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Uranium's radioactivity can present health and environmental issues in the case of nuclear waste produced by nuclear power plants or weapons manufacturing. Uranium is weakly radioactive and remains so because of its long physical half-life (4.468 billion years for uranium-238).
Natural uranium contains about 0.72% 235 U. Depleted uranium has lower mass fractions—up to three times less—of 235 U and 234 U than natural uranium. Since 238 U has a much longer half-life than the lighter isotopes, DU is about 40% less radioactive than natural uranium.
Some uranium ore bodies contain higher concentrations of certain elements, such as selenium, than the surrounding host rock in which they are found. Certain plants that concentrate these elements act as indicator species for likely ore body locations. Mapping these plants provides information about areas in which further prospecting should be done.
Uranium tailings or uranium tails are a radioactive waste byproduct of conventional uranium mining and uranium enrichment. They contain the radioactive decay products from the uranium decay chains, mainly the U-238 chain, and heavy metals. Long-term storage or disposal of tailings may pose a danger for public health and safety.
It became popular in the U.S. and uranium was widely used to color glassware until 1943, when the government started regulating its use so that they could save uranium to build atom bombs.
Plants absorb some uranium from soil. Dry weight concentrations of uranium in plants range from 5 to 60 parts per billion, and ash from burnt wood can have concentrations up to 4 parts per million. [30] Dry weight concentrations of uranium in food plants are typically lower with one to two micrograms per day ingested through the food people eat ...
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One of the advantages of this method is that any sample provides two clocks, one based on uranium-235's decay to lead-207 with a half-life of about 703 million years, and one based on uranium-238's decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that allows accurate determination of the age of the ...