INFLUENCE OF WATER CONTENT ON PERMEABILITY AND DISPERSION CHARACTERISTICS OF UNSATURATED CLAY AND RADIONUCLIDE MIGRATION

In view of the aeration zone of a future low and intermediate radioactive waste repository, variations on unsaturated permeability coefficient K() and dispersion coefficient D() of a clay with its volumetric water content were studied. The results indicate that the unsaturated clay is actually impermeable when 25%, and small change in will change the orders of magnitude of K() when 15%. The experiments show that dispersion coefficient of unsaturated clay tends to reduce with the decrease of . As =38%,the measured dispersion coefficient is 4.12m2a-1, and as =6%,the dispersion coefficient is 0.04m2a-1,which only about 1% of the former. The migration simulations show that as 25%,plutonium migrates very slowly in the clay barrier, whereas its migration rate will be enhanced obviously when 30%.