Uranium: Some Promises and Problems

                In his 2006 Elements article, Abdesselam Abdelouas describes the most hazardous part of the uranium fuel cycle: the mining and mill tailings. Uranium is generally extracted from the ground by three processes: open pit mining, underground mining, and chemical leaching. Both open pit and underground techniques produce a waste flow consisting of overburden (soil and rocks covering the main ores that contain trace amounts of ore and radioactive decay products), subeconomic ores with too little uranium for profitability, barren rock and drill cuttings. Once mined, the ores must be milled by extracting uranium with oxidants like sulfuric acid. Bases are then added to the byproducts to neutralize them before they are stored[1].    

                The uranium tailings generally contain unaltered minerals from the ores and surrounding rocks, and some new ionic species that have precipitated or dissolved from interactions with the processing chemicals. Hazardous elements like arsenic, lead and vanadium are commonly associated with uranium ore and therefore exist in high concentrations in tailings. Small amounts of unharvested uranium, along with the radioactive members of its decay series, are also present. Abdelouas focuses on the four radioactive elements uranium, radium, radon, and thorium and the toxic element arsenic as the major chemical hazards of tailings[2].

                If stored properly, of course, these waste products would not pose a problem. The US, as a top-ten uranium producer, has assumed a leadership role in global waste storage protocol. We have established codes for reducing the emissions of radon and preventing the weathering and leakage of containment structures. We also enforce standards for environmental and heath impact assessments. Despite the diligence of our regulations, many other countries have not met the same standards, often due to simple lack of funding for implementing them[3].

                Even in countries like the United States, uranium byproducts still constitute a serious hazard. In 2004, a breached containment dam in New Mexico released 370,000 cubic meters of radioactive water and 1000 tons of contaminated sediment that affected 110 km of the Rio Puerco. Hundreds of such acute failures have been reported, often due to slope instability, seepage, overtopping, and earthquakes. Gradual chronic leakage constitutes a more common issue that leads to radioactivity and acidification of groundwater[4].     

                I like the idea of nuclear power, despite my limited knowledge of the subject. I have never really accepted the concerns over unsafe waste disposal. Here's one reason why: http://www.youtube.com/watch?v=v3iRu71PGDA&feature=related. On that topic, I generally defer to an argument my physics professor once presented, which points out that the byproducts of fossil fuel combustion travel directly into the atmosphere, where we don’t really understand, and definitely can’t control their effects. Spent nuclear fuel, on the other hand, exists in a solid, transportable form that can be pretty well sequestered and monitored for the duration of its radioactive lifespan. I tend to focus on this end waste-based point of comparison, where I see nuclear poweras a clear winner worth expanding.I never really considered that mining and milling might actually pose a more serious hazard than end waste disposal. That was the most striking part of this article for me, and it has given me a new respect for the environmental effects of nuclear power.

Before reading this article, my main concern with uranium fuel was its nonrenewable nature. A variety of estimates exist as to the actual lifespan of the earth’s reserves. One pessimistic projection from the European Commission in 2001 provided a figure of 42 years at current rates of consumption[5]. Another projection from the International Atomic Energy Agency cited the figure of 47,000 years before all primary known reserves, secondary reserves, undiscovered and unconventional sources of uranium are depleted[6].         

The second estimate is probably overly optimistic, since the qualification of “undiscovered and unconventional” resources provides it lots of leeway for unfounded speculation. Some very real technologies and unconventional resources, however, could provide a significant boost to the longevity of uranium. Current nuclear technology generally doesn’t recycle or recover much fissionable material from waste, but breeder reactor technologies, which actually generate more fuel than they consume, could change net consumptive nature of current systems[7]. These reactors can be built to run on thorium, which is much more abundant in India than uranium. I also learned that seawater contains uranium at a concentration of about 3 ppb. If this could be economically extracted, it would amount to around 1000 times the current known terrestrial reserves[8]. That turns even the conservative estimate of 42 into a very large number.

So it seems that nuclear power has more potential for technological improvement than other nonrenewable resources. I don’t really know how long those will take to emerge, or if they will really be cleaner than the current mining and disposal practices. Uranium is definitely dirtier than I realized, but technology also holds more potential for the future.  

               

                 

               

               

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[1] Abdelouas, A. (2006, December). Uranium mill tailings: Geochemistry, minerology,
and environmental impact. Elements, 2, 335-341.

[2] Abdelouas, A. (2006, December). Uranium mill tailings: Geochemistry, minerology,
and environmental impact. Elements, 2, 335-341.

[3] Abdelouas, A. (2006, December). Uranium mill tailings: Geochemistry, minerology,
and environmental impact. Elements, 2, 335-341.

[4] Abdelouas, A. (2006, December). Uranium mill tailings: Geochemistry, minerology,
and environmental impact. Elements, 2, 335-341.

[5] Jameson, A. (2005, August 15). Uranium shortage poses threat. The Times of
London. Retrieved from http://business.timesonline.co.uk/tol/business/
industry_sectors/industrials/article555314.ece

[6] OECD, International Atomic Energy Agency. (2008). Uranium 2007: Resources,
production, and demand. Retrieved from http://www.oecdbookshop.org/oecd/
display.asp?CID=&LANG=EN&SF1=DI&ST1=5KZLLSXMT023

[7] Waltar, A.E.; Reynolds, A.B (1981). Fast breeder reactors. New York: Pergamon Press. pp. 853. ISBN 9780080259833

[8] Julian Ryall (2009-06-16). "Japan plans underwater sponges to soak up uranium". London: Telegraph Media Group Ltd.. http://www.telegraph.co.uk/news/worldnews/asia/japan/5550284/Japan-plans-underwater-sponges-to-soak-up-uranium.html. Retrieved 2009-07-05