Modeling water penetration through cracks in waste packages with impinging droplets

Static and dynamic models were developed to characterize and predict the hydraulic behavior in cracks in waste packages and drip shields for Yucca Mountain performance-assessment applications. A static model was developed to characterize the crack aperture based on steady, pressurized flow through the crack. Models were also developed to assess the range of apertures that would allow breakthrough of water during both static (pond water) and dynamic (dripping) conditions. Parameters such as temperature, contact angle, and drip height were also evaluated. For static conditions, results showed that the maximum head sustainable decreased as a function of aperture. Temperature and pendant droplet size had little effect on the maximum head relative to the range of aperture sizes considered. A dynamic model was developed to evaluate the impact of crack aperture, drip height, and contact angle on the potential penetration of water through cracks with impinging water droplets. Results showed that the net downward force caused by the droplets increased as the aperture increased. The drip height and the contact angle were also found to impact the potential for penetration. For low drip heights (0.4 m), the onset of flow through cracks was predicted to occur when the crack aperture was between approximately 20 microns and 200 microns. At high drip heights (2.2 m), the onset of flow through cracks was predicted to occur when the crack aperture was between approximately 10 microns and 60 microns. (authors)