Diffusion of carbon dioxide and iodine through Yucca Mountain tuffs

This paper reports that the effective diffusivity of carbon dioxide and iodine was measured for tuff samples from five locations near Yucca Mountain. Samples of G tunnel tuff, lower non-lithophysal zone of Topopah Spring tuff (outcrop sample of the layer right above the proposed repository site layer) and Tiva Canyon tuff samples (proposed repository layer) were studied. A steady state method, using chromatographic analysis, was used to determine the effective diffusivity of CO2 for all tuffs. An unsteady state method was used to determine effective diffusivity for Iodine on three tuffs. Empirical correlations are reported for each tuff to correlate the effect of temperature, and moisture content, on the diffusivity of CO2. Effective diffusivity, of all tuffs and both gases, increased with temperature. Effective diffusivity of CO2 decreased as the moisture content increased