Diffusion of Radionuclides in Clay-Based Ceramics

The diffusion coefficients of 22Na, 90Sr and 134Cs in clay-based ceramics were determined by the integral residual activity method. It was established that the diffusion coefficients of radionuclides decreased, at the investigated temperature range, in the following order: 22Na > 134Cs > 90Sr. The migration of 134Cs, in comparison with the migration of 22Na, was characterised by essentially the lowest values of the preexponential factor and of the activation energy of the diffusion process. It was shown that, in the case of a ceramic material containing 89% (w/w) of Cambrian clay and 11% (w/w) of perlite, increasing the relative moisture content from 0.05% to 0.3% resulted in a considerable (2–3 orders of magnitude) increase of the diffusion coefficients of radionuclides. A further increase of the relative moisture content did not influence appreciably their diffusion mobility.