Uranium tailings
Encyclopedia
Uranium tailings are a waste byproduct (tailings
) of uranium mining
. In mining, the raw uranium ore is brought to the surface and crushed into a fine sand. The valuable uranium-bearing minerals are then mechanically removed, and the remaining radioactive sand, called "uranium tailings", is stored in huge impoundments.
If these uranium tailings are left on the surface and allowed to dry out, the radioactive sand can be carried great distances by the wind, entering the food chain
and bodies of water. The danger posed by such sand dispersal is uncertain at best given the dilution effect of dispersal. The majority of tailing mass will be inert rock, just as it was in the raw ore before the extraction of the uranium, but physically altered, ground up, mixed with large amounts of water and exposed to atmospheric oxygen, which can substantailly alter chemical behaviour.
Uranium tailings contain over a dozen radioactive nuclides, which are the primary hazard posed by the tailings. The most important of these are thorium-230
, radium-226
, radon-222
(radon gas) and the daughter isotopes of radon decay, including polonium-210
.
An EPA estimate of risk based on uranium tailings deposits existing in the United States in 1983 gave the figure of 500 lung cancer deaths per century, if no countermeasures are taken. This unit of reporting the risk greatly underestimates risk to local populations.
Tailings
Tailings, also called mine dumps, slimes, tails, leach residue, or slickens, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore...
) of uranium mining
Uranium mining
Uranium mining is the process of extraction of uranium ore from the ground. The worldwide production of uranium in 2009 amounted to 50,572 tonnes, of which 27% was mined in Kazakhstan. Kazakhstan, Canada, and Australia are the top three producers and together account for 63% of world uranium...
. In mining, the raw uranium ore is brought to the surface and crushed into a fine sand. The valuable uranium-bearing minerals are then mechanically removed, and the remaining radioactive sand, called "uranium tailings", is stored in huge impoundments.
If these uranium tailings are left on the surface and allowed to dry out, the radioactive sand can be carried great distances by the wind, entering the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
and bodies of water. The danger posed by such sand dispersal is uncertain at best given the dilution effect of dispersal. The majority of tailing mass will be inert rock, just as it was in the raw ore before the extraction of the uranium, but physically altered, ground up, mixed with large amounts of water and exposed to atmospheric oxygen, which can substantailly alter chemical behaviour.
Uranium tailings contain over a dozen radioactive nuclides, which are the primary hazard posed by the tailings. The most important of these are thorium-230
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
, radium-226
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
, radon-222
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...
(radon gas) and the daughter isotopes of radon decay, including polonium-210
Polonium
Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie Skłodowska-Curie and Pierre Curie. A rare and highly radioactive element, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for...
.
An EPA estimate of risk based on uranium tailings deposits existing in the United States in 1983 gave the figure of 500 lung cancer deaths per century, if no countermeasures are taken. This unit of reporting the risk greatly underestimates risk to local populations.