EN
To assess the safety for disposal of radioactive waste-cement composition, the leaching of ⁶⁰Co from a waste composite into a surrounding fluid has been studied. Leaching tests were carried out in accordance with a method recommended by the IAEA. Determination of retardation factors, K F and coefficients of distribution, k d , using a simplified mathematical model for analyzing the migration of radionuclides, has been developed. Results presented in this paper are examples of results obtained in a 30-year mortar and concrete testing project, which will influence the design of the engineered trench system for a future central radioactive waste disposal center.