Lawrence Berkeley National Laboratory

Understanding microclimate dynamics in tunnels is important for designing and maintaining underground facilities. For example, in the geological disposal of radioactive materials, condensation of vapor should be minimized as it can accelerate waste package corrosion and radionuclide release. While microclimate dynamics are known to be dominated by the advection of heat and moisture, additional factors may also be important, such as the presence of fractures or faults. We present a relatively inexpensive method to assess microclimatic perturbations within a tunnel. By combining standard temperature and relative humidity sensors with low-cost sensors designed to detect changes in condensation, we monitored microclimate dynamics along a tunnel at the proposed geological repository at Yucca Mountain, Nevada. We observed significant differences in the pattern of condensation in a faulted zone relative to that of a nonfaulted zone, suggesting that the microclimate dynamics of excavated cavities in fractured, partially saturated rocks can be highly complex.