|Fig. 1: Diagram of the WIPP Facility. (Courtesy of the DOE)|
Deep geological repositories are designed to bury and contain nuclear waste within stable geologic environments usually over 1,000 ft below the surface. These repositories involve a series of waste form, waste package, engineered seals, and a geological formation or environment that provides a high level of long-term isolation of radioactive material from humans and their environment. The common international consensus is that engineered deep geological repositories at geologically suitable sites for storing nuclear waste is the end-point for radioactive waste management without need for future human intervention.  In the United States, the disposal of nuclear waste has been a pressing issue,the prevailing answer to what to do with nuclear waste is deep geological repositories. As of 2014, the U.S. currently has 70,000 metrics tons of spent nuclear material in the country. 
The United States has two deep geological repositories within its boarders, the currently operational Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, and Yucca Mountain in Nevada, where funding and development have been halted since 2010. As shown in Fig. 1, WIPP is built on a salt bed, which is the ideal geological environment for nuclear waste isolation because after the nuclear waste dry casks are buried and sealed with 13 layers of concrete and soil the salt seeps into any cracks or openings around the cask. The result of this is that after a 75 year time period, the waste will be entirely isolated from the outside environment.  Yucca Mountain, on the other hand, was built within a mountain that is made up of layers of tuff, or volcanic rock, which many scientists believe has unique chemical, physical, and thermal characteristics that make it a prime geological candidate to bury and isolate nuclear waste. However, Yucca Mountain does offer one geological set back that could potentially cause issues in the future. This is that water could come into contact with the waste over time and that the water could reduce the waste to microscopic radioactive particles that could seep into the environment. However, this concern is minimal due to the fact Yucca Mountain is in an extremely dry environment and about 95% of the precipitation in the area evaporates, runs off, or is consumed by desert wildlife and vegetation. 
Although WIPP continues to be the only current operational deep geological repository in the U.S., many of the major setbacks the developments of deep geological repositories, such as Yucca Mountain, have been primarily political and a result of the Obama administration adhering to public concerns regarding nuclear waste storage within our borders.  However, with a Republican Congress on the way in 2015, there is hope that funding and development of Yucca Mountain will resume in the near future. However, a number of other factors have inhibited the development of Yucca Mountain beyond politics, such as the high level of tectonic activity in that region of the country and the fact that Bow Ridge fault line runs directly beneath Yucca Mountain. Although the structural layout of the deep geological repository at Yucca Mountain has been designed to withstand severe and long-term seismic loading, there are still concerns that the caskets of waste within or being transported to the facility that have not yet been buried could be compromised.  While deep geological repositories may be facing public backlash in the U.S., the larger scientific community believes they still present the most viable solution at the present moment to discard nuclear waste as they provide both manmade and natural barriers that are designed to isolate the waste for at least 10,000 years.
© Wade Avery. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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