Leaching kinetics of 137Cs and 60Co radionuclides fixed in cement and cement-based materials

Leach characteristics of Cs-137 and Co-60 radionuclides from both ordinary Portland cement and cement mixed with two different ratios of silica fume and ilmenite have been studied using International Atomic Energy's (IAEA) standard leach method. A mathematical model has been simulated to predict the release rate of each nuclide from cubic geometry waste matrix and the predicted values are discussed in relation to experimentally observed leach rates to confirm the validity of the proposed mechanism in the model. The effect of temperature on the radionuclides leaching rates was also studied and the effective diffusion coefficients were obtained at different temperatures. The net fractional release of the two radionuclides from different waste forms showed a decreasing pattern as Cs-137 > (CO)-C-60, indicating the largest diffusion coefficient for cesium in all waste matrices. (C) 2002 Elsevier Science Ltd. All rights reserved.