Nuclear power has the potential to help meet world energy demand in the coming century and beyond. Nuclear power accounted for 12.3 percent of the world's electricity production in 2011 (Nuclear Energy Institute, 2012) with Uranium accounting for most of the total nuclear energy produced world wide. Unfortunately, there are serious safety and logistical concerns with uranium fission that must be overcome to make nuclear power viable in the long term ("Uranium," 2012).
Geology and Mining
Uranium is the most commonly used fuel in nuclear reactors because it is very abundant in the earth's crust. It is mined using in situ leaching where the ore is dissolved and then pumped to the surface. This liquid is then milled into a solid oxide form called yellow cake. This mining method is much less damaging to the environment than open pit mining ("Where does uranium," 2009).
Plutonium is not mined, but instead is obtained as a fission product of uranium. Another source is weapons grade plutonium that has been discarded as a part of disarmament agreements. ("World nuclear association ," 2010).
Thorium is currently underutilized, but shows great promise as a safe alternative to uranium-based reactors. Thorium is found primarily in the minerals thorite and monazite. Coincidentally, monazite is also mined due to its high concentration of REEs. Therefore obtaining a greater supply of thorium would not require completely new mining technology (Cordier).
New Reactor Fuel Technologies
Plutonium recovered from spent fissile fuel can be used to create MOX fuel which is then fed back into the reactor. Discarded weapons grade plutonium is also used for the purpose. This practice is currently in use today to recycle spent fuel ("World nuclear association ," 2010).
Thorium as a fissile fuel also shows promise. Not only is thorium less radioactive than uranium and plutonium, but it also is easier to control and its fission products are less harmful. These technologies will be discussed in further detail on the fissile elements solutions page (World Nuclear Association, 2012)
Supply and Demand
The fission elements are found in abundance. The limiting factor is demand to support the mining of these elements. For example, companies in the US stopped mining thorium in 1994 after the demand dropped due to the discovery of an abundance of uranium. As energy demand continues to rise, the demand for fission elements is projected to rise as well, however there little concern that world reserves of these elements will be depleted in the near future (Cordier).
One of the major problems regarding nuclear energy is dealing with the nuclear waste. With the end of the Cold War, the US and former Soviet Union began dismantling thousands of nuclear weapons which resulted in a huge excess of highly enriched Uranium and Plutonium. Over 1500 metric tons of plutonium have been produced worldwide [US NRC]. This Plutonium and much of the nuclear waste produced is extremely toxic and radioactive.
The U.S. Department of Energy (DOE) manage high-level nuclear wastes produced as byproducts of nuclear reactors. Plans to store the majority of our nation's spent nuclear fuel and radioactive waste in a central repository underneath Yucca Mountain in Nevada have been proposed for years, however, the Obama administration has made it clear that Yucca Mountain is not an option for waste storage. Without any central repository in the US, nuclear waste generated is stored at or near one of the 121 facilities closest to where it is generated. 
The DOE explicitly states no plant in the United States is currently reprocessing spent fuel. 
If we are to increase our reliance on nuclear reactors for energy, we must develop better ways to deal with nuclear waste. It is impractical to continue producing waste without having a plan on how to manage it.
. World Nuclear Association. (2012, August 28). Uranium from rare earths deposits. Retrieved from http://www.world-nuclear.org/info/uranium_rare_earth_deposits_inf130.html
(World Nuclear Association, 2012)
. Stwertka, Albert (1998). "Plutonium". Guide to the Elements (Revised ed.). Oxford (UK): Oxford University Press. ISBN 0-19-508083-1.
.Energy Watch Group. (2006). Uranium resources and nuclear energy. Retrieved from http://www.energywatchgroup.org/fileadmin/global/pdf/EWG_Report_Uranium_3-12-2006ms.pdf
 Energy from Thorium. (n.d.). The liquid fluoride thorium reactor. Retrieved from http://energyfromthorium.com/lftradsrisks.html
. World Nuclear Association (WNA). (2012, May). What is uranium? how does it work?. Retrieved from http://www.world-nuclear.org/education/uran.htm
.Uranium. (2012). Retrieved from http://www.ggg.gl/uranium/
. Schuler , D., Buchert , D. M., Liu , R., Dittrich , S., & Merz , C. (2011). Study on rare earths and their recycling. The Greens/EFA Group , Retrieved from http://reinhardbuetikofer.eu/wp-content/uploads/2011/01/Rare-earths-study_Oeko-Institut_Jan-2011.pdf
Karam, A. (2006, July 17). How do fast breeder reactors differ from regular nuclear power plants?. Retrieved from http://www.scientificamerican.com/article.cfm?id=how-do-fast-breeder-react
What is a nuclear breeder reactor?. (n.d.). Retrieved from http://www.wisegeek.com/what-is-a-nuclear-breeder-reactor.htm