Diffusion of Carbon Dioxide Through Upper Layers of Yucca Mountain

ABSTRACTThe effective diffusivities of carbon dioxide through Tiva Canyon tuff and the lower lithophysal zone of the Topopah Spring tuff (outcrop sample of the layer above the proposed nuclear repository site layer) were determined using a steady-state method (counter diffusion). The diffusivity of carbon dioxide through the Tiva Canyon and lithophysal zone tuffs increased with temperature and decreased with percent saturation. The following correlation was obtained to estimate the effective diffusivity of carbon dioxide through the Tiva Canyon tuff as a function temperature and percent saturation.De = 1.2168×10−2 − 3.7713×10−5 T + 9.9510×10−8 T2 − 4.2220×10−5 × (Percent Saturation)where De is in cm2/sec and T in K. These units hold for all other correlations in this paper.The effective diffusivity of carbon dioxide through the lower lithophysal zone of the Topopah Spring tuff (layer right above the proposed repository site) also increased with temperature and decreased with percent saturation. For this layer, the following correlation was obtained to estimate the effective diffusivity of carbon dioxide as a function temperature and percent saturation.De = − 1.119×10−3 + 1.2512×10−5 T + 1.8288×10−9 T2 × 2.0725×10−5 × (Percent Saturation)