A Criterion for Selecting Leach Test Spe

Leaching processes in nuclear waste management are critically contingent on the kinetics of diffusion, specifically when assessing the performance of various solid waste forms. This study aims to establish a criterion for selecting test specimen sizes for leach tests that approximates semi-infinite media, which simplifies the interpretation of leach test results. Utilizing a relationship among test duration, specimen radius, and the effective bulk diffusion coefficient, the research shows that the criterion is governed by the equation 1 - P = √πD T / R, where P indicates the degree of conformity to semi-infinite geometry. The resulting analysis suggests that for most glass waste forms, the semi-infinite geometry approximation holds true across different test samples, with the exception of finely crushed materials that could potentially deviate from this model. The findings emphasize the importance of correct specimen sizing in predicting the leaching behavior of radioactive waste forms, which is vital for evaluating their long-term safety and environmental impact. This work was supported by the U.S. Department of Energy through the Office of Nuclear Waste Isolation.