Study on migration behavior of radionuclides in engineered clay barrier (II)

*; *; *

JNC TJ8400 2000-018, 79 Pages, 2000/02

JNC-TJ8400-2000-018.pdf:2.09MB

As a basic research for geological disposal of high-level radioactive wastes, diffusion behavior of radionuclides and corrosion behavior of overpack materials in clay buffer materials (bentonite) were studied. In the study on the diffusion behavior of radionuclides, basal spacing and water content were determined for water saturated, compacted Na-montmorillonite that is major clay mineral of bentonite. The apparent diffusion coefficients of Na, Sr, Cs and Cl ions and their activation energies were also determined at different dry densities of montmorillonite. For all kinds of ions, the activation energies were found to increase as the dry density increased. These findings suggest that the diffusion mechanism of ions in compacted montmorillonite changed with increasing dry density. As a reasonable explanation for the changes in the activation energy, we proposed a multiprocess diffusion model, in which predominant diffusion process is considered to change from pore water diffusion to interlayer diffusion via surface diffusion when the dry density increases. The Na-montmorillonite is expected to alter by the ion exchange with Ca ions, which could be introduced from groundwater and/or cementitious materials in a repository. The apparent diffusion coefficients of Na and Cs ions and their activation energies were studied for Na/Ca montmorillonite mixtures in order to know the effect of this kind of alteration on the diffusion behavior of ions. It was found that the alteration of montmorillonite affected diffusion coefficients and the activation energies for both kinds of cations. These effects cannot be explained only by the pore water diffusion. The multiprocess diffusion model proposed in this study is suggested as the most reasonable explanation for the effects. The oxidation behavior of pyrite in bentonite during drying process was studied for understanding corrosion behavior of overpack materials in bentonite. There ...

A New type of amidoxime-group-containing adsorbent for the recovery of uranium from seawater, II; Effect of grafting of hydrophilic monomers

; Katakai, Akio; ;

Sep.Sci.Technol., 21(3), p.299 - 313, 1986/00

https://doi.org/10.1080/01496398608058379

no abstracts in English

Drying experiments of CeO granules produced using wet granulator

Ishii, Katsunori; Segawa, Tomoomi; Kawaguchi, Koichi

no journal, , 

The Japan Atomic Energy Agency is developing a simplified mixed oxide (MOX) fuel fabrication process. In this process, a wet granulator improves the flowability of MOX raw powder for the pelletizing process 1, 2). Following this granulation step, the formed granules have moisture content of approximately 10 wt.%. To adhere to the acceptance standards regarding moisture content for the fuel pellet fabrication step, drying the granules under the moisture content of 1 wt.% using a dryer is necessary. To maintain the granule shape during powder handling and shaker process of a pressing machine, the granules must be adjusted to enough crushing strength. However, the relation between dry conditions and granule crushing strength has not been reported. Therefore, to estimate the appropriate heating conditions of the dryer, we investigated the influence of varying heating conditions on moisture content and granule crushing strength.