Conceptual and mathematical models are presented for predicting waste package environment and radionuclide release in an unsaturated repository. Presence and ionic strength of water are viewed as a balance between water influx, evaporation, and condensation as modified by salinity-caused vapor pressure lowering. The model is used to examine the influence of thermal loading on waste package environment. Increased thermal gradients near the waste packages are shown to be as important as overall temperature in drying the waste package. The waste package environment is predicted to be highly variable, ranging from a concentrated brine to more dilute solutions. Under certain sets of conditions, water vapor condensation is predicted to occur on the waste package in the absence of liquid water influx. ¿ American Geophysical Union 1994 |