A SYSTEMATIC STUDY OF EPISODIC LOCALIZED INFILTRATION INTO SUPERHEATED FRACTURED ROCK
In this paper, the probability of episodic infiltration reaching waste packages during the heating phase of the repository is studied in a systematic manner. The assumed infiltration events, while generally short in duration, are large in magnitude relative to the average infiltration. A semi-analytical solution is developed to determine the complex flow processes of such infiltration events when entering the hot rock environment. The solution scheme features a time-marching algorithm that tracks the propagation of finite masses of water flowing in vertical fractures, while an analytical solution is applied to consider mass losses resulting from vaporization caused by heat conduction from the adjacent rock. The long-term evolution of thermal-hydrological conditions in the rock is considered by simulating infiltration events at several discrete times after emplacement, covering the entire time period that repository temperatures are above boiling. Results indicate that episodic infiltration may indeed allow water to infiltrate considerable distances into the hot fractured rock. However, the heat generated from the waste packages is sufficient to reduce the probability of water entering waste emplacement drifts by a significant amount.