Enhancement of Vapor Diffusion in Yucca Mountain Tuff

Wildenschild, D. and J.J. Roberts, 2001 "Experimental Tests of Enhancement of Vapor Diffusion in Topopah Spring Tuff." Journal of Porous Media, 4(1), 1-13.

The potential enhancement of thermally driven water vapor diffusion in Topopah Spring Tuff was investigated using a transient–state thermal conductivity measurement. Thermal conductivity was measured as a function of pressure, temperature and water content by the method of Parikh et al. (1979), which allows separation of thermal conductivity from thermally induced latent heat transport. The measured thermal conductivity of Topopah Spring Tuff ranged from 0.99 W/mK to 2.07 W/mK and showed an increase with increasing temperature above approximately 40oC. These values are slightly lower than the range of values measured for other samples from the Yucca Mountain, Nevada site, e.g. Nimick (1990). Enhancement of vapor diffusion in tuff was not observed at any of the investigated combinations of water contents, temperatures, and pressures. The method of Parikh et al. (1979) was subsequently tested on a mixture of quartz sand and 10% kaolinite. A considerable degree of enhancement was observed in the soil for a water saturation of 14%, demonstrating the capability of the method to estimate enhancement of vapor diffusion.