Temperature effect on diffusion of carbon dioxide through upper layers of Yucca Mountain

Abstract

The effective diffusivities of carbon dioxide through the Tiva Canyon tuff and the lower lithophysal zone of the Topopah Spring tuff (outcrop samples 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 lithopysal zone tuffs increased with temperature. The following correlation was obtained to estimate the effective diffusivity of carbon dioxide through the Tiva Canyon tuff in cm 2 s −1 as a function of temperature (K). D e = 1.22 × 10 −2 − 3.77 × 10 −5 T + 9.95 × 10 −8 T 2 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. For this layer, the following correlation was obtained to estimate the effective diffusivity of carbon dioxide in cm 2 s −1 as a function of temperature (K). D e = − 1.11 × 10 −3 + 1.25 × 10 −5 T + 1.83 × 10 −9 T 2