Leach characteristics of 137Cs and 60Co radionuclides from spent mix bead ion exchange resins and both ordinary Portland cement and cement mixed with two kind
of natural sorbents (bentonite and clinoptilolite) have been studied using the International Atomic Energy's (IAEA) standard
leach method. The waste immobilization performance of low-level wastes in natural sorbent mixtures was determined. The solidification
matrix was a standard Portland cement mixed with 290-350 (kg/m3) spent mix bead exchange resins, with or without 1-10% of bentonite or/and clinoptilolite. The leaching rates from the cement-bentonite
matrix were measured after 300 days as 60Co: (1.20-9.72) . 10-5 cm/d and 137Cs: (1.00-9.22) . 10-4 cm/d. From the leaching data, the apparent diffusivity of cobalt and cesium in cement-bentonite or/and clinoptilolite matrix
with a waste load of 350 kg/m3 of spent mix bead exchange resin was calculated as 60Co: (1.0-5.9) . 10-6 cm2/d and 137Cs: (0.48-2.4) . 10-4 cm2/d. The compressive strength of these samples is determined according to the ASTM standards.
Leach characteristics of 54Mn and 85Sr radionuclides from ordinary Portland cement have been studied using International Atomic Energy’s (IAEA) standard leach method. The retardation factors, KF, and coefficients of distribution, kd, have been determined using a simplified mathematical model for analyzing the migration of radionuclides. The lowest leaching values after 60 days were achieved in samples with 5% of vermiculite. Results presented in this paper are the examples of results obtained in a 10 year mortar and concrete testing project, which will influence the design of the engineered trench system for a future central Serbian radioactive waste storage center.