HCG34-P01

Room:Convention Hall

Time:May 26 18:15-19:30

Identifying influence factors on permeability of granite core samples
MATSUDA, Norihiro1∗ ; KUBO, Taiki1 ; KASHIWAYA, Koki1 ; KOIKE, Katsuaki1
1Kyoto University

A safe geological disposal of high-level radioactive waste for long term requires to evaluate the stability of facilities basedon the estimation of groundwater flow and mass transport. For the evaluation, it is indispensable to understand a regional
groundwater system and a slow diffusion phenomenon of radionuclide in the matrix of the rock body. However, the relation
between a permeability and macro/micro cracks in the rocks has not yet been clarified and the estimation accuracy of flow path islow. The main purpose of this study is to clarify the relationship by measuring spatial variation of permeability of granite rocks
and examining the dependence of permeability upon crack systems with different scales.
For the purpose, we used the core samples taken from a borehole in the Tono area (Gifu, central Japan) drilled by Japan
Atomic Energy Agency (JAEA). This area is mainly composed of Toki granite. Fault zones were drilled through the borehole.
First we measured the permeabilities of the 36 cores and compared them with the geological features. Next, in order to identify
the influence factors on the permeability of the rock matrix, thin-sections were produced from the cores after the infiltration offluorescent into the cores and cracks were extracted from the thin-section images. Furthermore, micro-scale features of the rocks
were compared with anisotropy of the permeability. We defined mesocrack as a visible crack with cm scale and microcrack as aninvisible cracks with mm scale, respectively. As the result, the permeabilities were enhanced in accordance with the degradationof rocks by the advanced weathering and alteration and the presence of faults. High permeabilities were also measured in the partsof thin-sections in which the mesocracks were developed. As for the microcracks, although the fluorescent infiltrated into themicrocracks, their attributes such as length, density, and angle did not have clear relationship with the magnitude of permeability.
These results suggest that mesocracks act as a path of fluids, while individual microcrack cannot have this function: formationof continuous network of microcracks is needed to enhance the permeability. Our next step is to add samples and undertake
image analyses more in detail to verify the interpretation.
Acknowledgement: We would like to express our sincere thanks to the co-researchers of Japan Atomic Energy Agency for
their supports and many constructive comments for this study.

Keywords: Permeability, Granite, Tono Area, Image analysis, Crack characteristics

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HCG34-P02

Room:Convention Hall

Time:May 26 18:15-19:30

Estimates of a sediment yield and a outflow of radioactive Cs with 3D laser scanner
WATANABE, Takayoshi1∗ ; OHYAMA, Takuya1 ; ISHII, Yasuo1 ; NIIZATO, Tadafumi1 ; ABE, Hironobu1 ;MITACHI, Katsuaki1 ; SASAKI, Yoshito1 ; KITAMURA, Akihiro1
1

Japan Atomic Energy Agency

For an estimate of movement from forest to living spheres, it is important to understand value of movement of soil andradioactive Cs from forest. We measured volumes of deposit with 3D laser scanner in an erosion control dam in Fukushima
prefecture on August 29, 2013 and December 3, 2014.
As a result of measurement, an amount of increase of sediment for 15 months is 0.5 m3 . A denudation rate is 0.02 mm/year.
This value is on the same level with denudation rates in meadows and forest, 10-2 - 10-1 mm/year (Fujiwara et al, 1999). And it
is estimated that a variation of radioactive Cs is Cs-137:200,000,000 Bq, Cs-134:80,000,000 Bq.

Keywords: F-TRACE project, accident at the Fukushima Daiichi Nuclear Power Station, 3D laser scanner, denudation rate

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