Jo. Lee et al., EFFECT OF DRY DENSITY ON SR-90 DIFFUSION IN A COMPACTED CA-BENTONITE FOR A BACKFILL OF RADIOACTIVE-WASTE REPOSITORY, Annals of nuclear energy, 23(9), 1996, pp. 727-738
The transport of radionuclides in compacted bentonite is dominated by
the diffusion process. The dry density is an important factor in the d
iffusion of radionuclides through the compacted bentonite. Through-dif
fusion tests were performed to investigate the effect of dry density o
n Sr-90 diffusion. In the diffusion tests the sample used was a benton
ite taken from the southeastern area of Korea and the experimental sol
ution was synthetic groundwater spiked with a tracer of Sr-90 (as (SrC
l2)-Sr-90). The dry density was adjusted in the range of 1.0-1.7 Mg/m(
3). The distribution coefficient of Sr-90 in the compacted bentonite w
as much lower than that obtained by a batch test. The formation factor
and porosity of the compacted bentonite were decreased with increasin
g dry density. The apparent and effective diffusion coefficients of Sr
-90 were in the range of 1.41 x 10(-12) 1.20 x 10-(12) m(2)/s, 1.81 x
10(-11)-1.11 x 10(-11) m(2)/s, respectively, and decreased with increa
sing dry density of compacted bentonite. It was found for Sr-90 that t
he higher the dry density increases, the more significant the surface
diffusion, as compared with the pore diffusion. The results obtained w
ill be used as basic data for the safety assessment of a repository.