resources and is inappropriate as a host rock, it is omitted in this database development. Rock was categorized into 4 kinds of rocks; acid crystalline rock, alkaline crystalline rock, scdimentaly rock (argillaceous/tuffaceous rock) and sedimentary rock (psammitic rock/sandy stone) from the viewpoint of geology and mass transport. In addition, rocks around neutrality among crystalline rock were categorized into the alkaline crystalline rock in this database. The database is composed of sub-databases for 4 kinds of rocks. Furthermore, the sub-databases for 4 kinds of the rocks are composed of databases to individual elements, in which totally, 24 items such as species, rock name, diffusion coefficients (De, Da, Do), obtained conditions (method, porewater, pH, Eh, temperature, atmosphere, etc.), etc. are input. As a result of literature survey, for De values for acid crystalline rock, totally, 207 data for 18 elements and one tracer (hydrocarbon) have been reported and all data were for granitic rocks such as granite, granodiorite and biotitic granite. For alkaline crystallinc rock, ...
Sato, Haruo
JNC TN8400 99-060, 12 Pages, 1999/10
Apparent diffusion coefficients(Da) of Cs(Cs
), Ni(Ni
) and Se(SeO
) in a Na-bentonite (Kunigel-V1) were measured for a dry density of 1.8 Mg
m
with silica sand of 30 wt% at room temperature by in-diffusion method to evaluate the effect of the mixture of silica sand on Da in bentonite. The experiments for Cs and Ni were carried out under aerobic condition, but those for Se which is redox sensitive were carried out in an Ar glove-box (O
concentration 
0.1 ppm). Consequently, no significant effect of silica sand mixture to the bentonite on Da values of Cs and Se was found, and the obtained Da values were approximately the same as those in the system without silica sand reported so far. On the other hand, Da values of Ni in bentonite with silica sand were 2 orders of magnitude lower than those in bentonite without silica sand obtained to date. The Da values of Ni reported so far were obtained using stable isotopic tracer and a tracer solution with fairly high Ni concentration compared with concentration used in this study was introduced. Additionally, it is known that distribution coefficient (Kd) of Ni on Na-montmorillonite which is the major constituent clay mineral of Kunigel-V1 decreases with increasing Ni concentration. Based on this, the abrupt decrease in Da values of Ni for bentonite with silica sand is considered to be due to the difference of sorption caused by the difference of Ni concentration in the porewater of bentonite.
Yamaguchi, Tetsuji;
Journal of Contaminant Hydrology, 35, p.55 - 65, 1998/00
Times Cited Count：29 Percentile：62.91(Environmental Sciences)no abstracts in English
