Forecast of radionuclide release from full size waste forms

The complete understanding of the leaching mechanism of radionuclides from solid cementitious waste forms is still far from being reached. Much effort has been devoted, however, to identify and explain the main components which contribute to the dispersal of radionuclides out of the waste form to the environment. This is of prime importance when short term results are extrapolated into the future. The diffusion coefficient evaluation, based on experimental leaching data obtained from samples produced from the same batch was performed using the exact diffusion formulation applied to real geometric sample shape. The laboratory obtained diffusion coefficients are not constant in time nor are they the same for the different samples assayed precluding the use of laboratory scale leaching experiments to forecast the behavior of large scale samples. (author)