The Effect of Silica Sand Content and NaNO
Concentration on Diffusions of C, Cl and I in Compacted Bentonite
Ishidera, Takamitsu
; Miyamoto, Shinya*; Sato, Haruo
For safety assessment of geological disposal of TRU waste, it is necessary to obtain the diffusivities of C-14, Cl-36 and I-129 and to estimate the effects of the dissolution of NaNO
and high pH groundwater condition caused by dissolution of cementitious materials. Therefore, the effective diffusion coefficients (De) and the apparent diffusion coefficients (Da) of CO
, Cl
and I
in compacted bentonite were obtained as a function of silica sand content and NaNO
concentration under high pH condition by Through-diffusion method. Furthermore, the diffusion mechanisms of CO
, Cl
and I
were discussed.The obtained De values of CO
, Cl
and I
were in a range of 10
to 10
m
/s order and Da values in a range of 10
to 10
m
/s order (CO
) and 10
m
/s order (Cl
and I
The De and Da values of CO
, Cl
and I
increased with increasing silica sand content. The changes of De and Da values appeared to be estimated by smectite partial density. The De values of CO
, Cl
and I
increased with increasing NaNO
concentration. The increases were interpreted by the decrease of anion exclusion effect. Furthermore, it seems that the pathways of Cl
and I
were limited to the interstitial pore space. The CO
ions were probably retained in the Kunigel V1 as the precipitation of calcite.