Influence of natural sorbents on the immobilization of spent ion exchange resins in cement

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.