Diffusion of Radionuclides in Clay-Based Ceramics

Abstract

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.