Diffusion experiments with 32Si in Boom Clay, FoCa Clay and the M2 mixture

The sorption behavior of Si on Boom Clay, FoCa clay and the M2 backfill mixture at 25°C has been studied at SCK·CEN by means of diffusion experiments with 32Si. This report completes the results obtained in the period 1991-2006. Three types of diffusion tests were performed: (1) through-diffusion experiments with Boom Clay, (2) C4 Percolation experiments with Boom Clay, (3) D2 Pulse injection Percolation experiments with FoCa Clay and with the M2 mixture. The values of the Si retardation factor R, of the apparent diffusion coefficient Dapp of dissolved silica, and the the pore diffusion coefficient Dp value are reported for Boom Clay. The apparent Si diffusion coefficient is reported for FoCa clay and the M2 mixture. It is possible that the three types of test (through-diffusion, C4 and D2 percolation) lead to (slightly) different values of the diffusion parameters.