Mechanics fractured tuff

The DST is the second underground thermal test to be carried out in the Exploratory Studies Facility (ESF) at Yucca Mountain, Nevada. The purpose of the test is to evaluate the effect of coupled thermal, hydrological, chemical, and mechanical processes that take place in unsaturated fractured tuff over a range of temperatures (approximately 25°C to 200°C). The DST heaters were activated on December 3,1997, with a planned period of 4 years of heating, followed by 4 years of cooling. After just over 4 years, the heaters were switched off and since that time the system has been slowly cooling. 

Sorption also is a potential retardation mechanism for radionuclide transport through fractures. The surfaces of fractures are often lined with minerals that may be capable of sorbing some of the radionuclides however, there is limited characterization of the extent and distribution of fracture-lining minerals along potential flow paths (Carlos et al., 1995). In the conceptual model used for Yucca Mountain, it is conservatively assumed that there is no sorption (i.e., = 0) in fractured tuff... 

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