The Effect of Silica Sand Content and NaNOConcentration 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 NaNOand high pH groundwater condition caused by dissolution of cementitious materials. Therefore, the effective diffusion coefficients (De) and the apparent diffusion coefficients (Da) of CO, Cland Iin compacted bentonite were obtained as a function of silica sand content and NaNOconcentration under high pH condition by Through-diffusion method. Furthermore, the diffusion mechanisms of CO, Cland Iwere discussed.The obtained De values of CO, Cland Iwere in a range of 10to 10m/s order and Da values in a range of 10to 10m/s order (CO) and 10m/s order (Cland IThe De and Da values of CO, Cland Iincreased 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, Cland Iincreased with increasing NaNOconcentration. The increases were interpreted by the decrease of anion exclusion effect. Furthermore, it seems that the pathways of Cland Iwere limited to the interstitial pore space. The COions were probably retained in the Kunigel V1 as the precipitation of calcite.